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

#! /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
"""

from multipledispatch import Dispatcher
from ..MO.mo import MO, MOnumber
from ..MO.fraction import MOFraction
from .exceptions import MinusError

minus_doc = """ Opposite of a MO

:param left: None
:param right: right MO
:returns: Tree or MO

"""

minus = Dispatcher("minus", doc=minus_doc)

@minus.register(type(None), MOnumber)
def monumber(left, right):
    """

    >>> a = MOnumber(4)
    >>> minus(None, a)
    <MOnumber - 4>

    """
    return MO.factory(- right.value)

@minus.register(type(None), MOFraction)
def mofraction(left, right):
    """ 4 differents cases

    Either fraction , numerator or denominator is negative

    >>> a = MOFraction(6, 5)
    >>> print(minus(None, a))
    -
     > None
     > /
     | > 6
     | > 5

    The fraction is negative

    >>> a = MOFraction(6, 5, True)
    >>> 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))
    /
     > 6
     > 5
    """
    if right.negative:
        return MOFraction(right._numerator, right._denominator)

    try:
        if right._numerator.value < 0:
            return MOFraction(-right._numerator.value, right._denominator)
    except TypeError:
        pass
    try:

        if right._denominator.value < 0:
            return MOFraction(right._numerator, -right._denominator.value)
    except TypeError:
        pass

    return MOFraction(right._numerator, right._denominator, True)

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