def unroll_indexsum(expressions, predicate):
"""Unrolls IndexSums below a specified extent.
:arg expressions: list of expression DAGs
:arg predicate: a predicate function on :py:class:`Index` objects
that tells whether to unroll a particular index
:returns: list of expression DAGs with some unrolled IndexSums
"""
mapper = Memoizer(_unroll_indexsum)
mapper.predicate = predicate
return list(map(mapper, expressions))
def expand_conditional(expressions, predicate):
"""Applies the following substitution rule on selected :py:class:`Conditional`s:
Conditional(a, b, c) => Conditional(a, 1, 0)*b + Conditional(a, 0, 1)*c
:arg expressions: expression DAG roots
:arg predicate: a predicate function on :py:class:`Conditional`s to determine
whether to apply the substitution rule or not
:returns: expression DAG roots with some :py:class:`Conditional` nodes expanded
"""
mapper = Memoizer(_expand_conditional)
mapper.predicate = predicate
return list(map(mapper, expressions))
def remove_if(expr: Expr, predicate: Callable[[Expr], bool]) -> Expr:
"""Remove terms from an expression that match a predicate.
This is done by replacing matching terms by an
appropriately-shaped :class:`~.Zero`, so only works to remove
terms that are linear in the expression.
:arg expr: the expression to remove terms from.
:arg predicate: a function that indicates if an expression should
be kept or not.
:returns: A potentially new expression with terms matching the
predicate removed."""
mapper = Memoizer(_filter)
mapper.predicate = predicate
return mapper(expr)