147 lines
3.1 KiB
Python
147 lines
3.1 KiB
Python
#! /usr/bin/env python
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# -*- coding: utf-8 -*-
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# vim:fenc=utf-8
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#
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# Copyright © 2017 lafrite <lafrite@Poivre>
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#
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# Distributed under terms of the MIT license.
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"""
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Minus MO: take the opposit
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"""
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from multipledispatch import Dispatcher
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from .exceptions import MinusError
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from ..MO import MO, MOnumber, MOstr
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from ..MO.fraction import MOFraction
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from ..MO.monomial import MOstrPower, MOMonomial
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from ..MO.polynomial import MOpolynomial
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from ..tree import Tree
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minus_doc = """ Opposite of a MO
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:param left: None
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:param right: right MO
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: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)
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def monumber(_, right):
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"""
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>>> a = MOnumber(4)
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>>> minus(None, a)
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<MOnumber -4>
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"""
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return MO.factory(-right.value)
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@minus.register(type(None), MOFraction)
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def mofraction(_, right):
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""" 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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- 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))
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6 / 5
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Numerator is negative
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>>> a = MOFraction(-6, 5)
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>>> print(minus(None, a))
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6 / 5
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Denominators is negative
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>>> a = MOFraction(6, -5)
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>>> print(minus(None, a))
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6 / 5
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"""
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if right.negative:
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return MOFraction(right._numerator, right._denominator)
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try:
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if right._numerator.value < 0:
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return MOFraction(-right._numerator.value, right._denominator)
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except TypeError:
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pass
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try:
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if right._denominator.value < 0:
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return MOFraction(right._numerator, -right._denominator.value)
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except TypeError:
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pass
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return MOFraction(right._numerator, right._denominator, True)
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@minus.register(type(None), MOstr)
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def mostr(_, right):
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""" Opposite of 'x' is '-x'
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:example:
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>>> x = MOstr("x")
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>>> print(minus(None, x))
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- x
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"""
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return MOMonomial(-1, right)
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@minus.register(type(None), MOstrPower)
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def mostrpower(_, right):
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""" Opposite of 'x^n' is '-x^n'
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:example:
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>>> x2 = MOstrPower("x", 2)
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>>> print(minus(None, x2))
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- x^2
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"""
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return MOMonomial(-1, right.variable, right.power)
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@minus.register(type(None), MOMonomial)
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def momonomial(_, right):
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""" Opposite of 'ax^n' is '-ax^n'
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:example:
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>>> tx2 = MOMonomial(3, "x", 2)
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>>> print(minus(None, tx2))
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- 3x^2
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"""
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try:
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return MOMonomial(-right.coefficient.value, right.variable, right.power)
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except TypeError:
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coef = Tree("-", None, right.coefficient)
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return Tree("*", coef, right.strpower)
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@minus.register(type(None), MOpolynomial)
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def mopolynomial(_, right):
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""" Opposite of a polynomial
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:example:
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>>> P = MOpolynomial('x', [1, -2, 3])
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>>> print(minus(None, P))
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- 3x^2 + 2x - 1
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"""
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neg_coefs = {p: -c.value for (p, c) in right.coefficients.items()}
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return MOpolynomial(right.variable, neg_coefs)
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# -----------------------------
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# Reglages pour 'vim'
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# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
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# cursor: 16 del
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