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// Copyright Louis Dionne 2013-2017
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
#ifndef BOOST_HANA_TEST_LAWS_MONAD_HPP
#define BOOST_HANA_TEST_LAWS_MONAD_HPP
#include <boost/hana/assert.hpp>
#include <boost/hana/bool.hpp>
#include <boost/hana/chain.hpp>
#include <boost/hana/concept/comparable.hpp>
#include <boost/hana/concept/monad.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/core/make.hpp>
#include <boost/hana/core/when.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/flatten.hpp>
#include <boost/hana/for_each.hpp>
#include <boost/hana/functional/compose.hpp>
#include <boost/hana/functional/id.hpp>
#include <boost/hana/lift.hpp>
#include <boost/hana/monadic_compose.hpp>
#include <boost/hana/transform.hpp>
#include <laws/base.hpp>
namespace boost { namespace hana { namespace test {
template <typename M, typename = when<true>>
struct TestMonad : TestMonad<M, laws> {
using TestMonad<M, laws>::TestMonad;
};
template <typename M>
struct TestMonad<M, laws> {
// Xs are Monads over something
// XXs are Monads over Monads over something
template <typename Xs, typename XXs>
TestMonad(Xs xs, XXs xxs) {
hana::for_each(xs, [](auto m) {
static_assert(Monad<decltype(m)>{}, "");
auto f = hana::compose(lift<M>, test::_injection<0>{});
auto g = hana::compose(lift<M>, test::_injection<1>{});
auto h = hana::compose(lift<M>, test::_injection<2>{});
auto x = test::ct_eq<0>{};
//////////////////////////////////////////////////////////////
// Laws formulated with `monadic_compose`
//////////////////////////////////////////////////////////////
// associativity
BOOST_HANA_CHECK(hana::equal(
hana::monadic_compose(h, hana::monadic_compose(g, f))(x),
hana::monadic_compose(hana::monadic_compose(h, g), f)(x)
));
// left identity
BOOST_HANA_CHECK(hana::equal(
hana::monadic_compose(lift<M>, f)(x),
f(x)
));
// right identity
BOOST_HANA_CHECK(hana::equal(
hana::monadic_compose(f, lift<M>)(x),
f(x)
));
//////////////////////////////////////////////////////////////
// Laws formulated with `chain`
//
// This just provides us with some additional cross-checking,
// but the documentation does not mention those.
//////////////////////////////////////////////////////////////
BOOST_HANA_CHECK(hana::equal(
hana::chain(hana::lift<M>(x), f),
f(x)
));
BOOST_HANA_CHECK(hana::equal(
hana::chain(m, lift<M>),
m
));
BOOST_HANA_CHECK(hana::equal(
hana::chain(m, [f, g](auto x) {
return hana::chain(f(x), g);
}),
hana::chain(hana::chain(m, f), g)
));
BOOST_HANA_CHECK(hana::equal(
hana::transform(m, f),
hana::chain(m, hana::compose(lift<M>, f))
));
//////////////////////////////////////////////////////////////
// Consistency of method definitions
//////////////////////////////////////////////////////////////
// consistency of `chain`
BOOST_HANA_CHECK(hana::equal(
hana::chain(m, f),
hana::flatten(hana::transform(m, f))
));
// consistency of `monadic_compose`
BOOST_HANA_CHECK(hana::equal(
hana::monadic_compose(f, g)(x),
hana::chain(g(x), f)
));
});
// consistency of `flatten`
hana::for_each(xxs, [](auto mm) {
BOOST_HANA_CHECK(hana::equal(
hana::flatten(mm),
hana::chain(mm, hana::id)
));
});
}
};
template <typename S>
struct TestMonad<S, when<Sequence<S>::value>>
: TestMonad<S, laws>
{
template <typename Xs, typename XXs>
TestMonad(Xs xs, XXs xxs)
: TestMonad<S, laws>{xs, xxs}
{
constexpr auto list = make<S>;
//////////////////////////////////////////////////////////////////
// flatten
//////////////////////////////////////////////////////////////////
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::flatten(list(list(), list())),
list()
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::flatten(list(list(ct_eq<0>{}), list())),
list(ct_eq<0>{})
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::flatten(list(list(), list(ct_eq<0>{}))),
list(ct_eq<0>{})
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::flatten(list(list(ct_eq<0>{}), list(ct_eq<1>{}))),
list(ct_eq<0>{}, ct_eq<1>{})
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::flatten(list(
list(ct_eq<0>{}, ct_eq<1>{}),
list(),
list(ct_eq<2>{}, ct_eq<3>{}),
list(ct_eq<4>{})
)),
list(ct_eq<0>{}, ct_eq<1>{}, ct_eq<2>{}, ct_eq<3>{}, ct_eq<4>{})
));
// just make sure we don't double move; this happened in hana::tuple
hana::flatten(list(list(Tracked{1}, Tracked{2})));
//////////////////////////////////////////////////////////////////
// chain
//////////////////////////////////////////////////////////////////
{
test::_injection<0> f{};
auto g = hana::compose(list, f);
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::chain(list(), g),
list()
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::chain(list(ct_eq<1>{}), g),
list(f(ct_eq<1>{}))
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::chain(list(ct_eq<1>{}, ct_eq<2>{}), g),
list(f(ct_eq<1>{}), f(ct_eq<2>{}))
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::chain(list(ct_eq<1>{}, ct_eq<2>{}, ct_eq<3>{}), g),
list(f(ct_eq<1>{}), f(ct_eq<2>{}), f(ct_eq<3>{}))
));
BOOST_HANA_CONSTANT_CHECK(hana::equal(
hana::chain(list(ct_eq<1>{}, ct_eq<2>{}, ct_eq<3>{}, ct_eq<4>{}), g),
list(f(ct_eq<1>{}), f(ct_eq<2>{}), f(ct_eq<3>{}), f(ct_eq<4>{}))
));
}
//////////////////////////////////////////////////////////////////
// monadic_compose
//////////////////////////////////////////////////////////////////
{
test::_injection<0> f{};
test::_injection<1> g{};
auto mf = [=](auto x) { return list(f(x), f(f(x))); };
auto mg = [=](auto x) { return list(g(x), g(g(x))); };
auto x = test::ct_eq<0>{};
BOOST_HANA_CHECK(hana::equal(
hana::monadic_compose(mf, mg)(x),
list(f(g(x)), f(f(g(x))), f(g(g(x))), f(f(g(g(x)))))
));
}
}
};
}}} // end namespace boost::hana::test
#endif // !BOOST_HANA_TEST_LAWS_MONAD_HPP
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