80 lines
1.8 KiB
Python
80 lines
1.8 KiB
Python
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from sympy.core.numbers import oo, Infinity, NegativeInfinity
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from sympy.core.singleton import S
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from sympy.core import Basic, Expr
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from sympy.multipledispatch import Dispatcher
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from sympy.sets import Interval, FiniteSet
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# XXX: The functions in this module are clearly not tested and are broken in a
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# number of ways.
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_set_add = Dispatcher('_set_add')
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_set_sub = Dispatcher('_set_sub')
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@_set_add.register(Basic, Basic)
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def _(x, y):
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return None
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@_set_add.register(Expr, Expr)
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def _(x, y):
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return x+y
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@_set_add.register(Interval, Interval)
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def _(x, y):
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"""
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Additions in interval arithmetic
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https://en.wikipedia.org/wiki/Interval_arithmetic
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"""
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return Interval(x.start + y.start, x.end + y.end,
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x.left_open or y.left_open, x.right_open or y.right_open)
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@_set_add.register(Interval, Infinity)
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def _(x, y):
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if x.start is S.NegativeInfinity:
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return Interval(-oo, oo)
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return FiniteSet({S.Infinity})
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@_set_add.register(Interval, NegativeInfinity)
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def _(x, y):
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if x.end is S.Infinity:
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return Interval(-oo, oo)
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return FiniteSet({S.NegativeInfinity})
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@_set_sub.register(Basic, Basic)
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def _(x, y):
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return None
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@_set_sub.register(Expr, Expr)
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def _(x, y):
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return x-y
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@_set_sub.register(Interval, Interval)
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def _(x, y):
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"""
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Subtractions in interval arithmetic
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https://en.wikipedia.org/wiki/Interval_arithmetic
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"""
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return Interval(x.start - y.end, x.end - y.start,
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x.left_open or y.right_open, x.right_open or y.left_open)
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@_set_sub.register(Interval, Infinity)
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def _(x, y):
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if x.start is S.NegativeInfinity:
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return Interval(-oo, oo)
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return FiniteSet(-oo)
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@_set_sub.register(Interval, NegativeInfinity)
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def _(x, y):
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if x.start is S.NegativeInfinity:
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return Interval(-oo, oo)
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return FiniteSet(-oo)
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