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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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_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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