Decorator for computing special cases

mapytex/calculus/core/compute/add.py

@@ -10,13 +10,14 @@
 Adding MO
 """
 
+from functools import wraps
 from multipledispatch import Dispatcher
 from ..tree import Tree
 from ..MO.mo import MO, MOnumber
 from ..MO.fraction import MOFraction
 from .exceptions import AddError
 from .arithmetic import lcm
-from .type_filter import args_are
+from .filters import special_case
 
 add_doc = """ Adding MOs
 
@@ -25,9 +26,36 @@ add_doc = """ Adding MOs
 :return: Tree or MO
 
 """
+
 add = Dispatcher("add", doc=add_doc)
 
+def add_filter(left, right):
+    """ Automatic add on MO
+
+    :param left: MO
+    :param right: MO
+    :returns: MO if it is a special case, nothing other wise
+
+    >>> a = MOnumber(0)
+    >>> b = MOFraction(1, 2)
+    >>> add(a, b)
+    <MOFraction 1 / 2>
+    >>> add(b, a)
+    <MOFraction 1 / 2>
+    """
+    try:
+        if left == 0:
+            return right
+    except TypeError:
+        pass
+    try:
+        if right == 0:
+            return left
+    except TypeError:
+        pass
+
 @add.register(MOnumber, MOnumber)
+@special_case(add_filter)
 def monumber_monumber(left, right):
     """ Simply add MO value
 
@@ -40,6 +68,7 @@ def monumber_monumber(left, right):
     return MO.factory(left.value + right.value)
 
 @add.register(MOnumber, MOFraction)
+@special_case(add_filter)
 def monumber_mofraction(left, right):
     """ Return a tree with the MOnumber transformed into a MOFraction
 
@@ -58,6 +87,7 @@ def monumber_mofraction(left, right):
     return Tree("+", left_fraction, right)
 
 @add.register(MOFraction, MOnumber)
+@special_case(add_filter)
 def mofraction_monumber(left, right):
     """ Return a tree with the MOnumber transformed into a MOFraction
 
@@ -76,6 +106,7 @@ def mofraction_monumber(left, right):
     return Tree("+", left, right_fraction)
 
 @add.register(MOFraction, MOFraction)
+@special_case(add_filter)
 def mofraction_mofraction(left, right):
     """ 3 differents cases: