mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-23 21:35:04 +03:00
268 lines
9.9 KiB
C++
268 lines
9.9 KiB
C++
///////////////////////////////////////////////////////////////////////////////
|
|
/// \file when.hpp
|
|
/// Definition of when transform.
|
|
//
|
|
// Copyright 2008 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_PROTO_TRANSFORM_WHEN_HPP_EAN_10_29_2007
|
|
#define BOOST_PROTO_TRANSFORM_WHEN_HPP_EAN_10_29_2007
|
|
|
|
#include <boost/preprocessor/cat.hpp>
|
|
#include <boost/preprocessor/repetition/enum_params.hpp>
|
|
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
|
|
#include <boost/preprocessor/iteration/iterate.hpp>
|
|
#include <boost/mpl/at.hpp>
|
|
#include <boost/mpl/if.hpp>
|
|
#include <boost/mpl/map.hpp>
|
|
#include <boost/mpl/eval_if.hpp>
|
|
#include <boost/proto/proto_fwd.hpp>
|
|
#include <boost/proto/traits.hpp>
|
|
#include <boost/proto/transform/call.hpp>
|
|
#include <boost/proto/transform/make.hpp>
|
|
#include <boost/proto/transform/impl.hpp>
|
|
#include <boost/proto/transform/env.hpp>
|
|
|
|
#if defined(_MSC_VER)
|
|
# pragma warning(push)
|
|
# pragma warning(disable : 4714) // function 'xxx' marked as __forceinline not inlined
|
|
#endif
|
|
|
|
namespace boost { namespace proto
|
|
{
|
|
namespace detail
|
|
{
|
|
template<typename Grammar, typename R, typename Fun>
|
|
struct when_impl
|
|
: transform<when<Grammar, Fun> >
|
|
{
|
|
typedef Grammar first;
|
|
typedef Fun second;
|
|
typedef typename Grammar::proto_grammar proto_grammar;
|
|
|
|
// Note: do not evaluate is_callable<R> in this scope.
|
|
// R may be an incomplete type at this point.
|
|
|
|
template<typename Expr, typename State, typename Data>
|
|
struct impl : transform_impl<Expr, State, Data>
|
|
{
|
|
// OK to evaluate is_callable<R> here. R should be compete by now.
|
|
typedef
|
|
typename mpl::if_c<
|
|
is_callable<R>::value
|
|
, proto::call<Fun> // "R" is a function to call
|
|
, proto::make<Fun> // "R" is an object to construct
|
|
>::type
|
|
which;
|
|
|
|
typedef typename which::template impl<Expr, State, Data>::result_type result_type;
|
|
|
|
/// Evaluate <tt>R(A0,A1,...)</tt> as a transform either with
|
|
/// <tt>call\<\></tt> or with <tt>make\<\></tt> depending on
|
|
/// whether <tt>is_callable\<R\>::value</tt> is \c true or
|
|
/// \c false.
|
|
///
|
|
/// \param e The current expression
|
|
/// \param s The current state
|
|
/// \param d An arbitrary data
|
|
/// \pre <tt>matches\<Expr, Grammar\>::value</tt> is \c true
|
|
/// \return <tt>which()(e, s, d)</tt>
|
|
BOOST_FORCEINLINE
|
|
result_type operator ()(
|
|
typename impl::expr_param e
|
|
, typename impl::state_param s
|
|
, typename impl::data_param d
|
|
) const
|
|
{
|
|
return typename which::template impl<Expr, State, Data>()(e, s, d);
|
|
}
|
|
};
|
|
};
|
|
}
|
|
|
|
/// \brief A grammar element and a PrimitiveTransform that associates
|
|
/// a transform with the grammar.
|
|
///
|
|
/// Use <tt>when\<\></tt> to override a grammar's default transform
|
|
/// with a custom transform. It is for used when composing larger
|
|
/// transforms by associating smaller transforms with individual
|
|
/// rules in your grammar, as in the following transform which
|
|
/// counts the number of terminals in an expression.
|
|
///
|
|
/// \code
|
|
/// // Count the terminals in an expression tree.
|
|
/// // Must be invoked with initial state == mpl::int_<0>().
|
|
/// struct CountLeaves
|
|
/// : or_<
|
|
/// when<terminal<_>, mpl::next<_state>()>
|
|
/// , otherwise<fold<_, _state, CountLeaves> >
|
|
/// >
|
|
/// {};
|
|
/// \endcode
|
|
///
|
|
/// In <tt>when\<G, T\></tt>, when \c T is a class type it is a
|
|
/// PrimitiveTransform and the following equivalencies hold:
|
|
///
|
|
/// <tt>boost::result_of\<when\<G,T\>(E,S,V)\>::type</tt> is the same as
|
|
/// <tt>boost::result_of\<T(E,S,V)\>::type</tt>.
|
|
///
|
|
/// <tt>when\<G,T\>()(e,s,d)</tt> is the same as
|
|
/// <tt>T()(e,s,d)</tt>.
|
|
template<typename Grammar, typename PrimitiveTransform /*= Grammar*/>
|
|
struct when
|
|
: PrimitiveTransform
|
|
{
|
|
typedef Grammar first;
|
|
typedef PrimitiveTransform second;
|
|
typedef typename Grammar::proto_grammar proto_grammar;
|
|
};
|
|
|
|
/// \brief A specialization that treats function pointer Transforms as
|
|
/// if they were function type Transforms.
|
|
///
|
|
/// This specialization requires that \c Fun is actually a function type.
|
|
///
|
|
/// This specialization is required for nested transforms such as
|
|
/// <tt>when\<G, T0(T1(_))\></tt>. In C++, functions that are used as
|
|
/// parameters to other functions automatically decay to funtion
|
|
/// pointer types. In other words, the type <tt>T0(T1(_))</tt> is
|
|
/// indistinguishable from <tt>T0(T1(*)(_))</tt>. This specialization
|
|
/// is required to handle these nested function pointer type transforms
|
|
/// properly.
|
|
template<typename Grammar, typename Fun>
|
|
struct when<Grammar, Fun *>
|
|
: when<Grammar, Fun>
|
|
{};
|
|
|
|
/// \brief Syntactic sugar for <tt>when\<_, Fun\></tt>, for use
|
|
/// in grammars to handle all the cases not yet handled.
|
|
///
|
|
/// Use <tt>otherwise\<T\></tt> in your grammars as a synonym for
|
|
/// <tt>when\<_, T\></tt> as in the following transform which
|
|
/// counts the number of terminals in an expression.
|
|
///
|
|
/// \code
|
|
/// // Count the terminals in an expression tree.
|
|
/// // Must be invoked with initial state == mpl::int_<0>().
|
|
/// struct CountLeaves
|
|
/// : or_<
|
|
/// when<terminal<_>, mpl::next<_state>()>
|
|
/// , otherwise<fold<_, _state, CountLeaves> >
|
|
/// >
|
|
/// {};
|
|
/// \endcode
|
|
template<typename Fun>
|
|
struct otherwise
|
|
: when<_, Fun>
|
|
{};
|
|
|
|
namespace envns_
|
|
{
|
|
// Define the transforms global
|
|
BOOST_PROTO_DEFINE_ENV_VAR(transforms_type, transforms);
|
|
}
|
|
|
|
using envns_::transforms;
|
|
|
|
/// \brief This specialization uses the Data parameter as a collection
|
|
/// of transforms that can be indexed by the specified rule.
|
|
///
|
|
/// Use <tt>when\<T, external_transform\></tt> in your code when you would like
|
|
/// to define a grammar once and use it to evaluate expressions with
|
|
/// many different sets of transforms. The transforms are found by
|
|
/// using the Data parameter as a map from rules to transforms.
|
|
///
|
|
/// See \c action_map for an example.
|
|
template<typename Grammar>
|
|
struct when<Grammar, external_transform>
|
|
: proto::transform<when<Grammar, external_transform> >
|
|
{
|
|
typedef Grammar first;
|
|
typedef external_transform second;
|
|
typedef typename Grammar::proto_grammar proto_grammar;
|
|
|
|
template<typename Expr, typename State, typename Data>
|
|
struct impl
|
|
: remove_reference<
|
|
typename mpl::eval_if_c<
|
|
proto::result_of::has_env_var<Data, transforms_type>::value
|
|
, proto::result_of::env_var<Data, transforms_type>
|
|
, proto::result_of::env_var<Data, data_type>
|
|
>::type
|
|
>::type::template when<Grammar>::template impl<Expr, State, Data>
|
|
{};
|
|
};
|
|
|
|
/// \brief For defining a map of Rule/Transform pairs for use with
|
|
/// <tt>when\<T, external_transform\></tt> to make transforms external to the grammar
|
|
///
|
|
/// The following code defines a grammar with a couple of external transforms.
|
|
/// It also defines an action_map that maps from rules to transforms. It then
|
|
/// passes that transforms map at the Data parameter to the grammar. In this way,
|
|
/// the behavior of the grammar can be modified post-hoc by passing a different
|
|
/// action_map.
|
|
///
|
|
/// \code
|
|
/// struct int_terminal
|
|
/// : proto::terminal<int>
|
|
/// {};
|
|
///
|
|
/// struct char_terminal
|
|
/// : proto::terminal<char>
|
|
/// {};
|
|
///
|
|
/// struct my_grammar
|
|
/// : proto::or_<
|
|
/// proto::when< int_terminal, proto::external_transform >
|
|
/// , proto::when< char_terminal, proto::external_transform >
|
|
/// , proto::when<
|
|
/// proto::plus< my_grammar, my_grammar >
|
|
/// , proto::fold< _, int(), my_grammar >
|
|
/// >
|
|
/// >
|
|
/// {};
|
|
///
|
|
/// struct my_transforms
|
|
/// : proto::external_transforms<
|
|
/// proto::when<int_terminal, print(proto::_value)>
|
|
/// , proto::when<char_terminal, print(proto::_value)>
|
|
/// >
|
|
/// {};
|
|
///
|
|
/// proto::literal<int> i(1);
|
|
/// proto::literal<char> c('a');
|
|
/// my_transforms trx;
|
|
///
|
|
/// // Evaluate "i+c" using my_grammar with the specified transforms:
|
|
/// my_grammar()(i + c, 0, trx);
|
|
/// \endcode
|
|
template<BOOST_PP_ENUM_PARAMS_WITH_A_DEFAULT(BOOST_MPL_LIMIT_MAP_SIZE, typename T, mpl::na)>
|
|
struct external_transforms
|
|
{
|
|
typedef mpl::map<BOOST_PP_ENUM_PARAMS(BOOST_MPL_LIMIT_MAP_SIZE, T)> map_type;
|
|
|
|
template<typename Rule>
|
|
struct when
|
|
: proto::when<_, typename mpl::at<map_type, Rule>::type>
|
|
{};
|
|
};
|
|
|
|
// Other specializations of proto::when are generated by the preprocessor...
|
|
#include <boost/proto/transform/detail/when.hpp>
|
|
|
|
/// INTERNAL ONLY
|
|
///
|
|
template<typename Grammar, typename Transform>
|
|
struct is_callable<when<Grammar, Transform> >
|
|
: mpl::true_
|
|
{};
|
|
|
|
}} // namespace boost::proto
|
|
|
|
#if defined(_MSC_VER)
|
|
# pragma warning(pop)
|
|
#endif
|
|
|
|
#endif
|