C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Q: Eliminate explicit template function argument          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Allan Odgaard Guest Posted: Tue Aug 26, 2003 12:44 am    Post subject: Q: Eliminate explicit template function argument Hi there, I have a function similar to this: template <typename T> void someFunc (someClass<T> const& arg) { /* ... */ } The thing is, 90% of the time 'T = char' and the argument get instantiated from a 'char const*'. So that would yeild the following syntax: someFunc(someClass<char>("foo")); We could set "T = char" in the definition of someClass (for the records): template <typename T = char> struct someClass { someClass (const char* name); /* ... */ }; That would reduce the syntax to the following: someFunc(someClass<>("foo")); Or perhaps better, we could specify the explicit 'char' type when calling someFunc, which would instead give us: someFunc<char>("foo"); The question now is, is there anyway we can get it down to simply: someFunc("foo"); I realize that I could do a special 'char const*' overload for someFunc, but there are many functions which take the 'someClass<T> const&' as argument, thus I would need to overload all of these (which makes me favor a way in which the compiler would be able to fill in the type, unfortunately default types for template functions are not allowed). Regards Allan [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Attila Feher Guest Posted: Tue Aug 26, 2003 6:41 pm    Post subject: Re: Eliminate explicit template function argument Allan Odgaard wrote: Quote: Hi there, I have a function similar to this: template <typename T void someFunc (someClass { /* ... */ } The thing is, 90% of the time 'T = char' and the argument get instantiated from a 'char const*'. So that would yeild the following syntax: someFunc(someClass<char>("foo")); [SNIP] The question now is, is there anyway we can get it down to simply: someFunc("foo"); I realize that I could do a special 'char const*' overload for someFunc, but there are many functions which take the 'someClass<T> const&' as argument, thus I would need to overload all of these (which makes me favor a way in which the compiler would be able to fill in the type, unfortunately default types for template functions are not allowed). How about specializations for "T const *" and "T const &"? That is two full specializations of the function template and it seems to solve your issue to get rid of the const and the ref or ptr from the T type. -- Attila aka WW [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan Odgaard Guest Posted: Wed Aug 27, 2003 10:14 pm    Post subject: Re: Eliminate explicit template function argument Attila Feher wrote: Quote: I have a function similar to this: template <typename T void someFunc (someClass [...] is there anyway we can get it down to someFunc("foo"); How about specializations for "T const *" and "T const &"? That is two full specializations of the function template and it seems to solve your issue to get rid of the const and the ref or ptr from the T type. The T type is never a pointer or reference, so I don't really see how this relates to my problem. Could you provide me with an example? Thanks in advance, Allan [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Attila Feher Guest Posted: Thu Aug 28, 2003 8:40 pm    Post subject: Re: Eliminate explicit template function argument Allan Odgaard wrote: Quote: Attila Feher wrote: I have a function similar to this: template <typename T void someFunc (someClass [...] is there anyway we can get it down to someFunc("foo"); How about specializations for "T const *" and "T const &"? That is two full specializations of the function template and it seems to solve your issue to get rid of the const and the ref or ptr from the T type. The T type is never a pointer or reference, so I don't really see how this relates to my problem. Could you provide me with an example? I did not pay enough attention I guess. I must remind myself not to post when having a headache... template <typename T> void someFunc (someClass<T> const& arg) { /* ... */ } I guess you will need some sort of overload(?) full specialization(?) (Andrei Help!) of this template with a template template parameter. But then again I might be wrong... In that case of course you will need overloads (pr specializations) for all kinds of templates you want to pass (I mean taking 1,2,3... parameters). -- Attila aka WW [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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