Feat: dirty sub (repeatition in explain)

mapytex/calculus/API/tokens/token.py

@@ -97,6 +97,10 @@ class Token(object):
                 _other = factory(Expression(moify(other)))
         else:
             _other = other
+
+        if operation == '-':
+            tree = Tree("+", self._mo, Tree("-", None,  _other._mo))
+        else:
             tree = Tree(operation, self._mo, _other._mo)
         return Expression(tree).simplify()
 
@@ -143,6 +147,32 @@ class Token(object):
         """
         return self._operate(other, "+")
 
+    def __sub__(self, other):
+        """ Subing 2 Tokens or a Token and a Expression
+
+        :example:
+        >>> from .number import Integer 
+        >>> a = Integer(3)
+        >>> b = Integer(7)
+        >>> c = a - b
+        >>> c
+        <Integer - 4>
+        >>> for i in c.explain():
+        ...    print(i)
+        3 - 7
+        3 - 7
+        - 4
+        >>> a = Integer(3)
+        >>> c = a - 7
+        >>> c
+        <Integer - 4>
+        >>> a = Integer(3)
+        >>> c = a - "x"
+        >>> c
+        <Linear 3 - x>
+        """
+        return self._operate(other, "-")
+
     def __mul__(self, other):
         """ Multiply 2 Tokens or a Token and a Expression
 
@@ -222,6 +252,9 @@ class Token(object):
                 _other = factory(Expression(moify(other)))
         else:
             _other = other
+        if operation == '-':
+            tree = Tree("+", _other._mo, Tree("-", None,  self._mo))
+        else:
             tree = Tree(operation, _other._mo, self._mo)
         return Expression(tree).simplify()
 
@@ -240,6 +273,21 @@ class Token(object):
         """
         return self._roperate(other, "+")
 
+    def __rsub__(self, other):
+        """ Subing 2 Tokens or a Token and a Expression
+
+        :example:
+        >>> from .number import Integer 
+        >>> a = Integer(3)
+        >>> c = 7 - a
+        >>> c
+        <Integer 4>
+        >>> a = Integer(3)
+        >>> c = "x" - a
+        >>> c
+        <Linear x - 3>
+        """
+        return self._roperate(other, "-")
     def __rmul__(self, other):
         """ Multiply 2 Tokens or a Token and a Expression