c++ - Value Type from Arbitrary Iterator in Template Function -

i trying retrieve value type iterator parameter. how that? googled , see iterator_trait features, couldn't figure out how implement on function. iterator templated t can take either integers or float numbers, , on following function trying iterate through container of either integers or float numbers, , store them, depending on value type, new vector container.

to summarize, how value type information arbitrary iterator

template<typename t> void merge_function(t begin, t mid, t end) {     vector<auto> left_half (begin, mid);     left_half.push_back(infinite);     vector<auto> right_half (mid+1, end);     right_half.push_back(infinite); } 

update: trying sort of in-place merge sort.

vector<int> numbers = {5, 6, 3, 4, 1, 2, 7, 13, -6, 0, 3, 1, -2}; vector<int> l_half(numbers.begin(), numbers.end()); 

this works, try similar thing on following

 template<typename t>  void practice(t begin, t end) {    auto length = end - begin;    auto mid = length/2;    typedef typename std::iterator_traits<t>::value_type value_type;    vector<value_type> l_half(begin, mid);    vector<value_type> r_half(mid+1, end);    r_half.push_back(10000);    } 

so in main function call

   practice(numbers.begin(), numbers.end()); 

and @ first including following

 #include <iostream>  using namespace std;  #include <algorithm>  #include <vector>  #include <iterator>   template<typename t>  void practice(t begin, t end); 

but in line vector l_half(begin, mid);

i getting error

     /~~/main.cpp:105:14: no matching constructor initialization of 'vector<int>' 

i using macbook air, latest version.

typedef typename std::iterator_traits<t>::value_type value_type; std::vector<value_type> left_half(begin, mid); ... 

you can in c++11:

typedef typename std::remove_reference<decltype(*begin)>::type value_type; 

that work lazily implemented iterator classes don't have value_type definition.

if, reason, don't have actual iterator work with, iterator type, more general form this:

typedef typename std::remove_reference<decltype(*std::declval<t>())>::type value_type;