def __transform(self, ast):
changed = False
secondary_op = "AND" if ast.operator == "OR" else "OR"
to_delete = set()
# Check i (child1) against j to see if we can delete j.
for i, child1 in enumerate(ast.operands):
if i in to_delete:
continue
for j, child2 in enumerate(ast.operands):
if i == j or j in to_delete:
continue
# We're checking if child1 is contained in child2, so
# child2 has to be a compound object, not just a simple
# comparison expression. We also require the right operator
# for child2: "AND" if ast is "OR" and vice versa.
if not isinstance(child2, _BooleanExpression) \
or child2.operator != secondary_op:
continue
# The simple check: is child1 contained in child2?
if iter_in(
child1,
child2.operands,
comparison_expression_cmp,
):
to_delete.add(j)
# A more complicated check: does child1 occur in child2
# in a "flattened" form?
elif child1.operator == child2.operator:
if all(
iter_in(
child1_operand,
child2.operands,
comparison_expression_cmp,
) for child1_operand in child1.operands):
to_delete.add(j)
if to_delete:
changed = True
for i in reversed(sorted(to_delete)):
del ast.operands[i]
return ast, changed
def transform_or(self, ast):
changed = False
to_delete = set()
for i, child1 in enumerate(ast.operands):
if i in to_delete:
continue
# The simplification doesn't work across qualifiers
if isinstance(child1, QualifiedObservationExpression):
continue
for j, child2 in enumerate(ast.operands):
if i == j or j in to_delete:
continue
if isinstance(
child2,
(
AndObservationExpression,
FollowedByObservationExpression,
),
):
# The simple check: is child1 contained in child2?
if iter_in(
child1,
child2.operands,
observation_expression_cmp,
):
to_delete.add(j)
# A more complicated check: does child1 occur in child2
# in a "flattened" form?
elif type(child1) is type(child2):
if isinstance(child1, AndObservationExpression):
can_simplify = self.__is_contained_and(
child1.operands,
child2.operands,
)
else: # child1 and 2 are followedby nodes
can_simplify = self.__is_contained_followedby(
child1.operands,
child2.operands,
)
if can_simplify:
to_delete.add(j)
if to_delete:
changed = True
for i in reversed(sorted(to_delete)):
del ast.operands[i]
return ast, changed