Explain now explain thing only once

pymath/calculus/explicable.py

@@ -19,11 +19,13 @@ class Explicable(Renderable):
     def __init__(self, *args, **kwargs):
         super(Explicable, self).__init__()
         self.steps = []
+        self.explainator = 0
 
-    def explain(self, noself=True):
+    def explain(self):
         r""" Generate and render steps  which leed to itself
 
-        :param noself: does explain return self
+        After beening explained, the Explicable become amnesiac.
+        See 'history_generator' to explain it once again.
 
         >>> action = Explicable()
         >>> from .expression import Expression
@@ -34,10 +36,38 @@ class Explicable(Renderable):
         2 + 10 \times 4
         2 + 40
         42
+        >>> # Now action is amnesiac
+        >>> for i in action.explain():
+        ...    print(i)
 
+        """
+        if not self.explainator:
+            self.explainator = self.history_generator()
+
+        return self.explainator
+
+    def history_generator(self):
+        r""" Generator for rendered steps which leed to itself
+
+        This is the called method in explain which create the generator.
+        It create a new generator at each call.
+
+        >>> action = Explicable()
+        >>> from .expression import Expression
+        >>> action.postfix_tokens = Expression('42')
+        >>> action.this_append_before([Expression('2+10*4'), Expression('2+40')])
+        >>> for i in action.history_generator():
+        ...    print(i)
+        2 + 10 \times 4
+        2 + 40
+        42
+        >>> for i in action.history_generator():
+        ...    print(i)
+        2 + 10 \times 4
+        2 + 40
+        42
         """
         old_s = ''
-        # les étapes pour l'atteindre
         try:
             for s in self.steps:
                 try:
@@ -52,8 +82,7 @@ class Explicable(Renderable):
         except AttributeError:
             pass
 
-        if noself:
-            # Lui même
+        # if noself:
         new_s = self.STR_RENDER(self.postfix_tokens)
         if not self.is_same_step(new_s, old_s):
             yield new_s