PatternRestriction

PatternRestriction()

A restriction on wildcards.

Methods

Name	Description
req_matches	Create a pattern restriction based on the current matched variables.

req_matches

PatternRestriction.req_matches(_cls, match_fn)

Create a pattern restriction based on the current matched variables. match_fn is a Python function that takes a dictionary of wildcards and their matched values and should return an integer. If the integer is less than 0, the restriction is false. If the integer is 0, the restriction is inconclusive. If the integer is greater than 0, the restriction is true.

If your pattern restriction cannot decide if it holds since not all the required variables have been matched, it should return inclusive (0).

Examples

>>> from symbolica import *
>>> f, x_, y_, z_ = S('f', 'x_', 'y_', 'z_')
>>>
>>> def filter(m: dict[Expression, Expression]) -> int:
>>>    if x_ in m and y_ in m:
>>>        if m[x_] > m[y_]:
>>>            return -1  # no match
>>>        if z_ in m:
>>>            if m[y_] > m[z_]:
>>>                return -1
>>>            return 1  # match
>>>
>>>    return 0  # inconclusive
>>>
>>>
>>> e = f(1, 2, 3).replace_all(f(x_, y_, z_), 1,
>>>         PatternRestriction.req_matches(filter))