83 lines
1.8 KiB
Python
83 lines
1.8 KiB
Python
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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# TODO: Add examples
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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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