/** @file list5201.cpp */
/** Listing 52-1. Supporting Cast for the is_palindrome Function Template */
#include <algorithm>
#include <iostream>
#include <istream>
#include <iterator>
#include <locale>
#include <ostream>
#include <string>

/** Test for non-letter.
 * @param ch the character to test
 * @return true if @p ch is not a letter
 */
template<class Char>
bool non_letter(Char ch)
{
  return not std::isalpha(ch, std::locale());
}

/** Convert to lowercase.
 * Use a canonical form by converting to uppercase first,
 * and then to lowercase.
 * @param ch the character to test
 * @return the character converted to lowercase
 */
template<class Char>
Char lowercase(Char ch)
{
  return std::tolower(ch, std::locale());
}

/** Compare two characters without regard to case. */
template<class Char>
bool same_char(Char a, Char b)
{
  return lowercase(a) == lowercase(b);
}