Thanks for help, I have an additional question. Does anyone know why the following program gives different output on VC++ 6 and VC++ 2003 NET? It is pretty strange, isn't it? Thanks in advance. Pshemek #include <iostream> #include <cmath> using namespace std; class A { protected: char m_d; }; class B : public A { public: typedef char s; private: unsigned short g; }; class C : public A { public: typedef short unsigned s; private: unsigned d; }; template<bool cond> class Select {}; template<> class Select<true> { static void Statment1(double g) { cout << g*g << endl; } public: static void f(double g) { Statment1(g); } }; template<> class Select<false> { static void Statment2(double g) { cout << sqrt(g) << endl; } public: static void f(double g) { Statment2(g); } }; template<bool cond> void exec() { Select<cond>::f(3.0); } template<class T> void foo() { exec(); exec(); } int main() { foo<B>(); foo<C>(); return 0; } -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Eric Niebler Sent: 11 May 2005 18:37 To: boost-users@lists.boost.org Subject: [Boost-users] Re: Question Sliwa, Przemyslaw (London) wrote:

I would like to write a template which depending on the argument type does different things.

For example the pseudo code:

template foo(T& nT, C& nC) { // common code; if(T==C) // specific code; .....

// again common code; }

Can the template meta programming help me in this case?

It may. It depends on whether "specific code" compiles when T!=C. If it does, you could do this: template void foo(T& nT, C& nC) { // common code if(boost::is_same::value) { /* specific code */ } // again common code } where is is_same<> is defined in boost/type_traits/is_same.hpp. If "specific code" doesn't compile when T!=C, you need to get fancier. An overloaded helper function is the way to go: template void specific_code(T&, C&) {} template<class T> void specific_code(T&, T&) { // specific code here } template void foo(T& nT, C& nC) { // common code specific_code(nT, nC); // again common code } HTH, -- Eric Niebler Boost Consulting www.boost-consulting.com _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ --------------------------------------------------------