Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // env.hpp
Chris@16: // Helpers for producing and consuming tranform env variables.
Chris@16: //
Chris@16: //  Copyright 2012 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_PROTO_TRANSFORM_ENV_HPP_EAN_18_07_2012
Chris@16: #define BOOST_PROTO_TRANSFORM_ENV_HPP_EAN_18_07_2012
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/detail/workaround.hpp>
Chris@16: #include <boost/ref.hpp>
Chris@16: #include <boost/utility/enable_if.hpp>
Chris@16: #include <boost/type_traits/is_const.hpp>
Chris@16: #include <boost/type_traits/is_same.hpp>
Chris@16: #include <boost/type_traits/add_const.hpp>
Chris@16: #include <boost/type_traits/add_reference.hpp>
Chris@16: #include <boost/type_traits/remove_const.hpp>
Chris@16: #include <boost/mpl/assert.hpp>
Chris@16: #include <boost/mpl/bool.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/mpl/not.hpp>
Chris@16: #include <boost/proto/proto_fwd.hpp>
Chris@16: #include <boost/proto/transform/impl.hpp>
Chris@16: #include <boost/proto/detail/poly_function.hpp>
Chris@16: #include <boost/proto/detail/is_noncopyable.hpp>
Chris@16: 
Chris@16: #ifdef _MSC_VER
Chris@16: # pragma warning(push)
Chris@16: # pragma warning(disable: 4180) // qualifier applied to function type has no meaning; ignored
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost
Chris@16: {
Chris@16:     namespace proto
Chris@16:     {
Chris@16:         namespace detail
Chris@16:         {
Chris@16:             template<typename T>
Chris@16:             struct value_type
Chris@16:             {
Chris@16:                 typedef typename remove_const<T>::type value;
Chris@16:                 typedef typename add_reference<T>::type reference;
Chris@16:                 typedef typename mpl::if_c<is_noncopyable<T>::value, reference, value>::type type;
Chris@16:             };
Chris@16: 
Chris@16:             template<typename T>
Chris@16:             struct value_type<T &>
Chris@16:             {
Chris@16:                 typedef T &value;
Chris@16:                 typedef T &reference;
Chris@16:                 typedef T &type;
Chris@16:             };
Chris@16:         }
Chris@16: 
Chris@16:     #define BOOST_PROTO_DEFINE_ENV_VAR(TAG, NAME)                                                   \
Chris@16:         struct TAG                                                                                  \
Chris@16:         {                                                                                           \
Chris@16:             template<typename Value>                                                                \
Chris@16:             boost::proto::env<TAG, Value &> const                                                   \
Chris@16:                 operator =(boost::reference_wrapper<Value> &value) const                            \
Chris@16:             {                                                                                       \
Chris@16:                 return boost::proto::env<TAG, Value &>(value.get());                                \
Chris@16:             }                                                                                       \
Chris@16:             template<typename Value>                                                                \
Chris@16:             boost::proto::env<TAG, Value &> const                                                   \
Chris@16:                 operator =(boost::reference_wrapper<Value> const &value) const                      \
Chris@16:             {                                                                                       \
Chris@16:                 return boost::proto::env<TAG, Value &>(value.get());                                \
Chris@16:             }                                                                                       \
Chris@16:             template<typename Value>                                                                \
Chris@16:             typename boost::disable_if_c<                                                           \
Chris@16:                 boost::is_const<Value>::value                                                       \
Chris@16:               , boost::proto::env<TAG, typename boost::proto::detail::value_type<Value>::type>      \
Chris@16:             >::type const operator =(Value &value) const                                            \
Chris@16:             {                                                                                       \
Chris@16:                 return boost::proto::env<TAG, typename boost::proto::detail::value_type<Value>::type>(value); \
Chris@16:             }                                                                                       \
Chris@16:             template<typename Value>                                                                \
Chris@16:             boost::proto::env<TAG, typename boost::proto::detail::value_type<Value const>::type> const \
Chris@16:                 operator =(Value const &value) const                                                \
Chris@16:             {                                                                                       \
Chris@16:                 return boost::proto::env<TAG, typename boost::proto::detail::value_type<Value const>::type>(value); \
Chris@16:             }                                                                                       \
Chris@16:         };                                                                                          \
Chris@16:                                                                                                     \
Chris@16:         TAG const NAME = {}                                                                         \
Chris@16:         /**/
Chris@16: 
Chris@16:         namespace envns_
Chris@16:         {
Chris@16:             ////////////////////////////////////////////////////////////////////////////////////////////
Chris@16:             // env
Chris@16:             // A transform env is a slot-based storage mechanism, accessible by tag.
Chris@16:             template<typename Key, typename Value, typename Base /*= empty_env*/>
Chris@16:             struct env
Chris@16:               : private Base
Chris@16:             {
Chris@16:             private:
Chris@16:                 Value value_;
Chris@16: 
Chris@16:             public:
Chris@16:                 typedef Value value_type;
Chris@16:                 typedef typename add_reference<Value>::type reference;
Chris@16:                 typedef typename add_reference<typename add_const<Value>::type>::type const_reference;
Chris@16:                 typedef void proto_environment_; ///< INTERNAL ONLY
Chris@16: 
Chris@16:                 explicit env(const_reference value, Base const &base = Base())
Chris@16:                   : Base(base)
Chris@16:                   , value_(value)
Chris@16:                 {}
Chris@16: 
Chris@16:                 #if BOOST_WORKAROUND(__GNUC__, == 3) || (BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ <= 2)
Chris@16:                 /// INTERNAL ONLY
Chris@16:                 struct found
Chris@16:                 {
Chris@16:                     typedef Value type;
Chris@16:                     typedef typename add_reference<typename add_const<Value>::type>::type const_reference;
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename OtherKey, typename OtherValue = key_not_found>
Chris@16:                 struct lookup
Chris@16:                   : mpl::if_c<
Chris@16:                         is_same<OtherKey, Key>::value
Chris@16:                       , found
Chris@16:                       , typename Base::template lookup<OtherKey, OtherValue>
Chris@16:                     >::type
Chris@16:                 {};
Chris@16:                 #else
Chris@16:                 /// INTERNAL ONLY
Chris@16:                 template<typename OtherKey, typename OtherValue = key_not_found>
Chris@16:                 struct lookup
Chris@16:                   : Base::template lookup<OtherKey, OtherValue>
Chris@16:                 {};
Chris@16: 
Chris@16:                 /// INTERNAL ONLY
Chris@16:                 template<typename OtherValue>
Chris@16:                 struct lookup<Key, OtherValue>
Chris@16:                 {
Chris@16:                     typedef Value type;
Chris@16:                     typedef typename add_reference<typename add_const<Value>::type>::type const_reference;
Chris@16:                 };
Chris@16:                 #endif
Chris@16: 
Chris@16:                 // For key-based lookups not intended to fail
Chris@16:                 using Base::operator[];
Chris@16:                 const_reference operator[](Key) const
Chris@16:                 {
Chris@16:                     return this->value_;
Chris@16:                 }
Chris@16: 
Chris@16:                 // For key-based lookups that can fail, use the default if key not found.
Chris@16:                 using Base::at;
Chris@16:                 template<typename T>
Chris@16:                 const_reference at(Key, T const &) const
Chris@16:                 {
Chris@16:                     return this->value_;
Chris@16:                 }
Chris@16:             };
Chris@16: 
Chris@16:             // define proto::data_type type and proto::data global
Chris@16:             BOOST_PROTO_DEFINE_ENV_VAR(data_type, data);
Chris@16:         }
Chris@16: 
Chris@16:         using envns_::data;
Chris@16: 
Chris@16:         namespace functional
Chris@16:         {
Chris@16:             ////////////////////////////////////////////////////////////////////////////////////////
Chris@16:             // as_env
Chris@16:             struct as_env
Chris@16:             {
Chris@16:                 BOOST_PROTO_CALLABLE()
Chris@16:                 BOOST_PROTO_POLY_FUNCTION()
Chris@16: 
Chris@16:                 /// INTERNAL ONLY
Chris@16:                 template<typename T, bool B = is_env<T>::value>
Chris@16:                 struct impl
Chris@16:                 {
Chris@16:                     typedef env<data_type, typename detail::value_type<T>::type> result_type;
Chris@16: 
Chris@16:                     result_type const operator()(detail::arg<T> t) const
Chris@16:                     {
Chris@16:                         return result_type(t());
Chris@16:                     }
Chris@16:                 };
Chris@16: 
Chris@16:                 /// INTERNAL ONLY
Chris@16:                 template<typename T>
Chris@16:                 struct impl<T, true>
Chris@16:                 {
Chris@16:                     typedef T result_type;
Chris@16: 
Chris@16:                     typename add_const<T>::type operator()(detail::arg<T> t) const
Chris@16:                     {
Chris@16:                         return t();
Chris@16:                     }
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename Sig>
Chris@16:                 struct result;
Chris@16: 
Chris@16:                 template<typename This, typename T>
Chris@16:                 struct result<This(T)>
Chris@16:                 {
Chris@16:                     typedef typename impl<typename detail::normalize_arg<T>::type>::result_type type;
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename T>
Chris@16:                 typename impl<typename detail::normalize_arg<T &>::type>::result_type const
Chris@16:                     operator()(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T)) const
Chris@16:                 {
Chris@16:                     return impl<typename detail::normalize_arg<T &>::type>()(
Chris@16:                         static_cast<typename detail::normalize_arg<T &>::reference>(t)
Chris@16:                     );
Chris@16:                 }
Chris@16: 
Chris@16:                 template<typename T>
Chris@16:                 typename impl<typename detail::normalize_arg<T const &>::type>::result_type const
Chris@16:                     operator()(T const &t) const
Chris@16:                 {
Chris@16:                     return impl<typename detail::normalize_arg<T const &>::type>()(
Chris@16:                         static_cast<typename detail::normalize_arg<T const &>::reference>(t)
Chris@16:                     );
Chris@16:                 }
Chris@16:             };
Chris@16: 
Chris@16:             ////////////////////////////////////////////////////////////////////////////////////////
Chris@16:             // has_env_var
Chris@16:             template<typename Key>
Chris@16:             struct has_env_var
Chris@16:               : detail::poly_function<has_env_var<Key> >
Chris@16:             {
Chris@16:                 BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:                 template<typename Env, bool IsEnv = is_env<Env>::value>
Chris@16:                 struct impl
Chris@16:                 {
Chris@16:                     typedef
Chris@16:                         mpl::not_<
Chris@16:                             is_same<
Chris@16:                                 typename remove_reference<Env>::type::template lookup<Key>::type
Chris@16:                               , key_not_found
Chris@16:                             >
Chris@16:                         >
Chris@16:                     result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env>) const
Chris@16:                     {
Chris@16:                         return result_type();
Chris@16:                     }
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename Env>
Chris@16:                 struct impl<Env, false>
Chris@16:                 {
Chris@16:                     typedef mpl::false_ result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env>) const
Chris@16:                     {
Chris@16:                         return result_type();
Chris@16:                     }
Chris@16:                 };
Chris@16:             };
Chris@16: 
Chris@16:             template<>
Chris@16:             struct has_env_var<data_type>
Chris@16:               : detail::poly_function<has_env_var<data_type> >
Chris@16:             {
Chris@16:                 BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:                 template<typename Env, bool IsEnv = is_env<Env>::value>
Chris@16:                 struct impl
Chris@16:                 {
Chris@16:                     typedef
Chris@16:                         mpl::not_<
Chris@16:                             is_same<
Chris@16:                                 typename remove_reference<Env>::type::template lookup<data_type>::type
Chris@16:                               , key_not_found
Chris@16:                             >
Chris@16:                         >
Chris@16:                     result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env>) const
Chris@16:                     {
Chris@16:                         return result_type();
Chris@16:                     }
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename Env>
Chris@16:                 struct impl<Env, false>
Chris@16:                 {
Chris@16:                     typedef mpl::true_ result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env>) const
Chris@16:                     {
Chris@16:                         return result_type();
Chris@16:                     }
Chris@16:                 };
Chris@16:             };
Chris@16: 
Chris@16:             ////////////////////////////////////////////////////////////////////////////////////////
Chris@16:             // env_var
Chris@16:             template<typename Key>
Chris@16:             struct env_var
Chris@16:               : detail::poly_function<env_var<Key> >
Chris@16:             {
Chris@16:                 BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:                 template<typename Env>
Chris@16:                 struct impl
Chris@16:                 {
Chris@16:                     typedef
Chris@16:                         typename remove_reference<Env>::type::template lookup<Key>::type
Chris@16:                     result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env> e) const
Chris@16:                     {
Chris@16:                         return e()[Key()];
Chris@16:                     }
Chris@16:                 };
Chris@16:             };
Chris@16: 
Chris@16:             template<>
Chris@16:             struct env_var<data_type>
Chris@16:               : detail::poly_function<env_var<data_type> >
Chris@16:             {
Chris@16:                 BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:                 template<typename Env, bool B = is_env<Env>::value>
Chris@16:                 struct impl
Chris@16:                 {
Chris@16:                     typedef Env result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env> e) const
Chris@16:                     {
Chris@16:                         return e();
Chris@16:                     }
Chris@16:                 };
Chris@16: 
Chris@16:                 template<typename Env>
Chris@16:                 struct impl<Env, true>
Chris@16:                 {
Chris@16:                     typedef
Chris@16:                         typename remove_reference<Env>::type::template lookup<data_type>::type
Chris@16:                     result_type;
Chris@16: 
Chris@16:                     result_type operator()(detail::arg<Env> e) const
Chris@16:                     {
Chris@16:                         return e()[proto::data];
Chris@16:                     }
Chris@16:                 };
Chris@16:             };
Chris@16:         }
Chris@16: 
Chris@16:         namespace result_of
Chris@16:         {
Chris@16:             template<typename T>
Chris@16:             struct as_env
Chris@16:               : BOOST_PROTO_RESULT_OF<functional::as_env(T)>
Chris@16:             {};
Chris@16: 
Chris@16:             template<typename Env, typename Key>
Chris@16:             struct has_env_var
Chris@16:               : BOOST_PROTO_RESULT_OF<functional::has_env_var<Key>(Env)>::type
Chris@16:             {};
Chris@16: 
Chris@16:             template<typename Env, typename Key>
Chris@16:             struct env_var
Chris@16:               : BOOST_PROTO_RESULT_OF<functional::env_var<Key>(Env)>
Chris@16:             {};
Chris@16:         }
Chris@16: 
Chris@16:         ////////////////////////////////////////////////////////////////////////////////////////////
Chris@16:         // as_env
Chris@16:         template<typename T>
Chris@16:         typename proto::result_of::as_env<T &>::type const as_env(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T))
Chris@16:         {
Chris@16:             return proto::functional::as_env()(t);
Chris@16:         }
Chris@16: 
Chris@16:         template<typename T>
Chris@16:         typename proto::result_of::as_env<T const &>::type const as_env(T const &t)
Chris@16:         {
Chris@16:             return proto::functional::as_env()(t);
Chris@16:         }
Chris@16: 
Chris@16:         ////////////////////////////////////////////////////////////////////////////////////////////
Chris@16:         // has_env_var
Chris@16:         template<typename Key, typename Env>
Chris@16:         typename proto::result_of::has_env_var<Env &, Key>::type has_env_var(Env &e BOOST_PROTO_DISABLE_IF_IS_CONST(Env))
Chris@16:         {
Chris@16:             return functional::has_env_var<Key>()(e);
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Key, typename Env>
Chris@16:         typename proto::result_of::has_env_var<Env const &, Key>::type has_env_var(Env const &e)
Chris@16:         {
Chris@16:             return functional::has_env_var<Key>()(e);
Chris@16:         }
Chris@16: 
Chris@16:         ////////////////////////////////////////////////////////////////////////////////////////////
Chris@16:         // env_var
Chris@16:         template<typename Key, typename Env>
Chris@16:         typename proto::result_of::env_var<Env &, Key>::type env_var(Env &e BOOST_PROTO_DISABLE_IF_IS_CONST(Env))
Chris@16:         {
Chris@16:             return functional::env_var<Key>()(e);
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Key, typename Env>
Chris@16:         typename proto::result_of::env_var<Env const &, Key>::type env_var(Env const &e)
Chris@16:         {
Chris@16:             return functional::env_var<Key>()(e);
Chris@16:         }
Chris@16: 
Chris@16:         namespace envns_
Chris@16:         {
Chris@16:             ////////////////////////////////////////////////////////////////////////////////////////
Chris@16:             // env operator,
Chris@16:             template<typename T, typename T1, typename V1>
Chris@16:             inline typename disable_if_c<
Chris@16:                 is_const<T>::value
Chris@16:               , env<T1, V1, BOOST_PROTO_UNCVREF(typename result_of::as_env<T &>::type)>
Chris@16:             >::type const operator,(T &t, env<T1, V1> const &head)
Chris@16:             {
Chris@16:                 return env<T1, V1, BOOST_PROTO_UNCVREF(typename result_of::as_env<T &>::type)>(
Chris@16:                     head[T1()]
Chris@16:                   , proto::as_env(t)
Chris@16:                 );
Chris@16:             }
Chris@16: 
Chris@16:             template<typename T, typename T1, typename V1>
Chris@16:             inline env<T1, V1, BOOST_PROTO_UNCVREF(typename result_of::as_env<T const &>::type)> const
Chris@16:                 operator,(T const &t, env<T1, V1> const &head)
Chris@16:             {
Chris@16:                 return env<T1, V1, BOOST_PROTO_UNCVREF(typename result_of::as_env<T const &>::type)>(
Chris@16:                     head[T1()]
Chris@16:                   , proto::as_env(t)
Chris@16:                 );
Chris@16:             }
Chris@16:         }
Chris@16: 
Chris@16:         ////////////////////////////////////////////////////////////////////////////////////////////
Chris@16:         // _env_var
Chris@16:         template<typename Key>
Chris@16:         struct _env_var
Chris@16:           : proto::transform<_env_var<Key> >
Chris@16:         {
Chris@16:             template<typename Expr, typename State, typename Data>
Chris@16:             struct impl
Chris@16:               : transform_impl<Expr, State, Data>
Chris@16:             {
Chris@16:                 typedef typename impl::data::template lookup<Key>::type result_type;
Chris@16:                 BOOST_MPL_ASSERT_NOT((is_same<result_type, key_not_found>)); // lookup failed
Chris@16: 
Chris@16:                 BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::data::template lookup<Key>::const_reference)
Chris@16:                 operator ()(
Chris@16:                     typename impl::expr_param
Chris@16:                   , typename impl::state_param
Chris@16:                   , typename impl::data_param d
Chris@16:                 ) const
Chris@16:                 {
Chris@16:                     return d[Key()];
Chris@16:                 }
Chris@16:             };
Chris@16:         };
Chris@16: 
Chris@16:         struct _env
Chris@16:           : transform<_env>
Chris@16:         {
Chris@16:             template<typename Expr, typename State, typename Data>
Chris@16:             struct impl
Chris@16:               : transform_impl<Expr, State, Data>
Chris@16:             {
Chris@16:                 typedef Data result_type;
Chris@16: 
Chris@16:                 BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::data_param)
Chris@16:                 operator ()(
Chris@16:                     typename impl::expr_param
Chris@16:                   , typename impl::state_param
Chris@16:                   , typename impl::data_param d
Chris@16:                 ) const
Chris@16:                 {
Chris@16:                     return d;
Chris@16:                 }
Chris@16:             };
Chris@16:         };
Chris@16: 
Chris@16:         /// INTERNAL ONLY
Chris@16:         template<typename Key>
Chris@16:         struct is_callable<_env_var<Key> >
Chris@16:           : mpl::true_
Chris@16:         {};
Chris@16: 
Chris@16:         /// INTERNAL ONLY
Chris@16:         template<typename Key>
Chris@16:         struct is_callable<functional::has_env_var<Key> >
Chris@16:           : mpl::true_
Chris@16:         {};
Chris@16: 
Chris@16:         /// INTERNAL ONLY
Chris@16:         template<typename Key>
Chris@16:         struct is_callable<functional::env_var<Key> >
Chris@16:           : mpl::true_
Chris@16:         {};
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: #ifdef _MSC_VER
Chris@16: # pragma warning(pop)
Chris@16: #endif
Chris@16: 
Chris@16: #endif