uppercase to lower case string

Hi,
Thaddeus's answer using ::tolower() is OK for plain ANSI char based strings.

The following works as well with non-ANSI character sets or wchar_t based strings:

// Use with VC pre-2010 compilers
#include <string>
#include <locale>
#include <algorithm>
#include <iterator>

template <class C_type>
C_type CharLower(C_type in)
{
    return std::tolower(in, std::locale());
}
template <typename S_type>
S_type ToLower(const S_type& str)
{
    S_type out;
    std::transform(str.begin(), str.end(), std::back_inserter(out), CharLower<S_type::value_type>);
    return out;
}

or simpler for VC2010 because of C++0x partial implementation:

// Use with VC2010 compilers
#include <string>
#include <locale>
#include <algorithm>
#include <iterator>

template <typename S_type>
S_type ToLower(const S_type& in)
{
    S_type out;
    std::transform(in.begin(), in.end(), std::back_inserter(out), [](S_type::value_type ch){
        return std::tolower(ch, std::locale());});
    return out;
}

You can test both versions with:

#include <iostream>
int main ()
{
    using namespace std;
    string str="Test String.\n";
    cout << ToLower(str) << endl;

    wstring wstr= L"Test String.\n";
    wcout << ToLower(wstr) << endl;

    return 0;
}

cheers,
AR