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"""
The objects in this module allow the usage of the MatchPy pattern matching
library on SymPy expressions.
"""
import re
from typing import List, Callable
from sympy.core.sympify import _sympify
from sympy.external import import_module
from sympy.functions import (log, sin, cos, tan, cot, csc, sec, erf, gamma, uppergamma)
from sympy.functions.elementary.hyperbolic import acosh, asinh, atanh, acoth, acsch, asech, cosh, sinh, tanh, coth, sech, csch
from sympy.functions.elementary.trigonometric import atan, acsc, asin, acot, acos, asec
from sympy.functions.special.error_functions import fresnelc, fresnels, erfc, erfi, Ei
from sympy.core.add import Add
from sympy.core.basic import Basic
from sympy.core.expr import Expr
from sympy.core.mul import Mul
from sympy.core.power import Pow
from sympy.core.relational import (Equality, Unequality)
from sympy.core.symbol import Symbol
from sympy.functions.elementary.exponential import exp
from sympy.integrals.integrals import Integral
from sympy.printing.repr import srepr
from sympy.utilities.decorator import doctest_depends_on
matchpy = import_module("matchpy")
if matchpy:
from matchpy import Operation, CommutativeOperation, AssociativeOperation, OneIdentityOperation
from matchpy.expressions.functions import op_iter, create_operation_expression, op_len
Operation.register(Integral)
Operation.register(Pow)
OneIdentityOperation.register(Pow)
Operation.register(Add)
OneIdentityOperation.register(Add)
CommutativeOperation.register(Add)
AssociativeOperation.register(Add)
Operation.register(Mul)
OneIdentityOperation.register(Mul)
CommutativeOperation.register(Mul)
AssociativeOperation.register(Mul)
Operation.register(Equality)
CommutativeOperation.register(Equality)
Operation.register(Unequality)
CommutativeOperation.register(Unequality)
Operation.register(exp)
Operation.register(log)
Operation.register(gamma)
Operation.register(uppergamma)
Operation.register(fresnels)
Operation.register(fresnelc)
Operation.register(erf)
Operation.register(Ei)
Operation.register(erfc)
Operation.register(erfi)
Operation.register(sin)
Operation.register(cos)
Operation.register(tan)
Operation.register(cot)
Operation.register(csc)
Operation.register(sec)
Operation.register(sinh)
Operation.register(cosh)
Operation.register(tanh)
Operation.register(coth)
Operation.register(csch)
Operation.register(sech)
Operation.register(asin)
Operation.register(acos)
Operation.register(atan)
Operation.register(acot)
Operation.register(acsc)
Operation.register(asec)
Operation.register(asinh)
Operation.register(acosh)
Operation.register(atanh)
Operation.register(acoth)
Operation.register(acsch)
Operation.register(asech)
@op_iter.register(Integral) # type: ignore
def _(operation):
return iter((operation._args[0],) + operation._args[1])
@op_iter.register(Basic) # type: ignore
def _(operation):
return iter(operation._args)
@op_len.register(Integral) # type: ignore
def _(operation):
return 1 + len(operation._args[1])
@op_len.register(Basic) # type: ignore
def _(operation):
return len(operation._args)
@create_operation_expression.register(Basic)
def sympy_op_factory(old_operation, new_operands, variable_name=True):
return type(old_operation)(*new_operands)
if matchpy:
from matchpy import Wildcard
else:
class Wildcard: # type: ignore
def __init__(self, min_length, fixed_size, variable_name, optional):
self.min_count = min_length
self.fixed_size = fixed_size
self.variable_name = variable_name
self.optional = optional
@doctest_depends_on(modules=('matchpy',))
class _WildAbstract(Wildcard, Symbol):
min_length: int # abstract field required in subclasses
fixed_size: bool # abstract field required in subclasses
def __init__(self, variable_name=None, optional=None, **assumptions):
min_length = self.min_length
fixed_size = self.fixed_size
if optional is not None:
optional = _sympify(optional)
Wildcard.__init__(self, min_length, fixed_size, str(variable_name), optional)
def __getstate__(self):
return {
"min_length": self.min_length,
"fixed_size": self.fixed_size,
"min_count": self.min_count,
"variable_name": self.variable_name,
"optional": self.optional,
}
def __new__(cls, variable_name=None, optional=None, **assumptions):
cls._sanitize(assumptions, cls)
return _WildAbstract.__xnew__(cls, variable_name, optional, **assumptions)
def __getnewargs__(self):
return self.variable_name, self.optional
@staticmethod
def __xnew__(cls, variable_name=None, optional=None, **assumptions):
obj = Symbol.__xnew__(cls, variable_name, **assumptions)
return obj
def _hashable_content(self):
if self.optional:
return super()._hashable_content() + (self.min_count, self.fixed_size, self.variable_name, self.optional)
else:
return super()._hashable_content() + (self.min_count, self.fixed_size, self.variable_name)
def __copy__(self) -> '_WildAbstract':
return type(self)(variable_name=self.variable_name, optional=self.optional)
def __repr__(self):
return str(self)
def __str__(self):
return self.name
@doctest_depends_on(modules=('matchpy',))
class WildDot(_WildAbstract):
min_length = 1
fixed_size = True
@doctest_depends_on(modules=('matchpy',))
class WildPlus(_WildAbstract):
min_length = 1
fixed_size = False
@doctest_depends_on(modules=('matchpy',))
class WildStar(_WildAbstract):
min_length = 0
fixed_size = False
def _get_srepr(expr):
s = srepr(expr)
s = re.sub(r"WildDot\('(\w+)'\)", r"\1", s)
s = re.sub(r"WildPlus\('(\w+)'\)", r"*\1", s)
s = re.sub(r"WildStar\('(\w+)'\)", r"*\1", s)
return s
@doctest_depends_on(modules=('matchpy',))
class Replacer:
"""
Replacer object to perform multiple pattern matching and subexpression
replacements in SymPy expressions.
Examples
========
Example to construct a simple first degree equation solver:
>>> from sympy.utilities.matchpy_connector import WildDot, Replacer
>>> from sympy import Equality, Symbol
>>> x = Symbol("x")
>>> a_ = WildDot("a_", optional=1)
>>> b_ = WildDot("b_", optional=0)
The lines above have defined two wildcards, ``a_`` and ``b_``, the
coefficients of the equation `a x + b = 0`. The optional values specified
indicate which expression to return in case no match is found, they are
necessary in equations like `a x = 0` and `x + b = 0`.
Create two constraints to make sure that ``a_`` and ``b_`` will not match
any expression containing ``x``:
>>> from matchpy import CustomConstraint
>>> free_x_a = CustomConstraint(lambda a_: not a_.has(x))
>>> free_x_b = CustomConstraint(lambda b_: not b_.has(x))
Now create the rule replacer with the constraints:
>>> replacer = Replacer(common_constraints=[free_x_a, free_x_b])
Add the matching rule:
>>> replacer.add(Equality(a_*x + b_, 0), -b_/a_)
Let's try it:
>>> replacer.replace(Equality(3*x + 4, 0))
-4/3
Notice that it will not match equations expressed with other patterns:
>>> eq = Equality(3*x, 4)
>>> replacer.replace(eq)
Eq(3*x, 4)
In order to extend the matching patterns, define another one (we also need
to clear the cache, because the previous result has already been memorized
and the pattern matcher will not iterate again if given the same expression)
>>> replacer.add(Equality(a_*x, b_), b_/a_)
>>> replacer._replacer.matcher.clear()
>>> replacer.replace(eq)
4/3
"""
def __init__(self, common_constraints: list = []):
self._replacer = matchpy.ManyToOneReplacer()
self._common_constraint = common_constraints
def _get_lambda(self, lambda_str: str) -> Callable[..., Expr]:
exec("from sympy import *")
return eval(lambda_str, locals())
def _get_custom_constraint(self, constraint_expr: Expr, condition_template: str) -> Callable[..., Expr]:
wilds = [x.name for x in constraint_expr.atoms(_WildAbstract)]
lambdaargs = ', '.join(wilds)
fullexpr = _get_srepr(constraint_expr)
condition = condition_template.format(fullexpr)
return matchpy.CustomConstraint(
self._get_lambda(f"lambda {lambdaargs}: ({condition})"))
def _get_custom_constraint_nonfalse(self, constraint_expr: Expr) -> Callable[..., Expr]:
return self._get_custom_constraint(constraint_expr, "({}) != False")
def _get_custom_constraint_true(self, constraint_expr: Expr) -> Callable[..., Expr]:
return self._get_custom_constraint(constraint_expr, "({}) == True")
def add(self, expr: Expr, result: Expr, conditions_true: List[Expr] = [], conditions_nonfalse: List[Expr] = []) -> None:
expr = _sympify(expr)
result = _sympify(result)
lambda_str = f"lambda {', '.join((x.name for x in expr.atoms(_WildAbstract)))}: {_get_srepr(result)}"
lambda_expr = self._get_lambda(lambda_str)
constraints = self._common_constraint[:]
constraint_conditions_true = [
self._get_custom_constraint_true(cond) for cond in conditions_true]
constraint_conditions_nonfalse = [
self._get_custom_constraint_nonfalse(cond) for cond in conditions_nonfalse]
constraints.extend(constraint_conditions_true)
constraints.extend(constraint_conditions_nonfalse)
self._replacer.add(
matchpy.ReplacementRule(matchpy.Pattern(expr, *constraints), lambda_expr))
def replace(self, expr: Expr) -> Expr:
return self._replacer.replace(expr)