Is specialization of std::to_string for custom types allowed by the C++ standard?

Question

In C++11 and later, is it allowed to specialize std::to_string in the std namespace for custom types?

namespace std {
string to_str         


        

Answer 1

Better way would be to create your own function that make use of std::to_string if it's possible as well as the .toString() method whenever it's available for passed argument:

#include 
#include 
#include 

struct MyClass {
   std::string toString() const { return "MyClass"; }
};

template
typename std::enable_if().toString()), std::string>::value, std::string>::type my_to_string(const T &t) {
    return t.toString();
}

template
typename std::enable_if())), std::string>::value, std::string>::type my_to_string(const T &t) {
    return std::to_string(t);
}

int main() {
   std::cout << my_to_string(MyClass()) << std::endl; // will invoke .toString
   std::cout << my_to_string(1) << std::endl; //will invoke std::to_string
}