#include #include /** * Example 1 * Compute sum of all arguments */ template < typename... Args > constexpr auto foo1( Args... args ) { // expanded to ( ( ( v1 + v2 ) + v3 ) + ... ) return ( ... + args ); } /** * Example 2 * Specialization of Example 1 * -> also works with nontype template parameters */ template < int... Args > constexpr auto foo2() { // same expansion as above return ( ... + Args ); } /** * Example 3 * Perfect Forwarding of variadic arguments */ template < typename... Args > constexpr auto foo3( Args&&... args ) { // note missing operator when passing variadic pack as arguments return foo1( std::forward< Args >( args )... ); } /** * Example 4 * Check if all types match */ template < typename T1, typename... Types > constexpr auto foo4( T1, Types... ) { // expands to ( std::is_same_v< T1, Type1 > && ( std::is_same_v< T1, Type2 > && ... ) ) return ( std::is_same_v< T1, Types > && ... ); } /** * Example 5 * Simple variadic print */ template < typename... Args > auto print( const Args&... args ) { // lambda used as decorator to add a space // expands to ( ( ( std::cout << v1 ) << v2 ) << ... ) ( std::cout << ... << [&]( const auto& ref ) -> char { std::cout << ref; return ' '; }( args ) ) << '\n'; } int main() { // sample 1 // automatically deduces common return type [[maybe_unused]] constexpr auto v1 = foo1( 1, 42, 3.14, true, '!' ); // sample 2 // similar to 1, slightly different syntax [[maybe_unused]] constexpr auto v2 = foo2< 1, 2, 3, 4, 5 >(); // sample 3 [[maybe_unused]] constexpr auto v3 = foo3( 1, 42, 3.14, true, '!' ); // check equality static_assert( v1 == v3 ); // sample 4 [[maybe_unused]] constexpr auto v4_1 = foo4( 1, true, "Hello!" ); [[maybe_unused]] constexpr auto v4_2 = foo4( 1, 2, 3 ); // check results static_assert( v4_2 && v4_1 != v4_2 ); // sample 5 print( v1, v2, v3, v4_1, v4_2 ); return EXIT_SUCCESS; }

[Q&A] Fold Samples