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from sympy.assumptions import Predicate |
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from sympy.multipledispatch import Dispatcher |
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class FinitePredicate(Predicate): |
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""" |
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Finite number predicate. |
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Explanation |
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=========== |
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``Q.finite(x)`` is true if ``x`` is a number but neither an infinity |
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nor a ``NaN``. In other words, ``ask(Q.finite(x))`` is true for all |
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numerical ``x`` having a bounded absolute value. |
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Examples |
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======== |
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>>> from sympy import Q, ask, S, oo, I, zoo |
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>>> from sympy.abc import x |
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>>> ask(Q.finite(oo)) |
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False |
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>>> ask(Q.finite(-oo)) |
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False |
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>>> ask(Q.finite(zoo)) |
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False |
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>>> ask(Q.finite(1)) |
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True |
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>>> ask(Q.finite(2 + 3*I)) |
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True |
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>>> ask(Q.finite(x), Q.positive(x)) |
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True |
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>>> print(ask(Q.finite(S.NaN))) |
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None |
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References |
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========== |
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.. [1] https://en.wikipedia.org/wiki/Finite |
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""" |
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name = 'finite' |
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handler = Dispatcher( |
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"FiniteHandler", |
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doc=("Handler for Q.finite. Test that an expression is bounded respect" |
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" to all its variables.") |
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) |
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class InfinitePredicate(Predicate): |
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""" |
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Infinite number predicate. |
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``Q.infinite(x)`` is true iff the absolute value of ``x`` is |
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infinity. |
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""" |
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name = 'infinite' |
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handler = Dispatcher( |
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"InfiniteHandler", |
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doc="""Handler for Q.infinite key.""" |
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) |
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class PositiveInfinitePredicate(Predicate): |
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""" |
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Positive infinity predicate. |
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``Q.positive_infinite(x)`` is true iff ``x`` is positive infinity ``oo``. |
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""" |
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name = 'positive_infinite' |
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handler = Dispatcher("PositiveInfiniteHandler") |
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class NegativeInfinitePredicate(Predicate): |
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""" |
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Negative infinity predicate. |
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``Q.negative_infinite(x)`` is true iff ``x`` is negative infinity ``-oo``. |
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""" |
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name = 'negative_infinite' |
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handler = Dispatcher("NegativeInfiniteHandler") |
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