Re: [Boost-users] [EnableIf?] Seeking an example....

Mathias Gaunard a écrit :

Robert Jones wrote:

...

Somewhere in the Boost headers, or maybe the Boost documentation I have seen a bit of code which uses SFINAE, and also possibly the enable_if header to select either a find class method or find global template depending on what's available. That's something that was already explained indeed. Here is a way to do it. Let's say you want to test for presence of a go() method with the following prototype :

void go(); in any type : typedef char NotFound; struct Found { char x[2]; }; template struct test_for_member_go{ }; template<class T> static Found test_for_go(test_for_member_go*); template<class T> static NotFound test_for_go( ... ); template<class T> struct test { static const bool value = (sizeof( test_for_go<T>( 0 ) ) == sizeof(Found)); typedef boost::mpl::bool_<value> type; }; I *think* it can be made in a macro using BOOST_TYPEOF and some __LINE__ shenanigans to generate this for any method of any prototype.