From 25f791bd81500ffd07a2034b1716c136ae5fdf0d Mon Sep 17 00:00:00 2001
From: Bertrand Benjamin <benjamin.bertrand@opytex.org>
Date: Mon, 12 Mar 2018 19:27:01 +0300
Subject: [PATCH] Minus MO

---
 mapytex/calculus/core/compute/exceptions.py |   3 +
 mapytex/calculus/core/compute/minus.py      | 102 ++++++++++++++++++++
 2 files changed, 105 insertions(+)
 create mode 100644 mapytex/calculus/core/compute/minus.py

diff --git a/mapytex/calculus/core/compute/exceptions.py b/mapytex/calculus/core/compute/exceptions.py
index b804e01..bfd24a5 100644
--- a/mapytex/calculus/core/compute/exceptions.py
+++ b/mapytex/calculus/core/compute/exceptions.py
@@ -16,6 +16,9 @@ class ComputeError(Exception):
 class AddError(ComputeError):
     pass
 
+class MinusError(ComputeError):
+    pass
+
 class MultiplyError(ComputeError):
     pass
 
diff --git a/mapytex/calculus/core/compute/minus.py b/mapytex/calculus/core/compute/minus.py
new file mode 100644
index 0000000..b815e4a
--- /dev/null
+++ b/mapytex/calculus/core/compute/minus.py
@@ -0,0 +1,102 @@
+#! /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 ..tree import Tree
+from ..operator import OPERATORS
+from ..MO.mo import MO, MOnumber, MOstr
+from ..MO.fraction import MOFraction
+from .exceptions import MinusError
+from .arithmetic import lcm
+
+
+def minus(left, right):
+    """ Perform the minusition of left and right
+
+    :param left: left MO
+    :param right: right MO
+    :returns: Tree or MO
+
+    >>> a = MOnumber(4)
+    >>> minus(None, a)
+    <MOnumber - 4>
+    >>> a = MOnumber(-4)
+    >>> minus(None, a)
+    <MOnumber 4>
+    >>> b = MOnumber(0)
+    >>> minus(None, b)
+    <MOnumber 0>
+
+    """
+    if not left is None:
+        raise MinusError(f"'-' is a 1 arity operator, left should be None (got {left})")
+
+    return MINUSFUNCTIONS[type(right)](right)
+
+def monumber(right):
+    """ Minusing monumber
+
+    :param right: right MOnumber
+    :returns: MONumber
+
+    >>> a = MOnumber(4)
+    >>> monumber(a)
+    <MOnumber - 4>
+
+    """
+    return MO.factory(- right.value)
+
+def mofraction(right):
+    """ Minusing a mofraction
+
+    :param right: a mofraction
+    :returns: Tree with the number converted into a mofraction
+
+    >>> a = MOFraction(6, 5)
+    >>> print(mofraction(a))
+    -
+     > None
+     > /
+     | > 6
+     | > 5
+    >>> a = MOFraction(6, 5, True)
+    >>> print(mofraction(a))
+    /
+     > 6
+     > 5
+    """
+    if right.negative:
+        return MOFraction(right._numerator, right._denominator)
+
+    try:
+        if right._numerator < 0:
+            return MOFraction(-right._numerator, right._denominator)
+    except TypeError:
+        pass
+    try:
+
+        if right._denominator < 0:
+            return MOFraction(right._numerator, -right._denominator)
+    except TypeError:
+        pass
+
+    return MOFraction(right._numerator, right._denominator, True)
+
+# TODO: Faire un décorateur pour un enregistrement automatique |dim. mars 11 18:24:32 EAT 2018
+MINUSFUNCTIONS = {
+        MOnumber: monumber,
+        MOFraction: mofraction,
+        }
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del