82 lines
2.2 KiB
Python
82 lines
2.2 KiB
Python
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from sympy.assumptions import Predicate, AppliedPredicate, Q
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from sympy.core.relational import Eq, Ne, Gt, Lt, Ge, Le
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from sympy.multipledispatch import Dispatcher
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class CommutativePredicate(Predicate):
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"""
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Commutative predicate.
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Explanation
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===========
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``ask(Q.commutative(x))`` is true iff ``x`` commutes with any other
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object with respect to multiplication operation.
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"""
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# TODO: Add examples
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name = 'commutative'
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handler = Dispatcher("CommutativeHandler", doc="Handler for key 'commutative'.")
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binrelpreds = {Eq: Q.eq, Ne: Q.ne, Gt: Q.gt, Lt: Q.lt, Ge: Q.ge, Le: Q.le}
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class IsTruePredicate(Predicate):
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"""
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Generic predicate.
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Explanation
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===========
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``ask(Q.is_true(x))`` is true iff ``x`` is true. This only makes
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sense if ``x`` is a boolean object.
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Examples
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========
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>>> from sympy import ask, Q
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>>> from sympy.abc import x, y
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>>> ask(Q.is_true(True))
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True
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Wrapping another applied predicate just returns the applied predicate.
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>>> Q.is_true(Q.even(x))
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Q.even(x)
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Wrapping binary relation classes in SymPy core returns applied binary
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relational predicates.
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>>> from sympy import Eq, Gt
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>>> Q.is_true(Eq(x, y))
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Q.eq(x, y)
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>>> Q.is_true(Gt(x, y))
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Q.gt(x, y)
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Notes
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=====
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This class is designed to wrap the boolean objects so that they can
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behave as if they are applied predicates. Consequently, wrapping another
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applied predicate is unnecessary and thus it just returns the argument.
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Also, binary relation classes in SymPy core have binary predicates to
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represent themselves and thus wrapping them with ``Q.is_true`` converts them
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to these applied predicates.
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"""
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name = 'is_true'
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handler = Dispatcher(
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"IsTrueHandler",
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doc="Wrapper allowing to query the truth value of a boolean expression."
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)
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def __call__(self, arg):
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# No need to wrap another predicate
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if isinstance(arg, AppliedPredicate):
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return arg
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# Convert relational predicates instead of wrapping them
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if getattr(arg, "is_Relational", False):
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pred = binrelpreds[type(arg)]
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return pred(*arg.args)
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return super().__call__(arg)
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