libs/hana/test/_include/laws/comonad.hpp

   1 // Copyright Louis Dionne 2013-2017
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #ifndef BOOST_HANA_TEST_LAWS_COMONAD_HPP
   6 #define BOOST_HANA_TEST_LAWS_COMONAD_HPP
   7
   8 #include <boost/hana/assert.hpp>
   9 #include <boost/hana/concept/comonad.hpp>
  10 #include <boost/hana/concept/comparable.hpp>
  11 #include <boost/hana/core/when.hpp>
  12 #include <boost/hana/concept/foldable.hpp>
  13 #include <boost/hana/concept/functor.hpp>
  14
  15 #include <laws/base.hpp>
  16
  17
  18 namespace boost { namespace hana { namespace test {
  19     template <typename W, typename = when<true>>
  20     struct TestComonad : TestComonad<W, laws> {
  21         using TestComonad<W, laws>::TestComonad;
  22     };
  23
  24     template <typename W>
  25     struct TestComonad<W, laws> {
  26         template <typename Ws>
  27         TestComonad(Ws ws) {
  28             hana::for_each(ws, [](auto w) {
  29                 static_assert(Comonad<decltype(w)>{}, "");
  30
  31                 // extract(duplicate(w)) == w
  32                 BOOST_HANA_CHECK(hana::equal(
  33                     hana::extract(hana::duplicate(w)),
  34                     w
  35                 ));
  36
  37                 // transform(duplicate(w), extract) == w
  38                 BOOST_HANA_CHECK(hana::equal(
  39                     hana::transform(hana::duplicate(w), extract),
  40                     w
  41                 ));
  42
  43                 // duplicate(duplicate(w)) == transform(duplicate(w), duplicate)
  44                 BOOST_HANA_CHECK(hana::equal(
  45                     hana::duplicate(hana::duplicate(w)),
  46                     hana::transform(hana::duplicate(w), duplicate)
  47                 ));
  48             });
  49         }
  50     };
  51 }}} // end namespace boost::hana::test
  52
  53 #endif // !BOOST_HANA_TEST_LAWS_COMONAD_HPP