Improve AssociateTo for Part(Symbol,...) argument

Author: axkr

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

@@ -433,9 +433,9 @@ protected ISymbol getArithmeticSymbol() {
     }
 
     private IExpr assignPart(IExpr part, IExpr value, EvalEngine engine) {
-      IExpr oldResult = engine.evaluate(part);
+      IExpr oldValue = engine.evaluate(part);
       IASTMutable operator = getAST(value);
-      operator.set(1, oldResult);
+      operator.set(1, oldValue);
       IExpr newResult = engine.evaluate(operator);
       engine.evaluate(F.Set(part, newResult));
       return newResult;

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

@@ -146,16 +146,52 @@ public IExpr apply(final IExpr symbolValue) {
 
     @Override
     public IExpr evaluate(final IAST ast, EvalEngine engine) {
-      IExpr sym = Validate.checkSymbolType(ast, 1, engine);
-      if (sym.isPresent()) {
-        IExpr arg2 = engine.evaluate(ast.arg2());
-        Function<IExpr, IExpr> function = new AssociateToFunction(arg2);
-        IExpr[] results = ((ISymbol) sym).reassignSymbolValue(function, S.AssociateTo, engine);
-        if (results != null) {
-          return results[1];
+      IExpr leftHandSide = ast.arg1();
+      try {
+        if (leftHandSide.isSymbol()) {
+          ISymbol sym = (ISymbol) leftHandSide;
+          IExpr arg2 = engine.evaluate(ast.arg2());
+          Function<IExpr, IExpr> function = new AssociateToFunction(arg2);
+          IExpr[] results = ((ISymbol) sym).reassignSymbolValue(function, S.AssociateTo, engine);
+          if (results != null) {
+            return results[1];
+          }
+          return F.NIL;
+        }
+        if (leftHandSide.isASTSizeGE(S.Part, 3) && leftHandSide.first().isSymbol()) {
+          ISymbol sym = (ISymbol) leftHandSide.first();
+          return assignPartTo(sym, (IAST) leftHandSide, ast, engine);
+        }
+      } catch (ValidateException ve) {
+        if (FEConfig.SHOW_STACKTRACE) {
+          ve.printStackTrace();
+        }
+        return engine.printMessage(ast.topHead(), ve);
+      }
+      // `1` is not a variable with a value, so its value cannot be changed.
+      return IOFunctions.printMessage(ast.topHead(), "rvalue", F.List(leftHandSide), engine);
+    }
+
+    private static IExpr assignPartTo(
+        ISymbol symbol, IAST part, final IAST ast, EvalEngine engine) {
+      if (symbol.hasAssignedSymbolValue()) {
+        IExpr value = ast.arg2();
+        if (value.isRuleAST() || value.isListOfRules() || value.isAssociation()) {
+          IExpr oldValue = engine.evaluate(part);
+          if (oldValue.isAssociation()) {
+            IAssociation newResult = ((IAssociation) oldValue).copy();
+            newResult.appendRules((IAST) value);
+            engine.evaluate(F.Set(part, newResult));
+            return symbol.assignedValue();
+          }
+          // The argument `1` is not a valid Association.
+          return IOFunctions.printMessage(ast.topHead(), "invak", F.List(oldValue), EvalEngine.get());
         }
+        // The argument is not a rule or a list of rules.
+        return IOFunctions.printMessage(ast.topHead(), "invdt", F.List(), EvalEngine.get());
       }
-      return F.NIL;
+      // `1` is not a variable with a value, so its value cannot be changed.
+      return IOFunctions.printMessage(ast.topHead(), "rvalue", F.List(symbol), engine);
     }
 
     @Override

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

@@ -555,8 +555,10 @@ protected static void printExpression(
     "Positive machine-sized integer expected at position `2` in `1`.", //
     "intrange",
     "Integer expected in range `1` to `2`.", //
-    "invdt",
+    "invak",
     "The argument is not a rule or a list of rules.", //
+    "invdt",
+    "The argument `1` is not a valid Association.", //
     "invrl",
     "The argument `1` is not a valid Association or a list of rules.", //
     "iterb",

symja_android_library/matheclipse-io/src/test/java/org/matheclipse/io/system/AssociationTest.java

@@ -46,6 +46,16 @@ public void testAssociateTo() {
     check(
         "AppendTo(assoc, assoc2)", //
         "<|a->1,b->2,c->3|>");
+
+    check(
+        "a = {Association({a -> 1, b -> 2}), Association({c -> 3, d -> 4})}", //
+        "{<|a->1,b->2|>,<|c->3,d->4|>}");
+    check(
+        "AssociateTo(a[[2]], c->17)", //
+        "{<|a->1,b->2|>,<|c->17,d->4|>}");
+    check(
+        "a", //
+        "{<|a->1,b->2|>,<|c->17,d->4|>}");
   }
 
   public void testAssociation() {