def get_unique_variables(expr: Expr) -> List[Expr]:
"""
Get all unique variables in an expression.
To provide deterministic behavior, the list is sorted.
Args:
expr: Expression to parse.
Returns:
Sorted list of unique variables.
"""
l = set()
def add_to_set(e: Expr) -> Expr:
"""
Helper function to add variables to a set.
Args:
expr: Expression to add.
Returns:
Expression.
"""
if e.is_id():
l.add(e)
return e
expr.visit(add_to_set)
return sorted(l, key=lambda x: str(x))
def get_subexpressions(expr: Expr) -> Iterator[Expr]:
"""
Get all subexpressions in descending order.
This can be understood as a breadth-first search
on an abstract syntax tree from top to bottom.
Args:
expr: Expr
Returns:
Iterator of expressions.
"""
l = []
def add_to_list(e: Expr) -> Expr:
"""
Helper function to an expression
to a list.
Args:
expr: Expression to add.
Returns:
Expression.
"""
l.append(e)
return e
expr.visit(add_to_list)
return reversed(l)
def get_unification_candidates(expr: Expr) -> List[Expr]:
"""
Get all unification candidates in an expression.
A unification candidate is a leaf in an abstract
syntax tree (variable, memory or label). Integers
are excluded.
To provide deterministic behavior, the list is sorted.
Args:
expr: Expression to parse.
Returns:
Sorted list of unification candidates.
"""
results = set()
def add_to_set(e: Expr) -> Expr:
"""
Helper function to add variables, memory
and labels to a set.
Args:
expr: Expression to add.
Returns:
Expression.
"""
# memory
if e.is_mem():
results.add(e)
# registers
if e.is_id():
results.add(e)
# location IDs
if e.is_loc():
results.add(e)
return e
expr.visit(add_to_set)
return sorted(list(results), key=lambda x: str(x))