C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  static_assert and SFINAE          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message thoth39 Guest Posted: Mon May 15, 2006 7:21 pm    Post subject: static_assert and SFINAE Should this work? template <bool condition, typename T> enable_if { static_assert(condition, "overload not enabled"); typedef T type; }; I don't think I understand SFINAE completely. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Carl Barron Guest Posted: Tue May 16, 2006 10:21 am    Post subject: Re: static_assert and SFINAE In article <1147707917.848787.179660 (AT) j33g2000cwa (DOT) googlegroups.com>, thoth39 <pedro.lamarao (AT) gmail (DOT) com> wrote: Quote: Should this work? template <bool condition, typename T enable_if { static_assert(condition, "overload not enabled"); typedef T type; }; I don't think I understand SFINAE completely. no this generates an error if condition is false it SFINAE does not generate errors but uses an invalid syntax to eliminate candidates from the compiler. template <bool B,typename T=void> struct enable_if{}; template <typename T> struct enable_if<true,T> { typedef T type; }; template <class C> void foo(C x, typename enable_if<condition>::type *=0) {/* 1 */} template <class C> void foo(C x, typename enable_if<!condition>::type *=0){/* 2 */} if condition is a compile time constant convertable to bool and the boolean value is true /* 1 */ is a candidate but /* 2 */ is not since enable_if<false> has no member type type. That is the gist of enable_if. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.