diff --git a/calculus.py b/calculus.py
index 0f6402e..b76c887 100644
--- a/calculus.py
+++ b/calculus.py
@@ -2,60 +2,10 @@
 # encoding: utf-8
 
 
+from generic import Stack
 
 
 
-class Stack(object):
-	"""Docstring for Stack """
-
-	def __init__(self):
-		"""@todo: to be defined1 """
-		self.items = []
-
-	def isEmpty(self):
-		""" Says if the stack is empty
-		:returns: @todo
-
-		"""
-		return self.items == []
-
-	def push(self,  item):
-		"""Push an item in the stack
-
-		:param item: @todo
-		:returns: @todo
-
-		"""
-		self.items.append(item)
-
-	def pop(self):
-		"""Getting the last item and remove it
-		:returns: @todo
-
-		"""
-		return self.items.pop()
-
-	def peek(self):
-		"""Getting the last item
-		:returns: @todo
-
-		"""
-		return self.items[-1]
-
-	def size(self):
-		"""Lenght of the stack
-		:returns: @todo
-
-		"""
-		return len(self.items)
-
-	def __str__(self):
-		return str(self.items)
-
-	def __add__(self, addList):
-		return self.items + addList
-
-
 def infixToPostfix(infixExp):
 	"""Transform an infix expression into postfix expression
 
@@ -97,7 +47,8 @@ def computePostfix(postfixExp):
 	:returns: the result of the expression
 
 	"""
-    # where to save numbers or 
+	print(postfixToInfix(postfixExp))
+	# where to save numbers or 
 	operandeStack = Stack()
 
 	tokenList = postfixExp.split(" ")
@@ -150,10 +101,16 @@ def postfixToInfix(postfixExp):
 			op1 = operandeStack.pop()
 			res = "{op1} {op} {op2}".format(op1 = op1, op = token, op2 = op2)
 			
+			parenthesis = False
 			if i+1 < len(tokenList):
 				if tokenList[i+1] in "+-*/":
 					if priority[token] < priority[tokenList[i+1]]:
 						res = "( " + res + " )"
+						parenthesis = True 
+			if i+2 < len(tokenList) and not parenthesis:
+				if tokenList[i+2] in "+-*/":
+					if priority[token] < priority[tokenList[i+2]]:
+						res = "( " + res + " )"
 
 			operandeStack.push(res)
 
@@ -171,9 +128,9 @@ def test(exp):
 
 	"""
 	print("-------------")
-	print(exp)
+	print("Expression ",exp)
 	postfix = infixToPostfix(exp)
-	#print(postfix)
+	print("Postfix " , postfix)
 	print(computePostfix(postfix))
 	#print(postfixToInfix(postfix))
 
@@ -193,6 +150,12 @@ if __name__ == '__main__':
 	
 	exp = "2 * ( 2 - ( 3 + 4 ) ) + ( 3 - 4 ) * 5"
 	test(exp)
+	
+	exp = "2 * ( 2 - ( 3 + 4 ) ) + 5 * ( 3 - 4 )"
+	test(exp)
+	
+	exp = "2 + 5 * ( 3 - 4 )"
+	test(exp)
 
 
 # -----------------------------
diff --git a/generic.py b/generic.py
new file mode 100644
index 0000000..875b500
--- /dev/null
+++ b/generic.py
@@ -0,0 +1,58 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+
+class Stack(object):
+	"""Docstring for Stack """
+
+	def __init__(self):
+		"""@todo: to be defined1 """
+		self.items = []
+
+	def isEmpty(self):
+		""" Says if the stack is empty
+		:returns: @todo
+
+		"""
+		return self.items == []
+
+	def push(self,  item):
+		"""Push an item in the stack
+
+		:param item: @todo
+		:returns: @todo
+
+		"""
+		self.items.append(item)
+
+	def pop(self):
+		"""Getting the last item and remove it
+		:returns: @todo
+
+		"""
+		return self.items.pop()
+
+	def peek(self):
+		"""Getting the last item
+		:returns: @todo
+
+		"""
+		return self.items[-1]
+
+	def size(self):
+		"""Lenght of the stack
+		:returns: @todo
+
+		"""
+		return len(self.items)
+
+	def __str__(self):
+		return str(self.items)
+
+	def __add__(self, addList):
+		return self.items + addList
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del