Build minus with multipledispatcher

mapytex/calculus/core/compute/minus.py

@@ -10,62 +10,66 @@
 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
 
-def minus(left, right):
-    """ Perform the minusition of left and right
-
-    :param left: left MO
+:param left: None
 :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)
+minus = Dispatcher("minus", doc=minus_doc)
 
-def monumber(right):
-    """ Minusing monumber
-
-    :param right: right MOnumber
-    :returns: MONumber
+@minus.register(type(None), MOnumber)
+def monumber(left, right):
+    """
 
     >>> a = MOnumber(4)
-    >>> monumber(a)
+    >>> minus(None, a)
     <MOnumber - 4>
 
     """
     return MO.factory(- right.value)
 
-def mofraction(right):
-    """ Minusing a mofraction
+@minus.register(type(None), MOFraction)
+def mofraction(left, right):
+    """ 4 differents cases
 
-    :param right: a mofraction
-    :returns: Tree with the number converted into a mofraction
+    Either fraction , numerator or denominator is negative
 
     >>> a = MOFraction(6, 5)
-    >>> print(mofraction(a))
+    >>> print(minus(None, a))
     -
      > None
      > /
      | > 6
      | > 5
+
+    The fraction is negative
+
     >>> a = MOFraction(6, 5, True)
-    >>> print(mofraction(a))
+    >>> 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
@@ -87,12 +91,6 @@ def mofraction(right):
 
     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,
-    }
-
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