tie.hpp

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// ****************************************************************************
// entity/component/tie.hpp
//
// Ties component pools together to be used with algorithms
// iterators etc.  
// Replaces the need to use variadics everywhere and
// possibly makes client code more readable by explicitly
// tieing component pools together.
// 
// Copyright Chris Glover 2014-2015
//
// 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
//
// ****************************************************************************
#pragma once
#include <boost/fusion/container/vector.hpp>

// ----------------------------------------------------------------------------
//
namespace entity { namespace component
{
    // ------------------------------------------------------------------------
    //
#if ENTITY_SUPPORT_VARIADICS
    template<typename... Pools>
    boost::fusion::vector<Pools&...> tie(Pools&... pools)
    {
        return boost::fusion::vector<Pools&...>(pools...);
    }
#else
    template<typename Pool>
    boost::fusion::vector<Pool&> tie(Pool& pool)
    {
        return boost::fusion::vector<Pool&>(pool);
    }

    template<typename Pool1, typename Pool2>
    boost::fusion::vector<Pool1&, Pool2&> tie(Pool1& pool_1, Pool2& pool_2)
    {
        return boost::fusion::vector<Pool1&, Pool2&>(pool_1, pool_2);
    }

    template<typename Pool1, typename Pool2, typename Pool3>
    boost::fusion::vector<Pool1&, Pool2&, Pool3&> tie(Pool1& pool_1, Pool2& pool_2, Pool3& pool_3)
    {
        return boost::fusion::vector<Pool1&, Pool2&, Pool3&>(pool_1, pool_2, pool_3);
    }
#endif
} } // namespace entity { namespace component {