Add comments to incorrect rules and partially fix ExpandRule1

rules/src/main/java/rules/ExpandRule1.java

@@ -50,33 +50,33 @@ public class ExpandRule1 implements Rule {
 			if (fnc.getParameter1().equals(new Number(fnc.getMathContext(), -1))) {
 				final Function expr = fnc.getParameter2();
 				if (expr instanceof Sum)
-					isExecutable = true;
+					isExecutable = true; // -1 * (a + b)
 				else if (expr instanceof Subtraction)
-					isExecutable = true;
+					isExecutable = true; // -1 * (a - b)
 				else if (expr instanceof SumSubtraction)
-					isExecutable = true;
+					isExecutable = true; // -1 * (a +- b)
 			}
 		} else if (f instanceof Subtraction || f instanceof SumSubtraction) {
 			final FunctionOperator fnc = (FunctionOperator) f;
 			final Function expr = fnc.getParameter2();
 			if (expr instanceof Sum)
-				isExecutable = true;
+				isExecutable = true; // x [- +-] (a + b)
 			else if (expr instanceof Subtraction)
-				isExecutable = true;
+				isExecutable = true; // x [- +-] (a - b)
 			else if (expr instanceof SumSubtraction)
-				isExecutable = true;
+				isExecutable = true; // x [- +-] (a +- b)
 		}
 		if (isExecutable) {
 			final ObjectArrayList<Function> result = new ObjectArrayList<>();
 			final MathContext root = f.getMathContext();
 
-			Function expr = null;
+			Function expr = null; // f.getParameter1() [* - +-] expr
-			int fromSubtraction = 0;
+			int fromSubtraction = 0; // 0: (*), 1: (-), 2: (+-)
 			FunctionOperator subtraction = null;
 			if (f instanceof Multiplication)
 				expr = ((Multiplication) f).getParameter2();
 			else if (f instanceof Subtraction || f instanceof SumSubtraction) {
-				expr = ((Multiplication) f).getParameter2();
+				expr = ((FunctionOperator) f).getParameter2();
 				if (f instanceof Subtraction)
 					fromSubtraction = 1;
 				else
@@ -93,31 +93,37 @@ public class ExpandRule1 implements Rule {
 				final Function b = ((Sum) fnc).getParameter2();
 				final Function fnc2 = new Subtraction(root, new Multiplication(root, new Number(root, -1), a), b);
 				if (fromSubtraction > 0) {
-					subtraction = new Subtraction(root, ((FunctionOperator) f).getParameter1(), fnc2);
+					// FIXME SumSubtraction treated as just Subtraction
-					result.add(subtraction);
+					subtraction = new Sum(root, ((FunctionOperator) f).getParameter1(), fnc2);
+					result.add(subtraction); // x [- +-] (a + b) -> x + (-1*a - b)
 				} else
-					result.add(fnc2);
+					result.add(fnc2); // -1 * (a + b) -> -1*a - b
 			} else if (fnc instanceof Subtraction) {
 				final Function a = ((Subtraction) fnc).getParameter1();
 				final Function b = ((Subtraction) fnc).getParameter2();
 				final Function fnc2 = new Sum(root, new Multiplication(root, new Number(root, -1), a), b);
 				if (fromSubtraction > 0) {
-					subtraction = new Subtraction(root, ((FunctionOperator) f).getParameter1(), fnc2);
+					// FIXME SumSubtraction treated as just Subtraction
-					result.add(subtraction);
+					subtraction = new Sum(root, ((FunctionOperator) f).getParameter1(), fnc2);
+					result.add(subtraction); // x [- +-] (a - b) -> x + (-1*a + b)
 				} else
-					result.add(fnc2);
+					result.add(fnc2); // -1 * (a - b) -> -1*a + b
-			} else if (fnc instanceof SumSubtraction) {
+			} else if (fnc instanceof SumSubtraction) { // FIXME Subtraction and SumSubtraction confusion
 				final Function a = ((SumSubtraction) fnc).getParameter1();
 				final Function b = ((SumSubtraction) fnc).getParameter2();
-				final Function fnc2 = new Sum(root, new Multiplication(root, new Number(root, -1), a), b);
+				final Function fnc2 = new Sum(root, new Multiplication(root, new Number(root, -1), a), b); // -1*a + b
-				final Function fnc3 = new Subtraction(root, new Multiplication(root, new Number(root, -1), a), b);
+				final Function fnc3 = new Subtraction(root, new Multiplication(root, new Number(root, -1), a), b); // -1*a - b
 				if (fromSubtraction > 0) {
+					// x [- +-] (a +- b) -> [x +- (-1*a + b), x +- (-1*a - b), x +- (-1*a - b)]
 					subtraction = new SumSubtraction(root, ((FunctionOperator) f).getParameter1(), fnc2);
 					result.add(subtraction);
 					subtraction = new SumSubtraction(root, ((FunctionOperator) f).getParameter1(), fnc3);
+					// FIXME same result twice
 					result.add(subtraction);
 					result.add(subtraction);
 				} else {
+					// -1 * (a +- b) -> [-1*a + b, -1*a + b]
+					// FIXME same result twice
 					result.add(fnc2);
 					result.add(fnc2);
 				}

rules/src/main/java/rules/ExponentRule17.java

@@ -41,12 +41,12 @@ public class ExponentRule17 implements Rule {
 	*/
 
 	@Override
-	public ObjectArrayList<Function> execute(final Function f) {
+	public ObjectArrayList<Function> execute(final Function f) { // FIXME incorrect rule
 		boolean isExecutable = false;
 		if (f instanceof Root) {
 			final FunctionOperator fnc = (FunctionOperator) f;
 			if (fnc.getParameter1().equals(fnc.getParameter2()))
-				isExecutable = true;
+				isExecutable = true; // root(a, a)
 		}
 
 		if (isExecutable) {
@@ -57,7 +57,7 @@ public class ExponentRule17 implements Rule {
 			final Function two = new Number(root, 2);
 			final Function p = new Power(root, a, two);
 			result.add(p);
-			return result;
+			return result; // root(a, a) -> a^2
 		} else
 			return null;
 	}