Create merge_history method for Explicable

pymath/calculus/explicable.py

@@ -3,6 +3,7 @@
 
 from .render import Renderable
 from decimal import Decimal
+from .generic import transpose_fill
 
 
 class Explicable(Renderable):
@@ -88,6 +89,40 @@ class Explicable(Renderable):
         """
         self.steps = steps + self.steps
 
+    @staticmethod
+    def merge_history(expl1, expl2, operation):
+        """ Take two Explicable objects, explain where they are from and merge their history
+
+        /!\ Using this method make the two objects amnesiac
+
+        :param expl1: fist explicable
+        :param expl2: second explicable
+        :param operation: the operation that link them
+        :returns: the list of steps
+
+        >>> from .expression import Expression
+        >>> from .operator import op
+        >>> action1 = Explicable()
+        >>> action1.postfix_tokens = Expression('42')
+        >>> action1.this_append_before([Expression('2+10*4'), Expression('2+40')])
+        >>> action2 = Explicable()
+        >>> action2.postfix_tokens = Expression('24')
+        >>> action2.this_append_before([Expression('2*12')])
+        >>> m_history = Explicable().merge_history(action1, action2, op.add)
+        >>> m_history
+        <generator object transpose_fill ...>
+        >>> for i in m_history:
+        ...    print(i)
+        ['2 + 10 \\times 4', '2 \\times 12', +]
+        ['2 + 40', '24', +]
+        ['42', '24', +]
+
+        """
+        steps1 = list(expl1.explain())
+        steps2 = list(expl2.explain())
+
+        return transpose_fill([steps1, steps2, [operation]])
+
 
 class Explicable_int(int, Explicable):