diff --git a/pymath/calculus/operator/operator_set.py b/pymath/calculus/operator/operator_set.py
index 2a42cfb..c31137e 100644
--- a/pymath/calculus/operator/operator_set.py
+++ b/pymath/calculus/operator/operator_set.py
@@ -10,6 +10,7 @@ from .par import Par
 from .pw import Pw
 from .sub import Sub
 from .sub1 import Sub1
+from .operator import Operator
 
 
 class Operator_set(object):
@@ -20,19 +21,33 @@ class Operator_set(object):
         self._operators = {}
 
     def get_op(self, op, arity = 2):
-        """Return the corresponding operator
+        r"""Return the corresponding operator
 
         :op: symbole of the op
-        :arity: the arity
+        :arity: the arity (default is 2)
 
         >>> op = Operator_set()
+        >>> op.store_operator(Add())
         >>> op.get_op('+')
-        '+'
+        +
+        >>> mul = op.get_op('*')
+        Traceback (most recent call last): 
+            ...
+        KeyError: '* (arity: 2) is not available'
+        >>> op.store_operator(Mul())
         >>> mul = op.get_op('*')
         >>> mul.tex
-        '{op1} \\\\times {op2}'
+        '{op1} \\times {op2}'
         >>> mul.txt
         '{op1} * {op2}'
+        >>> op.store_operator(Sub1())
+        >>> sub1 = op.get_op('-')
+        Traceback (most recent call last): 
+            ...
+        KeyError: '- (arity: 2) is not available'
+        >>> sub1 = op.get_op('-', 1)
+        >>> sub1.tex
+        '- {op1}'
         """
         try:
             return getattr(self, self._operators[(op, arity)])
@@ -40,7 +55,17 @@ class Operator_set(object):
             raise KeyError("{theOp} (arity: {arity}) is not available".format(theOp = op, arity = arity))
 
     def can_be_operator(cls, symbole):
-        """ Tell if the symbole can be an operator """
+        r""" 
+        Tell if the symbole can be an operator
+
+        >>> op = Operator_set()
+        >>> op.can_be_operator("+")
+        False
+        >>> op.store_operator(Add())
+        >>> op.can_be_operator("+")
+        True
+        
+        """
         if type(symbole) == str:
             return symbole in [i[0] for i in cls._operators]
         else:
@@ -50,10 +75,23 @@ class Operator_set(object):
         """ Save the operator as a method and 
 
         :param operator: the operator (the class) (it will be accessible through .name method name.
+
+        >>> op = Operator_set()
+        >>> op._operators
+        {}
+        >>> op.store_operator(Add())
+        >>> op._operators
+        {('+', 2): 'add'}
+        >>> op.store_operator("+")
+        Traceback (most recent call last): 
+            ...
+        ValueError: + is not en Operator it's a <class 'str'>
         """
-        # TODO: faire une vérif si on peut utiliser operator_name |mar. févr. 23 09:09:44 EAT 2016
-        self._operators[operator.uniq_desc()] = operator.name
-        setattr(self, operator.name, operator)
+        if isinstance(operator, Operator):
+            self._operators[operator.uniq_desc()] = operator.name
+            setattr(self, operator.name, operator)
+        else:
+            raise ValueError("{} is not en Operator it's a {}".format(operator, type(operator)))
 
 
 op = Operator_set()
@@ -65,16 +103,6 @@ op.store_operator(Pw())
 op.store_operator(Sub())
 op.store_operator(Sub1())
 
-
-
-
-
-
-
-
-
-
-
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