value_at.hpp

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/*=============================================================================
    Copyright (c) 1999-2003 Jaakko Jarvi
    Copyright (c) 2001-2006 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying 
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#include <boost/detail/lightweight_test.hpp>
#include <boost/fusion/sequence/intrinsic/at.hpp>
#include <boost/fusion/sequence/intrinsic/value_at.hpp>
#include <boost/static_assert.hpp>
#include <iostream>

#if !defined(FUSION_AT)
#define FUSION_AT at_c
#endif

#if !defined(FUSION_VALUE_AT)
#define FUSION_VALUE_AT(S, N) result_of::value_at_c<S, N>
#endif

namespace test_detail
{
    // something to prevent warnings for unused variables
    template<class T> void dummy(const T&) {}

    class A {};
}

void
test()
{
    using namespace boost::fusion;
    using namespace test_detail;

    double d = 2.7;
    A a;
    FUSION_SEQUENCE<int, double&, const A&, int> t(1, d, a, 2);
    const FUSION_SEQUENCE<int, double&, const A, int> ct(t);

    int i  = FUSION_AT<0>(t);
    int i2 = FUSION_AT<3>(t);

    BOOST_TEST(i == 1 && i2 == 2);

    int j  = FUSION_AT<0>(ct);
    BOOST_TEST(j == 1);

    FUSION_AT<0>(t) = 5;
    BOOST_TEST(FUSION_AT<0>(t) == 5);

#if defined(FUSION_TEST_FAIL)
    FUSION_AT<0>(ct) = 5; // can't assign to const
#endif

    double e = FUSION_AT<1>(t);
    BOOST_TEST(e > 2.69 && e < 2.71);

    FUSION_AT<1>(t) = 3.14+i;
    BOOST_TEST(FUSION_AT<1>(t) > 4.13 && FUSION_AT<1>(t) < 4.15);

#if defined(FUSION_TEST_FAIL)
    FUSION_AT<4>(t) = A(); // can't assign to const
    dummy(FUSION_AT<5>(ct)); // illegal index
#endif

    ++FUSION_AT<0>(t);
    BOOST_TEST(FUSION_AT<0>(t) == 6);
    
    typedef FUSION_SEQUENCE<int, float> seq_type;

    BOOST_STATIC_ASSERT(!(
        boost::is_const<FUSION_VALUE_AT(seq_type, 0)::type>::value));

    // constness should not affect
    BOOST_STATIC_ASSERT(!(
        boost::is_const<FUSION_VALUE_AT(const seq_type, 0)::type>::value));

    BOOST_STATIC_ASSERT(!(
        boost::is_const<FUSION_VALUE_AT(seq_type, 1)::type>::value));

    // constness should not affect
    BOOST_STATIC_ASSERT(!(
        boost::is_const<FUSION_VALUE_AT(const seq_type, 1)::type>::value));

    dummy(i); dummy(i2); dummy(j); dummy(e); // avoid warns for unused variables
}