Improve Cancel and Together finding common factors

>> Together((1/x-1/3)^3/(x-3)^2) (3-x)/(27*x^3)"); >> Together((1/x-1/3)/(x-3)) -1/(3*x)
axkr · Nov 1, 2023 · af61595 · af61595
1 parent 1966bb3
commit af61595
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Showing 7 changed files with 540 additions and 443 deletions.
diff --git a/..._android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/Algebra.java b/..._android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/Algebra.java
@@ -4795,8 +4795,10 @@ private static IAST cancelCommonFactors(IExpr part0, IExpr part1) {
       }
     }
     if (p0.isTimes() || p1.isTimes()) {
-      final IAST p0Times = p0.isTimes() ? (IAST) p0 : F.Times(p0);
-      final IAST p1Times = p1.isTimes() ? (IAST) p1 : F.Times(p1);
+      IAST p0Times = AbstractFunctionEvaluator.getNegativePlusInTimes(p0);
+      IAST p1Times = AbstractFunctionEvaluator.getNegativePlusInTimes(p1);
+      // IAST p0Times = p0.isTimes() ? (IAST) p0 : F.Times(p0);
+      // IAST p1Times = p1.isTimes() ? (IAST) p1 : F.Times(p0);
       IASTAppendable t0 = p0Times.copyAppendable();
       IASTAppendable t1 = p1Times.copyAppendable();
       int i = 1;
@@ -4840,8 +4842,7 @@ private static IAST cancelCommonFactors(IExpr part0, IExpr part1) {
               t1Base = t1Arg.base();
               t1Exponent = t1Arg.exponent();
             }
-
-            if (t0Base.equals(t1Base) && t0Exponent.isReal() && t1Exponent.isReal()) {
+            if (t0Exponent.isReal() && t1Exponent.isReal() && t0Base.equals(t1Base)) {
               IReal exp0 = (IReal) t0Exponent;
               IReal exp1 = (IReal) t1Exponent;
               final IReal subtracted;
@@ -4862,6 +4863,7 @@ private static IAST cancelCommonFactors(IExpr part0, IExpr part1) {
                 subtracted = exp1.subtractFrom(exp0);
                 t0.remove(i);
                 t1.set(j, F.Power(t1Base, subtracted));
+                j++;
                 if (Config.TRACE_BASIC_ARITHMETIC) {
                   if (EvalEngine.get().isTraceMode()) {
                     if (commonFactors.isNIL()) {
@@ -4900,6 +4902,7 @@ private static IAST cancelCommonFactors(IExpr part0, IExpr part1) {
       }
     }
     return F.NIL;
+
   }
 
   /**
@@ -5315,17 +5318,23 @@ private static IRational factorTermsGCD(IAST plusAST, EvalEngine engine) {
    */
   public static IExpr[] getNumeratorDenominator(IAST ast, EvalEngine engine, boolean together) {
     if (together) {
-      IExpr[] result = new IExpr[3];
-      result[2] = together(ast, engine);
-      // split expr into numerator and denominator
-      result[1] = engine.evaluate(F.Denominator(result[2]));
-      if (!result[1].isOne()) {
-        // search roots for the numerator expression
-        result[0] = engine.evaluate(F.Numerator(result[2]));
-      } else {
-        result[0] = ast; // result[2];
+      boolean noSimplifyMode = engine.isNoSimplifyMode();
+      try {
+        engine.setNoSimplifyMode(true);
+        IExpr[] result = new IExpr[3];
+        result[2] = together(ast, engine);
+        // split expr into numerator and denominator
+        result[1] = engine.evaluate(F.Denominator(result[2]));
+        if (!result[1].isOne()) {
+          // search roots for the numerator expression
+          result[0] = engine.evaluate(F.Numerator(result[2]));
+        } else {
+          result[0] = ast; // result[2];
+        }
+        return result;
+      } finally {
+        engine.setNoSimplifyMode(noSimplifyMode);
       }
-      return result;
     }
 
     IExpr[] result = new IExpr[2];

diff --git a/..._android_library/matheclipse-core/src/main/java/org/matheclipse/core/eval/EvalEngine.java b/..._android_library/matheclipse-core/src/main/java/org/matheclipse/core/eval/EvalEngine.java
@@ -227,11 +227,16 @@ public static void setReset(final EvalEngine engine) {
   transient boolean fNumericMode;
 
   /**
-   * if <code>true</code> the engine evaluates in &quot;F.Together(expr)&quot; in IExpr#times()
-   * method.
+   * if <code>true</code> the engine evaluates &quot;F.Together(expr)&quot; in IExpr#times() method.
    */
   transient boolean fTogetherMode;
 
+  /**
+   * If <code>true</code> the engine does no simplification of &quot;negative {@link S#Plus}
+   * expressions&quot; inside {@link S#Times} expressions in common subexpression determining.
+   */
+  transient boolean fNoSimplifyMode;
+
   transient boolean fEvalLHSMode;
 
   transient boolean fEvalRHSMode;
@@ -601,6 +606,7 @@ public synchronized EvalEngine copy() {
     engine.fSessionID = fSessionID;
     engine.fStopRequested = false;
     engine.fTogetherMode = fTogetherMode;
+    engine.fNoSimplifyMode = fNoSimplifyMode;
     engine.fTraceMode = fTraceMode;
     engine.fTraceStack = fTraceStack;
     engine.f$Input = f$Input;
@@ -2982,6 +2988,7 @@ public final void init() {
     fRecursionCounter = 0;
     fNumericMode = false;
     fTogetherMode = false;
+    fNoSimplifyMode = false;
     fEvalLHSMode = false;
     fEvalRHSMode = false;
     fDisabledTrigRules = false;
@@ -3146,6 +3153,15 @@ public final boolean isTogetherMode() {
     return fTogetherMode;
   }
 
+  /**
+   * If <code>true</code> the engine does no simplification of &quot;negative {@link S#Plus}
+   * expressions&quot; inside {@link S#Times} expressions in common subexpression determining.
+   * 
+   */
+  public final boolean isNoSimplifyMode() {
+    return fNoSimplifyMode;
+  }
+
   /**
    * If the trace mode is set the system writes an evaluation trace list or if additionally the
    * <i>stop after evaluation mode</i> is set returns the first evaluated result.
@@ -3213,6 +3229,7 @@ private void reset() {
     fDisabledTrigRules = false;
     fRecursionCounter = 0;
     fTogetherMode = false;
+    fNoSimplifyMode = false;
     fTraceMode = false;
     fTraceStack = null;
     fStopRequested = false;
@@ -3495,12 +3512,22 @@ public void setStopRequested(final boolean stopRequested) {
    * {@link S#Together} command during the evaluation of the multiplication if the parameter is set
    * to <code>true</code>.
    *
-   * @param fTogetherMode if <code>true</code> the evaluation will be wrapped by a
-   *        {@link S#Together} function in basic multiplication
+   * @param togetherMode if <code>true</code> the evaluation will be wrapped by a {@link S#Together}
+   *        function in basic multiplication
    * @see #isTogetherMode()
    */
-  public void setTogetherMode(boolean fTogetherMode) {
-    this.fTogetherMode = fTogetherMode;
+  public void setTogetherMode(boolean togetherMode) {
+    this.fTogetherMode = togetherMode;
+  }
+
+  /**
+   * If set to <code>true</code> the engine does no simplification of &quot;negative {@link S#Plus}
+   * expressions&quot; inside {@link S#Times} expressions in common subexpression determining.
+   * 
+   * @param noSimplifyMode
+   */
+  public void setNoSimplifyMode(boolean noSimplifyMode) {
+    this.fNoSimplifyMode = noSimplifyMode;
   }
 
   /** @param b */