C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Link error using pointers to functions with templates.          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Filipe Valepereiro Guest Posted: Mon Sep 27, 2004 2:57 pm    Post subject: Link error using pointers to functions with templates. I all. I need to write a function that convert one string into a vector. This string represent a serialized form of the vector. So i come up with this piece of code, that compile just fine. The problem is linking, VC6++ give me this error: unresolved external symbol "class std::vector<double,class std::allocator __cdecl VectorFromStr(class EFAString &,double (__cdecl*)(class EFAString &))" (?VectorFromStr@@YA?AV?$vector@NV?$allocator@N@std@@@std@@A AVEFAString@@P6AN0@Z@Z) My question is: Can i pass pointers to template functions? If i can't how can i circunvent this problem? Thanks in advance Filipe /******** code here *********/ template <class T> vector<T> VectorFromStr (string& str, T (*convertTo) (string&)) { vector<T> v (0); // skip first [vector= char *data = strdup (str.data () + strlen ("[vector=")); // last ] becomes end of string *(data + strlen (data) - 1) = 0; T val; char *p; while (data) { p = strstr (data, ","); if (p) *p = 0; v.push_back (convertTo (data)); // go to next value data = p; if (data) data++; } return v; } Back to top Victor Bazarov Guest Posted: Mon Sep 27, 2004 3:06 pm    Post subject: Re: Link error using pointers to functions with templates. Filipe Valepereiro wrote: Quote: I need to write a function that convert one string into a vector. This string represent a serialized form of the vector. So i come up with this piece of code, that compile just fine. The piece of code you posted is a template. Unless there is a bad syntax error in it, there is no reason for the compiler not to let it compile. What we need to see is the place where you _use_ that function. Quote: The problem is linking, VC6++ give me this error: unresolved external symbol "class std::vector<double,class std::allocator __cdecl VectorFromStr(class EFAString &,double (__cdecl*)(class EFAString &))" (?VectorFromStr@@YA?AV?$vector@NV?$allocator@N@std@@@std@@A AVEFAString@@P6AN0@Z@Z) My question is: Can i pass pointers to template functions? There is no such thing as pointers to template functions. Pointers can only point to an instantiation of a template. Quote: If i can't how can i circunvent this problem? Perhaps you can post the complete code (without extraneous stuff not related to the problem at hand). Quote: [..] V Back to top David Hilsee Guest Posted: Tue Sep 28, 2004 2:18 am    Post subject: Re: Link error using pointers to functions with templates. "Filipe Valepereiro" <efann (AT) portugalmail (DOT) pt> wrote Quote: I all. I need to write a function that convert one string into a vector. This string represent a serialized form of the vector. So i come up with this piece of code, that compile just fine. The problem is linking, VC6++ give me this error: unresolved external symbol "class std::vector<double,class std::allocator __cdecl VectorFromStr(class EFAString &,double (__cdecl*)(class EFAString &))" (?VectorFromStr@@YA?AV?$vector@NV?$allocator@N@std@@@std@@A AVEFAString@@P6AN0@Z@Z) My question is: Can i pass pointers to template functions? If i can't how can i circunvent this problem? Thanks in advance Filipe /******** code here *********/ template <class T vector { vector<T> v (0); // skip first [vector= char *data = strdup (str.data () + strlen ("[vector=")); // last ] becomes end of string *(data + strlen (data) - 1) = 0; T val; char *p; while (data) { p = strstr (data, ","); if (p) *p = 0; v.push_back (convertTo (data)); // go to next value data = p; if (data) data++; } return v; } I'm going to take a guess and say that this is answered in the FAQ (http://www.parashift.com/c++-faq-lite/) Section 34 ("Container classes and templates") question 12("Why can't I separate the definition of my templates class from it's declaration and put it inside a .cpp file?") and byeond. If that's not the problem, post more code (preferably somewhat complete). -- David Hilsee Back to top Filipe Valepereiro Guest Posted: Tue Sep 28, 2004 9:44 am    Post subject: Re: Link error using pointers to functions with templates. Thank's guy's. It's the second time i fall in this error. I've defined the template in the cpp file, and didn't notice that. No problem now, the code work just fine :) Thank's for the help ... Quote: I'm going to take a guess and say that this is answered in the FAQ (http://www.parashift.com/c++-faq-lite/) Section 34 ("Container classes and templates") question 12("Why can't I separate the definition of my templates class from it's declaration and put it inside a .cpp file?") and byeond. If that's not the problem, post more code (preferably somewhat complete). 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