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at present this is mainly needed for facts.py , feel free however to improve
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this stuff for general purpose.
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from sympy.core.compatibility import iterable, cmp
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from __future__ import print_function, division
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from sympy.core.compatibility import iterable
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def _fuzzy_group(args, quick_exit=False):
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"""Return True if all args are True, None if there is any None else False
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unless ``quick_exit`` is True (then return None as soon as a second False
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``_fuzzy_group`` is like ``fuzzy_and`` except that it is more
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conservative in returning a False, waiting to make sure that all
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arguments are True or False and returning None if any arguments are
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None. It also has the capability of permiting only a single False and
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returning None if more than one is seen. For example, the presence of a
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single transcendental amongst rationals would indicate that the group is
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no longer rational; but a second transcendental in the group would make the
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determination impossible.
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>>> from sympy.core.logic import _fuzzy_group
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By default, multiple Falses mean the group is broken:
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>>> _fuzzy_group([False, False, True])
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If multiple Falses mean the group status is unknown then set
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`quick_exit` to True so None can be returned when the 2nd False is seen:
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>>> _fuzzy_group([False, False, True], quick_exit=True)
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But if only a single False is seen then the group is known to
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>>> _fuzzy_group([False, True, True], quick_exit=True)
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if quick_exit and saw_other:
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"""Return True (all True), False (any False) or None.
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If `a` is an iterable it must not be empty; it
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>>> from sympy.core.logic import fuzzy_and
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>>> from sympy import Dummy
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a, b = [fuzzy_bool(i) for i in args]
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if a is True and b is True:
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elif a is False or b is False:
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elif (len(args) == 1 and iterable(args[0]) or len(args) > 2):
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if rv: # this will stop updating if a None is ever trapped
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raise ValueError('fuzzy_and needs at least 1 argument')
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return fuzzy_bool(args[0])
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if rv: # this will stop updating if a None is ever trapped
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Not in fuzzy logic
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Will return Not if arg is a boolean value, and None if argument
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Return None if `v` is None else `not v`.
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>>> from sympy.core.logic import fuzzy_not
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>>> fuzzy_not(True)
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Or in fuzzy logic. Returns True (any True), False (all False), or None
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See the docstrings of fuzzy_and and fuzzy_not for more info. fuzzy_or is
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related to the two by the standard De Morgan's law.
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>>> from sympy.core.logic import fuzzy_or
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>>> fuzzy_or([True, False])
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>>> fuzzy_or([True, None])
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>>> fuzzy_or([False, False])
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>>> print(fuzzy_or([False, None]))
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return fuzzy_not(fuzzy_and(fuzzy_not(i) for i in args))
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class Logic(object):
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"""Logical expression"""
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# {} 'op' -> LogicClass
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def __cmp__(a, b):
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if type(a) is not type(b):
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return cmp( str(type(a)), str(type(b)) )
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return cmp(a.args, b.args)
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return (a > b) - (a < b)
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def __str__(self):
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return '%s(%s)' % (self.__class__.__name__, ', '.join(str(a) for a in self.args))
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'%s cannot be in the beginning of expression' % term)
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if '&' in term or '|' in term:
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raise ValueError('& and | must have space around them')
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if term[0] == '!':
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raise ValueError('do not include space after "!"')
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term = Not(term[1:])
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# already scheduled operation, e.g. '&'
added
removed
lib/py/sympy/core/logic.py
