#include <cctype>
#include <algorithm>
#include <locale>

class to_lower
{
	public:
		char operator() (char c) const        // notice the return type
	        {
		        return tolower(c);
		}
};

------------------------------------------------

string repl, key, get, temp;

temp = result;
std::transform(temp.begin(), temp.end(), temp.begin(), to_lower());
loc = temp.find( key, 0 );
while (loc != string::npos) {
        result.replace( loc, key.length(), repl );
        loc = result.find( key, 0 );
}
replace.erase(replace.begin());