c++ - Trying to illustrate Perfect Forwarding with pairs -

i think understood perfect forwarding , took code normaly illustrate it

template<typename t, typename u> std::pair<t, u> make_pair_wrapper(t&& t, u&& u) {     return std::make_pair(std::forward<t>(t),                           std::forward<u>(u)); }  int main() {     std::pair<std::string, int> p1 = make_pair_wrapper("foo", 42); } 

but doesn't compile, saying can't convert 'std::pair<const char*, int>' 'std::pair<const char (&)[4], int>

i have admit don't understand

you forgot pass variables instead of temporaries. line incorrect

pair<string, int> p1 = make_pair_wrapper("foo",42); 

pair stores std::string , int, pass function const char* , int. const char* not std::string. do:

make_pair_wrapper(s, i);

or:

make_pair_wrapper(std::string("foo"), 42); 

you must work temporaries, can't omitted. if want have "variable" feel, can extend life of temporaries:

const int& = 42; const string& s = "foo"; 

then, can pass them function (but don't recommend that).