c++ - Converting between types in function templates -

i have function template gives result reference variable defined template. function must convert value , assign reference variable. have problem compiling in line show in code.

what wrong , how can solve that?

the following code:

#include "stdafx.h" #include <iostream> #include <string> #include <map>  using namespace std;  map<wstring, wstring> my_data = {     { l"data1", l"123.456"  },     { l"data2", l"2213.323" },     { l"data3", l"3321.321" },     { l"data4", l"1000" },     { l"data5", l"2000" } };    template<class t> bool get_map_value(const wstring &map_key, t& map_value) {     auto tmp = my_data.find(map_key);      if (tmp == my_data.end())         return false;      if (typeid(t).name() == typeid(wstring).name())         map_value = tmp->second;         //error c2440   '=': cannot convert 'std::wstring' 'int'             //error c2440   '=': cannot convert 'std::wstring' 'double'       else if (typeid(t).name() == typeid(double).name())         map_value = _wtof(tmp->second.c_str());      else if (typeid(t).name() == typeid(int).name())         map_value = _wtoi(tmp->second.c_str());       return true; }   int main() {      double d = 0.0;     wstring w = l"";     int = 0;      get_map_value(l"data1", w);     get_map_value(l"data3", d);     get_map_value(l"data4", i);       return 0; } 

what wrong

the type of tmp->second wstring. when template instantiated t = int, type of map_value int&. line

map_value = tmp->second; 

has pretty self explanatory error message

error c2440   '=': cannot convert 'std::wstring' 'int' 

std::wstring not implicitly convertible int. problem. must remember entire function must formed, if execution cannot reach part of it.

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how can solve that?

what need few overloads. shall refactor differing part of function, don't need repeat identical part.

parse_value(int& variable, const std::wstring& value) {     variable = _wtoi(tmp->second.c_str()); } parse_value(double& variable, const std::wstring& value) {     variable = _wtof(tmp->second.c_str()); } parse_value(std::wstring& variable, const std::wstring& value) {     variable = value; }  template<class t> bool get_map_value(const wstring &map_key, t& map_value) {     auto tmp = my_data.find(map_key);      if (tmp == my_data.end())         return false;      parse_value(map_value, tmp->second);      return true; 

}