Mapytex/mapytex/calculus/core/compute/minus.py

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#! /usr/bin/env python
# -*- coding: utf-8 -*-
# vim:fenc=utf-8
#
# Copyright © 2017 lafrite <lafrite@Poivre>
#
# Distributed under terms of the MIT license.
"""
Minus MO: take the opposit
"""
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from multipledispatch import Dispatcher
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from ..MO.mo import MO, MOnumber
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from ..MO.fraction import MOFraction
from .exceptions import MinusError
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minus_doc = """ Opposite of a MO
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:param left: None
:param right: right MO
:returns: Tree or MO
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"""
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minus = Dispatcher("minus", doc=minus_doc)
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@minus.register(type(None), MOnumber)
def monumber(left, right):
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"""
>>> a = MOnumber(4)
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>>> minus(None, a)
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<MOnumber - 4>
"""
return MO.factory(- right.value)
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@minus.register(type(None), MOFraction)
def mofraction(left, right):
""" 4 differents cases
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Either fraction , numerator or denominator is negative
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>>> a = MOFraction(6, 5)
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>>> print(minus(None, a))
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-
> None
> /
| > 6
| > 5
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The fraction is negative
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>>> a = MOFraction(6, 5, True)
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>>> print(minus(None, a))
/
> 6
> 5
Numerator is negative
>>> a = MOFraction(-6, 5)
>>> print(minus(None, a))
/
> 6
> 5
Denominators is negative
>>> a = MOFraction(6, -5)
>>> print(minus(None, a))
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/
> 6
> 5
"""
if right.negative:
return MOFraction(right._numerator, right._denominator)
try:
if right._numerator.value < 0:
return MOFraction(-right._numerator.value, right._denominator)
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except TypeError:
pass
try:
if right._denominator.value < 0:
return MOFraction(right._numerator, -right._denominator.value)
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except TypeError:
pass
return MOFraction(right._numerator, right._denominator, True)
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