The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#ifndef ICSTRING_HPP
#define ICSTRING_HPP
#include <string>
#include <iostream>
#include <cctype>
// replace functions of the standard char_traits<char>
// so that strings behave in a case-insensitive way
struct ignorecase_traits : public std::char_traits<char> {
// return whether c1 and c2 are equal
static bool eq(const char& c1, const char& c2) {
return std::toupper(c1)==std::toupper(c2);
}
// return whether c1 is less than c2
static bool lt(const char& c1, const char& c2) {
return std::toupper(c1)<std::toupper(c2);
}
// compare up to n characters of s1 and s2
static int compare(const char* s1, const char* s2,
std::size_t n) {
for (std::size_t i=0; i<n; ++i) {
if (!eq(s1[i],s2[i])) {
return lt(s1[i],s2[i])?-1:1;
}
}
return 0;
}
// search c in s
static const char* find(const char* s, std::size_t n,
const char& c) {
for (std::size_t i=0; i<n; ++i) {
if (eq(s[i],c)) {
return &(s[i]);
}
}
return 0;
}
};
// define a special type for such strings
typedef std::basic_string<char,ignorecase_traits> icstring;
// define an output operator
// because the traits type is different from that for std::ostream
inline
std::ostream& operator << (std::ostream& strm, const icstring& s)
{
// simply convert the icstring into a normal string
return strm << std::string(s.data(),s.length());
}
#endif // ICSTRING_HPP