language: C++11 (gcc-4.7.2)
date: 753 days 16 hours ago
link:
visibility: public 
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#include <tuple>
 
// Generic pack array (metacontainer)
template< typename T, T ... seq > struct value_sequence {
    // Append a value to the array (metafunction)
    template< T val > struct append
        { typedef value_sequence< T, seq..., val > type; };
};
 
// Generate a sequential array (metafunction)
template< size_t N >
struct index_sequence {
    typedef typename index_sequence< N - 1 >::type
                      ::template append< N - 1 >::type type;
};
 
template<>
struct index_sequence< 0 >
    { typedef value_sequence< size_t > type; };
 
// Generate indexes up to size of given tuple (metafunction)
template< typename T >
struct index_tuple {
    typedef typename index_sequence< std::tuple_size< T >::value
                                   >::type type;
};
 
// The magic function: passes indexes, makes all the function calls
template< typename F, typename G,
          typename T, size_t ... N >
void compose_with_indexes_helper( F f, G g, T args,
        value_sequence< size_t, N ... > ) {
    f( g( std::get< N >( args ), N ) ... );
}
 
template< typename F, typename G, typename ... T >
void compose_with_indexes( F f, G g, T && ... args ) {
    typedef std::tuple< T && ... > tuple_t;
    compose_with_indexes_helper
//        forwarding seems broken on ideone.com/GCC 4.5.1, work around.
//        ( f, g, std::forward_as_tuple( std::forward( args ) ... ) );
        ( f, g, tuple_t( args ... ), typename index_tuple< tuple_t >::type() );
}
 
#include <iostream>
#include <sstream>
 
struct prepend_index {
template< typename T >
std::string operator()( T const &value, size_t n ) {
    std::ostringstream oss;
    oss << n << ": " << value << '\n';
    return oss.str();
}
};
 
struct print {
template< typename T, typename ... TN >
std::ostream &operator()( T const &head, TN const & ... tail ) {
    std::cout << head;
    return print()( tail ... );
}
 
std::ostream &operator()() { return std::cout; }
};
 
template< typename ... T >
void print_menu( T const & ... items ) {
    compose_with_indexes( print(), prepend_index(), items... );
}
 
int main() {
    print_menu( "Yes", 'n', 42 );
}