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