types/description: add a not-equal operator

types/description.hpp

@@ -90,6 +90,14 @@ namespace cruft::types {
     }
 
 
+    //-------------------------------------------------------------------------
+    constexpr bool
+    operator!= (description const &a, description const &b) noexcept
+    {
+        return !(a == b);
+    }
+
+
     //-------------------------------------------------------------------------
     template <typename T>
     struct category_traits;