Hi, Often I use enable_if and its cousins to add functionality to code which works okay on compilers without SFINAE. So I have a lot of code which looks like this: template<typename T> #ifndef BOOST_NO_SFINAE typename enable_if<is_xxx<T>, int>::type #else int #endif f(T t); or template<typename T> void f( T t #ifndef BOOST_NO_SFINAE , typename enable_if<is_xxx<T>, int>::type* = 0 #endif ); It would be nice to have macros BOOST_ENABLE_IF_RETURN(condition, result) and BOOST_ENABLE_IF_PARAM(condition) so that the above could be written template<typename T> BOOST_ENABLE_IF_RETURN(is_xxx<T>, void) f(T); template<typename T> void f(T BOOST_ENABLE_IF_PARAM(is_xxx<T>)); (And similarly for enable_if_c, etc.) It's straightforward to write macros which work for conditions which don't need to be enclosed in parentheses; e.g.: #ifndef BOOST_NO_SFINAE # define BOOST_ENABLE_IF_RETURN(condition, result) \ typename boost::enable_if<condition, result>::type #else # define BOOST_ENABLE_IF_RETURN(condition, result) result #endif With a little more work, you can allow use such as template<typename T, typename U> BOOST_ENABLE_IF_RETURN((is_base_and_derived<T, U>), void) f(T, U); e.g. #define BOOST_ENABLE_IF_RETURN(condition, result) \ typename boost::enable_if< \ typename boost::function_traits< \ void condition \ >::arg1_type, result \ >::type Here the parentheses in the macro invocation are required. (I've found I can make the parentheses in the macro invocation optional by surrounding 'condition' in the above #define with parentheses -- 'void(condition)' -- but I'm not sure this is standard conforming. It does work on a lot of good compilers, though.) Any thoughts? Jonathan