Function main

example/tutorial/type.cpp:35–176

struct storage { char weight[n]; };

int main() {

{

//! [tuple]
auto types = hana::make_tuple(hana::type_c<int*>, hana::type_c<char&>, hana::type_c<void>);
auto char_ref = types[1_c];

BOOST_HANA_CONSTANT_CHECK(char_ref == hana::type_c<char&>);
//! [tuple]

}{

//! [filter.MPL]
using types = mpl::vector<int, char&, void*>;
using ts = mpl::copy_if<types, mpl::or_<std::is_pointer<mpl::_1>,
                                        std::is_reference<mpl::_1>>>::type;
//                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//                             placeholder expression

static_assert(mpl::equal<ts, mpl::vector<char&, void*>>::value, "");
//! [filter.MPL]

}{

using hana::traits::is_pointer;   // the traits namespace was not introduced
using hana::traits::is_reference; // yet, so we use unqualified names for now

//! [filter.Hana]
auto types = hana::tuple_t<int*, char&, void>;

auto ts = hana::filter(types, [](auto t) {
  return is_pointer(t) || is_reference(t);
});

BOOST_HANA_CONSTANT_CHECK(ts == hana::tuple_t<int*, char&>);
//! [filter.Hana]

}{

//! [single_library.then]
// types (MPL)
using types = mpl::vector<int*, char&, void>;
using ts = mpl::copy_if<types, mpl::or_<std::is_pointer<mpl::_1>,
                                        std::is_reference<mpl::_1>>>::type;

// values (Fusion)
auto values = fusion::make_vector(1, 'c', nullptr, 3.5);
auto vs = fusion::filter_if<std::is_integral<mpl::_1>>(values);
//! [single_library.then]

static_assert(mpl::equal<ts, mpl::vector<int*, char&>>::value, "");
BOOST_HANA_RUNTIME_CHECK(vs == fusion::make_vector(1, 'c'));

}{

using hana::traits::is_pointer;
using hana::traits::is_reference;