// Boost.TypeErasure library
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//
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// Copyright 2011 Steven Watanabe
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//
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// Distributed under the Boost Software License Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// $Id$
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#ifndef BOOST_TYPE_ERASURE_PARAM_HPP_INCLUDED
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#define BOOST_TYPE_ERASURE_PARAM_HPP_INCLUDED
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#include <boost/config.hpp>
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#include <boost/utility/enable_if.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/remove_cv.hpp>
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#include <boost/type_traits/remove_reference.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/type_erasure/detail/access.hpp>
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#include <boost/type_erasure/detail/storage.hpp>
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#include <boost/type_erasure/is_placeholder.hpp>
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#include <boost/type_erasure/concept_of.hpp>
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namespace boost {
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namespace type_erasure {
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#ifndef BOOST_TYPE_ERASURE_DOXYGEN
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template<class Concept, class T>
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class any;
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template<class Concept>
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class binding;
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#endif
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namespace detail {
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struct access;
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}
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namespace detail {
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template<class From, class To>
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struct placeholder_conversion : boost::mpl::false_ {};
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template<class T>
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struct placeholder_conversion<T, T> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T, T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T, const T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<const T, T> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<const T, const T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T&, T> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T&, T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T&, const T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<const T&, T> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<const T&, const T&> : boost::mpl::true_ {};
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template<class T>
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struct placeholder_conversion<T&&, T> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T&&, const T&> : boost::mpl::true_ {};
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template<class T>
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struct placeholder_conversion<T&&, T&&> : boost::mpl::true_ {};
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#endif
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}
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/**
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* \brief A wrapper to help with overload resolution for functions
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* operating on an @ref any.
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*
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* The template arguments are interpreted in
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* the same way as @ref any.
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*
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* A parameter of type @ref param can be initialized
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* with an @ref any that has the same @c Concept
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* and base placeholder when there exists a corresponding
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* standard conversion for the placeholder.
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* A conversion sequence from @ref any "any<C, P>" to @ref param "param<C, P1>" is
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* a better conversion sequence than @ref any "any<C, P>" to @ref param "param<C, P2>"
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* iff the corresponding placeholder standard conversion
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* sequence from P to P1 is a better conversion sequence than
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* P to P2.
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*
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* \note Overloading based on cv-qualifiers and rvalue-ness is
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* only supported in C++11. In C++03, all conversion sequences
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* from @ref any to @ref param have the same rank.
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*
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* Example:
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*
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* \code
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* void f(param<C, _a&>);
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* void f(param<C, const _a&>);
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* void g(param<C, const _a&>);
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* void g(param<C, _a&&>);
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*
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* any<C, _a> a;
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* f(any<C, _a>()); // calls void f(param<C, const _a&>);
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* f(a); // calls void f(param<C, _a&>); (ambiguous in C++03)
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* g(any<C, _a>()); // calls void g(param<C, _a&&>); (ambiguous in C++03)
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* g(a); // calls void g(param<C, const _a&>);
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* \endcode
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*
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*/
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template<class Concept, class T>
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class param {
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public:
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friend struct boost::type_erasure::detail::access;
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/** INTERNAL ONLY */
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typedef void _boost_type_erasure_is_any;
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/** INTERNAL ONLY */
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typedef param _boost_type_erasure_derived_type;
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template<class U>
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param(any<Concept, U>& a
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#ifndef BOOST_TYPE_ERASURE_DOXYGEN
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, typename boost::enable_if<
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::boost::type_erasure::detail::placeholder_conversion<U, T>
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>::type* = 0
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#endif
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)
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: _impl(a)
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{}
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template<class U>
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param(const any<Concept, U>& a
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#ifndef BOOST_TYPE_ERASURE_DOXYGEN
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, typename boost::enable_if<
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::boost::type_erasure::detail::placeholder_conversion<
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typename ::boost::add_const<U>::type,
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T
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>
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>::type* = 0
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#endif
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)
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: _impl(a)
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{}
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template<class U>
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param(any<Concept, U>&& a
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#ifndef BOOST_TYPE_ERASURE_DOXYGEN
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, typename boost::enable_if<
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::boost::type_erasure::detail::placeholder_conversion<
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U&&,
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T
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>
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>::type* = 0
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#endif
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)
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: _impl(std::move(a))
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{}
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#endif
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/** INTERNAL ONLY */
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param(const ::boost::type_erasure::detail::storage& data,
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const ::boost::type_erasure::binding<Concept>& table)
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: _impl(data, table)
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{}
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/** Returns the stored @ref any. */
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any<Concept, T> get() const { return _impl; }
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private:
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any<Concept, T> _impl;
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};
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#if !defined(BOOST_NO_CXX11_REF_QUALIFIERS) && !defined(BOOST_TYPE_ERASURE_DOXYGEN)
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template<class Concept, class T>
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class param<Concept, const T&> {
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public:
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friend struct boost::type_erasure::detail::access;
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/** INTERNAL ONLY */
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typedef void _boost_type_erasure_is_any;
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/** INTERNAL ONLY */
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typedef param _boost_type_erasure_derived_type;
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param(const ::boost::type_erasure::detail::storage& data,
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const ::boost::type_erasure::binding<Concept>& table)
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: _impl(data, table)
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{}
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template<class U>
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param(U& u, typename boost::enable_if< ::boost::is_same<U, const any<Concept, T> > >::type* = 0) : _impl(u) {}
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any<Concept, const T&> get() const { return _impl; }
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protected:
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struct _impl_t {
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_impl_t(const ::boost::type_erasure::detail::storage& data_,
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const ::boost::type_erasure::binding<Concept>& table_)
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: table(table_), data(data_)
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{}
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_impl_t(const any<Concept, T>& u)
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: table(::boost::type_erasure::detail::access::table(u)),
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data(::boost::type_erasure::detail::access::data(u))
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{}
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// It's safe to capture the table by reference, because
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// the user's argument should out-live us. storage is
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// just a void*, so we don't need to add indirection.
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const ::boost::type_erasure::binding<Concept>& table;
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::boost::type_erasure::detail::storage data;
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} _impl;
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};
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template<class Concept, class T>
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class param<Concept, T&> : public param<Concept, const T&> {
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public:
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friend struct boost::type_erasure::detail::access;
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/** INTERNAL ONLY */
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typedef void _boost_type_erasure_is_any;
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/** INTERNAL ONLY */
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typedef param _boost_type_erasure_derived_type;
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param(const ::boost::type_erasure::detail::storage& data,
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const ::boost::type_erasure::binding<Concept>& table)
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: param<Concept, const T&>(data, table)
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{}
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any<Concept, T&> get() const
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{
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return any<Concept, T&>(
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::boost::type_erasure::detail::access::data(this->_impl),
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::boost::type_erasure::detail::access::table(this->_impl));
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}
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};
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template<class Concept, class T>
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class param<Concept, T&&> : public param<Concept, const T&> {
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public:
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friend struct boost::type_erasure::detail::access;
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/** INTERNAL ONLY */
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typedef void _boost_type_erasure_is_any;
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/** INTERNAL ONLY */
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typedef param _boost_type_erasure_derived_type;
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param(const ::boost::type_erasure::detail::storage& data,
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const ::boost::type_erasure::binding<Concept>& table)
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: param<Concept, const T&>(data, table)
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{}
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any<Concept, T&&> get() const
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{
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return any<Concept, T&&>(
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::boost::type_erasure::detail::access::data(this->_impl),
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::boost::type_erasure::detail::access::table(this->_impl));
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}
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};
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#endif
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#endif
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/**
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* \brief Metafunction that creates a @ref param.
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*
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* If @c T is a (cv/reference qualified) placeholder,
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* returns @ref param<@ref concept_of "concept_of<Any>::type", T>,
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* otherwise, returns T. This metafunction is intended
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* to be used for function arguments in specializations of
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* @ref concept_interface.
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*
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* \see derived, rebind_any
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*/
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template<class Any, class T>
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struct as_param {
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#ifdef BOOST_TYPE_ERASURE_DOXYGEN
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typedef detail::unspecified type;
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#else
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typedef typename ::boost::mpl::if_<
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::boost::type_erasure::is_placeholder<
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typename ::boost::remove_cv<
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typename ::boost::remove_reference<T>::type>::type>,
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param<typename ::boost::type_erasure::concept_of<Any>::type, T>,
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T
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>::type type;
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#endif
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};
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#ifndef BOOST_NO_CXX11_TEMPLATE_ALIASES
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template<class Any, class T>
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using as_param_t = typename ::boost::type_erasure::as_param<Any, T>::type;
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#endif
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}
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}
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#endif
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