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C-/C++-Quelltext

#include <string>
#include <functional>
#include <algorithm>
#include <cmath>
#include <cassert>

template< typename T >
void caesar( std::basic_string<T>& text, int shift )
{
    typedef std::basic_string<T> string;
    typedef string::value_type value_type;

    struct foo : std::unary_function<string::value_type, string::value_type>
    {
        foo( int shift ) : m_shift( shift )
        {
            assert( abs(shift) < 26 && "shift must be less than 26" );
        }

        string::value_type operator()( string::value_type c )
        {
            int idx = m_shift;
            int a, b;

            if ( c >= 'a' && c <= 'z' ) {
                idx += c - 'a';
                a = 'a';
                b = 'z'+1;
            }
            else if ( c >= 'A' && c <= 'Z' ) {
                idx += c - 'A';
                a = 'A';
                b = 'Z'+1;
            }
            else
                return c; 

            return static_cast<value_type>(( idx % 26 ) + ( idx < 0 ? b : a ));
        }
    private:
        int m_shift;
    } bar( shift );

    std::transform( text.begin(), text.end(), text.begin(), bar );
}