C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  const object instantiation          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Jing Chen Guest Posted: Tue Mar 29, 2005 9:33 am    Post subject: const object instantiation All: I don't understand why it is different to instantiate template using const object and non-const object. template<typename T,typename SubType = void> class TestTemplate { public: static void showType() { FMK_TRACE("TestTemplate::showType with explict instantion"); } }; // A template<typename T> class TestTemplate<T,void> { public: static void showType() { FMK_TRACE("TestTemplate::showType with patial instantion"); } }; //B struct myStruct { }; int main() { typedef TestTemplate<const myStruct> myConstObj; //1 myConstObj::showType(); typedef TestTemplate<myStruct> myObj; //2 myObj::showType(); } in SUN solaris 9 with C++ compiler Forte 7, 1 was instantiated from full specialization of template(A), while 2 was instantiated from partial specialization of template(B). while use Forte 6.1 both are instantiated from partial specialization (B). why they are different? thanks jing [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Shantanu Garg Guest Posted: Tue Mar 29, 2005 10:03 pm    Post subject: Re: const object instantiation Quote: int main() { typedef TestTemplate<const myStruct> myConstObj; //1 myConstObj::showType(); typedef TestTemplate<myStruct> myObj; //2 myObj::showType(); } in SUN solaris 9 with C++ compiler Forte 7, 1 was instantiated from full specialization of template(A), while 2 was instantiated from partial specialization of template(B). while use Forte 6.1 both are instantiated from partial specialization (B). why they are different? I think your compiler is wrong. In both the cases Version B of the function should be called. I think 'const' shouldn't have any affect on template instantiation. -Shantanu [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top annamalai.gurusami@gmail. Guest Posted: Thu Mar 31, 2005 2:10 pm    Post subject: Re: const object instantiation Jing Chen wrote: (snip) Quote: template class TestTemplate { public: static void showType() { FMK_TRACE("TestTemplate::showType with patial instantion"); } }; //B It is better called as "partial specialization" rather than "partial instantiation". Also, when the above template class is called without specifying the second template argument the default is void, which will then call the template class that has been specialized with void for second argument. So both the times, the partially specialized template should be called. This behaviour is exhibited by g++ 3.3.4. Also, since the const qualifier is applied to the first template argument and the partial specialization is done with the second argument, I doubt whether this behaviour is related to the const qualifier. (Maybe, I will try to reproduce similar stranger behaviour without using const!) BTW, I haven't read the C++ standards about this. But what I am stating is my understanding of C++ and what its "logical" behaviour would be! Rgds, anna [ 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.