diff --git a/pymath/expression.py b/pymath/expression.py
index 57e764b..f4ce7e4 100644
--- a/pymath/expression.py
+++ b/pymath/expression.py
@@ -1,9 +1,9 @@
 #!/usr/bin/env python
 # encoding: utf-8
 
-from .generic import Stack, flatten_list, expand_list
+from .generic import Stack, flatten_list, expand_list, isNumber, isOperator
 from .renders import txt, post2in_fix, tex
-from .str2tokens import str2tokens, isNumber, isOperator
+from .str2tokens import str2tokens
 
 __all__ = ['Expression']
 
diff --git a/pymath/fraction.py b/pymath/fraction.py
index 3cff715..72ad861 100644
--- a/pymath/fraction.py
+++ b/pymath/fraction.py
@@ -60,6 +60,15 @@ class Fraction(object):
     def __repr__(self):
         return "< Fraction " + self.__str__() + ">"
 
+    def __txt__(self):
+        return str(self)
+
+    def __tex__(self):
+        if self._denom == 1:
+            return str(self._num)
+        else:
+            return "\\frac{{ {a} }}{{ {b} }}".format(a = self._num, b = self._denom)
+
     def __float__(self):
         return self._num / self._denom
 
diff --git a/pymath/generic.py b/pymath/generic.py
index 959c66a..8980977 100644
--- a/pymath/generic.py
+++ b/pymath/generic.py
@@ -243,6 +243,37 @@ def convolution_dict(D1, D2, op = lambda x,y:x*y,\
 
     return new_dict
 
+def isOperator(exp):
+    """Check if the expression is an opération in "+-*/:^"
+
+    :param exp: an expression
+    :returns: boolean
+
+    """
+    
+    #return (type(exp) == str and exp in "+-*/:^")
+    try:
+        exp.isOperator
+    except AttributeError:
+        return 0
+    return 1
+
+def isNumber(exp):
+    """Check if the expression can be a number
+
+    :param exp: an expression
+    :returns: True if the expression can be a number and false otherwise
+
+    """
+    try:
+        exp.isNumber
+    except AttributeError:
+        if type(exp) == int:
+            return 1
+        else:
+            return 0
+    return  1
+
 if __name__ == '__main__':
     import doctest
     doctest.testmod()
diff --git a/pymath/operator.py b/pymath/operator.py
index a8a0fc7..dbe95d4 100644
--- a/pymath/operator.py
+++ b/pymath/operator.py
@@ -3,7 +3,7 @@
 
 
 from .fraction import Fraction
-from .generic import flatten_list
+from .generic import flatten_list, isNumber
 
 class Operator(str):
 
@@ -75,25 +75,23 @@ class Operator(str):
         >>> add = Operator("+", 2)
         >>> sub1 = Operator("-", 1)
         >>> div = Operator("/", 1)
-        >>> mul.__txt__(1,2)
+        >>> mul.__txt__('1','2')
         '1 * 2'
-        >>> add.__txt__(1,2)
+        >>> add.__txt__('1','2')
         '1 + 2'
         >>> f = save_mainOp('2 + 3',add)
-        >>> mul.__txt__(f, 4)
+        >>> mul.__txt__(f, '4')
         '( 2 + 3 ) * 4'
         >>> f = save_mainOp('-3',sub1)
         >>> sub1.__txt__(f)
         '- ( -3 )'
-        >>> sub1.__txt__(-3)
+        >>> sub1.__txt__('-3')
         '- ( -3 )'
         >>> f = save_mainOp('2 + 3',add)
         >>> sub1.__txt__(f)
         '- ( 2 + 3 )'
         """
-        
-        #vive le inline? ...
-        replacement = {"op"+str(i+1): ' '.join([str(o) if type(o)==int else o for o in self.add_parenthesis(op)]) for (i,op) in enumerate(args)}
+        replacement = {"op"+str(i+1): ' '.join(self.add_parenthesis(op)) for (i,op) in enumerate(args)}
         
         ans = self._txt.format(**replacement)
         ans = save_mainOp(ans, self)
@@ -109,23 +107,23 @@ class Operator(str):
         >>> add = Operator("+", 2)
         >>> sub1 = Operator("-", 1)
         >>> div = Operator("/", 1)
-        >>> mul.__tex__(1,2)
+        >>> mul.__tex__('1','2')
         '1 \\\\times 2'
-        >>> add.__tex__(1,2)
+        >>> add.__tex__('1','2')
         '1 + 2'
         >>> f = save_mainOp('2 + 3',add)
-        >>> mul.__tex__(f, 4)
+        >>> mul.__tex__(f, '4')
         '( 2 + 3 ) \\\\times 4'
         >>> f = save_mainOp('-3',sub1)
         >>> sub1.__tex__(f)
         '- ( -3 )'
-        >>> sub1.__tex__(-3)
+        >>> sub1.__tex__('-3')
         '- ( -3 )'
         >>> f = save_mainOp('2 + 3',add)
         >>> sub1.__tex__(f)
         '- ( 2 + 3 )'
         """
-        replacement = {"op"+str(i+1): ' '.join([str(o) if type(o)==int else o for o in self.add_parenthesis(op)]) for (i,op) in enumerate(args)}
+        replacement = {"op"+str(i+1): ' '.join(self.add_parenthesis(op)) for (i,op) in enumerate(args)}
         
         ans = self._tex.format(**replacement)
         ans = save_mainOp(ans, self)
@@ -174,13 +172,15 @@ class Operator(str):
             if op.mainOp.priority < self.priority:
                 op = flatten_list(["("] + [op] + [")"])
         except AttributeError:
-            if type(op) == int and op < 0:
-                op = ['(', op, ')']
+            try:
+                if int(op) < 0:
+                    op = ['(', op, ')']
+            except ValueError:
+                pass
         return flatten_list([op])
 
 
 
-
 def save_mainOp(obj, mainOp):
     """Create a temporary class build over built-in type to stock the main operation of a calculus
     
@@ -198,21 +198,27 @@ def save_mainOp(obj, mainOp):
     return Fake(obj)
 
 if __name__ == '__main__':
-    #op = Operator("+", 2)
-    #print(op.__txt__(1,2))
-    #mul = Operator("*", 2)
-    #add = Operator("+", 2)
-    #sub1 = Operator("-", 1)
-    #div = Operator("/", 1)
-    #print(mul.__txt__(1,2))
-    #print(add.__txt__(1,2))
-    #f = save_mainOp('2 + 3',add)
-    #print(mul.__txt__(f, 4))
-    #f = save_mainOp('-3',sub1)
-    #print(sub1.__txt__(f))
-    #print(sub1.__txt__(-3))
-    #f = save_mainOp('2 + 3',add)
-    #print(sub1.__txt__(f))
+    op = Operator("+", 2)
+    print(op.__txt__('1','2'))
+    mul = Operator("*", 2)
+    add = Operator("+", 2)
+    sub1 = Operator("-", 1)
+    div = Operator("/", 1)
+    print(mul.__txt__('1','2'))
+    print(add.__txt__('1','2'))
+    f = save_mainOp('2 + 3',add)
+    print(mul.__txt__(f, '4'))
+    f = save_mainOp('-3',sub1)
+    print(sub1.__txt__(f))
+    print(sub1.__txt__('-3'))
+    f = save_mainOp('2 + 3',add)
+    print(sub1.__txt__(f))
+
+    from .fraction import Fraction
+    f = Fraction(1, 2)
+    print(add.__txt__(f.__txt__(),'2'))
+    print(add.__tex__(f.__tex__(),'2'))
+    
 
     import doctest
     doctest.testmod()
diff --git a/pymath/render.py b/pymath/render.py
index 2ad50da..394cb34 100644
--- a/pymath/render.py
+++ b/pymath/render.py
@@ -38,13 +38,36 @@ class Render(object):
                     # Switch op1 and op2 to respect order
                     operandeStack.push(self.render(token)(op2, op1))
             else:
-                operandeStack.push(token)
+                operandeStack.push(self.render(token)())
 
         return operandeStack.pop()
 
-txt = Render(lambda x:x.__txt__)
-tex = Render(lambda x:x.__tex__)
-p2i = Render(lambda x:x.__p2i__)
+def txt_render(token):
+    def render(*args):
+        try:
+            return getattr(token, '__txt__')(*args)
+        except AttributeError:
+            return str(token)
+    return render
+
+txt = Render(txt_render)
+def tex_render(token):
+    def render(*args):
+        try:
+            return getattr(token, '__tex__')(*args)
+        except AttributeError:
+            return str(token)
+    return render
+tex = Render(tex_render)
+
+def p2i_render(token):
+    def render(*args):
+        try:
+            return getattr(token, '__p2i__')(*args)
+        except AttributeError:
+            return list(token)
+    return render
+p2i = Render(p2i_render)
 
 if __name__ == '__main__':
     from .operator import Operator
diff --git a/pymath/renders.py b/pymath/renders.py
deleted file mode 100644
index 5eaa635..0000000
--- a/pymath/renders.py
+++ /dev/null
@@ -1,103 +0,0 @@
-#!/usr/bin/env python
-# encoding: utf-8
-
-from .render import Render
-from .fraction import Fraction
-from .generic import first_elem, last_elem
-
-__all__ = ['post2in_fix', 'tex', 'txt']
-
-# ------------------------
-# A infix to postfix list convertor
-
-p2i_infix = {"+": "+", "-": "-", "*": "*", "/" : "/", ":": ":", "^":"^"}
-p2i_postfix = {}
-p2i_other = {"(": "(", ")": ")"}
-
-post2in_fix = Render(p2i_infix, p2i_postfix, p2i_other, join = False)
-
-# ------------------------
-# A console render
-
-def txtMult(op1,op2):
-    """ Tex render for *
-    Cases where \\times won't be displayed
-        * nbr  letter 
-        * nbr  (
-        * )(
-    """
-    first_nbr = type(op1) in [int, Fraction]
-    seg_letter = type(op2) == str and op2.isalpha()
-    first_par = (first_elem(op2) == "(")
-    seg_par = (last_elem(op1) == ")")
-
-    if (first_nbr and (seg_letter or seg_par)) \
-            or (first_par and seg_par):
-        return [op1, op2]
-    else:
-        return [op1, "*", op2]
-
-txt_infix = {"+": "+", "-": "-", "*": txtMult, "/" : "/", ":":":", "^":"^"}
-txt_postfix = {}
-txt_other = {"(": "(", ")": ")"}
-
-txt = Render(txt_infix, txt_postfix, txt_other)
-
-# ------------------------
-# A latex render
-
-def texSlash(op1, op2):
-    """ Tex render for / """
-    if not Render.isNumerande(op1) and op1[0] == "(" and op1[-1] == ")":
-        op1 = op1[1:-1]
-    if not Render.isNumerande(op2) and op2[0] == "(" and op2[-1] == ")":
-        op2 = op2[1:-1]
-    return ["\\frac{" , op1 , "}{" , op2 , "}"]
-
-def texFrac(frac):
-    """ Tex render for Fractions"""
-    return ["\\frac{" , str(frac._num) , "}{" , str(frac._denom) , "}"]
-
-def texMult(op1,op2):
-    """ Tex render for *
-    Cases where \\times won't be displayed
-        * nbr  letter 
-        * nbr  (
-        * )(
-    """
-    first_nbr = type(op1) in [int, Fraction]
-    seg_letter = type(op2) == str and op2.isalpha()
-    first_par = (first_elem(op2) == "(")
-    seg_par = (last_elem(op1) == ")")
-
-    if (first_nbr and (seg_letter or seg_par)) \
-            or (first_par and seg_par):
-        return [op1, op2]
-    else:
-        return [op1, "\\times", op2]
-
-tex_infix = {"+": " + ", "-": " - ", "*": texMult , ":": ":", "^":"^"}
-tex_postfix = {"/": texSlash}
-tex_other = {"(": "(", ")": ")"}
-tex_type_render = {str:str, int: str, Fraction: texFrac}
-
-tex = Render(tex_infix, tex_postfix, tex_other, type_render = tex_type_render)
-
-
-
-if __name__ == '__main__':
-    #exp = [2, 5, '^', 1, '-', 3, 4, '*', ':']
-    #print(txt(exp))
-    #exp = [2, 5, '^', 1, '-', 3, 4, '*', '/', 3, 5, '/', ':']
-    exp = [2, -3, "*"]
-    print(tex(exp))
-    #exp = [2, 5, '^', 1, '-', 3, 4, '*', '/', 3, '+']
-    #print(post2in_fix(exp))
-
-
-
-
-# -----------------------------
-# Reglages pour 'vim'
-# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
diff --git a/pymath/str2tokens.py b/pymath/str2tokens.py
index d770ab5..f0eff71 100644
--- a/pymath/str2tokens.py
+++ b/pymath/str2tokens.py
@@ -2,7 +2,7 @@
 # encoding: utf-8
 
 from .operator import Operator
-from .generic import Stack
+from .generic import Stack, isOperator, isNumber
 
 def str2tokens(exp):
     """ Parse the string into tokens then turn it into postfix form
@@ -147,36 +147,6 @@ def in2post_fix(infix_tokens):
     return postfix_tokens
 
 
-def isOperator(exp):
-    """Check if the expression is an opération in "+-*/:^"
-
-    :param exp: an expression
-    :returns: boolean
-
-    """
-    
-    #return (type(exp) == str and exp in "+-*/:^")
-    try:
-        exp.isOperator
-    except AttributeError:
-        return 0
-    return 1
-
-def isNumber(exp):
-    """Check if the expression can be a number
-
-    :param exp: an expression
-    :returns: True if the expression can be a number and false otherwise
-
-    """
-    try:
-        exp.isNumber
-    except AttributeError:
-        if type(exp) == int:
-            return 1
-        else:
-            return 0
-    return  1
 
 if __name__ == '__main__':
     #a, s, m, d, p = Operator("+"), Operator("-"), Operator("*"), Operator("/"), Operator("^")
diff --git a/test/test_renders.py b/test/test_render.py
similarity index 73%
rename from test/test_renders.py
rename to test/test_render.py
index 6453dff..aa22126 100644
--- a/test/test_renders.py
+++ b/test/test_render.py
@@ -4,7 +4,7 @@
 
 import unittest
 
-from pymath.renders import tex, txt
+from pymath.render import tex, txt,p2i
 from pymath.fraction import Fraction
 from pymath.operator import Operator 
 
@@ -43,8 +43,24 @@ class TestTexRender(unittest.TestCase):
             rend = tex(e)
             self.assertEqual(rend, wanted_render[i])
 
-    def test_mult_exp(self):
-        pass
+    def test_parentheses(self):
+        mul = Operator("*", 2)
+        add = Operator("+", 2)
+        exps = [\
+            [ 2, 3, add, 4, mul],\
+            [ 2, 3, mul, 4, add],\
+            [ 2, 3, 4, mul, add],\
+            [ 2, 3, 4, add, add],\
+            ]
+        wanted_render = [\
+                '( 2 + 3 ) \\times 4',\
+                '2 \\times 3 + 4',\
+                '2 + 3 \\times 4',\
+                '2 + 3 + 4',\
+                ]
+        for (i,e) in enumerate(exps):
+            rend = tex(e)
+            self.assertEqual(rend, wanted_render[i])
 
     def test_slash(self):
         pass
@@ -91,8 +107,24 @@ class TesttxtRender(unittest.TestCase):
             rend = txt(e)
             self.assertEqual(rend, wanted_render[i])
 
-    def test_mult_exp(self):
-        pass
+    def test_parentheses(self):
+        mul = Operator("*", 2)
+        add = Operator("+", 2)
+        exps = [\
+            [ 2, 3, add, 4, mul],\
+            [ 2, 3, mul, 4, add],\
+            [ 2, 3, 4, mul, add],\
+            [ 2, 3, 4, add, add],\
+            ]
+        wanted_render = [\
+                '( 2 + 3 ) * 4',\
+                '2 * 3 + 4',\
+                '2 + 3 * 4',\
+                '2 + 3 + 4',\
+                ]
+        for (i,e) in enumerate(exps):
+            rend = txt(e)
+            self.assertEqual(rend, wanted_render[i])
 
     def test_slash(self):
         pass