diff --git a/std/traits.d b/std/traits.d
index e840da9ce..8664efa3f 100644
--- a/std/traits.d
+++ b/std/traits.d
@@ -364,6 +364,29 @@ unittest
     static assert(is(P_dglit[0] == int));
 }
 
+/**
+Returns the number of arguments of function $(D func)
+
+Example:
+---
+void foo(){}
+static assert(arity!foo==0);
+void bar(uint){}
+static assert(arity!bar==1);
+---
+ */
+template arity(alias func) 
+    if (isCallable!func)
+{
+	enum uint arity = (ParameterTypeTuple!func).length;
+}
+
+unittest {
+	void foo(){}
+	static assert(arity!foo==0);
+	void bar(uint){}
+	static assert(arity!bar==1);
+}
 
 /**
 Returns a tuple consisting of the storage classes of the parameters of a