Merge pull request #8 from razzolini/rules-dsl

Implement a domain-specific language for the definition of algebraic manipulation rules

.editorconfig

@@ -0,0 +1,4 @@
+root = true
+
+[*]
+indent_style = tab

core/pom.xml

@@ -46,8 +46,8 @@
 			<artifactId>commons-lang3</artifactId>
 		</dependency>
 		<dependency>
-			<groupId>junit</groupId>
-			<artifactId>junit</artifactId>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter</artifactId>
 			<scope>test</scope>
 		</dependency>
 	</dependencies>

core/src/main/java/it/cavallium/warppi/Platform.java

@@ -60,13 +60,15 @@ public interface Platform {
 
 	String[] stacktraceToString(Error e);
 
-	void loadPlatformRules();
-
-	void zip(String targetPath, String destinationFilePath, String password);
-
-	void unzip(String targetZipFilePath, String destinationFolderPath, String password);
-
-	boolean compile(String[] command, PrintWriter printWriter, PrintWriter errors);
+	/**
+	 * Determines the list of files containing DSL rules to load.
+	 *
+	 * @return a <code>List</code> of paths of files which contain DSL rules.
+	 * 		   Each <code>String</code> in the returned <code>List</code> can be passed as an argument to
+	 * 		   {@link StorageUtils#getResourceStream(String)} to access the corresponding file's contents.
+	 * @throws IOException if an IO error occurs while getting the list of rule file paths.
+	 */
+	List<String> getRuleFilePaths() throws IOException;
 
 	public interface Gpio {
 		int valueOutput();

core/src/main/java/it/cavallium/warppi/math/Function.java

@@ -1,6 +1,12 @@
 package it.cavallium.warppi.math;
 
 import it.cavallium.warppi.gui.expression.blocks.Block;
+import it.cavallium.warppi.math.functions.*;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.equations.Equation;
+import it.cavallium.warppi.math.functions.equations.EquationsSystem;
+import it.cavallium.warppi.math.functions.equations.EquationsSystemPart;
+import it.cavallium.warppi.math.functions.trigonometry.*;
 import it.cavallium.warppi.math.rules.Rule;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
@@ -15,6 +21,16 @@ public interface Function {
 	@Override
 	String toString();
 
+	/**
+	 * Indicates whether some other object is a <code>Function</code> which is <em>identical</em> to this one.
+	 * <p>
+	 * Two functions which are not identical, but only equivalent (due to, for example, the commutative property) aren't
+	 * considered equal.
+	 *
+	 * @param o the other object to compare.
+	 * @return <code>true</code> if the other object is identical to this <code>Function</code>, <code>false</code>
+	 * otherwise.
+	 */
 	@Override
 	boolean equals(Object o);
 
@@ -80,4 +96,49 @@ public interface Function {
 	 * @throws Error
 	 */
 	ObjectArrayList<Block> toBlock(MathContext context) throws Error;
+
+	/**
+	 * Accepts a {@code Function.Visitor<Argument, Result>} by calling the correct overload of <code>visit</code>.
+	 *
+	 * @param visitor    The visitor to be accepted.
+	 * @param argument   An additional argument to be passed to <code>visit</code>.
+	 * @param <Argument> The type of an additional argument to be passed to the <code>visit</code> method.
+	 * @param <Result>   The return type of the <code>visit</code> method.
+	 * @return The value returned by <code>visit</code>.
+	 */
+	<Argument, Result> Result accept(Visitor<Argument, Result> visitor, Argument argument);
+
+	/**
+	 * Executes a different overload of a method for each <code>Function</code> implementation.
+	 *
+	 * @param <Argument> The type of an additional argument which can be passed to all <code>visit</code> method overloads.
+	 *                   If the argument is not required, this type parameter should be set to {@link Void}.
+	 * @param <Result>   The return type of all <code>visit</code> method overloads.
+	 */
+	interface Visitor<Argument, Result> {
+		Result visit(ArcCosine arcCosine, Argument argument);
+		Result visit(ArcSine arcSine, Argument argument);
+		Result visit(ArcTangent arcTangent, Argument argument);
+		Result visit(Cosine cosine, Argument argument);
+		Result visit(Division division, Argument argument);
+		Result visit(Equation equation, Argument argument);
+		Result visit(EquationsSystem equationsSystem, Argument argument);
+		Result visit(EquationsSystemPart equationsSystemPart, Argument argument);
+		Result visit(Expression expression, Argument argument);
+		Result visit(Joke joke, Argument argument);
+		Result visit(Logarithm logarithm, Argument argument);
+		Result visit(Multiplication multiplication, Argument argument);
+		Result visit(Negative negative, Argument argument);
+		Result visit(Number number, Argument argument);
+		Result visit(Power power, Argument argument);
+		Result visit(Root root, Argument argument);
+		Result visit(RootSquare rootSquare, Argument argument);
+		Result visit(Sine sine, Argument argument);
+		Result visit(Subtraction subtraction, Argument argument);
+		Result visit(SumSubtraction sumSubtraction, Argument argument);
+		Result visit(Sum sum, Argument argument);
+		Result visit(Tangent tangent, Argument argument);
+		Result visit(Undefined undefined, Argument argument);
+		Result visit(Variable variable, Argument argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/FunctionDynamic.java

@@ -133,14 +133,12 @@ public abstract class FunctionDynamic implements Function {
 
 	@Override
 	public abstract FunctionDynamic clone();
-	
+
 	@Override
 	public int hashCode() {
-		return functions.hashCode() + 883 * super.hashCode();
+		return Arrays.hashCode(functions);
 	}
 
 	@Override
-	public boolean equals(final Object o) {
-		return false;
-	}
+	public abstract boolean equals(Object o);
 }

core/src/main/java/it/cavallium/warppi/math/FunctionOperator.java

@@ -6,6 +6,8 @@ import it.cavallium.warppi.util.Errors;
 import it.cavallium.warppi.util.Utils;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
+import java.util.Objects;
+
 public abstract class FunctionOperator implements Function {
 	
 	/**
@@ -175,7 +177,7 @@ public abstract class FunctionOperator implements Function {
 
 	@Override
 	public int hashCode() {
-		return parameter1.hashCode() + 7 * parameter2.hashCode() + 883 * super.hashCode();
+		return Objects.hash(parameter1, parameter2);
 	}
 
 	@Override

core/src/main/java/it/cavallium/warppi/math/FunctionSingle.java

@@ -4,6 +4,8 @@ import it.cavallium.warppi.math.rules.Rule;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
+import java.util.Objects;
+
 public abstract class FunctionSingle implements Function {
 
 	private boolean simplified;
@@ -117,7 +119,7 @@ public abstract class FunctionSingle implements Function {
 
 	@Override
 	public int hashCode() {
-		return parameter.hashCode() + 883 * super.hashCode();
+		return Objects.hash(parameter);
 	}
 
 	@Override

core/src/main/java/it/cavallium/warppi/math/functions/Division.java

@@ -59,4 +59,9 @@ public class Division extends FunctionOperator {
 		result.add(bd);
 		return result;
 	}
+
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Expression.java

@@ -582,6 +582,11 @@ public class Expression extends FunctionSingle {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+
 	@Override
 	public String toString() {
 		String s = "(";

core/src/main/java/it/cavallium/warppi/math/functions/Joke.java

@@ -61,4 +61,8 @@ public class Joke implements Function {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Logarithm.java

@@ -55,4 +55,8 @@ public class Logarithm extends FunctionOperator {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Multiplication.java

@@ -3,10 +3,7 @@ package it.cavallium.warppi.math.functions;
 import it.cavallium.warppi.gui.expression.blocks.Block;
 import it.cavallium.warppi.gui.expression.blocks.BlockChar;
 import it.cavallium.warppi.gui.expression.blocks.BlockParenthesis;
-import it.cavallium.warppi.math.Function;
-import it.cavallium.warppi.math.FunctionOperator;
-import it.cavallium.warppi.math.MathContext;
-import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.*;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
@@ -24,11 +21,7 @@ public class Multiplication extends FunctionOperator {
 	public boolean equals(final Object o) {
 		if (o instanceof Multiplication) {
 			final FunctionOperator f = (FunctionOperator) o;
-			if (parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2())) {
-				return true;
-			} else if (parameter1.equals(f.getParameter2()) && parameter2.equals(f.getParameter1())) {
-				return true;
-			}
+			return parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2());
 		}
 		return false;
 	}
@@ -87,6 +80,11 @@ public class Multiplication extends FunctionOperator {
 		}
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+
 	public boolean isNegative() {
 		return parameter1.equals(new Number(getMathContext(), -1)) || parameter2.equals(new Number(getMathContext(), -1));
 	}
@@ -104,4 +102,4 @@ public class Multiplication extends FunctionOperator {
 	public static Multiplication newNegative(final MathContext context, final Function value2) {
 		return new Multiplication(context, new Number(context, -1), value2);
 	}
-}
+}

core/src/main/java/it/cavallium/warppi/math/functions/Negative.java

@@ -3,10 +3,7 @@ package it.cavallium.warppi.math.functions;
 import it.cavallium.warppi.gui.expression.blocks.Block;
 import it.cavallium.warppi.gui.expression.blocks.BlockChar;
 import it.cavallium.warppi.gui.expression.blocks.BlockParenthesis;
-import it.cavallium.warppi.math.Function;
-import it.cavallium.warppi.math.FunctionSingle;
-import it.cavallium.warppi.math.MathContext;
-import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.*;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
@@ -52,4 +49,9 @@ public class Negative extends FunctionSingle {
 		return blocks;
 		// throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
+
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Number.java

@@ -273,6 +273,11 @@ public class Number implements Function {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+
 	@Override
 	public Function setParameter(final int index, final Function var) throws IndexOutOfBoundsException {
 		throw new IndexOutOfBoundsException();

core/src/main/java/it/cavallium/warppi/math/functions/Power.java

@@ -50,4 +50,9 @@ public class Power extends FunctionOperator {
 		result.add(bp);
 		return result;
 	}
+
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Root.java

@@ -39,4 +39,8 @@ public class Root extends FunctionOperator {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/RootSquare.java

@@ -17,7 +17,7 @@ public class RootSquare extends FunctionOperator {
 
 	@Override
 	public boolean equals(final Object o) {
-		if (o instanceof Root) {
+		if (o instanceof RootSquare) {
 			final FunctionOperator f = (FunctionOperator) o;
 			return parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2());
 		}
@@ -48,4 +48,8 @@ public class RootSquare extends FunctionOperator {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Subtraction.java

@@ -2,10 +2,7 @@ package it.cavallium.warppi.math.functions;
 
 import it.cavallium.warppi.gui.expression.blocks.Block;
 import it.cavallium.warppi.gui.expression.blocks.BlockChar;
-import it.cavallium.warppi.math.Function;
-import it.cavallium.warppi.math.FunctionOperator;
-import it.cavallium.warppi.math.MathContext;
-import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.*;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
@@ -43,4 +40,8 @@ public class Subtraction extends FunctionOperator {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Sum.java

@@ -2,10 +2,7 @@ package it.cavallium.warppi.math.functions;
 
 import it.cavallium.warppi.gui.expression.blocks.Block;
 import it.cavallium.warppi.gui.expression.blocks.BlockChar;
-import it.cavallium.warppi.math.Function;
-import it.cavallium.warppi.math.FunctionOperator;
-import it.cavallium.warppi.math.MathContext;
-import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.*;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
@@ -19,11 +16,7 @@ public class Sum extends FunctionOperator {
 	public boolean equals(final Object o) {
 		if (o instanceof Sum) {
 			final FunctionOperator f = (FunctionOperator) o;
-			if (parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2())) {
-				return true;
-			} else if (parameter1.equals(f.getParameter2()) && parameter2.equals(f.getParameter1())) {
-				return true;
-			}
+			return parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2());
 		}
 		return false;
 	}
@@ -47,4 +40,8 @@ public class Sum extends FunctionOperator {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/SumSubtraction.java

@@ -2,10 +2,7 @@ package it.cavallium.warppi.math.functions;
 
 import it.cavallium.warppi.gui.expression.blocks.Block;
 import it.cavallium.warppi.gui.expression.blocks.BlockChar;
-import it.cavallium.warppi.math.Function;
-import it.cavallium.warppi.math.FunctionOperator;
-import it.cavallium.warppi.math.MathContext;
-import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.*;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
@@ -43,4 +40,8 @@ public class SumSubtraction extends FunctionOperator {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/Undefined.java

@@ -28,7 +28,7 @@ public class Undefined implements Function {
 
 	@Override
 	public boolean equals(final Object o) {
-		return false;
+		return o instanceof Undefined;
 	}
 
 	@Override
@@ -58,6 +58,11 @@ public class Undefined implements Function {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+
 	@Override
 	public String toString() {
 		return "UNDEFINED";

core/src/main/java/it/cavallium/warppi/math/functions/Variable.java

@@ -8,6 +8,8 @@ import it.cavallium.warppi.math.rules.Rule;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
+import java.util.Objects;
+
 public class Variable implements Function {
 
 	protected char var;
@@ -84,7 +86,7 @@ public class Variable implements Function {
 
 	@Override
 	public int hashCode() {
-		return toString().hashCode();
+		return Objects.hash(var, type);
 	}
 
 	@Override
@@ -131,4 +133,9 @@ public class Variable implements Function {
 		result.add(new BlockChar(getChar()));
 		return result;
 	}
+
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/equations/Equation.java

@@ -58,7 +58,10 @@ public class Equation extends FunctionOperator {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof Equation) {
+			final FunctionOperator f = (FunctionOperator) o;
+			return parameter1.equals(f.getParameter1()) && parameter2.equals(f.getParameter2());
+		}
 		return false;
 	}
 
@@ -68,4 +71,8 @@ public class Equation extends FunctionOperator {
 		return null;
 	}
 
-}
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/functions/equations/EquationsSystem.java

@@ -22,6 +22,26 @@ public class EquationsSystem extends FunctionDynamic {
 		super(root, value);
 	}
 
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof EquationsSystem)) {
+			return false;
+		}
+		final FunctionDynamic f = (FunctionDynamic) o;
+
+		if (functions.length != f.getParametersLength()) {
+			return false;
+		}
+
+		for (int i = 0; i < functions.length; i++) {
+			if (!functions[i].equals(f.getParameter(i))) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
 	@Override
 	public EquationsSystem clone() {
 		Function[] newFuncs = functions.clone();
@@ -46,4 +66,8 @@ public class EquationsSystem extends FunctionDynamic {
 		return null;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/equations/EquationsSystemPart.java

@@ -1,6 +1,7 @@
 package it.cavallium.warppi.math.functions.equations;
 
 import it.cavallium.warppi.gui.expression.blocks.Block;
+import it.cavallium.warppi.math.Function;
 import it.cavallium.warppi.math.FunctionSingle;
 import it.cavallium.warppi.math.MathContext;
 import it.cavallium.warppi.util.Error;
@@ -34,4 +35,8 @@ public class EquationsSystemPart extends FunctionSingle {
 		return null;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/ArcCosine.java

@@ -16,7 +16,10 @@ public class ArcCosine extends FunctionSingle {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof ArcCosine) {
+			final FunctionSingle f = (FunctionSingle) o;
+			return parameter.equals(f.getParameter());
+		}
 		return false;
 	}
 
@@ -38,4 +41,9 @@ public class ArcCosine extends FunctionSingle {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
+
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/ArcSine.java

@@ -16,7 +16,10 @@ public class ArcSine extends FunctionSingle {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof ArcSine) {
+			final FunctionSingle f = (FunctionSingle) o;
+			return parameter.equals(f.getParameter());
+		}
 		return false;
 	}
 
@@ -38,4 +41,8 @@ public class ArcSine extends FunctionSingle {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/ArcTangent.java

@@ -16,7 +16,10 @@ public class ArcTangent extends FunctionSingle {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof ArcTangent) {
+			final FunctionSingle f = (FunctionSingle) o;
+			return parameter.equals(f.getParameter());
+		}
 		return false;
 	}
 
@@ -38,4 +41,8 @@ public class ArcTangent extends FunctionSingle {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/Cosine.java

@@ -16,7 +16,10 @@ public class Cosine extends FunctionSingle {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof Cosine) {
+			final FunctionSingle f = (FunctionSingle) o;
+			return parameter.equals(f.getParameter());
+		}
 		return false;
 	}
 
@@ -38,4 +41,8 @@ public class Cosine extends FunctionSingle {
 		throw new Error(Errors.NOT_IMPLEMENTED, "Unknown function " + getClass().getSimpleName());
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/Sine.java

@@ -19,9 +19,7 @@ public class Sine extends FunctionSingle {
 	public boolean equals(final Object o) {
 		if (o instanceof Sine) {
 			final FunctionSingle f = (FunctionSingle) o;
-			if (parameter.equals(f.getParameter())) {
-				return true;
-			}
+			return parameter.equals(f.getParameter());
 		}
 		return false;
 	}
@@ -51,4 +49,8 @@ public class Sine extends FunctionSingle {
 		return result;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/functions/trigonometry/Tangent.java

@@ -15,7 +15,10 @@ public class Tangent extends FunctionSingle {
 
 	@Override
 	public boolean equals(final Object o) {
-		// TODO Auto-generated method stub
+		if (o instanceof Tangent) {
+			final FunctionSingle f = (FunctionSingle) o;
+			return parameter.equals(f.getParameter());
+		}
 		return false;
 	}
 
@@ -37,4 +40,8 @@ public class Tangent extends FunctionSingle {
 		return null;
 	}
 
+	@Override
+	public <Argument, Result> Result accept(final Function.Visitor<Argument, Result> visitor, final Argument argument) {
+		return visitor.visit(this, argument);
+	}
 }

core/src/main/java/it/cavallium/warppi/math/rules/RulesManager.java

@@ -1,30 +1,25 @@
 package it.cavallium.warppi.math.rules;
 
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.PrintWriter;
-import java.net.URISyntaxException;
-import java.net.URL;
-import java.util.ArrayList;
-import java.util.List;
-
 import it.cavallium.warppi.Engine;
+import it.cavallium.warppi.Platform;
 import it.cavallium.warppi.Platform.ConsoleUtils;
-import it.cavallium.warppi.Platform.StorageUtils;
-import it.cavallium.warppi.Platform.URLClassLoader;
-import it.cavallium.warppi.StaticVars;
 import it.cavallium.warppi.math.Function;
 import it.cavallium.warppi.math.MathContext;
 import it.cavallium.warppi.math.functions.Expression;
 import it.cavallium.warppi.math.functions.Variable;
 import it.cavallium.warppi.math.functions.Variable.V_TYPE;
+import it.cavallium.warppi.math.rules.dsl.DslAggregateException;
+import it.cavallium.warppi.math.rules.dsl.RulesDsl;
+import it.cavallium.warppi.math.rules.dsl.errorutils.DslFilesException;
+import it.cavallium.warppi.math.rules.functions.*;
 import it.cavallium.warppi.math.solver.MathSolver;
 import it.cavallium.warppi.util.Error;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.stream.Stream;
+
 public class RulesManager {
 
 	public static ObjectArrayList<Rule>[] rules;
@@ -38,189 +33,69 @@ public class RulesManager {
 		for (final RuleType val : RuleType.values()) {
 			RulesManager.rules[val.ordinal()] = new ObjectArrayList<>();
 		}
+
+		loadBuiltinRules();
+
 		try {
-			boolean compiledSomething = false;
-			InputStream defaultRulesList;
-			try {
-				defaultRulesList = Engine.getPlatform().getStorageUtils().getResourceStream("/default-rules.lst");
-			} catch (final IOException ex) {
-				throw new FileNotFoundException("default-rules.lst not found!");
-			}
-			final List<String> ruleLines = new ArrayList<>();
-			final File rulesPath = Engine.getPlatform().getStorageUtils().get("rules/");
-			if (rulesPath.exists()) {
-				for (final File f : Engine.getPlatform().getStorageUtils().walk(rulesPath)) {
-					if (f.toString().endsWith(".java")) {
-						String path = Engine.getPlatform().getStorageUtils().relativize(rulesPath, f).toString();
-						path = path.substring(0, path.length() - ".java".length());
-						ruleLines.add(path);
-						Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_NODEBUG, "RulesManager", "Found external rule: " + f.getAbsolutePath());
-					}
-				}
-			}
-			ruleLines.addAll(Engine.getPlatform().getStorageUtils().readAllLines(defaultRulesList));
-
-			final File tDir = Engine.getPlatform().getStorageUtils().resolve(Engine.getPlatform().getStorageUtils().get(System.getProperty("java.io.tmpdir"), "WarpPi-Calculator"), "rules-rt");
-			//				try {
-			//				final Path defaultResource = Utils.getResource("/math-rules-cache.zip");
-			//			}
-			InputStream cacheFileStream = null;
-			File cacheFilePath = null;
-			cacheFilePath = new File("math-rules-cache.zip");
-			boolean cacheFileExists = false;
-			if (Engine.getPlatform().isJavascript()) {
-				Engine.getPlatform().loadPlatformRules();
-			} else {
-				if (cacheFilePath.exists()) {
-					cacheFileExists = true;
-					cacheFileStream = new FileInputStream(cacheFilePath);
-				} else {
-					try {
-						cacheFileStream = Engine.getPlatform().getStorageUtils().getResourceStream("/math-rules-cache.zip");//Paths.get(Utils.getJarDirectory().toString()).resolve("math-rules-cache.zip").toAbsolutePath(
-						org.apache.commons.io.FileUtils.copyInputStreamToFile(cacheFileStream, cacheFilePath);
-						cacheFileExists = true;
-					} catch (final IOException ex) { //File does not exists.
-					}
-				}
-				boolean useCache = false;
-				if (cacheFileExists) {
-					try {
-						if (tDir.exists()) {
-							tDir.delete();
-						}
-						Engine.getPlatform().unzip(cacheFilePath.toString(), tDir.getParent().toString(), "");
-						useCache = !StaticVars.startupArguments.isUncached();
-					} catch (final Exception ex) {
-						ex.printStackTrace();
-					}
-				}
-
-				for (final String rulesLine : ruleLines) {
-					if (rulesLine.length() > 0) {
-						final String[] ruleDetails = rulesLine.split(",", 1);
-						final String ruleName = ruleDetails[0];
-						final String ruleNameEscaped = ruleName.replace(".", "_");
-						Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_DEBUG_MIN, "RulesManager", "Evaluating /rules/" + ruleNameEscaped + ".java");
-						final String pathWithoutExtension = "/rules/" + ruleNameEscaped;
-						final String scriptFile = pathWithoutExtension + ".java";
-						final InputStream resourcePath = Engine.getPlatform().getStorageUtils().getResourceStream(scriptFile);
-						if (resourcePath == null) {
-							System.err.println(new FileNotFoundException("/rules/" + ruleName + ".java not found!"));
-						} else {
-							Rule r = null;
-							if (useCache) {
-								try {
-									Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_DEBUG_MIN, "RulesManager", ruleName, "Trying to load cached rule");
-									r = RulesManager.loadClassRuleFromSourceFile(scriptFile, tDir);
-									if (r != null) {
-										Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_DEBUG_MIN, "RulesManager", ruleName, "Loaded cached rule");
-									}
-								} catch (final Exception e) {
-									e.printStackTrace();
-									Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_NODEBUG, "RulesManager", ruleName, "Can't load the rule " + ruleNameEscaped + "!");
-								}
-							}
-							if (r == null || !useCache) {
-								Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_DEBUG_MIN, "RulesManager", ruleName, "This rule is not cached. Compiling");
-								try {
-									r = RulesManager.compileJavaRule(scriptFile, tDir);
-									compiledSomething = true;
-								} catch (InstantiationException | IllegalAccessException | ClassNotFoundException | IOException e) {
-									e.printStackTrace();
-								}
-
-							}
-							if (r != null) {
-								RulesManager.addRule(r);
-							}
-						}
-					}
-				}
-			}
-			Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_NODEBUG, "RulesManager", "Loaded all the rules successfully");
-			if (!Engine.getPlatform().isJavascript() && compiledSomething) {
-				if (cacheFileExists || cacheFilePath.exists()) {
-					cacheFilePath.delete();
-				}
-				Engine.getPlatform().zip(tDir.toString(), cacheFilePath.toString(), "");
-				Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_NODEBUG, "RulesManager", "Cached the compiled rules");
-			}
-			if (cacheFileStream != null) {
-				cacheFileStream.close();
-			}
-		} catch (URISyntaxException | IOException e) {
+			loadDslRules();
+		} catch (IOException | DslFilesException e) {
 			e.printStackTrace();
+			if (e instanceof DslFilesException) {
+				System.err.println();
+				System.err.print(((DslFilesException) e).format());
+			}
 			Engine.getPlatform().exit(1);
 		}
 	}
 
-	public static Rule compileJavaRule(final String scriptFile, final File tDir) throws IOException, URISyntaxException,
-			InstantiationException, IllegalAccessException, ClassNotFoundException {
-		final InputStream resource = Engine.getPlatform().getStorageUtils().getResourceStream(scriptFile);
-		final String text = Engine.getPlatform().getStorageUtils().read(resource);
-		final String[] textArray = text.split("\\n", 6);
-		if (textArray[3].contains("PATH=")) {
-			final String javaClassDeclaration = textArray[3].substring(6);
-			int extIndex = javaClassDeclaration.lastIndexOf('.');
-			final String javaClassNameOnly = javaClassDeclaration.substring(extIndex + 1, javaClassDeclaration.length());
-			final String javaClassNameAndPath = new StringBuilder("it.cavallium.warppi.math.rules.").append(javaClassDeclaration).toString();
-			extIndex = javaClassNameAndPath.lastIndexOf('.');
-			final String javaCode = new StringBuilder("package ").append(javaClassNameAndPath.substring(0, extIndex >= 0 ? extIndex : javaClassNameAndPath.length())).append(";\n").append(textArray[5]).toString();
-			final File tDirPath = Engine.getPlatform().getStorageUtils().getParent(Engine.getPlatform().getStorageUtils().resolve(tDir, javaClassNameAndPath.replace('.', File.separatorChar)));
-			final File tFileJava = Engine.getPlatform().getStorageUtils().resolve(tDirPath, javaClassNameOnly + ".java");
-			final File tFileClass = Engine.getPlatform().getStorageUtils().resolve(tDirPath, javaClassNameOnly + ".class");
-			if (!tDirPath.exists()) {
-				Engine.getPlatform().getStorageUtils().createDirectories(tDirPath);
-			}
-			if (tFileJava.exists()) {
-				tFileJava.delete();
-			}
-			Engine.getPlatform().getStorageUtils();
-			Engine.getPlatform().getStorageUtils();
-			Engine.getPlatform().getStorageUtils().write(tFileJava, javaCode.getBytes("UTF-8"), StorageUtils.OpenOptionWrite, StorageUtils.OpenOptionCreate);
-			final boolean compiled = Engine.getPlatform().compile(new String[] { "-nowarn", "-1.8", "-proc:none", tFileJava.toString() }, new PrintWriter(System.out), new PrintWriter(System.err));
-			if (StaticVars.startupArguments.isUncached()) {
-				tFileJava.deleteOnExit();
-			} else {
-				tFileJava.delete();
-			}
-			if (compiled) {
-				tFileClass.deleteOnExit();
-				return RulesManager.loadClassRuleDirectly(javaClassNameAndPath, tDir);
-			} else {
-				throw new IOException("Can't build script file '" + scriptFile + "'");
-			}
-		} else {
-			throw new IOException("Can't build script file '" + scriptFile + "', the header is missing or wrong.");
-		}
+	private static void loadBuiltinRules() {
+		Stream.of(
+				new DivisionRule(),
+				new EmptyNumberRule(),
+				new ExpressionRule(),
+				new JokeRule(),
+				new MultiplicationRule(),
+				new NegativeRule(),
+				new NumberRule(),
+				new PowerRule(),
+				new RootRule(),
+				new SubtractionRule(),
+				new SumRule(),
+				new SumSubtractionRule(),
+				new VariableRule()
+		).forEach(RulesManager::addRule);
 	}
 
-	public static Rule loadClassRuleFromSourceFile(final String scriptFile, final File tDir) throws IOException,
-			URISyntaxException, InstantiationException, IllegalAccessException, ClassNotFoundException {
-		final InputStream resource = Engine.getPlatform().getStorageUtils().getResourceStream(scriptFile);
-		final String text = Engine.getPlatform().getStorageUtils().read(resource);
-		final String[] textArray = text.split("\\n", 6);
-		if (textArray[3].contains("PATH=")) {
-			final String javaClassName = textArray[3].substring(6);
-			Engine.getPlatform().getConsoleUtils().out().println(ConsoleUtils.OUTPUTLEVEL_DEBUG_VERBOSE, "RulesManager", "Rule java class name: " + javaClassName);
-			final String javaClassNameAndPath = new StringBuilder("it.cavallium.warppi.math.rules.").append(javaClassName).toString();
+	private static void loadDslRules() throws IOException, DslFilesException {
+		final Platform platform = Engine.getPlatform();
+
+		final DslFilesException fileErrors = new DslFilesException();
+		for (final String path : platform.getRuleFilePaths()) {
+			platform.getConsoleUtils().out().println(
+					ConsoleUtils.OUTPUTLEVEL_NODEBUG,
+					"RulesManager",
+					"Found DSL rules file: " + path
+			);
+
+			final String source;
+			try (final InputStream resource = platform.getStorageUtils().getResourceStream(path)) {
+				source = platform.getStorageUtils().read(resource);
+			}
+
 			try {
-				return RulesManager.loadClassRuleDirectly(javaClassNameAndPath, tDir);
-			} catch (final Exception ex) {
-				ex.printStackTrace();
-				return null;
+				// This loop used to be written as RulesDsl.makeRules(source).forEach(RulesManager::addRule),
+				// but the forEach method hangs on TeaVM.
+				for (Rule rule : RulesDsl.makeRules(source)) {
+					addRule(rule);
+				}
+			} catch (DslAggregateException e) {
+				fileErrors.addFileErrors(path, source, e.getErrors());
 			}
-		} else {
-			throw new IOException("Can't load script file '" + scriptFile + "', the header is missing or wrong.");
 		}
-	}
 
-	public static Rule loadClassRuleDirectly(final String javaClassNameAndPath, final File tDir) throws IOException,
-			URISyntaxException, InstantiationException, IllegalAccessException, ClassNotFoundException {
-		final URLClassLoader cl = Engine.getPlatform().newURLClassLoader(new URL[] { tDir.toURI().toURL() });
-		final Class<?> aClass = cl.loadClass(javaClassNameAndPath);
-		cl.close();
-		return (Rule) aClass.newInstance();
+		if (fileErrors.hasErrors()) {
+			throw fileErrors;
+		}
 	}
 
 	public static void warmUp() throws Error, InterruptedException {

core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslAggregateException.java

@@ -0,0 +1,32 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * Thrown when processing DSL code which contains one or more errors.
+ *
+ * Contains a non-empty list of {@link DslError}s.
+ */
+public class DslAggregateException extends Exception {
+	private final List<DslError> errors;
+
+	/**
+	 * Constructs a <code>DslAggregateException</code> containing the specified list of errors.
+	 * @param errors The (non-empty) list of errors.
+	 * @throws IllegalArgumentException If the list of errors is empty.
+	 */
+	public DslAggregateException(final List<DslError> errors) {
+		if (errors.isEmpty()) {
+			throw new IllegalArgumentException("The list of errors can't be empty");
+		}
+		this.errors = errors;
+	}
+
+	/**
+	 * @return The list of errors detected in the DSL code.
+	 */
+	public List<DslError> getErrors() {
+		return errors;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslError.java

@@ -0,0 +1,43 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.rules.dsl.frontend.IncompleteNumberLiteral;
+import it.cavallium.warppi.math.rules.dsl.frontend.UnexpectedCharacters;
+import it.cavallium.warppi.math.rules.dsl.frontend.UnexpectedToken;
+import it.cavallium.warppi.math.rules.dsl.frontend.UnterminatedComment;
+
+/**
+ * Represents an error in DSL code.
+ */
+public interface DslError {
+	/**
+	 * @return The index at which the error starts in the source string.
+	 */
+	int getPosition();
+
+	/**
+	 * @return The length of the error in the source string.
+	 */
+	int getLength();
+
+	/**
+	 * Accepts a <code>DslError.Visitor</code> by calling the correct overload of <code>visit</code>.
+	 *
+	 * @param visitor The visitor to be accepted.
+	 * @param <T> The return type of the <code>visit</code> method.
+	 * @return The value returned by <code>visit</code>.
+	 */
+	<T> T accept(Visitor<T> visitor);
+
+	/**
+	 * Executes a different overload of a method for each <code>DslError</code> implementation.
+	 *
+	 * @param <T> The return type of all <code>visit</code> method overloads.
+	 */
+	interface Visitor<T> {
+		T visit(IncompleteNumberLiteral incompleteNumberLiteral);
+		T visit(UndefinedSubFunction undefinedSubFunction);
+		T visit(UnexpectedCharacters unexpectedCharacters);
+		T visit(UnexpectedToken unexpectedToken);
+		T visit(UnterminatedComment unterminatedComment);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/Pattern.java

@@ -0,0 +1,60 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.rules.dsl.patterns.SubFunctionPattern;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+/**
+ * Recognizes and generates functions of some specific shape.
+ */
+public interface Pattern {
+	/**
+	 * Tries to match this pattern against a function and capture sub-functions.
+	 *
+	 * @param function The function to test the pattern against.
+	 * @return The captured sub-functions, or an empty <code>Optional</code> if
+	 *         the pattern doesn't match.
+	 */
+	default Optional<Map<String, Function>> match(Function function) {
+		Map<String, Function> subFunctions = new HashMap<>();
+		return match(function, subFunctions) ? Optional.of(subFunctions) : Optional.empty();
+	}
+
+	/**
+	 * Tries to match this pattern against a function and capture sub-functions.
+	 * <p>
+	 * This overload is provided to allow for a more efficient implementation of matching, by mutating the given
+	 * <code>Map</code> instead of creating and merging multiple ones.
+	 * For all other purposes, use of the {@link #match(Function)} overload is recommended instead.
+	 * <p>
+	 * When the pattern matches, all captured sub-functions are added to the map (if not present already).
+	 * If, instead, the pattern doesn't match, the contents of the map are undefined.
+	 *
+	 * @param function The function to test the pattern against.
+	 * @param subFunctions The map used to capture sub-functions.
+	 * @return <code>true</code> if the pattern matches, or <code>false</code> otherwise.
+	 */
+	boolean match(Function function, Map<String, Function> subFunctions);
+
+	/**
+	 * Creates a new function by filling in sub-functions within this pattern.
+	 *
+	 * @param mathContext The <code>MathContext</code> used to construct <code>Function</code>s.
+	 * @param subFunctions A map of named sub-functions to be inserted into this pattern.
+	 * @return The resulting function.
+	 */
+	Function replace(MathContext mathContext, Map<String, Function> subFunctions);
+
+	/**
+	 * @return A (possibly empty) <code>Stream</code> of all sub-function patterns
+	 *         found within this pattern and its children.
+	 *         If there are multiple sub-function patterns with the same name, the stream still contains all of them.
+	 *         The order of the patterns within the stream is unspecified.
+	 */
+	Stream<SubFunctionPattern> getSubFunctions();
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/PatternRule.java

@@ -0,0 +1,130 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.rules.Rule;
+import it.cavallium.warppi.math.rules.RuleType;
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+/**
+ * A <code>Rule</code> which uses <code>Pattern</code>s to match and replace functions.
+ */
+public class PatternRule implements Rule {
+	private final String ruleName;
+	private final RuleType ruleType;
+	private final Pattern target;
+	private final List<Pattern> replacements;
+
+	/**
+	 * Constructs a <code>PatternRule</code> with the given name, type and <code>Pattern</code>s.
+	 *
+	 * @param ruleName     the name of the rule.
+	 * @param ruleType     the type of the rule.
+	 * @param target       the <code>Pattern</code> used to match functions and capture sub-functions.
+	 * @param replacements the list of <code>Pattern</code>s used to construct replacement functions.
+	 *                     All sub-functions which are referenced within these <code>Pattern</code>s must be captured
+	 *                     by <code>target</code>, otherwise the {@link #execute} method will throw an
+	 *                     {@link UndefinedSubFunction} exception when constructing the replacement functions.
+	 */
+	public PatternRule(
+			final String ruleName,
+			final RuleType ruleType,
+			final Pattern target,
+			final List<Pattern> replacements
+	) {
+		this.ruleName = ruleName;
+		this.ruleType = ruleType;
+		this.target = target;
+		this.replacements = replacements;
+	}
+
+	/**
+	 * Constructs a <code>PatternRule</code> with the given name, type and <code>Pattern</code>s.
+	 *
+	 * @param ruleName     the name of the rule.
+	 * @param ruleType     the type of the rule.
+	 * @param target       the <code>Pattern</code> used to match functions and capture sub-functions.
+	 * @param replacements the <code>Pattern</code>s used to construct replacement functions.
+	 *                     All sub-functions which are referenced within these <code>Pattern</code>s must be captured
+	 *                     by <code>target</code>, otherwise the {@link #execute} method will throw an
+	 *                     {@link UndefinedSubFunction} exception when constructing the replacement functions.
+	 */
+	public PatternRule(
+			final String ruleName,
+			final RuleType ruleType,
+			final Pattern target,
+			final Pattern... replacements
+	) {
+		this(ruleName, ruleType, target, Arrays.asList(replacements));
+	}
+
+	@Override
+	public String getRuleName() {
+		return ruleName;
+	}
+
+	@Override
+	public RuleType getRuleType() {
+		return ruleType;
+	}
+
+	/**
+	 * @return the <code>Pattern</code> used to match functions and capture sub-functions.
+	 */
+	public Pattern getTarget() {
+		return target;
+	}
+
+	/**
+	 * @return the list of <code>Pattern</code>s used to construct replacement functions.
+	 */
+	public List<Pattern> getReplacements() {
+		return replacements;
+	}
+
+	/**
+	 * @throws UndefinedSubFunctionException if the target pattern matches, but it doesn't capture all of the
+	 *                                       sub-functions required by the replacement patterns.
+	 *                                       This exception will never be thrown for well-formed rules (like the ones
+	 *                                       returned by {@link RulesDsl#makeRules}), in which the target pattern
+	 *                                       correctly captures all sub-functions referenced by the replacement patterns.
+	 */
+	@Override
+	public ObjectArrayList<Function> execute(final Function func) {
+		return target.match(func)
+				.map(subFunctions -> applyReplacements(func.getMathContext(), subFunctions))
+				.orElse(null);
+	}
+
+	private ObjectArrayList<Function> applyReplacements(
+			final MathContext mathContext,
+			final Map<String, Function> subFunctions
+	) {
+		return replacements.stream()
+				.map(replacement -> replacement.replace(mathContext, subFunctions))
+				.collect(Collectors.toCollection(ObjectArrayList::new));
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof PatternRule)) {
+			return false;
+		}
+		final PatternRule other = (PatternRule) o;
+		return ruleName.equals(other.ruleName)
+				&& ruleType == other.ruleType
+				&& target.equals(other.target)
+				&& replacements.equals(other.replacements);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(ruleName, ruleType, target, replacements);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/RulesDsl.java

@@ -0,0 +1,60 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.rules.Rule;
+import it.cavallium.warppi.math.rules.dsl.frontend.Lexer;
+import it.cavallium.warppi.math.rules.dsl.frontend.Parser;
+import it.cavallium.warppi.math.rules.dsl.patterns.SubFunctionPattern;
+
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+/**
+ * Implements a domain-specific language (DSL) for the definition of {@link Rule}s.
+ */
+public class RulesDsl {
+	private RulesDsl() {}
+
+	/**
+	 * Creates rules from DSL source code.
+	 *
+	 * @param source The source code.
+	 * @return An unmodifiable list containing the rules defined in the DSL code.
+	 * @throws DslAggregateException if the code contains any errors.
+	 */
+	public static List<Rule> makeRules(final String source) throws DslAggregateException {
+		final List<DslError> errors = new ArrayList<>();
+
+		final Lexer lexer = new Lexer(source, errors::add);
+		final Parser parser = new Parser(lexer.lex(), errors::add);
+		final List<PatternRule> rules = parser.parse();
+
+		for (final PatternRule rule : rules) {
+			undefinedSubFunctions(rule)
+					.map(subFunc -> new UndefinedSubFunction(
+						parser.getSubFunctionIdentifier(subFunc)
+					))
+					.forEach(errors::add);
+		}
+
+		if (!errors.isEmpty()) {
+			throw new DslAggregateException(errors);
+		}
+
+		return Collections.unmodifiableList(rules);
+	}
+
+	/**
+	 * Finds any sub-functions that are used in the replacement patterns of a <code>PatternRule</code>
+	 * without being defined (captured) in the target pattern.
+	 *
+	 * @param rule The rule to analyze.
+	 * @return A (possibly empty) <code>Stream</code> of undefined sub-functions.
+	 */
+	private static Stream<SubFunctionPattern> undefinedSubFunctions(final PatternRule rule) {
+		final Set<SubFunctionPattern> defined = rule.getTarget().getSubFunctions().collect(Collectors.toSet());
+		return rule.getReplacements().stream()
+			.flatMap(Pattern::getSubFunctions)
+			.filter(subFunc -> !defined.contains(subFunc));
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunction.java

@@ -0,0 +1,53 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.rules.dsl.frontend.Token;
+
+import java.util.Objects;
+
+/**
+ * Occurs when a sub-function is used in one of the replacement pattern of a <code>PatternRule</code>,
+ * but not defined (captured) in the target pattern.
+ */
+public class UndefinedSubFunction implements DslError {
+	private final Token identifier;
+
+	public UndefinedSubFunction(final Token identifier) {
+		this.identifier = identifier;
+	}
+
+	@Override
+	public int getPosition() {
+		return identifier.position;
+	}
+
+	@Override
+	public int getLength() {
+		return identifier.lexeme.length();
+	}
+
+	@Override
+	public <T> T accept(final DslError.Visitor<T> visitor) {
+		return visitor.visit(this);
+	}
+
+	/**
+	 * @return The name of the undefined sub-function.
+	 */
+	public String getName() {
+		return identifier.lexeme;
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof UndefinedSubFunction)) {
+			return false;
+		}
+		final UndefinedSubFunction other = (UndefinedSubFunction) o;
+		return this.identifier.equals(other.identifier);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(identifier);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunctionException.java

@@ -0,0 +1,26 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+/**
+ * Thrown when a <code>SubFunctionPattern</code> is used to generate a <code>Function</code>, but the named sub-function
+ * it references is not defined.
+ */
+public class UndefinedSubFunctionException extends RuntimeException {
+	private final String subFunctionName;
+
+	/**
+	 * Constructs an <code>UndefinedSubFunction</code> instance with the specified sub-function name.
+	 *
+	 * @param subFunctionName the name of the undefined sub-function.
+	 */
+	public UndefinedSubFunctionException(final String subFunctionName) {
+		super("Sub-function '" + subFunctionName + "' is not defined");
+		this.subFunctionName = subFunctionName;
+	}
+
+	/**
+	 * @return the name of the undefined sub-function.
+	 */
+	public String getSubFunctionName() {
+		return subFunctionName;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/VisitorPattern.java

@@ -0,0 +1,141 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.functions.*;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.equations.Equation;
+import it.cavallium.warppi.math.functions.equations.EquationsSystem;
+import it.cavallium.warppi.math.functions.equations.EquationsSystemPart;
+import it.cavallium.warppi.math.functions.trigonometry.*;
+
+import java.util.Map;
+
+/**
+ * A <code>Pattern</code> which implements <code>match</code> as a visitor.
+ */
+public abstract class VisitorPattern implements Pattern, Function.Visitor<Map<String, Function>, Boolean> {
+	@Override
+	public boolean match(Function function, Map<String, Function> subFunctions) {
+		return function.accept(this, subFunctions);
+	}
+
+	@Override
+	public Boolean visit(final ArcCosine arcCosine, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final ArcSine arcSine, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final ArcTangent arcTangent, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Cosine cosine, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Division division, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Equation equation, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final EquationsSystem equationsSystem, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final EquationsSystemPart equationsSystemPart, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Expression expression, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Joke joke, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Logarithm logarithm, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Multiplication multiplication, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Negative negative, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Number number, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Power power, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Root root, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final RootSquare rootSquare, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Sine sine, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Subtraction subtraction, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final SumSubtraction sumSubtraction, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Sum sum, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Tangent tangent, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Undefined undefined, final Map<String, Function> subFunctions) {
+		return false;
+	}
+
+	@Override
+	public Boolean visit(final Variable variable, final Map<String, Function> subFunctions) {
+		return false;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/DslErrorMessageFormatter.java

@@ -0,0 +1,124 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+import it.cavallium.warppi.math.rules.dsl.UndefinedSubFunction;
+import it.cavallium.warppi.math.rules.dsl.frontend.*;
+
+import java.util.stream.Collectors;
+
+/**
+ * Creates human-readable error messages from instances of {@link DslError}.
+ */
+public class DslErrorMessageFormatter implements DslError.Visitor<String> {
+	/**
+	 * Formats the given <code>DslError</code> as a human-readable message, according to its type.
+	 *
+	 * @param error The error to format.
+	 * @return One or more lines of text which describe the error (without a trailing newline).
+	 */
+	public String format(final DslError error) {
+		return error.accept(this);
+	}
+
+	@Override
+	public String visit(final IncompleteNumberLiteral incompleteNumberLiteral) {
+		return String.format(
+				"Number has a decimal point but no digits following it: %s",
+				incompleteNumberLiteral.getLiteral()
+		);
+	}
+
+	@Override
+	public String visit(final UndefinedSubFunction undefinedSubFunction) {
+		return String.format(
+				"Sub-function \"%s\" is used in a replacement pattern,\nbut not defined in the target pattern",
+				undefinedSubFunction.getName()
+		);
+	}
+
+	@Override
+	public String visit(final UnexpectedCharacters unexpectedCharacters) {
+		final String plural = unexpectedCharacters.getLength() > 1 ? "s" : "";
+		return String.format("Unexpected character%s: %s", plural, unexpectedCharacters.getUnexpectedCharacters());
+	}
+
+	@Override
+	public String visit(final UnexpectedToken unexpectedToken) {
+		final String suggestions;
+		if (unexpectedToken.getSuggested().isEmpty()) {
+			suggestions = "";
+		} else {
+			suggestions = "\nSome suggestions are: " + unexpectedToken.getSuggested().stream()
+					.map(DslErrorMessageFormatter::tokenTypeName)
+					.collect(Collectors.joining(", "));
+		}
+
+		return String.format(
+				"Unexpected %s%s",
+				tokenTypeName(unexpectedToken.getUnexpected().type),
+				suggestions
+		);
+	}
+
+	@Override
+	public String visit(final UnterminatedComment unterminatedComment) {
+		return "Unterminated comment";
+	}
+
+	private static String tokenTypeName(final TokenType type) {
+		switch (type) {
+			case EOF:
+				return "end of input";
+			case COLON:
+				return "\":\"";
+			case ARROW:
+				return "\"->\"";
+			case COMMA:
+				return "\",\"";
+			case LEFT_PAREN:
+				return "\"(\"";
+			case RIGHT_PAREN:
+				return "\")\"";
+			case LEFT_BRACKET:
+				return "\"[\"";
+			case RIGHT_BRACKET:
+				return "\"]\"";
+			case EQUALS:
+				return "\"=\"";
+			case PLUS:
+				return "\"+\"";
+			case MINUS:
+				return "\"-\"";
+			case PLUS_MINUS:
+				return "\"+-\"";
+			case TIMES:
+				return "\"*\"";
+			case DIVIDE:
+				return "\"/\"";
+			case POWER:
+				return "\"^\"";
+			case REDUCTION:
+			case EXPANSION:
+			case CALCULATION:
+			case EXISTENCE:
+			case ARCCOS:
+			case ARCSIN:
+			case ARCTAN:
+			case COS:
+			case SIN:
+			case TAN:
+			case ROOT:
+			case SQRT:
+			case LOG:
+			case UNDEFINED:
+			case PI:
+			case E:
+				return '"' + type.name().toLowerCase() + '"';
+			case NUMBER:
+				return "number";
+			case IDENTIFIER:
+				return "identifier";
+		}
+		throw new RuntimeException("unknown token type");
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/DslFilesException.java

@@ -0,0 +1,46 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Thrown when one or more DSL source files contain errors.
+ */
+public class DslFilesException extends Exception {
+	private final List<FileErrors> filesErrors = new ArrayList<>();
+
+	/**
+	 * Registers errors which have been found in the specified DSL source file.
+	 *
+	 * @param filePath The path of the DSL source file in which the errors occurred.
+	 * @param source   The entire contents of the DSL source file in which the errors occurred.
+	 * @param errors   The (non-empty) list of errors found in the DSL source file.
+	 * @throws IllegalArgumentException If the list of errors is empty.
+	 */
+	public void addFileErrors(final String filePath, final String source, final List<DslError> errors) {
+		filesErrors.add(new FileErrors(filePath, source, errors));
+	}
+
+	/**
+	 * Checks if any errors have been registered.
+	 * <p>
+	 * Instances of this class should only be thrown as exceptions if they actually contain errors.
+	 *
+	 * @return <code>true</code> if at least one error has been added, otherwise <code>false</code>.
+	 */
+	public boolean hasErrors() {
+		return !filesErrors.isEmpty();
+	}
+
+	/**
+	 * Formats all errors using a {@link FilesErrorsFormatter}.
+	 *
+	 * @return A formatted representation of all errors for display to the user.
+	 * @see FilesErrorsFormatter#format(List)
+	 */
+	public String format() {
+		return new FilesErrorsFormatter().format(filesErrors);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/FileErrors.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.List;
+
+/**
+ * Groups one or more errors from the same DSL source file.
+ * <p>
+ * Also stores the file's path and contents (for error reporting).
+ */
+public class FileErrors {
+	private final String filePath;
+	private final String source;
+	private final List<DslError> errors;
+
+	/**
+	 * Constructs a <code>FileErrors</code> instance with the given file and error data.
+	 *
+	 * @param filePath The path of the DSL source file in which the errors occurred.
+	 * @param source   The entire contents of the DSL source file in which the errors occurred.
+	 * @param errors   The (non-empty) list of errors found in the DSL source file.
+	 * @throws IllegalArgumentException If the list of errors is empty.
+	 */
+	public FileErrors(final String filePath, final String source, final List<DslError> errors) {
+		if (errors.isEmpty()) {
+			throw new IllegalArgumentException("The list of errors can't be empty");
+		}
+		this.filePath = filePath;
+		this.source = source;
+		this.errors = errors;
+	}
+
+	/**
+	 * @return The path of the DSL source file in which the errors occurred.
+	 */
+	public String getFilePath() {
+		return filePath;
+	}
+
+	/**
+	 * @return The entire contents of the DSL source file in which the errors occurred.
+	 */
+	public String getSource() {
+		return source;
+	}
+
+	/**
+	 * @return The list of errors found in the DSL source file.
+	 */
+	public List<DslError> getErrors() {
+		return errors;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/FilesErrorsFormatter.java

@@ -0,0 +1,105 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+/**
+ * Formats DSL errors from (potentially) multiple files for display to the user.
+ */
+public class FilesErrorsFormatter {
+	private static final int INDENT = 2;
+	private static final int TAB_WIDTH = 4;
+
+	private final DslErrorMessageFormatter messageFormatter = new DslErrorMessageFormatter();
+
+	/**
+	 * Formats all errors in the given list.
+	 *
+	 * @param filesErrors The list of errors to format.
+	 * @return A human-readable textual representation of all errors (with a trailing newline).
+	 */
+	public String format(final List<FileErrors> filesErrors) {
+		return filesErrors.stream()
+				.sorted(Comparator.comparing(FileErrors::getFilePath))
+				.flatMap(this::formatFileErrors)
+				.collect(Collectors.joining(System.lineSeparator()));
+	}
+
+	private Stream<String> formatFileErrors(final FileErrors fileErrors) {
+		final LineMap lines = new LineMap(fileErrors.getSource());
+		return fileErrors.getErrors().stream()
+				.sorted(Comparator.comparing(DslError::getPosition).thenComparing(DslError::getLength))
+				.map(error -> formatError(fileErrors.getFilePath(), lines, error));
+	}
+
+	private String formatError(final String filePath, final LineMap lines, final DslError error) {
+		final StringBuilder builder = new StringBuilder();
+
+		final List<LineMap.Line> spannedLines = lines.getSpannedLines(error.getPosition(), error.getLength());
+		final LineMap.Line firstLine = spannedLines.get(0);
+
+		final int positionInFirstLine = error.getPosition() - firstLine.getStartPosition();
+		final TabExpandedString expandedFirstLine = new TabExpandedString(firstLine.getText(), TAB_WIDTH);
+		// When computing the column number, each tab character is counted as the number of spaces it expands to
+		final int column = 1 + expandedFirstLine.substringLength(0, positionInFirstLine);
+
+		builder.append(filePath).append(":")
+				.append(firstLine.getNumber()).append(":")
+				.append(column).append(":")
+				.append(System.lineSeparator());
+
+		final int lastLineNum = spannedLines.get(spannedLines.size() - 1).getNumber();
+		final int numberWidth = String.valueOf(lastLineNum).length();
+		final int padding = INDENT + numberWidth;
+
+		// Preceding line with just separator
+		builder.append(StringUtils.repeat(' ', padding))
+				.append(" |")
+				.append(System.lineSeparator());
+
+		for (final LineMap.Line line : spannedLines) {
+			// Error text line
+			final TabExpandedString expanded = new TabExpandedString(line.getText(), TAB_WIDTH);
+			builder.append(StringUtils.leftPad(String.valueOf(line.getNumber()), padding))
+					.append(" | ")
+					.append(expanded.getExpanded())
+					.append(System.lineSeparator());
+
+			// Error underlining line
+			builder.append(StringUtils.repeat(' ', padding)).append(" | ");
+			underline(builder, line, expanded, error);
+			builder.append(System.lineSeparator());
+		}
+
+		builder.append(messageFormatter.format(error)).append(System.lineSeparator());
+
+		return builder.toString();
+	}
+
+	private void underline(
+			final StringBuilder builder,
+			final LineMap.Line line,
+			final TabExpandedString expanded,
+			final DslError error
+	) {
+		final int errorStartInLine = Math.max(line.getStartPosition(), error.getPosition());
+		final int charsBeforeError = errorStartInLine - line.getStartPosition();
+		final int spacesBeforeError = expanded.substringLength(0, charsBeforeError);
+		builder.append(StringUtils.repeat(' ', spacesBeforeError));
+
+		final int underlineLength;
+		if (error.getLength() == 0) {
+			underlineLength = 1; // Special case for "unexpected EOF" error
+		} else {
+			final int errorEnd = error.getPosition() + error.getLength();
+			final int errorLengthInLine = Math.min(line.getText().length() - charsBeforeError, errorEnd - errorStartInLine);
+			underlineLength = expanded.substringLength(charsBeforeError, charsBeforeError + errorLengthInLine);
+		}
+		builder.append(StringUtils.repeat('^', underlineLength));
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/LineMap.java

@@ -0,0 +1,191 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * Splits a string into lines and associates positions within the string to the lines they belong to.
+ * <p>
+ * For each line, the number (starting from 1), start position and content are stored.
+ * <p>
+ * A line can end at the end of the string, or with a line terminator ("\r", "\n" or "\r\n").
+ * The terminator defines the end of a line, but not necessarily the beginning of a new one: it's considered to be part
+ * of the line (however, for convenience, it's not included in the content), and a terminator at the end of the string
+ * doesn't start a new empty line.
+ * For example, the string <code>"abc\n\n"</code> contains two lines:
+ * <ul>
+ * <li> line 1 starts at position 0, and its content is <code>"abc"</code>;
+ * <li> line 2 starts at position 4 (the index of the second '\n'), and its content is <code>""</code>  (the empty string).
+ * </ul>
+ * As a consequence of these criteria, an empty string has no lines.
+ */
+public class LineMap {
+	private final String text;
+	private final NavigableMap<Integer, LineInfo> lines;
+
+	/**
+	 * Constructs a <code>LineMap</code> for the given string.
+	 *
+	 * @param text The string to split into lines.
+	 */
+	public LineMap(final String text) {
+		this.text = text;
+		this.lines = splitLines(text);
+	}
+
+	/**
+	 * Gets all lines which the specified substring spans.
+	 * <p>
+	 * A substring spans a line if it contains at least one of the characters which belong to the line,
+	 * including the terminator ("\r", "\n" or "\r\n"), within the original string.
+	 * However, as a special case, an empty substring (<code>length == 0</code>) still spans the line corresponding to
+	 * its <code>startPosition</code>, even though it doesn't contain any characters.
+	 * Therefore, any substring spans at least one line, unless there are no lines at all (because the original string
+	 * is empty).
+	 *
+	 * @param startPosition The index at which the substring starts within the original string.
+	 * @param length The length of the substring within the original string.
+	 * @return The (potentially empty) list of spanned lines (each one without the terminator characters).
+	 * @throws StringIndexOutOfBoundsException If the specified substring isn't valid, because:
+	 *                                         <ul>
+	 *                                         <li> <code>startPosition</code> is negative, or
+	 *                                         <li> <code>startPosition</code> is larger than the length of the original string, or
+	 *                                         <li> <code>length</code> is negative, or
+	 *                                         <li> there are less than <code>length</code> characters from <code>startPosition</code>
+	 *                                              to the end of the original string.
+	 *                                         </ul>
+	 */
+	public List<Line> getSpannedLines(final int startPosition, final int length) {
+		if (startPosition < 0 || startPosition > text.length()) {
+			throw new StringIndexOutOfBoundsException("Substring start position out of range: " + startPosition);
+		}
+		int endPosition = startPosition + length;
+		if (endPosition < startPosition || endPosition > text.length()) {
+			throw new StringIndexOutOfBoundsException("Substring length out of range: " + length);
+		}
+
+		if (lines.isEmpty()) {
+			return Collections.emptyList();
+		}
+
+		final Map.Entry<Integer, LineInfo> firstSpannedLine = lines.floorEntry(startPosition);
+		if (length == 0) {
+			// For empty substrings, firstSpannedLine.getKey() may be equal to endPosition.
+			// In this case, the submap would be empty (because the upper bound is exclusive),
+			// so the single spanned line has to be returned manually.
+			return Collections.singletonList(lineFromMapEntry(firstSpannedLine));
+		}
+		final SortedMap<Integer, LineInfo> spannedLines = lines.subMap(firstSpannedLine.getKey(), endPosition);
+		return spannedLines.entrySet().stream()
+				.map(this::lineFromMapEntry)
+				.collect(Collectors.toList());
+	}
+
+	private static NavigableMap<Integer, LineInfo> splitLines(final String string) {
+		final TreeMap<Integer, LineInfo> lines = new TreeMap<>();
+
+		int lineNum = 1;
+		int lineStart = 0;
+		int pos = 0;
+		while (pos < string.length()) {
+			final char cur = string.charAt(pos);
+			int nextPos = pos + 1;
+			if (nextPos < string.length() && cur == '\r' && string.charAt(nextPos) == '\n') {
+				nextPos++; // Skip \n after \r because \r\n is a single line separator
+			}
+			if (cur == '\r' || cur == '\n') {
+				lines.put(lineStart, new LineInfo(lineNum, pos));
+				lineNum++;
+				lineStart = nextPos;
+			}
+			pos = nextPos;
+		}
+		// If the last line has no trailing separator, the loop won't add it to the map
+		if (lineStart < string.length()) {
+			lines.put(lineStart, new LineInfo(lineNum, string.length()));
+		}
+
+		return lines;
+	}
+
+	private Line lineFromMapEntry(final Map.Entry<Integer, LineInfo> entry) {
+		final int start = entry.getKey();
+		final LineInfo lineInfo = entry.getValue();
+		return new Line(
+				lineInfo.number,
+				start,
+				text.substring(start, lineInfo.end)
+		);
+	}
+
+	private static class LineInfo {
+		public final int number;
+		public final int end;
+
+		LineInfo(final int number, final int end) {
+			this.number = number;
+			this.end = end;
+		}
+	}
+
+	/**
+	 * Represents a line of text within a string.
+	 */
+	public static class Line {
+		private final int number;
+		private final int startPosition;
+		private final String text;
+
+		Line(final int number, final int startPosition, final String text) {
+			this.number = number;
+			this.startPosition = startPosition;
+			this.text = text;
+		}
+
+		/**
+		 * @return The line number (starting from 1).
+		 */
+		public int getNumber() {
+			return number;
+		}
+
+		/**
+		 * @return The index at which this line starts within the original string.
+		 * 		   If the line is empty, this is the index of the terminator characters ("\r", "\n" or "\r\n").
+		 */
+		public int getStartPosition() {
+			return startPosition;
+		}
+
+		/**
+		 * @return The contents of this line, <em>without</em> the terminator characters ("\r", "\n" or "\r\n").
+		 */
+		public String getText() {
+			return text;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o) return true;
+			if (o == null || getClass() != o.getClass()) return false;
+			Line line = (Line) o;
+			return number == line.number &&
+				startPosition == line.startPosition &&
+				Objects.equals(text, line.text);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(number, startPosition, text);
+		}
+
+		@Override
+		public String toString() {
+			return "Line{" +
+				"number=" + number +
+				", startPosition=" + startPosition +
+				", text='" + text + '\'' +
+				'}';
+		}
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/errorutils/TabExpandedString.java

@@ -0,0 +1,67 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import java.util.Arrays;
+
+/**
+ * Represents a line of text in which tabs have been expanded (replaced with spaces).
+ * <p>
+ * Each tab character is replaced with the number of spaces required to get to the next tab stop
+ * (that is, the next column which is a multiple of the tab stop width).
+ */
+public class TabExpandedString {
+	private final String expanded;
+	private final int[] charWidths;
+
+	/**
+	 * Constructs a tab-expanded string with the given tab stop width.
+	 *
+	 * @param string The string to expand. Must not contain any line separator characters ('\r' or '\n').
+	 * @param tabWidth The tab stop width.
+	 * @throws IllegalArgumentException If <code>string</code> contains any line separator characters.
+	 */
+	public TabExpandedString(final String string, final int tabWidth) {
+		final StringBuilder builder = new StringBuilder();
+		charWidths = new int[string.length()];
+
+		for (int i = 0; i < string.length(); i++) {
+			final char c = string.charAt(i);
+			charWidths[i] = 1;
+
+			switch (c) {
+				case '\r':
+				case '\n':
+					throw new IllegalArgumentException("The string to expand is not a single line: " + string);
+				case '\t':
+					builder.append(' ');
+					while (builder.length() % tabWidth != 0) {
+						builder.append(' ');
+						charWidths[i]++;
+					}
+					break;
+				default:
+					builder.append(c);
+					break;
+			}
+		}
+
+		expanded = builder.toString();
+	}
+
+	/**
+	 * @return The tab-expanded string.
+	 */
+	public String getExpanded() {
+		return expanded;
+	}
+
+	/**
+	 * Computes the length of a substring of the original string after tab expansion.
+	 *
+	 * @param beginIndex The beginning index (inclusive) within the original string.
+	 * @param endIndex The ending index (exclusive) within the original string.
+	 * @return The length of the specified substring, after tabs have been expanded.
+	 */
+	public int substringLength(final int beginIndex, final int endIndex) {
+		return Arrays.stream(charWidths, beginIndex, endIndex).sum();
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/IncompleteNumberLiteral.java

@@ -0,0 +1,56 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.Objects;
+
+/**
+ * Occurs when DSL source code contains a number literal with a decimal separator which is not followed by digits.
+ * <p>
+ * An example of an incomplete literal is <code>2.</code>, while <code>2</code> and <code>2.2</code> are valid.
+ */
+public class IncompleteNumberLiteral implements DslError {
+	private final int position;
+	private final String literal;
+
+	public IncompleteNumberLiteral(final int position, final String literal) {
+		this.position = position;
+		this.literal = literal;
+	}
+
+	@Override
+	public int getPosition() {
+		return position;
+	}
+
+	@Override
+	public int getLength() {
+		return literal.length();
+	}
+
+	@Override
+	public <T> T accept(final DslError.Visitor<T> visitor) {
+		return visitor.visit(this);
+	}
+
+	/**
+	 * @return The incomplete number literal.
+	 */
+	public String getLiteral() {
+		return literal;
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof IncompleteNumberLiteral)) {
+			return false;
+		}
+		final IncompleteNumberLiteral other = (IncompleteNumberLiteral) o;
+		return this.position == other.position && this.literal.equals(other.literal);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(position, literal);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/Lexer.java

@@ -0,0 +1,230 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.*;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+import static it.cavallium.warppi.math.rules.dsl.frontend.TokenType.*;
+
+/**
+ * Converts the source <code>String</code> to a list of {@link Token}s.
+ */
+public class Lexer {
+	private static final Map<String, TokenType> KEYWORDS;
+	static {
+		TokenType[] keywordTokenTypes = {
+			REDUCTION, EXPANSION, CALCULATION, EXISTENCE,
+			ARCCOS, ARCSIN, ARCTAN, COS, SIN, TAN, ROOT, SQRT, LOG,
+			UNDEFINED, PI, E
+		};
+		Map<String, TokenType> map = new HashMap<>();
+		for (TokenType type : keywordTokenTypes) {
+			map.put(type.name().toLowerCase(), type);
+		}
+		KEYWORDS = Collections.unmodifiableMap(map);
+	}
+
+	private final String source;
+	private final Consumer<? super DslError> errorReporter;
+
+	private boolean used = false;
+	private final List<Token> tokens = new ArrayList<>();
+	private int startOfLexeme = 0;
+	private int curPosition = 0;
+	private UnexpectedCharacters unexpectedCharacters = null;
+
+	/**
+	 * Constructs a <code>Lexer</code> that will split the given source code into {@link Token}s.
+	 *
+	 * @param source        a <code>String</code> containing the DSL source code to process.
+	 * @param errorReporter a <code>Consumer</code> used to report each <code>DslError</code> that the
+	 *                      <code>Lexer</code> finds within the source string.
+	 */
+	public Lexer(final String source, final Consumer<? super DslError> errorReporter) {
+		this.source = source;
+		this.errorReporter = errorReporter;
+	}
+
+	/**
+	 * Runs the <code>Lexer</code>.
+	 * <p>
+	 * This method can only be called once per instance.
+	 *
+	 * @return the list of <code>Token</code>s extracted from the source string.
+	 * 		   If any errors are reported, this list should not be considered to represent a valid set of DSL rules,
+	 * 		   but it can still be parsed to potentially find additional errors (which may allow the user to fix more
+	 * 		   errors before having to rerun the <code>Lexer</code>).
+	 * @throws IllegalStateException if called multiple times on the same instance.
+	 */
+	public List<Token> lex() {
+		if (used) {
+			throw new IllegalStateException("Lexer.lex can only be called once per instance");
+		}
+		used = true;
+
+		while (!atEnd()) {
+			startOfLexeme = curPosition;
+			lexAndHandleErrors();
+		}
+		// lexAndHandleErrors reports unexpected characters when they're followed by expected ones:
+		// if there are unexpected characters at the end of the source, they have to be reported here
+		reportAndClearUnexpectedCharacters();
+		tokens.add(new Token(EOF, "", source.length()));
+		return tokens;
+	}
+
+	private void lexAndHandleErrors() {
+		try {
+			lexToken();
+			reportAndClearUnexpectedCharacters(); // After finding some expected characters
+		} catch (final SyntaxException e) {
+			final DslError error = e.getError();
+			if (error instanceof UnexpectedCharacters) {
+				addUnexpectedCharacters((UnexpectedCharacters) error);
+			} else {
+				// If there are multiple errors, report them in the order in which they occur in the source
+				reportAndClearUnexpectedCharacters();
+				errorReporter.accept(error);
+			}
+		}
+	}
+
+	private void addUnexpectedCharacters(final UnexpectedCharacters unexpected) {
+		if (unexpectedCharacters == null) {
+			unexpectedCharacters = unexpected;
+		} else {
+			unexpectedCharacters = unexpectedCharacters.concat(unexpected);
+		}
+	}
+
+	private void reportAndClearUnexpectedCharacters() {
+		if (unexpectedCharacters == null) {
+			return;
+		}
+		errorReporter.accept(unexpectedCharacters);
+		unexpectedCharacters = null;
+	}
+
+	private void lexToken() throws SyntaxException {
+		char current = popChar();
+		switch (current) {
+			case ':': emitToken(COLON); break;
+			case ',': emitToken(COMMA); break;
+			case '(': emitToken(LEFT_PAREN); break;
+			case ')': emitToken(RIGHT_PAREN); break;
+			case '[': emitToken(LEFT_BRACKET); break;
+			case ']': emitToken(RIGHT_BRACKET); break;
+			case '=': emitToken(EQUALS); break;
+			case '*': emitToken(TIMES); break;
+			case '^': emitToken(POWER); break;
+
+			case '+':
+				if (matchChar('-')) {
+					emitToken(PLUS_MINUS);
+				} else {
+					emitToken(PLUS);
+				}
+				break;
+
+			case '-':
+				if (matchChar('>')) {
+					emitToken(ARROW);
+				} else {
+					emitToken(MINUS);
+				}
+				break;
+
+			case '/':
+				if (matchChar('/')) {
+					singleLineComment();
+				} else if (matchChar('*')) {
+					multiLineComment();
+				} else {
+					emitToken(DIVIDE);
+				}
+				break;
+
+			default:
+				if (isAsciiDigit(current)) {
+					number();
+				} else if (Character.isJavaIdentifierStart(current)) {
+					keywordOrIdentifier();
+				} else if (!Character.isWhitespace(current)) {
+					throw new SyntaxException(
+							new UnexpectedCharacters(curPosition - 1, String.valueOf(current))
+					);
+				}
+		}
+	}
+
+	private void singleLineComment() {
+		matchWhile(c -> c != '\n');
+	}
+
+	private void multiLineComment() throws SyntaxException {
+		while (!(matchChar('*') && matchChar('/'))) {
+			if (atEnd()) {
+				throw new SyntaxException(new UnterminatedComment(startOfLexeme));
+			}
+			popChar();
+		}
+	}
+
+	private void number() throws SyntaxException {
+		matchWhile(Lexer::isAsciiDigit);
+		if (matchChar('.') && matchWhile(Lexer::isAsciiDigit) == 0) {
+			throw new SyntaxException(
+					new IncompleteNumberLiteral(startOfLexeme, currentLexeme())
+			);
+		}
+		emitToken(NUMBER);
+	}
+
+	private void keywordOrIdentifier() {
+		matchWhile(Character::isJavaIdentifierPart);
+		TokenType type = KEYWORDS.getOrDefault(currentLexeme(), IDENTIFIER);
+		emitToken(type);
+	}
+
+	private char popChar() {
+		char current = source.charAt(curPosition);
+		curPosition++;
+		return current;
+	}
+
+	private boolean matchChar(char expected) {
+		if (atEnd() || source.charAt(curPosition) != expected) {
+			return false;
+		}
+		curPosition++;
+		return true;
+	}
+
+	private int matchWhile(Predicate<Character> predicate) {
+		int matched = 0;
+		while (!atEnd() && predicate.test(source.charAt(curPosition))) {
+			curPosition++;
+			matched++;
+		}
+		return matched;
+	}
+
+	private void emitToken(TokenType type) {
+		tokens.add(new Token(type, currentLexeme(), startOfLexeme));
+	}
+
+	private String currentLexeme() {
+		return source.substring(startOfLexeme, curPosition);
+	}
+
+	private boolean atEnd() {
+		return curPosition >= source.length();
+	}
+
+	// Character.isDigit also allows various Unicode digits
+	private static boolean isAsciiDigit(char c) {
+		return '0' <= c && c <= '9';
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/Parser.java

@@ -0,0 +1,334 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.rules.RuleType;
+import it.cavallium.warppi.math.rules.dsl.DslError;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.PatternRule;
+import it.cavallium.warppi.math.rules.dsl.patterns.*;
+import it.cavallium.warppi.util.MapFactory;
+
+import java.math.BigDecimal;
+import java.util.*;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import static it.cavallium.warppi.math.rules.dsl.frontend.TokenType.*;
+
+/**
+ * Converts a list of {@link Token}s to a list of {@link PatternRule}s.
+ */
+public class Parser {
+	private static final Map<TokenType, RuleType> RULE_TYPES = MapFactory.fromEntries(
+		MapFactory.entry(REDUCTION, RuleType.REDUCTION),
+		MapFactory.entry(EXPANSION, RuleType.EXPANSION),
+		MapFactory.entry(CALCULATION, RuleType.CALCULATION),
+		MapFactory.entry(EXISTENCE, RuleType.EXISTENCE)
+	);
+
+	private final List<Token> tokens;
+	private final Consumer<? super DslError> errorReporter;
+	private boolean used = false;
+	private int currentIndex = 0;
+
+	// For error reporting
+	// An IdentityHashMap is used to distinguish SubFunctionPatterns even if they're identical (equal)
+	private final IdentityHashMap<SubFunctionPattern, Token> subFunctionIdentifiers = new IdentityHashMap<>();
+
+	/**
+	 * Constructs a <code>Parser</code> that will produce a list of {@link PatternRule}s from the the given list of {@link Token}s.
+	 *
+	 * @param tokens        the list of <code>Token</code>s to process.
+	 * @param errorReporter a <code>Consumer</code> used to report each <code>DslError</code> that the
+	 *                      <code>Parser</code> finds within the source string.
+	 */
+	public Parser(final List<Token> tokens, final Consumer<? super DslError> errorReporter) {
+		this.tokens = tokens;
+		this.errorReporter = errorReporter;
+	}
+
+	/**
+	 * Runs the <code>Parser</code>.
+	 * <p>
+	 * This method can only be called once per instance.
+	 *
+	 * @return the list of all valid <code>PatternRule</code>s constructed from the given tokens.
+	 * 	       If any errors are reported, this list should not be considered to represent a valid set of DSL rules,
+	 * 		   but each rule can still be analyzed to look for undefined sub-functions in replacement patterns and
+	 * 		   report them (which may allow the user to fix more errors before having to rerun the <code>Lexer</code>
+	 * 		   and <code>Parser</code>).
+	 * @throws IllegalStateException if called multiple times on the same instance.
+	 */
+	public List<PatternRule> parse() {
+		if (used) {
+			throw new IllegalStateException("Parser.parse can only be called once per instance");
+		}
+		used = true;
+
+		return rules();
+	}
+
+	/**
+	 * Retrieves the <code>IDENTIFIER</code> token which corresponds to the given <code>SubFunctionPattern</code>.
+	 * <p>
+	 * The information returned by this method can be used to point out the location of sub-function related errors
+	 * within the DSL source code.
+	 *
+	 * @param subFunction a <code>SubFunctionsPattern</code> from one of the rules returned by this <code>Parser</code>
+	 *                    instance. While <code>SubFunctionPattern</code>s with the same name are considered equal,
+	 *                    this method can distinguish between them, in order to return the exact identifier which led
+	 *                    to the creation of the specified <code>SubFunctionPattern</code> object.
+	 * @return the <code>Token</code> (of type <code>IDENTIFIER</code>) which corresponds to the given
+	 * 	       <code>SubFunctionPattern</code>.
+	 */
+	public Token getSubFunctionIdentifier(final SubFunctionPattern subFunction) {
+		return subFunctionIdentifiers.get(subFunction);
+	}
+
+	// rules = { rule } , EOF ;
+	private List<PatternRule> rules() {
+		final List<PatternRule> rules = new ArrayList<>();
+		while (!atEnd()) {
+			try {
+				rules.add(rule());
+			} catch (final SyntaxException e) {
+				errorReporter.accept(e.getError());
+				synchronizeTo(RULE_TYPES.keySet()); // Skip to the next rule to minimize "false" errors
+			}
+		}
+		return rules;
+	}
+
+	// rule = rule header , rule body ;
+	// rule header = rule type , IDENTIFIER , COLON ;
+	// rule body = pattern , ARROW , replacements ;
+	private PatternRule rule() throws SyntaxException {
+		final RuleType type = ruleType();
+		final String name = matchOrFail(IDENTIFIER).lexeme;
+		matchOrFail(COLON);
+		final Pattern target = pattern();
+		matchOrFail(ARROW);
+		final List<Pattern> replacements = replacements();
+		return new PatternRule(name, type, target, replacements);
+	}
+
+	// rule type = REDUCTION | EXPANSION | CALCULATION | EXISTENCE ;
+	private RuleType ruleType() throws SyntaxException {
+		final Token curToken = pop();
+		if (!RULE_TYPES.containsKey(curToken.type)) {
+			throw new SyntaxException(
+					new UnexpectedToken(curToken, RULE_TYPES.keySet())
+			);
+		}
+		return RULE_TYPES.get(curToken.type);
+	}
+
+	// pattern = equation ;
+	private Pattern pattern() throws SyntaxException {
+		return equation();
+	}
+
+	// replacements = pattern
+	//              | LEFT_BRACKET , patterns , RIGHT_BRACKET ;
+	// patterns = [ pattern , { COMMA , pattern } , [ COMMA ] ] ;
+	private List<Pattern> replacements() throws SyntaxException {
+		if (match(LEFT_BRACKET) == null) {
+			return Collections.singletonList(pattern());
+		}
+
+		if (match(RIGHT_BRACKET) != null) {
+			return Collections.emptyList();
+		} else {
+			final List<Pattern> pats = new ArrayList<>();
+			do {
+				pats.add(pattern());
+			} while (match(COMMA) != null && peek().type != RIGHT_BRACKET);
+			matchOrFail(RIGHT_BRACKET);
+			return pats;
+		}
+	}
+
+	// equation = sum , [ EQUALS , sum ] ;
+	private Pattern equation() throws SyntaxException {
+		Pattern pat = sum();
+		if (match(EQUALS) != null) {
+			pat = new EquationPattern(pat, sum());
+		}
+		return pat;
+	}
+
+	// sum = product , { ( PLUS | MINUS | PLUS_MINUS ) product } ;
+	private Pattern sum() throws SyntaxException {
+		return matchLeftAssoc(this::product, MapFactory.fromEntries(
+				MapFactory.entry(PLUS, SumPattern::new),
+				MapFactory.entry(MINUS, SubtractionPattern::new),
+				MapFactory.entry(PLUS_MINUS, SumSubtractionPattern::new)
+		));
+	}
+
+	// product = unary , { ( TIMES | DIVIDE ) unary } ;
+	private Pattern product() throws SyntaxException {
+		return matchLeftAssoc(this::unary, MapFactory.fromEntries(
+				MapFactory.entry(TIMES, MultiplicationPattern::new),
+				MapFactory.entry(DIVIDE, DivisionPattern::new)
+		));
+	}
+
+	// unary = ( PLUS | MINUS ) unary
+	//       | power ;
+	private Pattern unary() throws SyntaxException {
+		if (match(PLUS) != null) {
+			return unary();
+		} else if (match(MINUS) != null) {
+			return new NegativePattern(unary());
+		} else {
+			return power();
+		}
+	}
+
+	// power = ( function | primary ) , [ POWER , unary ] ;
+	private Pattern power() throws SyntaxException {
+		Pattern pat = functionOrPrimary();
+		if (match(POWER) != null) {
+			pat = new PowerPattern(pat, unary());
+		}
+		return pat;
+	}
+
+	private Pattern functionOrPrimary() throws SyntaxException {
+		final Pattern function = tryFunction();
+		return function != null ? function : primary();
+	}
+
+	// function = ( ARCCOS | ARCSIN | ARCTAN | COS | SIN | SQRT | TAN ) , LEFT_PAREN , sum , RIGHT_PAREN
+	//          | ( LOG | ROOT ) LEFT_PAREN , sum , COMMA , sum , RIGHT_PAREN ;
+	private Pattern tryFunction() throws SyntaxException {
+		final Map<TokenType, Function<Pattern, Pattern>> oneArg = MapFactory.fromEntries(
+				MapFactory.entry(ARCCOS, ArcCosinePattern::new),
+				MapFactory.entry(ARCSIN, ArcSinePattern::new),
+				MapFactory.entry(ARCTAN, ArcTangentPattern::new),
+				MapFactory.entry(COS, CosinePattern::new),
+				MapFactory.entry(SIN, SinePattern::new),
+				MapFactory.entry(SQRT, arg -> new RootPattern(new NumberPattern(new BigDecimal(2)), arg)),
+				MapFactory.entry(TAN, TangentPattern::new)
+		);
+		final Map<TokenType, BiFunction<Pattern, Pattern, Pattern>> twoArg = MapFactory.fromEntries(
+				MapFactory.entry(LOG, LogarithmPattern::new),
+				MapFactory.entry(ROOT, RootPattern::new)
+		);
+
+		final TokenType curType = peek().type;
+		if (oneArg.containsKey(curType)) {
+			pop();
+			return oneArgFunction(oneArg.get(curType));
+		} else if (twoArg.containsKey(curType)) {
+			pop();
+			return twoArgFunction(twoArg.get(curType));
+		}
+
+		return null;
+	}
+
+	private Pattern oneArgFunction(final Function<Pattern, Pattern> constructor) throws SyntaxException {
+		matchOrFail(LEFT_PAREN);
+		final Pattern arg = pattern();
+		matchOrFail(RIGHT_PAREN);
+		return constructor.apply(arg);
+	}
+
+	private Pattern twoArgFunction(final BiFunction<Pattern, Pattern, Pattern> constructor) throws SyntaxException {
+		matchOrFail(LEFT_PAREN);
+		final Pattern firstArg = pattern();
+		matchOrFail(COMMA);
+		final Pattern secondArg = pattern();
+		matchOrFail(RIGHT_PAREN);
+		return constructor.apply(firstArg, secondArg);
+	}
+
+	// primary = NUMBER | constant | IDENTIFIER | UNDEFINED
+	//         | LEFT_PAREN sum RIGHT_PAREN ;
+	// constant = PI | E ;
+	private Pattern primary() throws SyntaxException {
+		final Token curToken = pop();
+		switch (curToken.type) {
+			case PI:
+				return new ConstantPattern(MathematicalSymbols.PI);
+			case E:
+				return new ConstantPattern(MathematicalSymbols.EULER_NUMBER);
+			case UNDEFINED:
+				return new UndefinedPattern();
+			case NUMBER:
+				return new NumberPattern(new BigDecimal(curToken.lexeme));
+			case IDENTIFIER:
+				final SubFunctionPattern subFunction = new SubFunctionPattern(curToken.lexeme);
+				subFunctionIdentifiers.put(subFunction, curToken);
+				return subFunction;
+			case LEFT_PAREN:
+				final Pattern grouped = sum();
+				matchOrFail(RIGHT_PAREN);
+				return grouped;
+		}
+		throw new SyntaxException(new UnexpectedToken(curToken));
+	}
+
+	private Pattern matchLeftAssoc(
+			final PatternParser operandParser,
+			final Map<TokenType, BiFunction<Pattern, Pattern, Pattern>> operators
+	) throws SyntaxException {
+		Pattern pat = operandParser.parse();
+		while (operators.containsKey(peek().type)) {
+			final Token operatorToken = pop();
+			final BiFunction<Pattern, Pattern, Pattern> constructor = operators.get(operatorToken.type);
+			pat = constructor.apply(pat, operandParser.parse());
+		}
+		return pat;
+	}
+
+	private Token matchOrFail(final TokenType expectedType) throws SyntaxException {
+		final Token matched = match(expectedType);
+		if (matched == null) {
+			throw new SyntaxException(
+					new UnexpectedToken(tokens.get(currentIndex), expectedType)
+			);
+		}
+		return matched;
+	}
+
+	private Token match(final TokenType expectedType) {
+		final Token curToken = tokens.get(currentIndex);
+		if (curToken.type != expectedType) {
+			return null;
+		}
+		currentIndex++;
+		return curToken;
+	}
+
+	private void synchronizeTo(final Set<TokenType> types) {
+		while (!atEnd() && !types.contains(tokens.get(currentIndex).type)) {
+			currentIndex++;
+		}
+	}
+
+	private Token pop() throws SyntaxException {
+		final Token curToken = tokens.get(currentIndex);
+		if (atEnd()) {
+			throw new SyntaxException(new UnexpectedToken(curToken)); // Avoid popping EOF
+		}
+		currentIndex++;
+		return curToken;
+	}
+
+	private Token peek() {
+		return tokens.get(currentIndex);
+	}
+
+	private boolean atEnd() {
+		return tokens.get(currentIndex).type == EOF;
+	}
+
+	@FunctionalInterface
+	private interface PatternParser {
+		Pattern parse() throws SyntaxException;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/SyntaxException.java

@@ -0,0 +1,20 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+/**
+ * Thrown when DSL source code contains a syntax error.
+ * <p>
+ * Used for error reporting and recovery in the implementation of {@link Lexer} and {@link Parser}.
+ */
+class SyntaxException extends Exception {
+	private final DslError error;
+
+	SyntaxException(final DslError error) {
+		this.error = error;
+	}
+
+	public DslError getError() {
+		return error;
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/Token.java

@@ -0,0 +1,60 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import java.util.Objects;
+
+/**
+ * Represents a single token extracted from DSL source code.
+ * <p>
+ * <code>Token</code>s are produced by the {@link Lexer} and consumed by the {@link Parser}.
+ */
+public class Token {
+	/** The type of the token. */
+	public final TokenType type;
+	/**
+	 * The part of the source code which corresponds to the token.
+	 * <p>
+	 * Some types of token always have the same lexemes (for example, <code>PLUS</code> is always represented by
+	 * <code>"+"</code>), while others have variable lexemes (like <code>IDENTIFIER</code>, which may correspond to any
+	 * valid identifier).
+	 * <p>
+	 * As a special case, tokens of type <code>EOF</code> (which signal the end of the source code) have empty lexemes
+	 * (<code>""</code>). Such tokens only exist to simplify the parser code, by allowing the end of the input to be
+	 * treated like any other token (which is especially useful for error handling, because an unexpected end of input
+	 * just becomes an "unexpected token" error).
+	 */
+	public final String lexeme;
+	/** The index at which the token starts in the source string. */
+	public final int position;
+
+	/**
+	 * Constructs a <code>Token</code>.
+	 *
+	 * @param type     the type of the token.
+	 * @param lexeme   the part of the source string which corresponds to the token.
+	 * @param position the index at which the token starts in the source string.
+	 */
+	public Token(final TokenType type, final String lexeme, final int position) {
+		this.type = type;
+		this.lexeme = lexeme;
+		this.position = position;
+	}
+
+	@Override
+	public String toString() {
+		return String.format("%s(\"%s\")@%d", type, lexeme, position);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (!(o instanceof Token)) {
+			return false;
+		}
+		Token other = (Token) o;
+		return type == other.type && lexeme.equals(other.lexeme) && position == other.position;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(type, lexeme, position);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/TokenType.java

@@ -0,0 +1,18 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+/**
+ * Specifies the type of a <code>Token</code>.
+ */
+public enum TokenType {
+	EOF,
+	// Separators and grouping
+	COLON, ARROW, COMMA, LEFT_PAREN, RIGHT_PAREN, LEFT_BRACKET, RIGHT_BRACKET,
+	// Operators
+	EQUALS, PLUS, MINUS, PLUS_MINUS, TIMES, DIVIDE, POWER,
+	// Rule types
+	REDUCTION, EXPANSION, CALCULATION, EXISTENCE,
+	// Functions
+	ARCCOS, ARCSIN, ARCTAN, COS, SIN, TAN, ROOT, SQRT, LOG,
+	// Literals
+	UNDEFINED, PI, E, NUMBER, IDENTIFIER,
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/UnexpectedCharacters.java

@@ -0,0 +1,58 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.Objects;
+
+/**
+ * Occurs when DSL source code contains one or more (consecutive) characters which are not expected by the lexer.
+ */
+public class UnexpectedCharacters implements DslError {
+	private final int position;
+	private final String unexpectedCharacters;
+
+	public UnexpectedCharacters(final int position, final String unexpectedCharacters) {
+		this.position = position;
+		this.unexpectedCharacters = unexpectedCharacters;
+	}
+
+	@Override
+	public int getPosition() {
+		return position;
+	}
+
+	@Override
+	public int getLength() {
+		return unexpectedCharacters.length();
+	}
+
+	@Override
+	public <T> T accept(final DslError.Visitor<T> visitor) {
+		return visitor.visit(this);
+	}
+
+	/**
+	 * @return The string of one or more consecutive unexpected characters.
+	 */
+	public String getUnexpectedCharacters() {
+		return unexpectedCharacters;
+	}
+
+	UnexpectedCharacters concat(UnexpectedCharacters other) {
+		return new UnexpectedCharacters(this.position, this.unexpectedCharacters + other.unexpectedCharacters);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof UnexpectedCharacters)) {
+			return false;
+		}
+		final UnexpectedCharacters other = (UnexpectedCharacters) o;
+		return this.position == other.position && this.unexpectedCharacters.equals(other.unexpectedCharacters);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(position, unexpectedCharacters);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/UnexpectedToken.java

@@ -0,0 +1,71 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Objects;
+import java.util.Set;
+
+/**
+ * Occurs when DSL source code contains a token which doesn't match the grammar.
+ */
+public class UnexpectedToken implements DslError {
+	private final Token unexpected;
+	private final Set<TokenType> suggested;
+
+	public UnexpectedToken(final Token unexpected, final Set<TokenType> suggested) {
+		this.unexpected = unexpected;
+		this.suggested = suggested;
+	}
+
+	public UnexpectedToken(final Token unexpected, final TokenType... suggested) {
+		this.unexpected = unexpected;
+		this.suggested = new HashSet<>(Arrays.asList(suggested)); // TeaVM doesn't support Set.of
+	}
+
+	@Override
+	public int getPosition() {
+		return unexpected.position;
+	}
+
+	@Override
+	public int getLength() {
+		return unexpected.lexeme.length();
+	}
+
+	@Override
+	public <T> T accept(final DslError.Visitor<T> visitor) {
+		return visitor.visit(this);
+	}
+
+	/**
+	 * @return The unexpected token.
+	 */
+	public Token getUnexpected() {
+		return unexpected;
+	}
+
+	/**
+	 * @return A (possibly empty) set of <code>TokenType</code>s which would match the grammar.
+	 *         As the name implies, this is only a suggestion: the parser can't list all allowed token types
+	 *         when it detects an error.
+	 */
+	public Set<TokenType> getSuggested() {
+		return suggested;
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof UnexpectedToken)) {
+			return false;
+		}
+		final UnexpectedToken other = (UnexpectedToken) o;
+		return this.unexpected.equals(other.unexpected) && this.suggested.equals(other.suggested);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(unexpected, suggested);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/frontend/UnterminatedComment.java

@@ -0,0 +1,45 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+
+import java.util.Objects;
+
+/**
+ * Occurs when DSL source code contains a multiline comment which is never terminated (closed).
+ */
+public class UnterminatedComment implements DslError {
+	private final int position;
+
+	public UnterminatedComment(final int position) {
+		this.position = position;
+	}
+
+	@Override
+	public int getPosition() {
+		return position;
+	}
+
+	@Override
+	public int getLength() {
+		return 2; // Length of comment start marker: "/*"
+	}
+
+	@Override
+	public <T> T accept(final DslError.Visitor<T> visitor) {
+		return visitor.visit(this);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof UnterminatedComment)) {
+			return false;
+		}
+		final UnterminatedComment other = (UnterminatedComment) o;
+		return this.position == other.position;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(position);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/ArcCosinePattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.ArcCosine;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the arccosine of another pattern.
+ */
+public class ArcCosinePattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public ArcCosinePattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final ArcCosine arcCosine, final Map<String, Function> subFunctions) {
+		return argument.match(arcCosine.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new ArcCosine(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof ArcCosinePattern)) {
+			return false;
+		}
+		final ArcCosinePattern other = (ArcCosinePattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/ArcSinePattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.ArcSine;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the arcsine of another pattern.
+ */
+public class ArcSinePattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public ArcSinePattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final ArcSine arcSine, final Map<String, Function> subFunctions) {
+		return argument.match(arcSine.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new ArcSine(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof ArcSinePattern)) {
+			return false;
+		}
+		final ArcSinePattern other = (ArcSinePattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/ArcTangentPattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.ArcTangent;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the arctangent of another pattern.
+ */
+public class ArcTangentPattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public ArcTangentPattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final ArcTangent arcTangent, final Map<String, Function> subFunctions) {
+		return argument.match(arcTangent.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new ArcTangent(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof ArcTangentPattern)) {
+			return false;
+		}
+		final ArcTangentPattern other = (ArcTangentPattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/ConstantPattern.java

@@ -0,0 +1,51 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Variable;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a specific symbolic constant.
+ */
+public class ConstantPattern extends VisitorPattern {
+	private final char symbol;
+
+	public ConstantPattern(final char symbol) {
+		this.symbol = symbol;
+	}
+
+	@Override
+	public Boolean visit(final Variable variable, final Map<String, Function> subFunctions) {
+		return variable.getType().equals(Variable.V_TYPE.CONSTANT)
+			&& variable.getChar() == symbol;
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Variable(mathContext, symbol, Variable.V_TYPE.CONSTANT);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.empty();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof ConstantPattern)) {
+			return false;
+		}
+		final ConstantPattern other = (ConstantPattern) o;
+		return symbol == other.symbol;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(symbol);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/CosinePattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.Cosine;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the cosine of another pattern.
+ */
+public class CosinePattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public CosinePattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final Cosine cosine, final Map<String, Function> subFunctions) {
+		return argument.match(cosine.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Cosine(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof CosinePattern)) {
+			return false;
+		}
+		final CosinePattern other = (CosinePattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/DivisionPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Division;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a division of two other patterns.
+ */
+public class DivisionPattern extends VisitorPattern {
+	private final Pattern dividend;
+	private final Pattern divisor;
+
+	public DivisionPattern(final Pattern dividend, final Pattern divisor) {
+		this.dividend = dividend;
+		this.divisor = divisor;
+	}
+
+	@Override
+	public Boolean visit(final Division division, final Map<String, Function> subFunctions) {
+		return dividend.match(division.getParameter1(), subFunctions)
+			&& divisor.match(division.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Division(
+			mathContext,
+			dividend.replace(mathContext, subFunctions),
+			divisor.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(dividend, divisor)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof DivisionPattern)) {
+			return false;
+		}
+		final DivisionPattern other = (DivisionPattern) o;
+		return dividend.equals(other.dividend) && divisor.equals(other.divisor);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(dividend, divisor);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/EquationPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.equations.Equation;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates an equation of two other patterns.
+ */
+public class EquationPattern extends VisitorPattern {
+	private final Pattern left;
+	private final Pattern right;
+
+	public EquationPattern(final Pattern left, final Pattern right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public Boolean visit(final Equation equation, final Map<String, Function> subFunctions) {
+		return left.match(equation.getParameter1(), subFunctions)
+			&& right.match(equation.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Equation(
+			mathContext,
+			left.replace(mathContext, subFunctions),
+			right.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(left, right)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof EquationPattern)) {
+			return false;
+		}
+		final EquationPattern other = (EquationPattern) o;
+		return left.equals(other.left) && right.equals(other.right);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(left, right);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/EquationsSystemPattern.java

@@ -0,0 +1,67 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.equations.EquationsSystem;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Arrays;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a system of equations of multiple other patterns.
+ */
+public class EquationsSystemPattern extends VisitorPattern {
+	private final Pattern[] patterns;
+
+	public EquationsSystemPattern(final Pattern[] patterns) {
+		this.patterns = patterns;
+	}
+
+	@Override
+	public Boolean visit(final EquationsSystem equationsSystem, final Map<String, Function> subFunctions) {
+		if (patterns.length != equationsSystem.getParametersLength()) {
+			return false;
+		}
+
+		for (int i = 0; i < patterns.length; i++) {
+			final Pattern curPattern = patterns[i];
+			final Function curFunction = equationsSystem.getParameter(i);
+			if (!curPattern.match(curFunction, subFunctions)) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		final Function[] functions = Arrays.stream(patterns)
+			.map(pattern -> pattern.replace(mathContext, subFunctions))
+			.toArray(Function[]::new);
+		return new EquationsSystem(mathContext, functions);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(patterns)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof EquationsSystemPattern)) {
+			return false;
+		}
+		final EquationsSystemPattern other = (EquationsSystemPattern) o;
+		return Arrays.equals(patterns, other.patterns);
+	}
+
+	@Override
+	public int hashCode() {
+		return Arrays.hashCode(patterns);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/LogarithmPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Logarithm;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a logarithm of base and argument patterns.
+ */
+public class LogarithmPattern extends VisitorPattern {
+	private final Pattern base;
+	private final Pattern argument;
+
+	public LogarithmPattern(final Pattern base, final Pattern argument) {
+		this.base = base;
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final Logarithm logarithm, final Map<String, Function> subFunctions) {
+		return base.match(logarithm.getParameter1(), subFunctions)
+			&& argument.match(logarithm.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Logarithm(
+			mathContext,
+			base.replace(mathContext, subFunctions),
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(base, argument)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof LogarithmPattern)) {
+			return false;
+		}
+		final LogarithmPattern other = (LogarithmPattern) o;
+		return base.equals(other.base) && argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(base, argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/MultiplicationPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Multiplication;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a multiplication of two other patterns.
+ */
+public class MultiplicationPattern extends VisitorPattern {
+	private final Pattern left;
+	private final Pattern right;
+
+	public MultiplicationPattern(final Pattern left, final Pattern right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public Boolean visit(final Multiplication multiplication, final Map<String, Function> subFunctions) {
+		return left.match(multiplication.getParameter1(), subFunctions)
+			&& right.match(multiplication.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Multiplication(
+			mathContext,
+			left.replace(mathContext, subFunctions),
+			right.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(left, right)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof MultiplicationPattern)) {
+			return false;
+		}
+		final MultiplicationPattern other = (MultiplicationPattern) o;
+		return left.equals(other.left) && right.equals(other.right);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(left, right);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/NegativePattern.java

@@ -0,0 +1,72 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Negative;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.math.BigDecimal;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the negative of another pattern.
+ */
+public class NegativePattern extends VisitorPattern {
+	private final Pattern inner;
+
+	public NegativePattern(final Pattern inner) {
+		this.inner = inner;
+	}
+
+	@Override
+	public Boolean visit(final Negative negative, final Map<String, Function> subFunctions) {
+		return inner.match(negative.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Boolean visit(final Number number, final Map<String, Function> subFunctions) {
+		final BigDecimal value = number.getTerm();
+		if (value.signum() >= 0) {
+			return false;
+		}
+		final Number absoluteValue = new Number(number.getMathContext(), value.abs());
+		return inner.match(absoluteValue, subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		final Function newInner = inner.replace(mathContext, subFunctions);
+
+		if (newInner instanceof Number) {
+			return ((Number) newInner).multiply(new Number(mathContext, -1));
+		} else {
+			return new Negative(
+				mathContext,
+				inner.replace(mathContext, subFunctions)
+			);
+		}
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return inner.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof NegativePattern)) {
+			return false;
+		}
+		final NegativePattern other = (NegativePattern) o;
+		return inner.equals(other.inner);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(inner);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/NumberPattern.java

@@ -0,0 +1,51 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.math.BigDecimal;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a specific number.
+ */
+public class NumberPattern extends VisitorPattern {
+	private final BigDecimal value;
+
+	public NumberPattern(final BigDecimal value) {
+		this.value = value;
+	}
+
+	@Override
+	public Boolean visit(final Number number, final Map<String, Function> subFunctions) {
+		return number.getTerm().compareTo(value) == 0;
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Number(mathContext, value);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.empty();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof NumberPattern)) {
+			return false;
+		}
+		final NumberPattern other = (NumberPattern) o;
+		return value.compareTo(other.value) == 0;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(value);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/PowerPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Power;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a power (exponentiation) of base and exponent patterns.
+ */
+public class PowerPattern extends VisitorPattern {
+	private final Pattern base;
+	private final Pattern exponent;
+
+	public PowerPattern(final Pattern base, final Pattern exponent) {
+		this.base = base;
+		this.exponent = exponent;
+	}
+
+	@Override
+	public Boolean visit(final Power power, final Map<String, Function> subFunctions) {
+		return base.match(power.getParameter1(), subFunctions)
+			&& exponent.match(power.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Power(
+			mathContext,
+			base.replace(mathContext, subFunctions),
+			exponent.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(base, exponent)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof PowerPattern)) {
+			return false;
+		}
+		final PowerPattern other = (PowerPattern) o;
+		return base.equals(other.base) && exponent.equals(other.exponent);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(base, exponent);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/RootPattern.java

@@ -0,0 +1,74 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.Root;
+import it.cavallium.warppi.math.functions.RootSquare;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.math.BigDecimal;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a root of degree and radicand patterns.
+ * <p>
+ * Also matches and generates functions of type <code>RootSquare</code>.
+ */
+public class RootPattern extends VisitorPattern {
+	private final Pattern degree;
+	private final Pattern radicand;
+
+	public RootPattern(final Pattern degree, final Pattern radicand) {
+		this.degree = degree;
+		this.radicand = radicand;
+	}
+
+	@Override
+	public Boolean visit(final Root root, final Map<String, Function> subFunctions) {
+		return degree.match(root.getParameter1(), subFunctions)
+			&& radicand.match(root.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Boolean visit(final RootSquare rootSquare, final Map<String, Function> subFunctions) {
+		return degree.match(rootSquare.getParameter1(), subFunctions)
+			&& radicand.match(rootSquare.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		final Function newDegree = degree.replace(mathContext, subFunctions);
+		final Function newRadicand = radicand.replace(mathContext, subFunctions);
+
+		if (newDegree instanceof Number
+			&& ((Number) newDegree).getTerm().compareTo(new BigDecimal(2)) == 0) {
+			return new RootSquare(mathContext, newRadicand);
+		} else {
+			return new Root(mathContext, newDegree, newRadicand);
+		}
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(degree, radicand)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof RootPattern)) {
+			return false;
+		}
+		final RootPattern other = (RootPattern) o;
+		return degree.equals(other.degree) && radicand.equals(other.radicand);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(degree, radicand);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SinePattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.Sine;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the sine of another pattern.
+ */
+public class SinePattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public SinePattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final Sine sine, final Map<String, Function> subFunctions) {
+		return argument.match(sine.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Sine(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof SinePattern)) {
+			return false;
+		}
+		final SinePattern other = (SinePattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SubFunctionPattern.java

@@ -0,0 +1,64 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.UndefinedSubFunctionException;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates any function as a named sub-function.
+ * <p>
+ * For a <code>Function</code> to match a <code>Pattern</code>, all <code>SubFunctionPattern</code>s with the same name
+ * must capture equal sub-functions (according to the <code>equals</code> method).
+ * For example, the <code>x + x</code> <code>Pattern</code> matches <code>2 + 2</code> and <code>2 + 2.0</code>,
+ * but not <code>2 + 3</code>, while the <code>x + y</code> <code>Pattern</code> matches all three <code>Function</code>s.
+ */
+public class SubFunctionPattern implements Pattern {
+	private final String name;
+
+	public SubFunctionPattern(final String name) {
+		this.name = name;
+	}
+
+	@Override
+	public boolean match(final Function function, final Map<String, Function> subFunctions) {
+		final Function existingSubFunction = subFunctions.putIfAbsent(name, function);
+		return existingSubFunction == null || existingSubFunction.equals(function);
+	}
+
+	/**
+	 * @throws UndefinedSubFunctionException if the <code>subFunctions</code> <code>Map</code> doesn't contain a
+	 *                                       sub-function with the name specified in this
+	 *                                       <code>SubFunctionPattern</code>'s constructor.
+	 */
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		if (!subFunctions.containsKey(name)) {
+			throw new UndefinedSubFunctionException(name);
+		}
+		return subFunctions.get(name);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(this);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof SubFunctionPattern)) {
+			return false;
+		}
+		final SubFunctionPattern other = (SubFunctionPattern) o;
+		return name.equals(other.name);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(name);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SubtractionPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Subtraction;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a subtraction of two other patterns.
+ */
+public class SubtractionPattern extends VisitorPattern {
+	private final Pattern left;
+	private final Pattern right;
+
+	public SubtractionPattern(final Pattern left, final Pattern right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public Boolean visit(final Subtraction subtraction, final Map<String, Function> subFunctions) {
+		return left.match(subtraction.getParameter1(), subFunctions)
+			&& right.match(subtraction.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Subtraction(
+			mathContext,
+			left.replace(mathContext, subFunctions),
+			right.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(left, right)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof SubtractionPattern)) {
+			return false;
+		}
+		final SubtractionPattern other = (SubtractionPattern) o;
+		return left.equals(other.left) && right.equals(other.right);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(left, right);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Sum;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a sum of two other patterns.
+ */
+public class SumPattern extends VisitorPattern {
+	private final Pattern left;
+	private final Pattern right;
+
+	public SumPattern(final Pattern left, final Pattern right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public Boolean visit(final Sum sum, final Map<String, Function> subFunctions) {
+		return left.match(sum.getParameter1(), subFunctions)
+			&& right.match(sum.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Sum(
+			mathContext,
+			left.replace(mathContext, subFunctions),
+			right.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(left, right)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof SumPattern)) {
+			return false;
+		}
+		final SumPattern other = (SumPattern) o;
+		return left.equals(other.left) && right.equals(other.right);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(left, right);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumSubtractionPattern.java

@@ -0,0 +1,59 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.SumSubtraction;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates a sum/subtraction (±) of two other patterns.
+ */
+public class SumSubtractionPattern extends VisitorPattern {
+	private final Pattern left;
+	private final Pattern right;
+
+	public SumSubtractionPattern(final Pattern left, final Pattern right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	@Override
+	public Boolean visit(final SumSubtraction sumSubtraction, final Map<String, Function> subFunctions) {
+		return left.match(sumSubtraction.getParameter1(), subFunctions)
+			&& right.match(sumSubtraction.getParameter2(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new SumSubtraction(
+			mathContext,
+			left.replace(mathContext, subFunctions),
+			right.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.of(left, right)
+			.flatMap(Pattern::getSubFunctions);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof SumSubtractionPattern)) {
+			return false;
+		}
+		final SumSubtractionPattern other = (SumSubtractionPattern) o;
+		return left.equals(other.left) && right.equals(other.right);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(left, right);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/TangentPattern.java

@@ -0,0 +1,54 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.trigonometry.Tangent;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates the tangent of another pattern.
+ */
+public class TangentPattern extends VisitorPattern {
+	private final Pattern argument;
+
+	public TangentPattern(final Pattern argument) {
+		this.argument = argument;
+	}
+
+	@Override
+	public Boolean visit(final Tangent tangent, final Map<String, Function> subFunctions) {
+		return argument.match(tangent.getParameter(), subFunctions);
+	}
+
+	@Override
+	public Function replace(final MathContext mathContext, final Map<String, Function> subFunctions) {
+		return new Tangent(
+			mathContext,
+			argument.replace(mathContext, subFunctions)
+		);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return argument.getSubFunctions();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof TangentPattern)) {
+			return false;
+		}
+		final TangentPattern other = (TangentPattern) o;
+		return argument.equals(other.argument);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(argument);
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/UndefinedPattern.java

@@ -0,0 +1,39 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Undefined;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.stream.Stream;
+
+/**
+ * Matches and generates <code>Undefined</code>.
+ */
+public class UndefinedPattern extends VisitorPattern {
+	@Override
+	public Boolean visit(final Undefined undefined, final Map<String, Function> subFunctions) {
+		return true;
+	}
+
+	@Override
+	public Function replace(MathContext mathContext, Map<String, Function> subFunctions) {
+		return new Undefined(mathContext);
+	}
+
+	@Override
+	public Stream<SubFunctionPattern> getSubFunctions() {
+		return Stream.empty();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		return o instanceof UndefinedPattern;
+	}
+
+	@Override
+	public int hashCode() {
+		return UndefinedPattern.class.hashCode();
+	}
+}

core/src/main/java/it/cavallium/warppi/math/rules/functions/DivisionRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.DivisionRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/EmptyNumberRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.EmptyNumberRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/ExpressionRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.ExpressionRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/JokeRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.JokeRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/MultiplicationRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.MultiplicationRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/NegativeRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.NegativeRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/NumberRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.NumberRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/PowerRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.PowerRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/RootRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.RootRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/SubtractionRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.SubtractionRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/SumRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.SumRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/SumSubtractionRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.SumSubtractionRule

core/src/main/java/it/cavallium/warppi/math/rules/functions/VariableRule.java

@@ -1,4 +1,4 @@
-package rules.functions;
+package it.cavallium.warppi.math.rules.functions;
 /*
 SETTINGS: (please don't move this part)
  PATH=functions.VariableRule

core/src/main/java/it/cavallium/warppi/util/MapFactory.java

@@ -0,0 +1,52 @@
+package it.cavallium.warppi.util;
+
+import java.util.AbstractMap;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Reimplements map creation methods which are not available on TeaVM.
+ */
+public class MapFactory {
+	private MapFactory() {}
+
+	/**
+	 * Returns an unmodifiable map containing keys and values extracted from the given entries.
+	 * <p>
+	 * This method is equivalent to {@link Map#ofEntries(Map.Entry...)}.
+	 *
+	 * @param entries <code>Map.Entry</code>s containing the keys and values from which the map is populated
+	 * @param <K> the <code>Map</code>'s key type
+	 * @param <V> the <code>Map</code>'s value type
+	 * @return a Map containing the specified mappings
+	 * @see MapFactory#entry(K, V)
+	 */
+	@SafeVarargs
+	public static <K, V> Map<K, V> fromEntries(Map.Entry<? extends K, ? extends V>... entries) {
+		HashMap<K, V> map = new HashMap<>();
+		for (Map.Entry<? extends K, ? extends V> entry : entries) {
+			map.put(entry.getKey(), entry.getValue());
+		}
+		return Collections.unmodifiableMap(map);
+	}
+
+	/**
+	 * Returns an unmodifiable <code>Map.Entry</code> containing the given key and value.
+	 * These entries are suitable for populating Map instances using the {@link MapFactory#fromEntries(Map.Entry...)}
+	 * or {@link Map#ofEntries(Map.Entry...)} methods.
+	 * <p>
+	 * This method can be used as a replacement for {@link Map#entry(K, V)}, if the latter is not available (for example,
+	 * when compiling for TeaVM). However, unlike <code>Map.entry</code>, <code>null</code> keys and values are allowed,
+	 * and the returned <code>Entry</code> is serializable.
+	 *
+	 * @param key the key
+	 * @param value the value
+	 * @param <K> the key's type
+	 * @param <V> the value's type
+	 * @return an <code>Entry</code> containing the specified key and value
+	 */
+	public static <K, V> Map.Entry<K, V> entry(K key, V value) {
+		return new AbstractMap.SimpleImmutableEntry<>(key, value);
+	}
+}

core/src/main/resources/default-rules.lst

@@ -1,49 +0,0 @@
-functions/DivisionRule
-functions/EmptyNumberRule
-functions/ExpressionRule
-functions/JokeRule
-functions/MultiplicationRule
-functions/NegativeRule
-functions/NumberRule
-functions/PowerRule
-functions/RootRule
-functions/SubtractionRule
-functions/SumRule
-functions/SumSubtractionRule
-functions/VariableRule
-ExpandRule1
-ExpandRule2
-ExpandRule5
-ExponentRule1
-ExponentRule2
-ExponentRule3
-ExponentRule4
-ExponentRule8
-ExponentRule9
-ExponentRule15
-ExponentRule16
-ExponentRule17
-FractionsRule1
-FractionsRule2
-FractionsRule3
-FractionsRule4
-FractionsRule5
-FractionsRule6
-FractionsRule7
-FractionsRule8
-FractionsRule9
-FractionsRule10
-FractionsRule11
-FractionsRule12
-FractionsRule14
-NumberRule1
-NumberRule2
-NumberRule3
-NumberRule4
-NumberRule5
-NumberRule7
-UndefinedRule1
-UndefinedRule2
-VariableRule1
-VariableRule2
-VariableRule3

core/src/test/java/it/cavallium/warppi/AppTest.java

@@ -1,35 +0,0 @@
-package it.cavallium.warppi;
-
-import junit.framework.Assert;
-import junit.framework.Test;
-import junit.framework.TestCase;
-import junit.framework.TestSuite;
-
-/**
- * Unit test for simple App.
- */
-public class AppTest extends TestCase {
-	/**
-	 * Create the test case
-	 *
-	 * @param testName
-	 *            name of the test case
-	 */
-	public AppTest(final String testName) {
-		super(testName);
-	}
-
-	/**
-	 * @return the suite of tests being tested
-	 */
-	public static Test suite() {
-		return new TestSuite(AppTest.class);
-	}
-
-	/**
-	 * Rigourous Test :-)
-	 */
-	public void testApp() {
-		Assert.assertTrue(true);
-	}
-}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternRuleTest.java

@@ -0,0 +1,127 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.Subtraction;
+import it.cavallium.warppi.math.functions.Sum;
+import it.cavallium.warppi.math.functions.SumSubtraction;
+import it.cavallium.warppi.math.rules.RuleType;
+import it.cavallium.warppi.math.rules.dsl.patterns.*;
+import it.cavallium.warppi.util.Error;
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PatternRuleTest {
+	private final MathContext mathContext = new MathContext();
+
+	private final Pattern x = new SubFunctionPattern("x");
+	private final Pattern xPlus0 = new SumPattern(
+			x,
+			new NumberPattern(new BigDecimal(0))
+	);
+
+	@Test
+	void testNonMatching() throws InterruptedException, Error {
+		final Function func = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+
+		final PatternRule rule = new PatternRule("TestRule", RuleType.REDUCTION, xPlus0, xPlus0);
+		assertNull(func.simplify(rule));
+	}
+
+	@Test
+	void testMatching() throws InterruptedException, Error {
+		final Function func = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 0)
+		);
+
+		final PatternRule identityRule = new PatternRule("Identity", RuleType.REDUCTION, xPlus0, xPlus0);
+		final ObjectArrayList<Function> identityResult = func.simplify(identityRule);
+		assertEquals(1, identityResult.size());
+		assertEquals(func, identityResult.get(0));
+
+		final PatternRule simplifyRule = new PatternRule("Simplify", RuleType.REDUCTION, xPlus0, x);
+		final ObjectArrayList<Function> simplifyResult = func.simplify(simplifyRule);
+		assertEquals(1, identityResult.size());
+		assertEquals(new Number(mathContext, 1), simplifyResult.get(0));
+	}
+
+	@Test
+	void testMatchingRecursive() throws InterruptedException, Error {
+		final Function func = new Sum(
+				mathContext,
+				new Number(mathContext, 3),
+				new Sum(
+						mathContext,
+						new Number(mathContext, 5),
+						new Number(mathContext, 0)
+				)
+		);
+
+		final PatternRule identityRule = new PatternRule("Identity", RuleType.REDUCTION, xPlus0, xPlus0);
+		final ObjectArrayList<Function> identityResult = func.simplify(identityRule);
+		assertEquals(1, identityResult.size());
+		assertEquals(func, identityResult.get(0));
+
+		final PatternRule simplifyRule = new PatternRule("Simplify", RuleType.REDUCTION, xPlus0, x);
+		final ObjectArrayList<Function> simplifyResult = func.simplify(simplifyRule);
+		assertEquals(1, identityResult.size());
+		final Function expected = new Sum(
+				mathContext,
+				new Number(mathContext, 3),
+				new Number(mathContext, 5)
+		);
+		assertEquals(expected, simplifyResult.get(0));
+	}
+
+	@Test
+	void testMultipleReplacements() throws InterruptedException, Error {
+		final Number one = new Number(mathContext, 1);
+		final Number two = new Number(mathContext, 2);
+		final Function func = new SumSubtraction(mathContext, one, two);
+
+		final Pattern x = new SubFunctionPattern("x");
+		final Pattern y = new SubFunctionPattern("y");
+		@SuppressWarnings("SuspiciousNameCombination")
+		final PatternRule rule = new PatternRule(
+				"TestRule",
+				RuleType.EXPANSION,
+				new SumSubtractionPattern(x, y),
+				new SumPattern(x, y), new SubtractionPattern(x, y)
+		);
+
+		final ObjectArrayList<Function> result = func.simplify(rule);
+		final ObjectArrayList<Function> expected = ObjectArrayList.wrap(new Function[]{
+				new Sum(mathContext, one, two),
+				new Subtraction(mathContext, one, two)
+		});
+		assertEquals(expected, result);
+	}
+
+	@Test
+	void testNoReplacements() throws InterruptedException, Error {
+		final Function func = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+
+		final PatternRule rule = new PatternRule(
+				"TestRule",
+				RuleType.REDUCTION,
+				new SubFunctionPattern("x")
+		);
+
+		assertTrue(func.simplify(rule).isEmpty());
+	}
+}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternTest.java

@@ -0,0 +1,336 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.MathContext;
+import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.functions.*;
+import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.equations.Equation;
+import it.cavallium.warppi.math.functions.equations.EquationsSystem;
+import it.cavallium.warppi.math.functions.trigonometry.*;
+import it.cavallium.warppi.math.rules.dsl.patterns.*;
+import org.apache.commons.lang3.tuple.ImmutablePair;
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PatternTest {
+	private final MathContext mathContext = new MathContext();
+
+	@Test
+	void subFunctionPattern() {
+		final Pattern pattern = new SubFunctionPattern("x");
+
+		final Function func = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+
+		final Optional<Map<String, Function>> subFunctions = pattern.match(func);
+		assertTrue(subFunctions.isPresent());
+
+		assertEquals(func, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void undefinedSubFunction() {
+		final Pattern pattern = new SubFunctionPattern("x");
+		final Map<String, Function> subFunctions = Collections.singletonMap("y", new Number(mathContext, 1));
+
+		final var exception = assertThrows(UndefinedSubFunctionException.class, () ->
+			pattern.replace(mathContext, subFunctions)
+		);
+		assertEquals("x", exception.getSubFunctionName());
+	}
+
+	@Test
+	void sumPattern() {
+		final Pattern pattern = new SumPattern(
+				new SubFunctionPattern("x"),
+				new SubFunctionPattern("y")
+		);
+
+		final Function shouldNotMatch = new Subtraction(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void repeatedSubFunction() {
+		final Pattern pattern = new SumPattern(
+				new SubFunctionPattern("x"),
+				new SubFunctionPattern("x")
+		);
+
+		final Function shouldMatch = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 1)
+		);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+
+		final Function shouldNotMatch = new Sum(
+				mathContext,
+				new Number(mathContext, 1),
+				new Number(mathContext, 2)
+		);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+	}
+
+	@Test
+	void numberPattern() {
+		final Pattern pattern = new NumberPattern(BigDecimal.valueOf(Math.PI));
+
+		final Function shouldNotMatch = new Number(mathContext, 2);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Number(mathContext, Math.PI);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void negativePattern() {
+		final Pattern pattern = new NegativePattern(
+				new SubFunctionPattern("x")
+		);
+
+		final Function shouldNotMatch = new Number(mathContext, 1);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Negative(
+				mathContext,
+				new Variable(mathContext, 'x', Variable.V_TYPE.VARIABLE)
+		);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void negativePatternForNumber() {
+		final Pattern pattern = new NegativePattern(
+				new NumberPattern(new BigDecimal(1))
+		);
+
+		final Function shouldNotMatch = new Number(mathContext, 1);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Number(mathContext, -1);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void undefinedPattern() {
+		final Pattern pattern = new UndefinedPattern();
+
+		final Function shouldNotMatch = new Number(mathContext, 0);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Undefined(mathContext);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertTrue(pattern.replace(mathContext, subFunctions.get()) instanceof Undefined);
+	}
+
+	@Test
+	void equationsSystemPattern() {
+		final Pattern pattern = new EquationsSystemPattern(new Pattern[]{
+				new SubFunctionPattern("x"),
+				new SubFunctionPattern("y"),
+				new SubFunctionPattern("z")
+		});
+
+		final Function shouldNotMatch = new EquationsSystem(
+				mathContext,
+				new Function[]{
+						new Number(mathContext, 1),
+						new Number(mathContext, 2),
+				}
+		);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new EquationsSystem(
+				mathContext,
+				new Function[]{
+						new Number(mathContext, 1),
+						new Number(mathContext, 2),
+						new Number(mathContext, 3)
+				}
+		);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void rootPatternForRootSquare() {
+		final Pattern pattern = new RootPattern(
+				new SubFunctionPattern("x"),
+				new SubFunctionPattern("y")
+		);
+
+		final Function root = new Root(
+				mathContext,
+				new Number(mathContext, 2),
+				new Number(mathContext, 1)
+		);
+		final Optional<Map<String, Function>> rootSubFunctions = pattern.match(root);
+		assertTrue(rootSubFunctions.isPresent());
+
+		final Function rootSquare = new RootSquare(
+				mathContext,
+				new Number(mathContext, 1)
+		);
+		final Optional<Map<String, Function>> rootSquareSubFunctions = pattern.match(rootSquare);
+		assertTrue(rootSquareSubFunctions.isPresent());
+		assertEquals(rootSubFunctions.get(), rootSquareSubFunctions.get());
+
+		final Function replacement = pattern.replace(mathContext, rootSubFunctions.get());
+		assertTrue(replacement instanceof RootSquare);
+		assertEquals(rootSquare, replacement);
+	}
+
+	@Test
+	void constantPattern() {
+		final Pattern pattern = new ConstantPattern(MathematicalSymbols.PI);
+
+		final Function shouldNotMatch = new Variable(
+				mathContext,
+				MathematicalSymbols.EULER_NUMBER,
+				Variable.V_TYPE.CONSTANT
+		);
+		assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+		final Function shouldMatch = new Variable(
+				mathContext,
+				MathematicalSymbols.PI,
+				Variable.V_TYPE.CONSTANT
+		);
+		final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+		assertTrue(subFunctions.isPresent());
+		assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+	}
+
+	@Test
+	void otherBinaryPatterns() {
+		final Number one = new Number(mathContext, 1);
+		final Number two = new Number(mathContext, 2);
+		final SubFunctionPattern x = new SubFunctionPattern("x");
+		final SubFunctionPattern y = new SubFunctionPattern("y");
+
+		final Function shouldNotMatch = new Sum(mathContext, one, two);
+
+		@SuppressWarnings("SuspiciousNameCombination")
+		final List<ImmutablePair<Pattern, Function>> patternsAndMatchingFunctions = Arrays.asList(
+				new ImmutablePair<>(
+						new DivisionPattern(x, y),
+						new Division(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new EquationPattern(x, y),
+						new Equation(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new LogarithmPattern(x, y),
+						new Logarithm(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new MultiplicationPattern(x, y),
+						new Multiplication(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new PowerPattern(x, y),
+						new Power(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new RootPattern(x, y),
+						new Root(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new SubtractionPattern(x, y),
+						new Subtraction(mathContext, one, two)
+				),
+				new ImmutablePair<>(
+						new SumSubtractionPattern(x, y),
+						new SumSubtraction(mathContext, one, two)
+				)
+		);
+
+		testMultiplePatterns(shouldNotMatch, patternsAndMatchingFunctions);
+	}
+
+	@Test
+	void otherUnaryPatterns() {
+		final Number one = new Number(mathContext, 1);
+		final SubFunctionPattern x = new SubFunctionPattern("x");
+
+		final Function shouldNotMatch = new Negative(mathContext, one);
+
+		final List<ImmutablePair<Pattern, Function>> patternsAndMatchingFunctions = Arrays.asList(
+				new ImmutablePair<>(
+						new ArcCosinePattern(x),
+						new ArcCosine(mathContext, one)
+				),
+				new ImmutablePair<>(
+						new ArcSinePattern(x),
+						new ArcSine(mathContext, one)
+				),
+				new ImmutablePair<>(
+						new ArcTangentPattern(x),
+						new ArcTangent(mathContext, one)
+				),
+				new ImmutablePair<>(
+						new CosinePattern(x),
+						new Cosine(mathContext, one)
+				),
+				new ImmutablePair<>(
+						new SinePattern(x),
+						new Sine(mathContext, one)
+				),
+				new ImmutablePair<>(
+						new TangentPattern(x),
+						new Tangent(mathContext, one)
+				)
+		);
+
+		testMultiplePatterns(shouldNotMatch, patternsAndMatchingFunctions);
+	}
+
+	private void testMultiplePatterns(
+			final Function shouldNotMatch,
+			final List<ImmutablePair<Pattern, Function>> patternsAndMatchingFunctions
+	) {
+		for (final ImmutablePair<Pattern, Function> patternAndMatchingFunction : patternsAndMatchingFunctions) {
+			final Pattern pattern = patternAndMatchingFunction.getLeft();
+			final Function shouldMatch = patternAndMatchingFunction.getRight();
+
+			assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+			final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+			assertTrue(subFunctions.isPresent());
+			assertEquals(shouldMatch, pattern.replace(mathContext, subFunctions.get()));
+		}
+	}
+}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/RulesDslTest.java

@@ -0,0 +1,92 @@
+package it.cavallium.warppi.math.rules.dsl;
+
+import it.cavallium.warppi.math.rules.Rule;
+import it.cavallium.warppi.math.rules.RuleType;
+import it.cavallium.warppi.math.rules.dsl.frontend.IncompleteNumberLiteral;
+import it.cavallium.warppi.math.rules.dsl.frontend.Token;
+import it.cavallium.warppi.math.rules.dsl.frontend.TokenType;
+import it.cavallium.warppi.math.rules.dsl.frontend.UnexpectedToken;
+import it.cavallium.warppi.math.rules.dsl.patterns.NegativePattern;
+import it.cavallium.warppi.math.rules.dsl.patterns.NumberPattern;
+import it.cavallium.warppi.math.rules.dsl.patterns.SubFunctionPattern;
+import it.cavallium.warppi.math.rules.dsl.patterns.SumPattern;
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class RulesDslTest {
+	@Test
+	void validRules() throws DslAggregateException {
+		final List<Rule> rules = RulesDsl.makeRules(
+				"reduction test1: x -> x\n" +
+				"expansion test2:\n" +
+				"  x -> --x\n" +
+				"calculation test3:\n" +
+				"  1 + 1 -> 2\n"
+		);
+
+		final List<Rule> expected = Arrays.asList(
+				new PatternRule(
+						"test1",
+						RuleType.REDUCTION,
+						new SubFunctionPattern("x"),
+						new SubFunctionPattern("x")
+				),
+				new PatternRule(
+						"test2",
+						RuleType.EXPANSION,
+						new SubFunctionPattern("x"),
+						new NegativePattern(new NegativePattern(new SubFunctionPattern("x")))
+				),
+				new PatternRule(
+						"test3",
+						RuleType.CALCULATION,
+						new SumPattern(
+								new NumberPattern(new BigDecimal(1)),
+								new NumberPattern(new BigDecimal(1))
+						),
+						new NumberPattern(new BigDecimal(2))
+				)
+		);
+
+		assertEquals(expected, rules);
+	}
+
+	@Test
+	void lexerError() {
+		final var exception = assertThrows(DslAggregateException.class, () ->
+			RulesDsl.makeRules("reduction test: 2. 5 -> 1")
+		);
+		final var expectedErrors = Collections.singletonList(
+			new IncompleteNumberLiteral(16, "2.")
+		);
+		assertEquals(expectedErrors, exception.getErrors());
+	}
+
+	@Test
+	void parserError() {
+		final var exception = assertThrows(DslAggregateException.class, () ->
+			RulesDsl.makeRules("existence test: x + y ->")
+		);
+		final var expectedErrors = Collections.singletonList(
+			new UnexpectedToken(new Token(TokenType.EOF, "", 24))
+		);
+		assertEquals(expectedErrors, exception.getErrors());
+	}
+
+	@Test
+	void undefinedSubFunction() {
+		final var exception = assertThrows(DslAggregateException.class, () ->
+			RulesDsl.makeRules("expansion test: x -> x + y")
+		);
+		final var expectedErrors = Collections.singletonList(
+			new UndefinedSubFunction(new Token(TokenType.IDENTIFIER, "y", 25))
+		);
+		assertEquals(expectedErrors, exception.getErrors());
+	}
+}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/errorutils/LineMapTest.java

@@ -0,0 +1,141 @@
+package it.cavallium.warppi.math.rules.dsl.errorutils;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class LineMapTest {
+	@Test
+	void emptyText() {
+		String text = "";
+		LineMap map = new LineMap(text);
+
+		assertEquals(Collections.emptyList(), map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void noLineSeparators() {
+		String text = "single line";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, text)
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void trailingLf() {
+		String text = "single line\n";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "single line")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void trailingCr() {
+		String text = "single line\r";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "single line")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void trailingCrLf() {
+		String text = "single line\r\n";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "single line")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void multipleNonEmptyLines() {
+		String text = "line 1\nline 2\rline 3\r\nline 4";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Arrays.asList(
+			new LineMap.Line(1, 0, "line 1"),
+			new LineMap.Line(2, 7, "line 2"),
+			new LineMap.Line(3, 14, "line 3"),
+			new LineMap.Line(4, 22, "line 4")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void singleEmptyLine() {
+		String text = "\n";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void multipleEmptyLines() {
+		String text = "\r\n\n\r";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Arrays.asList(
+			new LineMap.Line(1, 0, ""), // Terminated by \r\n
+			new LineMap.Line(2, 2, ""), // Terminated by \n
+			new LineMap.Line(3, 3, "") // Terminated by \r
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void mixedEmptyAndNonEmptyLines() {
+		String text = "line 1\nline 2\r\r\nline 4\n\n";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Arrays.asList(
+			new LineMap.Line(1, 0, "line 1"),
+			new LineMap.Line(2, 7, "line 2"),
+			new LineMap.Line(3, 14, ""),
+			new LineMap.Line(4, 16, "line 4"),
+			new LineMap.Line(5, 23, "")
+		);
+		assertEquals(expected, map.getSpannedLines(0, text.length()));
+	}
+
+	@Test
+	void emptySubstrings() {
+		String text = "single line\n";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "single line")
+		);
+		for (int start = 0; start <= text.length(); start++) {
+			assertEquals(expected, map.getSpannedLines(start, 0));
+		}
+	}
+
+	@Test
+	void substringIsJustLineSeparator() {
+		String separator = "\n";
+		String text = "line 1" + separator + "line 2";
+		LineMap map = new LineMap(text);
+
+		List<LineMap.Line> expected = Collections.singletonList(
+			new LineMap.Line(1, 0, "line 1")
+		);
+		assertEquals(expected, map.getSpannedLines(text.indexOf(separator), separator.length()));
+	}
+}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/frontend/LexerTest.java

@@ -0,0 +1,178 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.rules.dsl.DslError;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static it.cavallium.warppi.math.rules.dsl.frontend.TokenType.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+class LexerTest {
+	private final List<DslError> errors = new ArrayList<>();
+
+	@BeforeEach
+	void setUp() {
+		errors.clear();
+	}
+
+	@Test
+	void emptyInput() {
+		final Lexer lexer = new Lexer("", errors::add);
+		final List<Token> expected = Collections.singletonList(
+			new Token(EOF, "", 0)
+		);
+		assertEquals(expected, lexer.lex());
+	}
+
+	@Test
+	void multipleLexCalls() {
+		final Lexer lexer = new Lexer("", errors::add);
+		lexer.lex();
+		assertThrows(IllegalStateException.class, lexer::lex);
+	}
+
+	@Test
+	void validRule() {
+		final Lexer lexer = new Lexer(
+				"reduction TestRule_123:\n" +
+				"  x + y * z = -(a_123 +- 3 / 2.2) -> [\n" +
+				"    x^a_123 = cos(pi) - log(e, e), // comment\n" +
+				"    undefined, /*\n" +
+				"comment */ ]\n",
+				errors::add
+		);
+		final List<Token> expected = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "TestRule_123", 10),
+				new Token(COLON, ":", 22),
+				new Token(IDENTIFIER, "x", 26),
+				new Token(PLUS, "+", 28),
+				new Token(IDENTIFIER, "y", 30),
+				new Token(TIMES, "*", 32),
+				new Token(IDENTIFIER, "z", 34),
+				new Token(EQUALS, "=", 36),
+				new Token(MINUS, "-", 38),
+				new Token(LEFT_PAREN, "(", 39),
+				new Token(IDENTIFIER, "a_123", 40),
+				new Token(PLUS_MINUS, "+-", 46),
+				new Token(NUMBER, "3", 49),
+				new Token(DIVIDE, "/", 51),
+				new Token(NUMBER, "2.2", 53),
+				new Token(RIGHT_PAREN, ")", 56),
+				new Token(ARROW, "->", 58),
+				new Token(LEFT_BRACKET, "[", 61),
+				new Token(IDENTIFIER, "x", 67),
+				new Token(POWER, "^", 68),
+				new Token(IDENTIFIER, "a_123", 69),
+				new Token(EQUALS, "=", 75),
+				new Token(COS, "cos", 77),
+				new Token(LEFT_PAREN, "(", 80),
+				new Token(PI, "pi", 81),
+				new Token(RIGHT_PAREN, ")", 83),
+				new Token(MINUS, "-", 85),
+				new Token(LOG, "log", 87),
+				new Token(LEFT_PAREN, "(", 90),
+				new Token(E, "e", 91),
+				new Token(COMMA, ",", 92),
+				new Token(E, "e", 94),
+				new Token(RIGHT_PAREN, ")", 95),
+				new Token(COMMA, ",", 96),
+				new Token(UNDEFINED, "undefined", 113),
+				new Token(COMMA, ",", 122),
+				new Token(RIGHT_BRACKET, "]", 138),
+				new Token(EOF, "", 140)
+		);
+		assertEquals(expected, lexer.lex());
+		assertTrue(errors.isEmpty());
+	}
+
+	@Test
+	void incompleteNumberOtherChar() {
+		final Lexer lexer = new Lexer("2. 5 + 3", errors::add);
+
+		final List<Token> expectedTokens = Arrays.asList(
+				new Token(NUMBER, "5", 3),
+				new Token(PLUS, "+", 5),
+				new Token(NUMBER, "3", 7),
+				new Token(EOF, "", 8)
+		);
+		assertEquals(expectedTokens, lexer.lex());
+
+		final List<DslError> expectedErrors = Collections.singletonList(
+				new IncompleteNumberLiteral(0, "2.")
+		);
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void incompleteNumberEof() {
+		final Lexer lexer = new Lexer("2.", errors::add);
+
+		final List<Token> expectedTokens = Collections.singletonList(
+				new Token(EOF, "", 2)
+		);
+		assertEquals(expectedTokens, lexer.lex());
+
+		final List<DslError> expectedErrors = Collections.singletonList(
+				new IncompleteNumberLiteral(0, "2.")
+		);
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void unexpectedCharacters() {
+		final Lexer lexer = new Lexer("reduction @| .: {}", errors::add);
+
+		final List<Token> expectedTokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(COLON, ":", 14),
+				new Token(EOF, "", 18)
+		);
+		assertEquals(expectedTokens, lexer.lex());
+
+		final List<DslError> expectedErrors = Arrays.asList(
+				new UnexpectedCharacters(10, "@|"),
+				new UnexpectedCharacters(13, "."),
+				new UnexpectedCharacters(16, "{}")
+		);
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void unterminatedComment() {
+		final Lexer lexer = new Lexer("reduction /* test:\n x -> x", errors::add);
+
+		final List<Token> expectedTokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(EOF, "", 26)
+		);
+		assertEquals(expectedTokens, lexer.lex());
+
+		final List<DslError> expectedErrors = Collections.singletonList(
+				new UnterminatedComment(10)
+		);
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void errorOrder() {
+		final Lexer lexer = new Lexer(".2. @", errors::add);
+
+		final List<Token> expectedTokens = Collections.singletonList(
+				new Token(EOF, "", 5)
+		);
+		assertEquals(expectedTokens, lexer.lex());
+
+		final List<DslError> expectedErrors = Arrays.asList(
+				new UnexpectedCharacters(0, "."),
+				new IncompleteNumberLiteral(1, "2."),
+				new UnexpectedCharacters(4, "@")
+		);
+		assertEquals(expectedErrors, errors);
+	}
+}

core/src/test/java/it/cavallium/warppi/math/rules/dsl/frontend/ParserTest.java

@@ -0,0 +1,780 @@
+package it.cavallium.warppi.math.rules.dsl.frontend;
+
+import it.cavallium.warppi.math.MathematicalSymbols;
+import it.cavallium.warppi.math.rules.RuleType;
+import it.cavallium.warppi.math.rules.dsl.DslError;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.PatternRule;
+import it.cavallium.warppi.math.rules.dsl.patterns.*;
+import org.apache.commons.lang3.ObjectUtils;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static it.cavallium.warppi.math.rules.dsl.frontend.TokenType.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+class ParserTest {
+	private final List<DslError> errors = new ArrayList<>();
+
+	@BeforeEach
+	void setUp() {
+		errors.clear();
+	}
+
+	@Test
+	void noRules() {
+		final List<Token> tokens = Collections.singletonList(
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+		assertEquals(Collections.emptyList(), parser.parse());
+	}
+
+	@Test
+	void multipleParseCalls() {
+		final List<Token> tokens = Collections.singletonList(
+			new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+		parser.parse();
+		assertThrows(IllegalStateException.class, parser::parse);
+	}
+
+	@Test
+	void validRuleMultipleReplacements() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "TestRule_123", 10),
+				new Token(COLON, ":", 22),
+				new Token(IDENTIFIER, "x", 26),
+				new Token(PLUS, "+", 28),
+				new Token(IDENTIFIER, "y", 30),
+				new Token(TIMES, "*", 32),
+				new Token(IDENTIFIER, "z", 34),
+				new Token(EQUALS, "=", 36),
+				new Token(MINUS, "-", 38),
+				new Token(LEFT_PAREN, "(", 39),
+				new Token(IDENTIFIER, "a_123", 40),
+				new Token(PLUS_MINUS, "+-", 46),
+				new Token(NUMBER, "3", 49),
+				new Token(DIVIDE, "/", 51),
+				new Token(NUMBER, "2.2", 53),
+				new Token(RIGHT_PAREN, ")", 56),
+				new Token(ARROW, "->", 58),
+				new Token(LEFT_BRACKET, "[", 61),
+				new Token(IDENTIFIER, "x", 67),
+				new Token(POWER, "^", 68),
+				new Token(IDENTIFIER, "a_123", 69),
+				new Token(EQUALS, "=", 75),
+				new Token(COS, "cos", 77),
+				new Token(LEFT_PAREN, "(", 80),
+				new Token(PI, "pi", 81),
+				new Token(RIGHT_PAREN, ")", 83),
+				new Token(MINUS, "-", 85),
+				new Token(LOG, "log", 87),
+				new Token(LEFT_PAREN, "(", 90),
+				new Token(E, "e", 91),
+				new Token(COMMA, ",", 92),
+				new Token(E, "e", 94),
+				new Token(RIGHT_PAREN, ")", 95),
+				new Token(COMMA, ",", 96),
+				new Token(UNDEFINED, "undefined", 113),
+				new Token(COMMA, ",", 122),
+				new Token(RIGHT_BRACKET, "]", 138),
+				new Token(EOF, "", 140)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		// x + y * z = -(a_123 +- 3 / 2.2)
+		final Pattern target = new EquationPattern(
+				new SumPattern(
+						new SubFunctionPattern("x"),
+						new MultiplicationPattern(
+								new SubFunctionPattern("y"),
+								new SubFunctionPattern("z")
+						)
+				),
+				new NegativePattern(new SumSubtractionPattern(
+						new SubFunctionPattern("a_123"),
+						new DivisionPattern(
+								new NumberPattern(new BigDecimal(3)),
+								new NumberPattern(new BigDecimal("2.2"))
+						)
+				))
+		);
+		// x^a_123 = cos(pi) - log(e, e)
+		final Pattern replacement1 = new EquationPattern(
+				new PowerPattern(
+						new SubFunctionPattern("x"),
+						new SubFunctionPattern("a_123")
+				),
+				new SubtractionPattern(
+						new CosinePattern(new ConstantPattern(MathematicalSymbols.PI)),
+						new LogarithmPattern(
+								new ConstantPattern(MathematicalSymbols.EULER_NUMBER),
+								new ConstantPattern(MathematicalSymbols.EULER_NUMBER)
+						)
+				)
+		);
+		final Pattern replacement2 = new UndefinedPattern();
+		final List<PatternRule> expected = Collections.singletonList(new PatternRule(
+				"TestRule_123",
+				RuleType.REDUCTION,
+				target,
+				replacement1,
+				replacement2
+		));
+
+		assertEquals(expected, parser.parse());
+	}
+
+	@Test
+	void validRuleNoReplacements() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(PLUS, "+", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		final List<PatternRule> expected = Collections.singletonList(new PatternRule(
+				"test",
+				RuleType.EXISTENCE,
+				new SumPattern(
+						new SubFunctionPattern("x"),
+						new SubFunctionPattern("y")
+				)
+		));
+		assertEquals(expected, parser.parse());
+	}
+
+	@Test
+	void validRuleOneReplacement() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(MINUS, "-", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(TIMES, "*", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(MINUS, "-", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(POWER, "^", 0),
+				new Token(NUMBER, "2", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		final List<PatternRule> expected = Collections.singletonList(new PatternRule(
+				"test",
+				RuleType.REDUCTION,
+				new MultiplicationPattern(
+						new NegativePattern(new SubFunctionPattern("x")),
+						new SubFunctionPattern("x")
+				),
+				new NegativePattern(new PowerPattern(
+						new SubFunctionPattern("x"),
+						new NumberPattern(new BigDecimal(2))
+				))
+		));
+		assertEquals(expected, parser.parse());
+	}
+
+	@Test
+	void validRuleOneReplacementBrackets() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(DIVIDE, "/", 0),
+				new Token(LEFT_PAREN, "(", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(TIMES, "*", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(RIGHT_PAREN, ")", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(POWER, "^", 0),
+				new Token(MINUS, "-", 0),
+				new Token(NUMBER, "2", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		final List<PatternRule> expected = Collections.singletonList(new PatternRule(
+				"test",
+				RuleType.REDUCTION,
+				new DivisionPattern(
+						new NumberPattern(new BigDecimal(1)),
+						new MultiplicationPattern(
+								new SubFunctionPattern("x"),
+								new SubFunctionPattern("x")
+						)
+				),
+				new PowerPattern(
+						new SubFunctionPattern("x"),
+						new NegativePattern(
+								new NumberPattern(new BigDecimal(2))
+						)
+				)
+		));
+		assertEquals(expected, parser.parse());
+	}
+
+	@Test
+	void multipleValidRules() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test1", 0),
+				new Token(COLON, ":", 0),
+				new Token(PLUS, "+", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(IDENTIFIER, "x", 0),
+
+				new Token(EXPANSION, "expansion", 0),
+				new Token(IDENTIFIER, "test2", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(MINUS, "-", 0),
+				new Token(MINUS, "-", 0),
+				new Token(IDENTIFIER, "x", 0),
+
+				new Token(CALCULATION, "calculation", 0),
+				new Token(IDENTIFIER, "test3", 0),
+				new Token(COLON, ":", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(PLUS, "+", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(ARROW, "->", 0),
+				new Token(NUMBER, "2", 0),
+
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		final List<PatternRule> expected = Arrays.asList(
+				new PatternRule(
+						"test1",
+						RuleType.REDUCTION,
+						new SubFunctionPattern("x"),
+						new SubFunctionPattern("x")
+				),
+				new PatternRule(
+						"test2",
+						RuleType.EXPANSION,
+						new SubFunctionPattern("x"),
+						new NegativePattern(new NegativePattern(new SubFunctionPattern("x")))
+				),
+				new PatternRule(
+						"test3",
+						RuleType.CALCULATION,
+						new SumPattern(
+								new NumberPattern(new BigDecimal(1)),
+								new NumberPattern(new BigDecimal(1))
+						),
+						new NumberPattern(new BigDecimal(2))
+				)
+		);
+		assertEquals(expected, parser.parse());
+	}
+
+	@Test
+	void subFunctionIdentifiers() {
+		final List<ReferenceEqualityToken> rule0x = new ArrayList<>();
+		final List<ReferenceEqualityToken> rule1x = new ArrayList<>();
+		final List<ReferenceEqualityToken> rule1y = new ArrayList<>();
+		final List<ReferenceEqualityToken> rule2x = new ArrayList<>();
+		final List<ReferenceEqualityToken> rule3x = new ArrayList<>();
+
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test1", 0),
+				new Token(COLON, ":", 0),
+				new Token(PLUS, "+", 0),
+				addIdentifierToken(rule0x, "x"),
+				new Token(ARROW, "->", 0),
+				addIdentifierToken(rule0x, "x"),
+
+				new Token(EXPANSION, "expansion", 0),
+				new Token(IDENTIFIER, "test2", 0),
+				new Token(COLON, ":", 0),
+				addIdentifierToken(rule1x, "x"),
+				new Token(POWER, "^", 0),
+				new Token(MINUS, "-", 0),
+				addIdentifierToken(rule1y, "y"),
+				new Token(ARROW, "->", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(DIVIDE, "/", 0),
+				addIdentifierToken(rule1x, "x"),
+				new Token(POWER, "^", 0),
+				addIdentifierToken(rule1y, "y"),
+
+				// Rule with the same name (and type)
+				new Token(CALCULATION, "expansion", 0),
+				new Token(IDENTIFIER, "test2", 0),
+				new Token(COLON, ":", 0),
+				addIdentifierToken(rule2x, "x"),
+				new Token(ARROW, "->", 0),
+				addIdentifierToken(rule2x, "x"),
+				new Token(PLUS, "+", 0),
+				new Token(NUMBER, "0", 0),
+
+				// Identical rule
+				new Token(CALCULATION, "expansion", 0),
+				new Token(IDENTIFIER, "test2", 0),
+				new Token(COLON, ":", 0),
+				addIdentifierToken(rule3x, "x"),
+				new Token(ARROW, "->", 0),
+				addIdentifierToken(rule3x, "x"),
+				new Token(PLUS, "+", 0),
+				new Token(NUMBER, "0", 0),
+
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+		final List<PatternRule> rules = parser.parse();
+
+		assertEquals(rule0x, getSubFunctionIdentifiers(parser, rules.get(0), "x"));
+		assertEquals(rule1x, getSubFunctionIdentifiers(parser, rules.get(1), "x"));
+		assertEquals(rule1y, getSubFunctionIdentifiers(parser, rules.get(1), "y"));
+		assertEquals(rule2x, getSubFunctionIdentifiers(parser, rules.get(2), "x"));
+		assertEquals(rule3x, getSubFunctionIdentifiers(parser, rules.get(3), "x"));
+	}
+
+	private static Token addIdentifierToken(final List<ReferenceEqualityToken> list, final String identifier) {
+		final Token token = new Token(IDENTIFIER, identifier, 0);
+		list.add(new ReferenceEqualityToken(token));
+		return token;
+	}
+
+	private static List<ReferenceEqualityToken> getSubFunctionIdentifiers(
+		final Parser parser,
+		final PatternRule rule,
+		final String subFunctionName
+	) {
+		final SubFunctionPattern exampleSubFunction = new SubFunctionPattern(subFunctionName);
+		final Stream<SubFunctionPattern> allSubFunctions = Stream.concat(
+			rule.getTarget().getSubFunctions(),
+			rule.getReplacements().stream().flatMap(Pattern::getSubFunctions)
+		);
+		return allSubFunctions
+			.filter(subFunc -> subFunc.equals(exampleSubFunction)) // Match the name without having access to it directly
+			.map(subFunc -> new ReferenceEqualityToken(
+				parser.getSubFunctionIdentifier(subFunc)
+			))
+			.collect(Collectors.toList());
+	}
+
+	private static class ReferenceEqualityToken {
+		private final Token token;
+
+		ReferenceEqualityToken(final Token token) {
+			this.token = token;
+		}
+
+		@Override
+		public boolean equals(final Object o) {
+			if (!(o instanceof ReferenceEqualityToken)) {
+				return false;
+			}
+			return this.token == ((ReferenceEqualityToken) o).token;
+		}
+
+		@Override
+		public String toString() {
+			return "ReferenceEqualityToken{" + ObjectUtils.identityToString(token) + '}';
+		}
+	}
+
+	// The EOF token is inserted by the lexer, therefore it can only be missing
+	// in case of programming errors, and not directly because of user input.
+	@Test
+	void missingEof() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(PLUS, "+", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+		assertThrows(RuntimeException.class, parser::parse);
+	}
+
+	@Test
+	void incompleteRule() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(PLUS, "+", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(ARROW, "->", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(EOF, "", 0)
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingRuleType() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(IDENTIFIER, "test", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "test", 0),
+				REDUCTION, EXPANSION, CALCULATION, EXISTENCE
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void unexpectedTokenPrimary() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(PLUS, "+", 0),
+				new Token(CALCULATION, "calculation", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(CALCULATION, "calculation", 0)
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingRuleName() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(COLON, ":", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(COLON, ":", 0),
+				IDENTIFIER
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingColon() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "x", 0),
+				COLON
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingArrow() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "y", 0),
+				ARROW
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingRightBracket() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(EOF, "", 0),
+				RIGHT_BRACKET
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingOneArgFunctionLeftParen() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(SIN, "sin", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(RIGHT_PAREN, ")", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "x", 0),
+				LEFT_PAREN
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingOneArgFunctionRightParen() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(SIN, "sin", 0),
+				new Token(LEFT_PAREN, "(", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(ARROW, "->", 0),
+				RIGHT_PAREN
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingTwoArgFunctionLeftParen() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(LOG, "log", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(COMMA, ",", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(RIGHT_PAREN, ")", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "x", 0),
+				LEFT_PAREN
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingTwoArgFunctionComma() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(LOG, "log", 0),
+				new Token(LEFT_PAREN, "(", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(RIGHT_PAREN, ")", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(IDENTIFIER, "y", 0),
+				COMMA
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingTwoArgFunctionRightParen() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(LOG, "log", 0),
+				new Token(LEFT_PAREN, "(", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(COMMA, ",", 0),
+				new Token(IDENTIFIER, "y", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(ARROW, "->", 0),
+				RIGHT_PAREN
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void missingExpressionRightParen() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(EXISTENCE, "existence", 0),
+				new Token(IDENTIFIER, "test", 0),
+				new Token(COLON, ":", 0),
+				new Token(LEFT_PAREN, "(", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(LEFT_BRACKET, "[", 0),
+				new Token(RIGHT_BRACKET, "]", 0),
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		assertTrue(parser.parse().isEmpty());
+
+		final List<DslError> expectedErrors = Collections.singletonList(new UnexpectedToken(
+				new Token(ARROW, "->", 0),
+				RIGHT_PAREN
+		));
+		assertEquals(expectedErrors, errors);
+	}
+
+	@Test
+	void recoveryToNextRule() {
+		final List<Token> tokens = Arrays.asList(
+				new Token(REDUCTION, "reduction", 0),
+				new Token(IDENTIFIER, "test1", 0),
+				new Token(COLON, ":", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(TIMES, "+", 0),
+				new Token(ARROW, "->", 0),
+				new Token(IDENTIFIER, "x", 0),
+
+				new Token(EXPANSION, "expansion", 0),
+				new Token(IDENTIFIER, "test2", 0),
+				new Token(IDENTIFIER, "x", 0),
+				new Token(ARROW, "->", 0),
+				new Token(MINUS, "-", 0),
+				new Token(MINUS, "-", 0),
+				new Token(IDENTIFIER, "x", 0),
+
+				new Token(CALCULATION, "calculation", 0),
+				new Token(IDENTIFIER, "test3", 0),
+				new Token(COLON, ":", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(PLUS, "+", 0),
+				new Token(NUMBER, "1", 0),
+				new Token(ARROW, "->", 0),
+				new Token(NUMBER, "2", 0),
+
+				new Token(EOF, "", 0)
+		);
+		final Parser parser = new Parser(tokens, errors::add);
+
+		final List<PatternRule> expectedRules = Collections.singletonList(new PatternRule(
+				"test3",
+				RuleType.CALCULATION,
+				new SumPattern(
+						new NumberPattern(new BigDecimal(1)),
+						new NumberPattern(new BigDecimal(1))
+				),
+				new NumberPattern(new BigDecimal(2))
+		));
+		assertEquals(expectedRules, parser.parse());
+
+		final List<DslError> expectedErrors = Arrays.asList(
+				new UnexpectedToken(new Token(ARROW, "->", 0)),
+				new UnexpectedToken(new Token(IDENTIFIER, "x", 0), COLON)
+		);
+		assertEquals(expectedErrors, errors);
+	}
+}

desktop/pom.xml

@@ -28,16 +28,6 @@
 			<artifactId>jansi</artifactId>
 			<version>1.17.1</version>
 		</dependency>
-		<dependency>
-			<groupId>net.lingala.zip4j</groupId>
-			<artifactId>zip4j</artifactId>
-			<version>1.3.2</version>
-		</dependency>
-		<dependency>
-			<groupId>org.eclipse.tycho</groupId>
-			<artifactId>org.eclipse.jdt.core</artifactId>
-			<version>3.14.0.v20171206-0802</version>
-		</dependency>
 		<dependency>
 			<groupId>ar.com.hjg</groupId>
 			<artifactId>pngj</artifactId>

desktop/src/main/java/it/cavallium/warppi/desktop/DesktopPlatform.java

@@ -5,7 +5,9 @@ import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.net.URL;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.commons.io.FileUtils;
@@ -17,9 +19,6 @@ import it.cavallium.warppi.gui.graphicengine.impl.jogl.JOGLEngine;
 import it.cavallium.warppi.gui.graphicengine.impl.swing.SwingEngine;
 import it.cavallium.warppi.util.CacheUtils;
 import it.cavallium.warppi.util.Error;
-import net.lingala.zip4j.core.ZipFile;
-import net.lingala.zip4j.model.ZipParameters;
-import net.lingala.zip4j.util.Zip4jConstants;
 
 public class DesktopPlatform implements Platform {
 
@@ -157,53 +156,18 @@ public class DesktopPlatform implements Platform {
 	}
 
 	@Override
-	public void loadPlatformRules() {
-
-	}
-
-	@Override
-	public void zip(final String targetPath, final String destinationFilePath, final String password) {
-		try {
-			final ZipParameters parameters = new ZipParameters();
-			parameters.setCompressionMethod(Zip4jConstants.COMP_DEFLATE);
-			parameters.setCompressionLevel(Zip4jConstants.DEFLATE_LEVEL_NORMAL);
-
-			if (password.length() > 0) {
-				parameters.setEncryptFiles(true);
-				parameters.setEncryptionMethod(Zip4jConstants.ENC_METHOD_AES);
-				parameters.setAesKeyStrength(Zip4jConstants.AES_STRENGTH_256);
-				parameters.setPassword(password);
+	public List<String> getRuleFilePaths() throws IOException {
+		final File dslRulesPath = getStorageUtils().get("rules/");
+		List<String> paths = new ArrayList<>();
+		if (dslRulesPath.exists()) {
+			for (final File file : getStorageUtils().walk(dslRulesPath)) {
+				final String path = file.toString();
+				if (path.endsWith(".rules")) {
+					paths.add(path);
+				}
 			}
-
-			final ZipFile zipFile = new ZipFile(destinationFilePath);
-
-			final File targetFile = new File(targetPath);
-			if (targetFile.isFile())
-				zipFile.addFile(targetFile, parameters);
-			else if (targetFile.isDirectory())
-				zipFile.addFolder(targetFile, parameters);
-
-		} catch (final Exception e) {
-			e.printStackTrace();
 		}
-	}
-
-	@Override
-	public void unzip(final String targetZipFilePath, final String destinationFolderPath, final String password) {
-		try {
-			final ZipFile zipFile = new ZipFile(targetZipFilePath);
-			if (zipFile.isEncrypted())
-				zipFile.setPassword(password);
-			zipFile.extractAll(destinationFolderPath);
-
-		} catch (final Exception e) {
-			e.printStackTrace();
-		}
-	}
-
-	@Override
-	public boolean compile(final String[] command, final PrintWriter printWriter, final PrintWriter errors) {
-		return org.eclipse.jdt.internal.compiler.batch.Main.compile(command, printWriter, errors, null);
+		return paths;
 	}
 
 	@Override