How to concatenate a std::string and an int?

Question

I thought this would be really simple but it\'s presenting some difficulties. If I have

std::string name = \"John\";
int age = 21;

How do I

Answer 1

Here is an implementation of how to append an int to a string using the parsing and formatting facets from the IOStreams library.

#include 
#include 
#include 

template 
struct erasable_facet : Facet
{
    erasable_facet() : Facet(1) { }
    ~erasable_facet() { }
};

void append_int(std::string& s, int n)
{
    erasable_facet>> facet;
    std::ios str(nullptr);

    facet.put(std::back_inserter(s), str,
                                     str.fill(), static_cast(n));
}

int main()
{
    std::string str = "ID: ";
    int id = 123;

    append_int(str, id);

    std::cout << str; // ID: 123
}