c++ - passing reference to the templates -

nowadays m working on templates .so, got stuck in following problem code fills vector random values , count how many odd values in it:

#include <iostream> #include <vector> #include <numeric> #include <algorithm> #include <iterator> #include <ctime> using namespace std; class odd{ private:     int c; public:     bool operator()(int x){return x%2!=0;} }; template<typename t,typename q> int count_(t f1,t f2,q& check){     int count=0;     while(f1!=f2)     {         count+=check(*f1);         f1++;     }     return count; } int rand(){     return ((rand()%100)+1); } int main(){     srand(time(0));     vector<int> v(100);     odd o;     generate(v.begin(),v.end(),rand);     cout<<count_(v.begin(),v.end(),o); } 

this works fine when pass t& in arguments gives error ..i.e

template<typename t,typename q> int count_(t& f1,t& f2,q& check){     int count=0;     while(f1!=f2)     {         count+=check(*f1);         f1++;     } 

i dont know why because reference pointer work fine ...plz ..thankx

as alchemicalapples pointed out in comment, v.begin() , v.end() return rvalues, can bound const or rvalue references.

you don't need pass iterators reference - cheap copy. in fact, stl algorithms take iterator arguments value.

actually, shouldn't ever pass iterators reference, because function modify them, unexpected (none of standard algorithms that) , lead errors if use these iterators further in code.