/usr/include/boost/proto/transform
Edit: /usr/include/boost/proto/transform/when.hpp (9903B)
///////////////////////////////////////////////////////////////////////////////
/// \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
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#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
struct when_impl
: transform >
{
typedef Grammar first;
typedef Fun second;
typedef typename Grammar::proto_grammar proto_grammar;
// Note: do not evaluate is_callable in this scope.
// R may be an incomplete type at this point.
template
struct impl : transform_impl
{
// OK to evaluate is_callable here. R should be compete by now.
typedef
typename mpl::if_c<
is_callable::value
, proto::call // "R" is a function to call
, proto::make // "R" is an object to construct
>::type
which;
typedef typename which::template impl::result_type result_type;
/// Evaluate R(A0,A1,...) as a transform either with
/// call\<\> or with make\<\> depending on
/// whether is_callable\::value is \c true or
/// \c false.
///
/// \param e The current expression
/// \param s The current state
/// \param d An arbitrary data
/// \pre matches\::value is \c true
/// \return which()(e, s, d)
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()(e, s, d);
}
};
};
}
/// \brief A grammar element and a PrimitiveTransform that associates
/// a transform with the grammar.
///
/// Use when\<\> 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, mpl::next<_state>()>
/// , otherwise >
/// >
/// {};
/// \endcode
///
/// In when\, when \c T is a class type it is a
/// PrimitiveTransform and the following equivalencies hold:
///
/// boost::result_of\(E,S,V)\>::type is the same as
/// boost::result_of\::type.
///
/// when\()(e,s,d) is the same as
/// T()(e,s,d).
template
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
/// when\. In C++, functions that are used as
/// parameters to other functions automatically decay to funtion
/// pointer types. In other words, the type T0(T1(_)) is
/// indistinguishable from T0(T1(*)(_)). This specialization
/// is required to handle these nested function pointer type transforms
/// properly.
template
struct when
: when
{};
/// \brief Syntactic sugar for when\<_, Fun\>, for use
/// in grammars to handle all the cases not yet handled.
///
/// Use otherwise\ in your grammars as a synonym for
/// when\<_, T\> 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, mpl::next<_state>()>
/// , otherwise >
/// >
/// {};
/// \endcode
template
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 when\ 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
struct when
: proto::transform >
{
typedef Grammar first;
typedef external_transform second;
typedef typename Grammar::proto_grammar proto_grammar;
template
struct impl
: remove_reference<
typename mpl::eval_if_c<
proto::result_of::has_env_var::value
, proto::result_of::env_var
, proto::result_of::env_var
>::type
>::type::template when::template impl
{};
};
/// \brief For defining a map of Rule/Transform pairs for use with
/// when\ 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
/// {};
///
/// struct char_terminal
/// : proto::terminal
/// {};
///
/// 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
/// , proto::when
/// >
/// {};
///
/// proto::literal i(1);
/// proto::literal c('a');
/// my_transforms trx;
///
/// // Evaluate "i+c" using my_grammar with the specified transforms:
/// my_grammar()(i + c, 0, trx);
/// \endcode
template
struct external_transforms
{
typedef mpl::map map_type;
template
struct when
: proto::when<_, typename mpl::at::type>
{};
};
// Other specializations of proto::when are generated by the preprocessor...
#include
/// INTERNAL ONLY
///
template
struct is_callable >
: mpl::true_
{};
}} // namespace boost::proto
#if defined(_MSC_VER)
# pragma warning(pop)
#endif
#endif