#include #include #include #include #include #include template < typename T > int compare( const void *a, const void *b ) { if ( *static_cast< const T* >( a ) == *static_cast< const T* >( b ) ) { return 0; } return ( *static_cast< const T* >( b ) < *static_cast< const T* >( a ) ? 1 : -1 ); } template < typename Iterator > void print( Iterator first, Iterator last ) { while ( first != last ) { std::cout << *first++ << ' '; } std::cout << '\n'; } template < typename Iterator > void test_sort( Iterator first, Iterator last, int ( *comp )( const void*, const void* ) ) { std::cout << "Before: "; print( first, last ); std::qsort( first, std::distance( first, last ), sizeof( typename std::iterator_traits< Iterator >::value_type ), comp ); std::cout << "After: "; print( first, last ); } int main( int argc, char** argv ) { constexpr std::size_t SIZE{ 10 }; unsigned seed{ static_cast< unsigned >( std::chrono::high_resolution_clock::now().time_since_epoch().count() ) }; std::mt19937 generator{ seed }; char range_c[ SIZE ] = {}; std::generate( range_c, range_c + SIZE, [ &generator ]() -> char { return ( 65 + generator() % 26 ); } ); std::cout << "Sorting characters:\n"; test_sort( range_c, range_c + SIZE, compare< char > ); int range_i[ SIZE ] = {}; std::generate( range_i, range_i + SIZE, [ &generator ]() -> int { return ( generator() % 100 ); } ); std::cout << "\nSorting integers:\n"; test_sort( range_i, range_i + SIZE, compare< int > ); return EXIT_SUCCESS; }

Function pointers with qsort()