Question

I am trying to compare std::strings in a locale-dependent manner.

For ordinary C-style strings, I’ve found strcoll, which does exactly what I want, after doing std::setlocale

#include <iostream>
#include <locale>
#include <cstring>

bool cmp(const char* a, const char* b)
{
    return strcoll(a, b) < 0;
}

int main()
{
    const char* s1 = "z", *s2 = "å", *s3 = "ä", *s4 = "ö";

    std::cout << (cmp(s1,s2) && cmp(s2,s3) && cmp(s3,s4)) << "\n"; //Outputs 0
    std::setlocale(LC_ALL, "sv_SE.UTF-8");
    std::cout << (cmp(s1,s2) && cmp(s2,s3) && cmp(s3,s4)) << "\n"; //Outputs 1, like it should

    return 0;
}

However, I’d like to have this behaviour for std::string as well. I could just overload operator< to do something like

bool operator<(const std::string& a, const std::string& b)
{
    return strcoll(a.c_str(), b.c_str());
}

but then I’d have to worry about code using std::less and std::string::compare, so it doesn’t feel right.

Is there a way to make this kind of collation work for strings in a seamless manner?

Answer 1

operator() of std::locale is just what you are searching. To get the current global locale, just use the default constructor.