split assignment

CHANGES.rst

@@ -159,6 +159,7 @@ Internals
 
 #. ``boxes_to_`` methods are now optional for ``BoxElement`` subclasses. Most of the code is now moved to the ``mathics.format`` submodule, and implemented in a more scalable way.
 #. ``from_mpmath`` conversion supports a new parameter ``acc`` to set the accuracy of the number.
+#. Improving modularity in evaluating  expressions of the form ``*Set*[...]``.
 #. ``mathics.builtin.inout`` was split in several modules (``inout``, ``messages``, ``layout``, ``makeboxes``) in order to improve the documentation.
 #. ``mathics.eval`` was create to have code that might be put in an instruction interpreter. The opcodes-like functions start ``eval_``, other functions are helper functions for those.
 #. Operator name to Unicode or ASCII comes from Mathics scanner character tables.
@@ -177,6 +178,7 @@ Bugs
 # Reading certain GIFs now work again
 #. ``Random[]`` works now.
 #. ``RandomSample`` with one list argument now returns a random ordering of the list items. Previously it would return just one item.
+#. Improving compatibility in ``*Set*[...]`` expressions., For general cases, the LHS is evaluated before setting its value. For LHS also of the form ``*Set*[...]``, the LHS is keep unevaluated.
 #. Origin placement corrected on ``ListPlot`` and ``LinePlot``.
 #. Fix long-standing bugs in Image handling
 #. Some scikit image routines line ``EdgeDetect`` were getting omitted due to overly stringent PyPI requirements

mathics/builtin/assignments/assignment.py

@@ -20,6 +20,11 @@
 from mathics.core.builtin import BinaryOperator, Builtin
 from mathics.core.symbols import SymbolNull
 from mathics.core.systemsymbols import SymbolFailed
+from mathics.eval.set import (
+    SET_EVAL_FUNCTION_MAP,
+    assign_store_rules_by_tag,
+    normalize_lhs,
+)
 from mathics.eval.pymathics import PyMathicsLoadException, eval_LoadModule
 
 
@@ -47,7 +52,7 @@ def assign(self, lhs, rhs, evaluation, tags=None, upset=False):
         try:
             # Using a builtin name, find which assignment procedure to perform,
             # and then call that function.
-            assignment_func = ASSIGNMENT_FUNCTION_MAP.get(lookup_name, None)
+            assignment_func = SET_EVAL_FUNCTION_MAP.get(lookup_name, None)
             if assignment_func:
                 return assignment_func(self, lhs, rhs, evaluation, tags, upset)