diff --git a/mapytex/calculus/core/str2.py b/mapytex/calculus/core/str2.py
index 0fb6241..cac4c2b 100644
--- a/mapytex/calculus/core/str2.py
+++ b/mapytex/calculus/core/str2.py
@@ -11,6 +11,7 @@ Converting a string with coroutines
 """
 
 from functools import partial
+from decimal import Decimal
 from .coroutine import *
 
 __all__ = ["str2", ]
@@ -158,7 +159,7 @@ def lookfor(condition, replace = lambda x:''.join(x)):
         else:
             if c is not None:
                 acc.append(c)
-            found = condition(''.join(acc))
+            found = condition(''.join([str(i) for i in acc]))
             if found == "maybe":
                 ans = "maybe"
             elif found:
@@ -322,14 +323,14 @@ def lookforNumbers(target):
     ...    str2list.send(i)
     >>> a = str2list.throw(STOOOP)
     >>> print(a)
-    ['12', '+', '1234', '*', '67']
+    [12, '+', 1234, '*', 67]
 
     >>> str2list = lookforNumbers(list_sink)
     >>> for i in "1.2+12.34*67":
     ...    str2list.send(i)
     >>> a = str2list.throw(STOOOP)
     >>> print(a)
-    ['1.2', '+', '12.34', '*', '67']
+    [Decimal('1.2'), '+', Decimal('12.34'), '*', 67]
 
     >>> str2list = lookforNumbers(list_sink)
     >>> for i in "12.3.4*67":
@@ -368,7 +369,7 @@ def lookforNumbers(target):
                             current += tok
                     else:
                         if current:
-                            target_.send(current)
+                            target_.send(typifiy_numbers(current))
                             current = ""
                         target_.send(tok)
                 else:
@@ -376,9 +377,16 @@ def lookforNumbers(target):
 
     except STOOOP as err:
             if current:
-                target_.send(current)
+                target_.send(typifiy_numbers(current))
             yield target_.throw(err)
 
+def typifiy_numbers(number):
+    """ Transform a str number into a integer or a decimal """
+    try:
+        return int(number)
+    except ValueError:
+        return Decimal(number)
+
 @coroutine
 def pparser(target):
     """ Parenthesis parser sink
@@ -447,15 +455,15 @@ def str2(sink):
     >>> exp = "12+3*4"
     >>> t = str2nestedlist(exp)
     >>> print(t)
-    ['12', '+', '3', '*', '4']
+    [12, '+', 3, '*', 4]
     >>> exp = "12*3+4"
     >>> t = str2nestedlist(exp)
     >>> print(t)
-    ['12', '*', '3', '+', '4']
+    [12, '*', 3, '+', 4]
     >>> exp = "12*(3+4)"
     >>> t = str2nestedlist(exp)
     >>> print(t)
-    ['12', '*', ['3', '+', '4']]
+    [12, '*', [3, '+', 4]]
 
     >>> from .tree import MutableTree
     >>> str2tree = str2(MutableTree.sink)