Richard Hazlewood wrote:
I've actually been looking for a way to check for: does (or, perhaps can) template function exist in type.
I've been experimenting with modifying your macro, so that the signature becomes a template argument. E.g. so code such as:
template <typename R, typename X> void foo() { bool const has = has_non_const_member_function_bar<X, R (*)()>::value; ... }
struct X { template <typename T> T bar(); };
foo<int, X>();
Could be made to work.
Trying:
1] #define BOOST_HAS_NON_CONST_MEMBER_FUNCTION(Name,Sig) \ 2] namespace boost \ 3] { \ 4] namespace introspection \ 5] { \ 6] template<class T, class F = Sig> \ 7] struct BOOST_PP_CAT(has_non_const_member_function_,Name) \ 8] { \ 9] typedef char NotFound; \ A] struct Found { char x[2]; }; \ B] \ C] template< typename build_member_type<T,F>::type \ D] > struct member {}; \ E] \ F] template<class X> static Found test(member<&X::Name>*); \ G] template<class X> static NotFound test( ... ); \ H] \ I] static const bool value = (sizeof(Found) == sizeof(test<T>(0))); \ J] typedef mpl::bool_<value> type; \ K] }; \ L] } \ M] } \ /**/
However, it doesn't appear to work (at least in VC71). It looks like the sizeof trick is not capable of stamping out the template function.
Do you know if this can be achieved?
Note: Lines [C-D, F] were modified from:
template< class X \ , typename build_const_member_type<X,F>::type \ > struct member {};
template<class X> static Found test(X, member<&X::Name>*); \
Because VC71 would not compile it that way when Sig was a template arg (F). [shrug].
This didn't seem to affect the original behaviour, was there a reason for it?
I've been able to get a has_mem_fn-type trait to work on MSVC 8 and 9 by using the technique in the Adobe Move library's class_has_move_assign, http://stlab.adobe.com/move_8hpp_source.html Your lines [C-F] would look slightly different, roughly like template< typename signature< T0, ..., TN >::type > struct sfinae { typedef yes_type type; }; template< class U > static typename sfinae< &U:: name >::type test(int); template< class U > static no_type test(...); I don't know if this is any better for MSVC 7, though, but you can try :/ - Jeff