text: // Copyright Louis Dionne 2013-2016
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
  
  #include <boost/hana/assert.hpp>
  #include <boost/hana/equal.hpp>
  #include <boost/hana/find_if.hpp>
  #include <boost/hana/map.hpp>
  #include <boost/hana/optional.hpp>
  
  #include <laws/base.hpp>
  #include <support/minimal_product.hpp>
  namespace hana = boost::hana;
  
  
  template <int i>
  auto key() { return hana::test::ct_eq<i>{}; }
  
  template <int i>
  auto val() { return hana::test::ct_eq<-i>{}; }
  
  template <int i, int j>
  auto p() { return ::minimal_product(key<i>(), val<j>()); }
  
  int main() {
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(), hana::equal.to(key<1>())),
          hana::nothing
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(p<1, 1>()), hana::equal.to(key<1>())),
          hana::just(val<1>())
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(p<1, 1>()), hana::equal.to(key<2>())),
          hana::nothing
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(p<1, 1>(), p<2, 2>()), hana::equal.to(key<1>())),
          hana::just(val<1>())
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(p<1, 1>(), p<2, 2>()), hana::equal.to(key<2>())),
          hana::just(val<2>())
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(hana::make_map(p<1, 1>(), p<2, 2>()), hana::equal.to(key<3>())),
          hana::nothing
      ));
  }
  