WIP #932 StackOverflowError - check if filterNIL method is not empty

Author: axkr

symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/Algebra.java

@@ -5498,9 +5498,13 @@ public static Optional<IExpr[]> fractionalPartsPower(final IAST powerAST, boolea
       // base ^ (a+b+c...)
       IAST plusAST = (IAST) exponent;
       IAST[] result = plusAST.filterNIL(AbstractFunctionEvaluator::getNormalizedNegativeExpression);
-      parts[1] = base.power(result[0].oneIdentity0());
-      parts[0] = base.power(result[1].oneIdentity0());
-      return Optional.of(parts);
+      IAST plus = result[0];
+      if (plus.argSize() > 0) {
+        parts[1] = base.power(plus.oneIdentity0());
+        parts[0] = base.power(result[1].oneIdentity0());
+        return Optional.of(parts);
+      }
+      return Optional.empty();
     }
     IExpr positiveExpr = AbstractFunctionEvaluator.getNormalizedNegativeExpression(exponent);
     if (positiveExpr.isPresent()) {

symja_android_library/matheclipse-core/src/test/java/org/matheclipse/core/system/LinearAlgebraTestCase.java

@@ -504,6 +504,14 @@ public void testDot() {
     check("Norm(a)^2", //
         "12");
   }
+  @Test
+  public void testDotIssue932() {
+    // issue #932 StackOverflowError
+    check("{{0,1,-1+2^m},{1-2^m,2,-1+2^m},{2^m,-2,-2^m}}.{{1,0,1},{0,1,1},{1,-1,-1}}", //
+        "{{-1+2^m,2-2^m,2-2^m},\n" //
+            + " {0,3-2^m,4-2^(1+m)},\n" //
+            + " {0,-2+2^m,-2+2^(1+m)}}");
+  }
 
   @Test
   public void testEigensystem() {