diff --git a/mapytex/calculus/core/operator.py b/mapytex/calculus/core/operator.py
index 21ce8d8..5cac730 100644
--- a/mapytex/calculus/core/operator.py
+++ b/mapytex/calculus/core/operator.py
@@ -35,6 +35,22 @@ OPERATORS = {
             },
 }
 
+def is_operator(string):
+    """ Return whether a string is an operator or not
+
+    :param string: string to test
+    :returns: boolean
+
+    :example:
+
+    >>> is_operator("+")
+    True
+    >>> is_operator("i")
+    False
+
+    """
+    return string in OPERATORS.keys()
+
 
 # -----------------------------
 # Reglages pour 'vim'