Multiple result support, Plus-Minus sign

src/org/warp/device/Keyboard.java

@@ -130,7 +130,7 @@ public class Keyboard {
 			if (shift) {
 				keyPressed(Key.NONE);
 			} else if (alpha) {
-				keyPressed(Key.NONE);
+				keyPressed(Key.LETTER_Y);
 			} else {
 				keyPressed(Key.DOT);
 			}
@@ -138,7 +138,7 @@ public class Keyboard {
 			if (shift) {
 				keyPressed(Key.NONE);
 			} else if (alpha) {
-				keyPressed(Key.NONE);
+				keyPressed(Key.LETTER_X);
 			} else {
 				keyPressed(Key.NUM0);
 			}
@@ -216,7 +216,7 @@ public class Keyboard {
 			}
 		} else if (row == 8 && col == 4) {
 			if (shift) {
-				keyPressed(Key.NONE);
+				keyPressed(Key.PLUS_MINUS);
 			} else if (alpha) {
 				keyPressed(Key.NONE);
 			} else {
@@ -484,7 +484,7 @@ public class Keyboard {
 	}
 
 	public static enum Key {
-		POWER, debug_DEG, debug_RAD, debug_GRA, SHIFT, ALPHA, NONE, HISTORY_BACK, HISTORY_FORWARD, DRG_CYCLE, LETTER_X, SIMPLIFY, SOLVE, BRIGHTNESS_CYCLE, BRIGHTNESS_CYCLE_REVERSE, DOT, NUM0, NUM1, NUM2, NUM3, NUM4, NUM5, NUM6, NUM7, NUM8, NUM9, PARENTHESIS_OPEN, PARENTHESIS_CLOSE, PLUS, MINUS, MULTIPLY, DIVIDE, EQUAL, DELETE, RESET, LEFT, RIGHT, UP, DOWN, OK, debug1, debug2, debug3, debug4, debug5, SQRT, ROOT, POWER_OF_2, POWER_OF_x
+		POWER, debug_DEG, debug_RAD, debug_GRA, SHIFT, ALPHA, NONE, HISTORY_BACK, HISTORY_FORWARD, DRG_CYCLE, LETTER_X, LETTER_Y, SIMPLIFY, SOLVE, BRIGHTNESS_CYCLE, BRIGHTNESS_CYCLE_REVERSE, DOT, NUM0, NUM1, NUM2, NUM3, NUM4, NUM5, NUM6, NUM7, NUM8, NUM9, PARENTHESIS_OPEN, PARENTHESIS_CLOSE, PLUS, MINUS, PLUS_MINUS, MULTIPLY, DIVIDE, EQUAL, DELETE, RESET, LEFT, RIGHT, UP, DOWN, OK, debug1, debug2, debug3, debug4, debug5, SQRT, ROOT, POWER_OF_2, POWER_OF_x
 	}
 }
 
@@ -527,7 +527,7 @@ public class Keyboard {
 |5,8---|4,8---|3,8---|2,8---|1,8-----------------|
 | 0    | .    |      |      | SOLVE              |
 |      |      |      |      | SIMPLIFY           |
-|      |      |      |DRGCYCL|                   |
+| X    | Y    | Z    |DRGCYCL|                   |
 |------|------|------|------|--------------------|
 
 

src/org/warp/device/PIFrame.java

@@ -88,6 +88,13 @@ public class PIFrame extends JFrame {
 							Keyboard.keyPressed(Key.NONE);
 						}
 						break;
+					case KeyEvent.VK_Y:
+						if (Keyboard.alpha) {
+							Keyboard.keyPressed(Key.LETTER_Y);
+						} else {
+							Keyboard.keyPressed(Key.NONE);
+						}
+						break;
 					case KeyEvent.VK_B:
 						if (Keyboard.shift) {
 							Keyboard.keyPressed(Key.BRIGHTNESS_CYCLE_REVERSE);
@@ -186,6 +193,8 @@ public class PIFrame extends JFrame {
 					case KeyEvent.VK_ADD:
 						if (!Keyboard.shift && !Keyboard.alpha) {
 							Keyboard.keyPressed(Key.PLUS);
+						} else if (Keyboard.shift) {
+							Keyboard.keyPressed(Key.PLUS_MINUS);
 						} else {
 							Keyboard.keyPressed(Key.NONE);
 						}

src/org/warp/picalculator/AnteriorFunction.java

@@ -3,6 +3,8 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.getStringWidth;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 
+import java.util.List;
+
 import org.nevec.rjm.NumeroAvanzatoVec;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
@@ -32,8 +34,17 @@ public abstract class AnteriorFunction implements Function {
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Function solve() throws Error;
+	public abstract List<Function> solveOneStep() throws Error;
 
+	protected int stepsCount = -1;
+	@Override
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			stepsCount = variable.getStepsCount()+1;
+		}
+		return stepsCount;
+	}
+	
 	@Override
 	public void generateGraphics() {
 		variable.setSmall(small);
@@ -77,11 +88,12 @@ public abstract class AnteriorFunction implements Function {
 
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+		return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override

src/org/warp/picalculator/AnteriorFunctionBase.java

@@ -3,6 +3,8 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.getStringWidth;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 
+import java.util.List;
+
 import org.nevec.rjm.NumeroAvanzatoVec;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
@@ -32,8 +34,17 @@ public abstract class AnteriorFunctionBase extends FunctionBase {
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Number solve() throws Error;
+	public abstract List<Function> solveOneStep() throws Error;
 
+	protected int stepsCount = -1;
+	@Override
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			stepsCount = variable.getStepsCount()+1;
+		}
+		return stepsCount;
+	}
+	
 	@Override
 	public void generateGraphics() {
 		variable.setSmall(small);
@@ -77,11 +88,12 @@ public abstract class AnteriorFunctionBase extends FunctionBase {
 
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+		return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override

src/org/warp/picalculator/Calculator.java

@@ -1,5 +1,9 @@
 package org.warp.picalculator;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 import org.nevec.rjm.NumeroAvanzato;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Screen;
@@ -13,12 +17,6 @@ public class Calculator {
 	public static int currentSession = 0;
 	public static boolean haxMode = true;
 
-	public static Number solveResult(String string) throws Error {
-		System.out.println("INPUT: " + string);
-		Expression expression = new Expression(string);
-		return expression.solve();
-	}
-
 	public static Function parseString(String string) throws Error {
 		if (string.contains("{")) {
 			if (!string.startsWith("{")) {
@@ -55,8 +53,29 @@ public class Calculator {
 			if (f instanceof Equation) {
 				PIDisplay.INSTANCE.setScreen(new SolveEquationScreen(es));
 			} else {
-				es.f2 = es.f.solve();
-				es.f2.generateGraphics();
+				List<Function> results = new ArrayList<>();
+				List<Function> partialResults = new ArrayList<>();
+				results.add(es.f);
+				while (Utils.allSolved(results) == false) {
+					for (Function itm : results) {
+						if (itm.getStepsCount() > 0) {
+							partialResults.addAll(itm.solveOneStep());
+						} else {
+							partialResults.add(itm);
+						}
+					}
+					results = new ArrayList<Function>(partialResults);
+					partialResults.clear();
+				}
+				if (results.size() == 0) {
+					
+				} else {
+					Collections.reverse(results);
+					es.f2 = results;
+					for (Function rf : es.f2) {
+						rf.generateGraphics();
+					}
+				}
 			}
 		}
 	}
@@ -66,8 +85,12 @@ public class Calculator {
 			EquationScreen es = (EquationScreen) Calculator.sessions[0];
 			Function f = es.f;
 			if (f instanceof Equation) {
-				es.f2 = ((Equation)f).solve(letter);
-				es.f2.generateGraphics();
+				List<Function> results = ((Equation)f).solve(letter);
+				Collections.reverse(results);
+				es.f2 = results;
+				for (Function rf : es.f2) {
+					rf.generateGraphics();
+				}
 			}
 		}
 	}

src/org/warp/picalculator/Division.java

@@ -5,6 +5,9 @@ import static org.warp.engine.Display.Render.glColor3f;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 import static org.warp.engine.Display.Render.glFillRect;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.nevec.rjm.NumeroAvanzatoVec;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
@@ -21,14 +24,53 @@ public class Division extends FunctionTwoValuesBase {
 	}
 
 	@Override
-	public Number solve() throws Error {
-		if (variable2 == null || variable1 == null) {
-			return new Number("0");
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
 		}
-		if (variable2.solve().getTerm().compareTo(NumeroAvanzatoVec.ZERO) == 0) {
-			throw new Error(Errors.DIVISION_BY_ZERO);
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			if (variable2 instanceof Number && ((Number)variable2).getTerm().compareTo(NumeroAvanzatoVec.ZERO) == 0) {
+				throw new Error(Errors.DIVISION_BY_ZERO);
+			}
+			result.add(((Number) variable1).divide((Number)variable2));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (size1 < size2 && cur2 % size1 == 0) {
+					cur2+=1;
+				}
+				if (size2 < size1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Division((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
 		}
-		return variable1.solve().divide(variable2.solve());
+		stepsCount=-1;
+		return result;
 	}
 
 	public boolean hasMinus() {

src/org/warp/picalculator/Equation.java

@@ -1,9 +1,13 @@
 package org.warp.picalculator;
 
+import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
+import org.nevec.rjm.NumeroAvanzatoVec;
+
 import com.rits.cloning.Cloner;
 
 public class Equation extends FunctionTwoValues {
@@ -16,13 +20,73 @@ public class Equation extends FunctionTwoValues {
 	public String getSymbol() {
 		return MathematicalSymbols.EQUATION;
 	}
-
+	
 	@Override
-	public Function solve() throws Error {
-		return new Equation(new Subtraction((FunctionBase)variable1.solve(), (FunctionBase)variable2.solve()).solve(), new Number("0"));
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			if (((Number)variable2).getTerm().isBigInteger(false) && ((Number)variable2).getTerm().toBigInteger(false).compareTo(new BigInteger("0")) == 0) {
+				result.add(this);
+			} else {
+				result.add(new Equation(new Subtraction((FunctionBase)variable1, (FunctionBase)variable2), new Number("0")));
+			}
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Equation((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+			stepsCount=-1;
+		}
+		return result;
+	}
+
+	private int stepsCount = -1;
+	@Override
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			int val1 = variable1.getStepsCount();
+			int val2 = variable2.getStepsCount();
+			if (val1 > val2) {
+				stepsCount = val1+1;
+			} else {
+				stepsCount = val2+1;
+			}
+		}
+		return stepsCount;
 	}
 	
-	public Function solve(char variableCharacter) {
+	public List<Function> solve(char variableCharacter) {
 		@SuppressWarnings("unused")
 		ArrayList<Equation> e;
 		//TODO: WORK IN PROGRESS.

src/org/warp/picalculator/EquationsSystem.java

@@ -2,6 +2,9 @@ package org.warp.picalculator;
 
 import static org.warp.engine.Display.Render.glDrawLine;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class EquationsSystem extends FunctionMultipleValues {
 	static final int spacing = 2;
 	
@@ -23,9 +26,14 @@ public class EquationsSystem extends FunctionMultipleValues {
 	}
 
 	@Override
-	public Function solve() throws NumberFormatException, Error {
+	public List<Function> solveOneStep() throws NumberFormatException, Error {
 		// TODO implementare il calcolo dei sistemi
-		return variables[0].solve();
+		if (stepsCount == 1) {
+			List<Function> l = new ArrayList<Function>();
+			l.add(variables[0]);
+			return l;
+		}
+		return variables[0].solveOneStep();
 	}
 
 	@Override

src/org/warp/picalculator/EquationsSystemPart.java

@@ -3,6 +3,8 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.glColor3f;
 import static org.warp.engine.Display.Render.glDrawLine;
 
+import java.util.List;
+
 public class EquationsSystemPart extends AnteriorFunction {
 
 	public EquationsSystemPart(Equation equazione) {
@@ -15,9 +17,9 @@ public class EquationsSystemPart extends AnteriorFunction {
 	}
 
 	@Override
-	public Equation solve() throws NumberFormatException, Error {
+	public List<Function> solveOneStep() throws NumberFormatException, Error {
 		// TODO implementare il calcolo dei sistemi
-		return (Equation) variable.solve();
+		return variable.solveOneStep();
 	}
 
 	@Override

src/org/warp/picalculator/Expression.java

@@ -8,11 +8,11 @@ import static org.warp.picalculator.Utils.concat;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.ArrayList;
+import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import org.nevec.rjm.NumeroAvanzato;
-import org.nevec.rjm.NumeroAvanzatoVec;
 
 public class Expression extends FunctionMultipleValuesBase {
 
@@ -195,6 +195,9 @@ public class Expression extends FunctionMultipleValuesBase {
 						case MathematicalSymbols.SUM:
 							f = new Sum(null, null);
 							break;
+						case MathematicalSymbols.SUM_SUBTRACTION:
+							f = new SumSubtraction(null, null);
+							break;
 						case MathematicalSymbols.MULTIPLICATION:
 							f = new Multiplication(null, null);
 							break;
@@ -396,7 +399,7 @@ public class Expression extends FunctionMultipleValuesBase {
 						if (funzioneTMP instanceof FunctionTwoValuesBase) {
 							if (step != "SN Functions") {
 								if (
-										(step == "sums" && (funzioneTMP instanceof Sum) == true && ((funzioneTMP instanceof AnteriorFunctionBase && ((AnteriorFunctionBase) funzioneTMP).variable == null) || (funzioneTMP instanceof FunctionTwoValuesBase && ((FunctionTwoValuesBase) funzioneTMP).variable1 == null && ((FunctionTwoValuesBase) funzioneTMP).variable2 == null) || (!(funzioneTMP instanceof AnteriorFunctionBase) && !(funzioneTMP instanceof FunctionTwoValuesBase))))
+										(step == "sums" && (funzioneTMP instanceof Sum || funzioneTMP instanceof SumSubtraction) == true && ((funzioneTMP instanceof AnteriorFunctionBase && ((AnteriorFunctionBase) funzioneTMP).variable == null) || (funzioneTMP instanceof FunctionTwoValuesBase && ((FunctionTwoValuesBase) funzioneTMP).variable1 == null && ((FunctionTwoValuesBase) funzioneTMP).variable2 == null) || (!(funzioneTMP instanceof AnteriorFunctionBase) && !(funzioneTMP instanceof FunctionTwoValuesBase))))
 										||
 										(
 											step.equals("prioritary multiplications")
@@ -427,6 +430,8 @@ public class Expression extends FunctionMultipleValuesBase {
 											&&
 											(funzioneTMP instanceof Sum) == false
 											&&
+											(funzioneTMP instanceof SumSubtraction) == false
+											&&
 											(funzioneTMP instanceof Multiplication) == false
 											&&
 											(funzioneTMP instanceof PrioritaryMultiplication) == false
@@ -471,13 +476,13 @@ public class Expression extends FunctionMultipleValuesBase {
 
 										Utils.debug.println(debugSpaces + "  •Set variable to expression:" + funzioneTMP.getSymbol());
 										try {
-											Utils.debug.println(debugSpaces + "    " + "var1=" + ((FunctionTwoValuesBase) funzioneTMP).getVariable1().solve());
+											Utils.debug.println(debugSpaces + "    " + "var1=" + ((FunctionTwoValuesBase) funzioneTMP).getVariable1().toString());
 										} catch (NullPointerException ex2) {}
 										try {
-											Utils.debug.println(debugSpaces + "    " + "var2=" + ((FunctionTwoValuesBase) funzioneTMP).getVariable2().solve());
+											Utils.debug.println(debugSpaces + "    " + "var2=" + ((FunctionTwoValuesBase) funzioneTMP).getVariable2().toString());
 										} catch (NullPointerException ex2) {}
 										try {
-											Utils.debug.println(debugSpaces + "    " + "(result)=" + ((FunctionTwoValuesBase) funzioneTMP).solve());
+											Utils.debug.println(debugSpaces + "    " + "(result)=" + ((FunctionTwoValuesBase) funzioneTMP).toString());
 										} catch (NullPointerException ex2) {}
 
 									} else {
@@ -502,7 +507,7 @@ public class Expression extends FunctionMultipleValuesBase {
 										oldFunctionsList.remove(i + 1);
 
 										Utils.debug.println(debugSpaces + "  •Set variable to expression:" + funzioneTMP.getSymbol());
-										FunctionBase var = ((AnteriorFunctionBase) funzioneTMP).getVariable().solve();
+										FunctionBase var = ((AnteriorFunctionBase) funzioneTMP).getVariable();
 										if (var == null) {
 											Utils.debug.println(debugSpaces + "    " + "var=null");
 										} else {
@@ -535,7 +540,7 @@ public class Expression extends FunctionMultipleValuesBase {
 			}
 			Utils.debug.println(debugSpaces + "•Finished correcting classes.");
 
-			Number result = solve();
+			String result = toString();
 			Utils.debug.println(debugSpaces + "•Result:" + result);
 		}
 	}
@@ -546,17 +551,39 @@ public class Expression extends FunctionMultipleValuesBase {
 	}
 
 	@Override
-	public Number solve() throws Error {
+	public List<Function> solveOneStep() throws Error {
+		List<Function> ret = new ArrayList<>();
 		if (variables.length == 0) {
-			return new Number("0");
+			stepsCount = -1;
+			return ret;
 		} else if (variables.length == 1) {
-			return (Number) variables[0].solve();
-		} else {
-			Number result = new Number("0");
-			for (Function f : variables) {
-				result = result.add((Number) f.solve());
+			if (variables[0].getStepsCount() > 0) {
+				List<Function> l = variables[0].solveOneStep();
+				for (Function f : l) {
+					if (f instanceof Number) {
+						ret.add(f);
+					} else {
+						ret.add(new Expression(new FunctionBase[]{(FunctionBase) f}));
+					}
+				}
+				stepsCount = -1;
+				return ret;
+			} else {
+				ret.add(variables[0]);
+				stepsCount = -1;
+				return ret;
 			}
-			return result;
+		} else {
+			for (Function f : variables) {
+				if (f.getStepsCount() >= stepsCount - 1) {
+					List<Function> partial = f.solveOneStep();
+					for (Function fnc : partial) {
+						ret.add(new Expression(new FunctionBase[]{(FunctionBase) fnc}));
+					}
+				}
+			}
+			stepsCount = -1;
+			return ret;
 		}
 	}
 

src/org/warp/picalculator/Function.java

@@ -1,9 +1,13 @@
 package org.warp.picalculator;
 
+import java.util.List;
+
 public interface Function {
 	public String getSymbol();
 
-	public Function solve() throws Error;
+	public int getStepsCount();
+
+	public List<Function> solveOneStep() throws Error;
 
 	public void generateGraphics();
 
@@ -16,4 +20,10 @@ public interface Function {
 	public int getLine();
 	
 	public void setSmall(boolean small);
+	
+	@Override
+	public int hashCode();
+	
+	@Override
+	public boolean equals(Object o);
 }

src/org/warp/picalculator/FunctionBase.java

@@ -1,12 +1,17 @@
 package org.warp.picalculator;
 
+import java.util.List;
+
 public abstract class FunctionBase implements Function {
 
 	@Override
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Number solve() throws Error;
+	public abstract int getStepsCount();
+	
+	@Override
+	public abstract List<Function> solveOneStep() throws Error;
 
 	@Override
 	public abstract void generateGraphics();

src/org/warp/picalculator/FunctionMultipleValues.java

@@ -61,20 +61,36 @@ public abstract class FunctionMultipleValues implements Function {
 
 	@Override
 	public abstract String getSymbol();
-
+	
+	protected int stepsCount = -1;
 	@Override
-	public abstract Function solve() throws Error;
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			int max = 0;
+			int cur = 0;
+			for (Function f : variables) {
+				cur = f.getStepsCount();
+				if (max < cur) {
+					max = cur;
+				}
+			}
+			return max+1;
+		} else {
+			return stepsCount;
+		}
+	}
 
 	@Override
 	public abstract void generateGraphics();
 	
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+			return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override

src/org/warp/picalculator/FunctionMultipleValuesBase.java

@@ -58,23 +58,39 @@ public abstract class FunctionMultipleValuesBase extends FunctionBase {
 	public void setVariablesLength(int length) {
 		variables = Arrays.copyOf(variables, length);
 	}
+	
+	protected int stepsCount = -1;
+	@Override
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			int max = 0;
+			int cur = 0;
+			for (Function f : variables) {
+				cur = f.getStepsCount();
+				if (max < cur) {
+					max = cur;
+				}
+			}
+			return max+1;
+		} else {
+			return stepsCount;
+		}
+	}
 
 	@Override
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Number solve() throws Error;
+	public abstract void generateGraphics();
 
-	@Override
-	public abstract void generateGraphics();
-	
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+		return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override

src/org/warp/picalculator/FunctionTwoValues.java

@@ -3,6 +3,8 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.getStringWidth;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 
+import java.util.List;
+
 import org.nevec.rjm.Rational;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
@@ -43,7 +45,10 @@ public abstract class FunctionTwoValues implements Function {
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Function solve() throws Error;
+	public abstract int getStepsCount();
+
+	@Override
+	public abstract List<Function> solveOneStep() throws Error;
 	
 	@Override
 	public void generateGraphics() {
@@ -93,11 +98,12 @@ public abstract class FunctionTwoValues implements Function {
 
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+			return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override

src/org/warp/picalculator/FunctionTwoValuesBase.java

@@ -3,6 +3,8 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.getStringWidth;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 
+import java.util.List;
+
 import org.nevec.rjm.Rational;
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
@@ -43,7 +45,7 @@ public abstract class FunctionTwoValuesBase extends FunctionBase {
 	public abstract String getSymbol();
 
 	@Override
-	public abstract Number solve() throws Error;
+	public abstract List<Function> solveOneStep() throws Error;
 	
 	@Override
 	public void generateGraphics() {
@@ -93,11 +95,12 @@ public abstract class FunctionTwoValuesBase extends FunctionBase {
 
 	@Override
 	public String toString() {
-		try {
-			return solve().toString();
-		} catch (Error e) {
-			return e.id.toString();
-		}
+//		try {
+//			return solve().toString();
+			return "TODO: fare una nuova alternativa a solve().toString()";
+//		} catch (Error e) {
+//			return e.id.toString();
+//		}
 	}
 
 	@Override
@@ -139,4 +142,19 @@ public abstract class FunctionTwoValuesBase extends FunctionBase {
 		}
 		return tl.getLine();
 	}
+	
+	protected int stepsCount = -1;
+	@Override
+	public int getStepsCount() {
+		if (stepsCount == -1) {
+			int val1 = variable1.getStepsCount();
+			int val2 = variable2.getStepsCount();
+			if (val1 > val2) {
+				stepsCount = val1+1;
+			} else {
+				stepsCount = val2+1;
+			}
+		}
+		return stepsCount;
+	}
 }

src/org/warp/picalculator/MathematicalSymbols.java

@@ -4,6 +4,7 @@ import static org.warp.picalculator.Utils.concat;
 
 public class MathematicalSymbols {
 	public static final String SUM = "+";
+	public static final String SUM_SUBTRACTION = "±";
 	public static final String SUBTRACTION = "-";
 	public static final String MULTIPLICATION = "*";
 	public static final String PRIORITARY_MULTIPLICATION = "▪";
@@ -29,7 +30,7 @@ public class MathematicalSymbols {
 	}
 
 	public static final String[] signums(boolean withMultiplication, boolean withPrioritaryMultiplication) {
-		String[] ret = new String[] { SUM, DIVISION };
+		String[] ret = new String[] { SUM, SUM_SUBTRACTION, DIVISION };
 		if (withMultiplication) {
 			ret = Utils.add(ret, MULTIPLICATION);
 		}

src/org/warp/picalculator/Multiplication.java

@@ -1,6 +1,8 @@
 package org.warp.picalculator;
 
 import java.math.BigInteger;
+import java.util.ArrayList;
+import java.util.List;
 
 public class Multiplication extends FunctionTwoValuesBase {
 
@@ -14,8 +16,49 @@ public class Multiplication extends FunctionTwoValuesBase {
 	}
 
 	@Override
-	public Number solve() throws Error {
-		return getVariable1().solve().multiply(getVariable2().solve());
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).multiply((Number)variable2));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Multiplication((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
 
 	@Override

src/org/warp/picalculator/Number.java

@@ -8,6 +8,8 @@ import static org.warp.engine.Display.Render.glFillRect;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.math.MathContext;
+import java.util.ArrayList;
+import java.util.List;
 
 import org.nevec.rjm.BigDecimalMath;
 import org.nevec.rjm.NumeroAvanzato;
@@ -64,11 +66,6 @@ public class Number extends FunctionBase {
 		height = calcHeight();
 		width = calcWidth();
 	}
-	
-	@Override
-	public Number solve() {
-		return this;
-	}
 
 	@Override
 	public String getSymbol() {
@@ -386,6 +383,18 @@ public class Number extends FunctionBase {
 		this.small = small;
 	}
 
+	@Override
+	public int getStepsCount() {
+		return 0;
+	}
+
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		List<Function> result = new ArrayList<>();
+		result.add(this);
+		return result;
+	}
+
 	/*
 	 * @Override
 	 * public void draw(int x, int y, Graphics g) {

src/org/warp/picalculator/Power.java

@@ -1,5 +1,8 @@
 package org.warp.picalculator;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class Power extends FunctionTwoValuesBase {
 
 	public Power(FunctionBase value1, FunctionBase value2) {
@@ -25,10 +28,51 @@ public class Power extends FunctionTwoValuesBase {
 	}
 
 	@Override
-	public Number solve() throws NumberFormatException, Error {
-		return getVariable1().solve().pow(getVariable2().solve());
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).pow((Number)variable2));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Power((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
-
+	
 	@Override
 	public void draw(int x, int y) {
 //		glColor3f(0, 127-50+new Random().nextInt(50), 0);

src/org/warp/picalculator/PrioritaryMultiplication.java

@@ -1,5 +1,8 @@
 package org.warp.picalculator;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class PrioritaryMultiplication extends FunctionTwoValuesBase {
 
 	public PrioritaryMultiplication(FunctionBase value1, FunctionBase value2) {
@@ -10,10 +13,51 @@ public class PrioritaryMultiplication extends FunctionTwoValuesBase {
 	public String getSymbol() {
 		return MathematicalSymbols.PRIORITARY_MULTIPLICATION;
 	}
-
+	
 	@Override
-	public Number solve() throws Error {
-		return getVariable1().solve().multiply(getVariable2().solve());
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).multiply((Number)variable2));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new PrioritaryMultiplication((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
 
 	@Override

src/org/warp/picalculator/Root.java

@@ -2,6 +2,9 @@ package org.warp.picalculator;
 
 import static org.warp.engine.Display.Render.glDrawLine;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.nevec.rjm.NumeroAvanzatoVec;
 
 public class Root extends FunctionTwoValuesBase {
@@ -27,12 +30,53 @@ public class Root extends FunctionTwoValuesBase {
 		height = variable1.getHeight() + variable2.getHeight() - 2;
 		line = variable1.getHeight() + variable2.getLine() - 2;
 	}
-
+	
 	@Override
-	public Number solve() throws NumberFormatException, Error {
-		Number exponent = new Number(NumeroAvanzatoVec.ONE);
-		exponent = exponent.divide(getVariable1().solve());
-		return getVariable2().solve().pow(exponent);
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			Number exponent = new Number(NumeroAvanzatoVec.ONE);
+			exponent = exponent.divide((Number) getVariable1());
+			result.add(((Number)variable1).pow(exponent));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Root((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
 
 	@Override

src/org/warp/picalculator/RootSquare.java

@@ -1,5 +1,9 @@
 package org.warp.picalculator;
 
+import java.util.ArrayList;
+import java.util.List;
+
+import org.nevec.rjm.NumeroAvanzatoVec;
 import org.nevec.rjm.Rational;
 
 public class RootSquare extends AnteriorFunctionBase {
@@ -22,20 +26,38 @@ public class RootSquare extends AnteriorFunctionBase {
 		width = 1 + 4 + getVariable().getWidth() + 1;
 		line = getVariable().getLine() + 2;
 	}
-
+	
 	@Override
-	public Number solve() throws Error {
-		try {
-			Number result = getVariable().solve();
-			result = result.pow(new Number(new Rational(1, 2)));
-			return result;
-		} catch(NullPointerException ex) {
-			throw new Error(Errors.ERROR);
-		} catch(NumberFormatException ex) {
+	public List<Function> solveOneStep() throws Error {
+		if (variable == null) {
 			throw new Error(Errors.SYNTAX_ERROR);
-		} catch(ArithmeticException ex) {
-			throw new Error(Errors.NUMBER_TOO_SMALL);
 		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			try {
+				Number var = (Number) getVariable();
+				result.add(var.pow(new Number(new Rational(1, 2))));
+			} catch(NullPointerException ex) {
+				throw new Error(Errors.ERROR);
+			} catch(NumberFormatException ex) {
+				throw new Error(Errors.SYNTAX_ERROR);
+			} catch(ArithmeticException ex) {
+				throw new Error(Errors.NUMBER_TOO_SMALL);
+			}
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			if (variable.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable.solveOneStep());
+			} else {
+				l1.add(variable);
+			}
+			
+			for (Function f : l1) {
+				result.add(new RootSquare((FunctionBase)f));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
 
 	@Override

src/org/warp/picalculator/Subtraction.java

@@ -1,5 +1,8 @@
 package org.warp.picalculator;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class Subtraction extends FunctionTwoValuesBase {
 
 	public Subtraction(FunctionBase value1, FunctionBase value2) {
@@ -12,8 +15,49 @@ public class Subtraction extends FunctionTwoValuesBase {
 	}
 
 	@Override
-	public Number solve() throws Error {
-		return getVariable1().solve().add(getVariable2().solve().multiply(new Number("-1")));
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).add(((Number)variable2).multiply(new Number("-1"))));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Subtraction((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
 	}
 
 }

src/org/warp/picalculator/Sum.java

@@ -3,6 +3,9 @@ package org.warp.picalculator;
 import static org.warp.engine.Display.Render.getStringWidth;
 import static org.warp.engine.Display.Render.glDrawStringLeft;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.warp.device.PIDisplay;
 import org.warp.engine.Display;
 
@@ -18,10 +21,48 @@ public class Sum extends FunctionTwoValuesBase {
 	}
 
 	@Override
-	public Number solve() throws Error {
-		Number val1 = getVariable1().solve();
-		Number val2 = getVariable2().solve();
-		Number result = val1.add(val2);
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).add((Number)variable2));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new Sum((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
 		return result;
 	}
 

src/org/warp/picalculator/SumSubtraction.java

@@ -0,0 +1,117 @@
+package org.warp.picalculator;
+
+import static org.warp.engine.Display.Render.getStringWidth;
+import static org.warp.engine.Display.Render.glDrawStringLeft;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.device.PIDisplay;
+import org.warp.engine.Display;
+
+public class SumSubtraction extends FunctionTwoValuesBase {
+
+	public SumSubtraction(FunctionBase value1, FunctionBase value2) {
+		super(value1, value2);
+	}
+
+	@Override
+	public String getSymbol() {
+		return MathematicalSymbols.SUM_SUBTRACTION;
+	}
+
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		if (variable1 == null || variable2 == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (stepsCount == 1) {
+			result.add(((Number)variable1).add((Number)variable2));
+			result.add(((Number)variable1).add(((Number)variable2).multiply(new Number("-1"))));
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			List<Function> l2 = new ArrayList<Function>();
+			if (variable1.getStepsCount() >= stepsCount - 1) {
+				l1.addAll(variable1.solveOneStep());
+			} else {
+				l1.add(variable1);
+			}
+			if (variable2.getStepsCount() >= stepsCount - 1) {
+				l2.addAll(variable2.solveOneStep());
+			} else {
+				l2.add(variable2);
+			}
+			
+			int size1 = l1.size();
+			int size2 = l2.size();
+			int cur1 = 0;
+			int cur2 = 0;
+			int total = l1.size()*l2.size();
+			Function[][] results = new Function[total][2];
+			for (int i = 0; i < total; i++) {
+				results[i] = new Function[]{l1.get(cur1), l2.get(cur2)};
+				if (cur1 < cur2 && cur2 % size1 == 0) {
+					cur2+=1;
+				} else if (cur2 < cur1 && cur1 % size2 == 0) {
+					cur1+=1;
+				}
+				if (cur1 >= size1) cur1 = 0;
+				if (cur2 >= size1) cur2 = 0;
+			}
+			for (Function[] f : results) {
+				result.add(new SumSubtraction((FunctionBase)f[0], (FunctionBase)f[1]));
+			}
+		}
+		stepsCount=-1;
+		return result;
+	}
+
+	@Override
+	public void generateGraphics() {
+		variable1.setSmall(small);
+		variable1.generateGraphics();
+		
+		variable2.setSmall(small);
+		variable2.generateGraphics();
+		
+		width = calcWidth();
+		height = calcHeight();
+		line = calcLine();
+	}
+	
+	@Override
+	public void draw(int x, int y) {
+//		glColor3f(127, 127-50+new Random().nextInt(50), 255);
+//		glFillRect(x,y,width,height);
+//		glColor3f(0, 0, 0);
+		
+		int ln = getLine();
+		int dx = 0;
+		variable1.draw(dx + x, ln - variable1.getLine() + y);
+		dx += variable1.getWidth();
+		if (small) {
+			Display.Render.setFont(PIDisplay.fonts[1]);
+		} else {
+			Display.Render.setFont(PIDisplay.fonts[0]);
+		}
+		dx += 1;
+		glDrawStringLeft(dx + x, ln - Utils.getFontHeight(small) / 2 + y, getSymbol());
+		dx += getStringWidth(getSymbol());
+		variable2.draw(dx + x, ln - variable2.getLine() + y);
+	}
+
+	@Override
+	public int getWidth() {
+		return width;
+	}
+	
+	@Override
+	protected int calcWidth() {
+		int dx = 0;
+		dx += variable1.getWidth();
+		dx += 1;
+		dx += getStringWidth(getSymbol());
+		return dx += variable2.getWidth();
+	}
+}

src/org/warp/picalculator/Utils.java

@@ -11,6 +11,7 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.math.RoundingMode;
 import java.util.ArrayList;
+import java.util.List;
 
 import org.nevec.rjm.BigDecimalMath;
 import org.nevec.rjm.Rational;
@@ -82,7 +83,7 @@ public class Utils {
 
 	public static boolean areThereOnlySettedUpFunctionsSumsEquationsAndSystems(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
+			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
 				if (fl.get(i) instanceof AnteriorFunctionBase) {
 					if (((AnteriorFunctionBase) fl.get(i)).variable == null) {
 						return false;
@@ -101,7 +102,7 @@ public class Utils {
 
 	public static boolean areThereOnlySettedUpFunctionsSumsMultiplicationsEquationsAndSystems(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Sum || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
+			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
 				if (fl.get(i) instanceof AnteriorFunctionBase) {
 					if (((AnteriorFunctionBase) fl.get(i)).variable == null) {
 						return false;
@@ -169,7 +170,7 @@ public class Utils {
 
 	public static boolean areThereOnlyEmptyNSNFunctions(ArrayList<FunctionBase> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (fl.get(i) instanceof FunctionTwoValuesBase && !(fl.get(i) instanceof Sum) && !(fl.get(i) instanceof Subtraction) && !(fl.get(i) instanceof Multiplication) && !(fl.get(i) instanceof PrioritaryMultiplication) && !(fl.get(i) instanceof Division)) {
+			if (fl.get(i) instanceof FunctionTwoValuesBase && !(fl.get(i) instanceof Sum) && !(fl.get(i) instanceof SumSubtraction) && !(fl.get(i) instanceof Subtraction) && !(fl.get(i) instanceof Multiplication) && !(fl.get(i) instanceof PrioritaryMultiplication) && !(fl.get(i) instanceof Division)) {
 				if (((FunctionTwoValuesBase) fl.get(i)).variable1 == null && ((FunctionTwoValuesBase) fl.get(i)).variable2 == null) {
 					return true;
 				}
@@ -203,7 +204,7 @@ public class Utils {
 
 	public static boolean areThereEmptySums(ArrayList<FunctionBase> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (fl.get(i) instanceof Sum) {
+			if (fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction) {
 				if (((FunctionTwoValuesBase) fl.get(i)).variable1 == null && ((FunctionTwoValuesBase) fl.get(i)).variable2 == null) {
 					return true;
 				}
@@ -225,7 +226,7 @@ public class Utils {
 
 	public static boolean areThereOtherSettedUpFunctions(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum || fl.get(i) instanceof Expression || fl.get(i) instanceof AnteriorFunctionBase || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Division)) {
+			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum ||  fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Expression || fl.get(i) instanceof AnteriorFunctionBase || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Division)) {
 				if (fl.get(i) instanceof AnteriorFunctionBase) {
 					if (((AnteriorFunctionBase) fl.get(i)).variable == null) {
 						return true;
@@ -382,4 +383,13 @@ public class Utils {
 		}
 		return realbytes;
 	}
+	
+	public static boolean allSolved(List<Function> expressions) {
+		for (Function itm : expressions) {
+			if (itm.getStepsCount() > 0) {
+				return false;
+			}
+		}
+		return true;
+	}
 }

src/org/warp/picalculator/screens/EquationScreen.java

@@ -4,6 +4,7 @@ import static org.warp.engine.Display.Render.*;
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.util.List;
 
 import org.warp.device.Keyboard.Key;
 import org.warp.device.PIDisplay;
@@ -24,7 +25,7 @@ public class EquationScreen extends Screen {
 	public volatile boolean showCaret = true;
 	public volatile float showCaretDelta = 0f;
 	public Function f;
-	public Function f2;
+	public List<Function> f2;
 	public int ew1;
 	public int ew2;
 	public int eh2;
@@ -150,8 +151,13 @@ public class EquationScreen extends Screen {
 		glDrawStringLeft(2, 22, nuovaEquazione.substring(0, caretPos)+(showCaret?"|":"")+nuovaEquazione.substring(((showCaret==false||nuovaEquazione.length()<=caretPos)?caretPos:caretPos+1), nuovaEquazione.length()));
 		if (f != null)
 			f.draw(2, 22+1+9+1);
-		if (f2 != null)
-			f2.draw(Display.getWidth() - 2 - f2.getWidth(), Display.getHeight() - 2 - f2.getHeight());
+		if (f2 != null) {
+			int bottomSpacing = 0;
+			for (Function f : f2) {
+				bottomSpacing += f.getHeight()+2;
+				f.draw(Display.getWidth() - 2 - f.getWidth(), Display.getHeight() - bottomSpacing);
+			}
+		}
 	}
 
 	@Override
@@ -184,6 +190,9 @@ public class EquationScreen extends Screen {
 								interpreta(nuovaEquazione);
 								solve();
 							} catch (Exception ex) {
+								if (Utils.debugOn) {
+									ex.printStackTrace();
+								}
 								throw new Error(Errors.ERROR);
 							}
 						} catch (Error e) {
@@ -234,6 +243,9 @@ public class EquationScreen extends Screen {
 			case MINUS:
 				typeChar("-");
 				return true;
+			case PLUS_MINUS:
+				typeChar("±");
+				return true;
 			case MULTIPLY:
 				typeChar("*");
 				return true;
@@ -265,6 +277,12 @@ public class EquationScreen extends Screen {
 			case POWER_OF_x:
 				typeChar("^");
 				return true;
+			case LETTER_X:
+				typeChar("X");
+				return true;
+			case LETTER_Y:
+				typeChar("Y");
+				return true;
 			case DELETE:
 				if (nuovaEquazione.length() > 0) {
 					if (caretPos > 0) {