AMDG Claude Brisson wrote:

I need to enable only if a type T is among a specific known list.

I tried to build an operator is_one_of< T, list of known types > condition that could be used within an enable_if (like others type_traits operators), like this:

or< is_same< T, type1 >, or< is_same< T, type2>, ... >

so I searched for an or< condition1, condition2> construct and didn't find anything...

It's boost::mpl::or_ (Note that or is a keyword) However, in this case, it's easier to use mpl::set: #include #include #include namespace mpl = boost::mpl; template<class T> typename boost::enable_if< mpl::has_key, T>

::type f(const T&) {}

int main() { f(1); // ok f("test"); // fails } In Christ, Steven Watanabe