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Address bug in structure cache None accessed as a dict #1406

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Merged
rocky merged 3 commits into from
Jun 7, 2025
Merged

Address bug in structure cache None accessed as a dict #1406

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09f4bfb
Initialize structure cache to {} rather than None.
rocky Jun 6, 2025
a158b5c
Use {} instead of None for inital structure cache
rocky Jun 6, 2025
a396f20
Set empty dict value via assignment
rocky Jun 7, 2025
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18 changes: 8 additions & 10 deletions mathics/core/expression.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1120,7 +1120,7 @@ def has_symbol(self, symbol_name: str) -> bool:
if hasattr(element, "has_symbol")
)

def restructure(self, head, elements, evaluation, structure_cache=None, deps=None):
def restructure(self, head, elements, evaluation, structure_cache={}, deps=None):
"""Faster equivalent of: ``Expression(head, *elements)``

The caller guarantees that _all_ elements are either from
Expand Down Expand Up @@ -1924,7 +1924,7 @@ def _is_neutral_head(head, cache, evaluation):
return _is_neutral_symbol(head.get_name(), cache, evaluation)


def structure(head, origins, evaluation, structure_cache=None):
def structure(head, origins, evaluation, structure_cache={}):
"""
Creates a Structure for building Expressions with head "head" and elements
originating (exclusively) from "origins" (elements are passed into the functions
Expand All @@ -1942,22 +1942,20 @@ def structure(head, origins, evaluation, structure_cache=None):

if isinstance(origins, (Expression, Structure)):
cache = origins._cache
if cache is not None and not _is_neutral_head(
head, structure_cache, evaluation
):
cache = None
if cache and not _is_neutral_head(head, structure_cache, evaluation):
cache = {}
elif isinstance(origins, (list, tuple)):
if _is_neutral_head(head, structure_cache, evaluation):
cache = ExpressionCache.union(origins, evaluation)
else:
cache = None
cache = {}
else:
raise ValueError("expected Expression, Structure, tuple or list as orig param")

if cache is None:
return UnlinkedStructure(head)
else:
if cache:
return LinkedStructure(head, cache)
else:
return UnlinkedStructure(head)


def atom_list_constructor(evaluation, head, *atom_names):
Expand Down
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