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/concept/struct.hpp>
  #include <boost/hana/equal.hpp>
  #include <boost/hana/find_if.hpp>
  #include <boost/hana/integral_constant.hpp>
  #include <boost/hana/optional.hpp>
  
  #include "minimal_struct.hpp"
  #include <laws/base.hpp>
  namespace hana = boost::hana;
  using hana::test::ct_eq;
  
  
  template <int i = 0>
  struct undefined { };
  
  int main() {
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(), undefined<>{}),
          hana::nothing
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(ct_eq<0>{}), hana::equal.to(hana::int_c<0>)),
          hana::just(ct_eq<0>{})
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(undefined<1>{}), hana::equal.to(hana::int_c<1>)),
          hana::nothing
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(ct_eq<0>{}, ct_eq<1>{}), hana::equal.to(hana::int_c<0>)),
          hana::just(ct_eq<0>{})
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(ct_eq<0>{}, ct_eq<1>{}), hana::equal.to(hana::int_c<1>)),
          hana::just(ct_eq<1>{})
      ));
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::find_if(obj(undefined<0>{}, undefined<1>{}), hana::equal.to(hana::int_c<2>)),
          hana::nothing
      ));
  }
  