///////////////////////////////////////////////////////////////////////////////

// is_pure.hpp

//

//  Copyright 2004 Eric Niebler. 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)

#ifndef BOOST_XPRESSIVE_DETAIL_STATIC_IS_PURE_HPP_EAN_10_04_2005

#define BOOST_XPRESSIVE_DETAIL_STATIC_IS_PURE_HPP_EAN_10_04_2005

// MS compatible compilers support #pragma once

#if defined(_MSC_VER) && (_MSC_VER >= 1020)

# pragma once

#endif

#include <vector>

#include <boost/ref.hpp>

#include <boost/shared_ptr.hpp>

#include <boost/mpl/and.hpp>

#include <boost/mpl/bool.hpp>

#include <boost/mpl/fold.hpp>

#include <boost/mpl/lambda.hpp>

#include <boost/mpl/assert.hpp>

#include <boost/mpl/not_equal_to.hpp>

#include <boost/mpl/transform_view.hpp>

#include <boost/xpressive/detail/detail_fwd.hpp>

#include <boost/xpressive/detail/static/as_xpr.hpp>

#include <boost/xpressive/detail/static/width_of.hpp>

namespace boost { namespace xpressive { namespace detail

{

    ///////////////////////////////////////////////////////////////////////////////

    // use_simple_repeat

    //

    template<typename Xpr>

    struct use_simple_repeat;

    ///////////////////////////////////////////////////////////////////////////////

    // is_pure

    //

    template<typename Xpr>

    struct is_pure;

    template<>

    struct is_pure<no_next>

      : mpl::true_

    {

    };

    template<typename Matcher>

    struct is_pure<proto::unary_op<Matcher, proto::noop_tag> >

      : as_matcher_type<Matcher>::type::pure

    {

    };

    template<typename Left, typename Right>

    struct is_pure<proto::binary_op<Left, Right, proto::right_shift_tag> >

      : mpl::and_<is_pure<Left>, is_pure<Right> >

    {

    };

    template<typename Left, typename Right>

    struct is_pure<proto::binary_op<Left, Right, proto::bitor_tag> >

      : mpl::and_<is_pure<Left>, is_pure<Right> >

    {

    };

    template<typename Right>

    struct is_pure<proto::binary_op<mark_tag, Right, proto::assign_tag> >

      : mpl::false_

    {

    };

    template<typename Right>

    struct is_pure<proto::binary_op<set_initializer_type, Right, proto::assign_tag> >

      : mpl::true_

    {

    };

    template<typename Modifier, typename Xpr>

    struct is_pure<proto::binary_op<Modifier, Xpr, modifier_tag> >

      : is_pure<Xpr>

    {

    };

    template<typename Xpr, bool Positive>

    struct is_pure<proto::unary_op<Xpr, lookahead_tag<Positive> > >

      : is_pure<Xpr>

    {

    };

    template<typename Xpr, bool Positive>

    struct is_pure<proto::unary_op<Xpr, lookbehind_tag<Positive> > >

      : is_pure<Xpr>

    {

    };

    template<typename Xpr>

    struct is_pure<proto::unary_op<Xpr, keeper_tag> >

      : is_pure<Xpr>

    {

    };

    template<typename Matcher, typename Next>

    struct is_pure<static_xpression<Matcher, Next> >

      : mpl::and_<typename Matcher::pure, is_pure<Next> >::type

    {

    };

    template<typename BidiIter>

    struct is_pure<shared_ptr<matchable<BidiIter> const> >

      : mpl::false_

    {

    };

    template<typename BidiIter>

    struct is_pure<std::vector<shared_ptr<matchable<BidiIter> const> > >

        : mpl::false_

    {

    };

    //template<typename BidiIter>

    //struct is_pure<basic_regex<BidiIter> >

    //    : mpl::false_

    //{

    //};

    template<typename BidiIter>

    struct is_pure<proto::unary_op<basic_regex<BidiIter>, proto::noop_tag> >

      : mpl::false_

    {

    };

    template<typename BidiIter>

    struct is_pure<proto::unary_op<reference_wrapper<basic_regex<BidiIter> const>, proto::noop_tag> >

      : mpl::false_

    {

    };

    // when complementing a set or an assertion, the purity is that of the set (true) or the assertion

    template<typename Op>

    struct is_pure<proto::unary_op<Op, proto::complement_tag> >

      : is_pure<Op>

    {

    };

    // The comma is used in list-initialized sets, which are pure

    template<typename Left, typename Right>

    struct is_pure<proto::binary_op<Left, Right, proto::comma_tag> >

      : mpl::true_

    {

    };

    // The subscript operator[] is used for sets, as in set['a' | range('b','h')]

    // It is also used for actions, which by definition have side-effects and thus are impure

    template<typename Left, typename Right>

    struct is_pure<proto::binary_op<Left, Right, proto::subscript_tag> >

      : is_same<Left, set_initializer_type>

    {

        // If Left is "set" then make sure that Right is pure

        BOOST_MPL_ASSERT

        ((

            mpl::or_

            <

                mpl::not_<is_same<Left, set_initializer_type> >

              , is_pure<Right>

            >

        ));

    };

    // Quantified expressions are pure IFF they use the simple_repeat_matcher

    template<typename Op>

    struct is_pure<proto::unary_op<Op, proto::unary_plus_tag> >

      : use_simple_repeat<Op>

    {

    };

    template<typename Op>

    struct is_pure<proto::unary_op<Op, proto::unary_star_tag> >

      : use_simple_repeat<Op>

    {

    };

    template<typename Op>

    struct is_pure<proto::unary_op<Op, proto::logical_not_tag> >

      : use_simple_repeat<Op>

    {

    };

    template<typename Op, uint_t Min, uint_t Max>

    struct is_pure<proto::unary_op<Op, generic_quant_tag<Min, Max> > >

      : use_simple_repeat<Op>

    {

    };

    template<typename Op>

    struct is_pure<proto::unary_op<Op, proto::unary_minus_tag> >

      : is_pure<Op>

    {

    };

    template<typename Alternates>

    struct is_pure<alternates_list<Alternates> >

      : mpl::fold

        <

            mpl::transform_view<Alternates, is_pure<mpl::_1> >

          , mpl::true_

          , mpl::and_<mpl::_1, mpl::_2>

        >::type

    {

    };

    ///////////////////////////////////////////////////////////////////////////////

    // use_simple_repeat

    // BUGBUG this doesn't handle +(_ >> s1) correctly, right?

    template<typename Xpr>

    struct use_simple_repeat

      : mpl::and_<mpl::not_equal_to<width_of<Xpr>, unknown_width>, is_pure<Xpr> >

    {

        // should never try to quantify something of 0-width

        BOOST_MPL_ASSERT((mpl::not_equal_to<width_of<Xpr>, mpl::size_t<0> >));

    };

    template<typename Matcher>

    struct use_simple_repeat<proto::unary_op<Matcher, proto::noop_tag> >

      : mpl::and_

        <

            mpl::equal_to

            <

                quant_type<typename as_matcher_type<Matcher>::type>

              , mpl::int_<quant_fixed_width>

            >

          , typename as_matcher_type<Matcher>::type::pure

        >

    {

        BOOST_MPL_ASSERT_RELATION(0, !=, as_matcher_type<Matcher>::type::width::value);

    };

    template<typename Op, typename Arg>

    struct is_pure<proto::op_proxy<Op, Arg> >

      : is_pure<Op>

    {

    };

}}} // namespace boost::xpressive::detail

#endif