338 lines
12 KiB
C++
338 lines
12 KiB
C++
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///////////////////////////////////////////////////////////////////////////////
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/// \file domain.hpp
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/// Contains definition of domain\<\> class template and helpers for
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/// defining domains with a generator and a grammar for controlling
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/// operator overloading.
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//
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// Copyright 2008 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_DOMAIN_HPP_EAN_02_13_2007
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#define BOOST_PROTO_DOMAIN_HPP_EAN_02_13_2007
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#include <boost/ref.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/proto/proto_fwd.hpp>
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#include <boost/proto/generate.hpp>
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#include <boost/proto/detail/as_expr.hpp>
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#include <boost/proto/detail/deduce_domain.hpp>
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#if defined(_MSC_VER)
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# pragma warning(push)
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# pragma warning(disable : 4714) // function 'xxx' marked as __forceinline not inlined
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#endif
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namespace boost { namespace proto
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{
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namespace detail
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{
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struct not_a_generator
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{};
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struct not_a_grammar
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{};
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struct not_a_domain
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{};
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}
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namespace domainns_
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{
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/// \brief For use in defining domain tags to be used
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/// with \c proto::extends\<\>. A \e Domain associates
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/// an expression type with a \e Generator, and optionally
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/// a \e Grammar.
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///
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/// The Generator determines how new expressions in the
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/// domain are constructed. Typically, a generator wraps
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/// all new expressions in a wrapper that imparts
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/// domain-specific behaviors to expressions within its
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/// domain. (See \c proto::extends\<\>.)
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///
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/// The Grammar determines whether a given expression is
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/// valid within the domain, and automatically disables
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/// any operator overloads which would cause an invalid
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/// expression to be created. By default, the Grammar
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/// parameter defaults to the wildcard, \c proto::_, which
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/// makes all expressions valid within the domain.
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///
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/// The Super declares the domain currently being defined
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/// to be a sub-domain of Super. Expressions in sub-domains
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/// can be freely combined with expressions in its super-
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/// domain (and <I>its</I> super-domain, etc.).
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///
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/// Example:
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/// \code
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/// template<typename Expr>
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/// struct MyExpr;
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///
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/// struct MyGrammar
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/// : or_< terminal<_>, plus<MyGrammar, MyGrammar> >
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/// {};
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///
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/// // Define MyDomain, in which all expressions are
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/// // wrapped in MyExpr<> and only expressions that
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/// // conform to MyGrammar are allowed.
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/// struct MyDomain
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/// : domain<generator<MyExpr>, MyGrammar>
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/// {};
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///
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/// // Use MyDomain to define MyExpr
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/// template<typename Expr>
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/// struct MyExpr
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/// : extends<Expr, MyExpr<Expr>, MyDomain>
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/// {
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/// // ...
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/// };
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/// \endcode
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///
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template<
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typename Generator // = default_generator
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, typename Grammar // = proto::_
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, typename Super // = no_super_domain
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>
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struct domain
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: Generator
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{
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typedef Generator proto_generator;
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typedef Grammar proto_grammar;
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typedef Super proto_super_domain;
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typedef domain proto_base_domain;
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/// INTERNAL ONLY
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typedef void proto_is_domain_;
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/// \brief A unary MonomorphicFunctionObject that turns objects into Proto
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/// expression objects in this domain.
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///
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/// The <tt>as_expr\<\></tt> function object turns objects into Proto expressions, if
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/// they are not already, by making them Proto terminals held by value if
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/// possible. Objects that are already Proto expressions are left alone.
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///
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/// If <tt>wants_basic_expr\<Generator\>::value</tt> is true, then let \c E be \c basic_expr;
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/// otherwise, let \t E be \c expr. Given an lvalue \c t of type \c T:
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///
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/// If \c T is not a Proto expression type the resulting terminal is
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/// calculated as follows:
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///
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/// If \c T is a function type, an abstract type, or a type derived from
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/// \c std::ios_base, let \c A be <tt>T &</tt>.
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/// Otherwise, let \c A be the type \c T stripped of cv-qualifiers.
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/// Then, the result of applying <tt>as_expr\<T\>()(t)</tt> is
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/// <tt>Generator()(E\<tag::terminal, term\<A\> \>::make(t))</tt>.
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///
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/// If \c T is a Proto expression type and its generator type is different from
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/// \c Generator, the result is <tt>Generator()(t)</tt>.
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///
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/// Otherwise, the result is \c t converted to an (un-const) rvalue.
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///
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template<typename T, typename IsExpr = void, typename Callable = proto::callable>
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struct as_expr
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: detail::as_expr<
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T
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, typename detail::base_generator<Generator>::type
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, wants_basic_expr<Generator>::value
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>
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{
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BOOST_PROTO_CALLABLE()
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct as_expr<T, typename T::proto_is_expr_, proto::callable>
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{
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BOOST_PROTO_CALLABLE()
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typedef typename remove_const<T>::type result_type;
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BOOST_FORCEINLINE
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result_type operator()(T &e) const
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{
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return e;
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}
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};
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/// \brief A unary MonomorphicFunctionObject that turns objects into Proto
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/// expression objects in this domain.
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///
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/// The <tt>as_child\<\></tt> function object turns objects into Proto expressions, if
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/// they are not already, by making them Proto terminals held by reference.
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/// Objects that are already Proto expressions are simply returned by reference.
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///
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/// If <tt>wants_basic_expr\<Generator\>::value</tt> is true, then let \c E be \c basic_expr;
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/// otherwise, let \t E be \c expr. Given an lvalue \c t of type \c T:
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///
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/// If \c T is not a Proto expression type the resulting terminal is
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/// <tt>Generator()(E\<tag::terminal, term\<T &\> \>::make(t))</tt>.
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///
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/// If \c T is a Proto expression type and its generator type is different from
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/// \c Generator, the result is <tt>Generator()(t)</tt>.
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///
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/// Otherwise, the result is the lvalue \c t.
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///
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template<typename T, typename IsExpr = void, typename Callable = proto::callable>
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struct as_child
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: detail::as_child<
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T
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, typename detail::base_generator<Generator>::type
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, wants_basic_expr<Generator>::value
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>
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{
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BOOST_PROTO_CALLABLE()
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct as_child<T, typename T::proto_is_expr_, proto::callable>
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{
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BOOST_PROTO_CALLABLE()
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typedef T &result_type;
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BOOST_FORCEINLINE
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result_type operator()(T &e) const
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{
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return e;
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}
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};
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};
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/// \brief The domain expressions have by default, if
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/// \c proto::extends\<\> has not been used to associate
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/// a domain with an expression.
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///
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struct default_domain
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: domain<>
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{};
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/// \brief A domain to use when you prefer the use of
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/// \c proto::basic_expr\<\> over \c proto::expr\<\>.
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///
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struct basic_default_domain
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: domain<basic_default_generator>
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{};
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/// \brief A pseudo-domain for use in functions and
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/// metafunctions that require a domain parameter. It
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/// indicates that the domain of the parent node should
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/// be inferred from the domains of the child nodes.
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///
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/// \attention \c deduce_domain is not itself a valid domain.
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///
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struct deduce_domain
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: domain<detail::not_a_generator, detail::not_a_grammar, detail::not_a_domain>
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{};
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/// \brief Given a domain, a tag type and an argument list,
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/// compute the type of the expression to generate. This is
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/// either an instance of \c proto::expr\<\> or
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/// \c proto::basic_expr\<\>.
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///
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template<typename Domain, typename Tag, typename Args, bool WantsBasicExpr>
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struct base_expr
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{
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typedef proto::expr<Tag, Args, Args::arity> type;
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};
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/// INTERNAL ONLY
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///
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template<typename Domain, typename Tag, typename Args>
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struct base_expr<Domain, Tag, Args, true>
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{
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typedef proto::basic_expr<Tag, Args, Args::arity> type;
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};
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}
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/// A metafunction that returns \c mpl::true_
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/// if the type \c T is the type of a Proto domain;
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/// \c mpl::false_ otherwise. If \c T inherits from
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/// \c proto::domain\<\>, \c is_domain\<T\> is
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/// \c mpl::true_.
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template<typename T, typename Void /* = void*/>
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struct is_domain
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: mpl::false_
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{};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct is_domain<T, typename T::proto_is_domain_>
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: mpl::true_
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{};
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/// A metafunction that returns the domain of
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/// a given type. If \c T is a Proto expression
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/// type, it returns that expression's associated
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/// domain. If not, it returns
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/// \c proto::default_domain.
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template<typename T, typename Void /* = void*/>
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struct domain_of
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{
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typedef default_domain type;
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct domain_of<T, typename T::proto_is_expr_>
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{
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typedef typename T::proto_domain type;
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct domain_of<T &, void>
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{
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typedef typename domain_of<T>::type type;
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct domain_of<boost::reference_wrapper<T>, void>
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{
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typedef typename domain_of<T>::type type;
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};
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/// INTERNAL ONLY
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///
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template<typename T>
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struct domain_of<boost::reference_wrapper<T> const, void>
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{
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typedef typename domain_of<T>::type type;
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};
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/// A metafunction that returns \c mpl::true_
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/// if the type \c SubDomain is a sub-domain of
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/// \c SuperDomain; \c mpl::false_ otherwise.
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template<typename SubDomain, typename SuperDomain>
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struct is_sub_domain_of
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: is_sub_domain_of<typename SubDomain::proto_super_domain, SuperDomain>
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{};
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/// INTERNAL ONLY
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///
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template<typename SuperDomain>
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struct is_sub_domain_of<proto::no_super_domain, SuperDomain>
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: mpl::false_
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{};
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/// INTERNAL ONLY
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///
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template<typename SuperDomain>
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struct is_sub_domain_of<SuperDomain, SuperDomain>
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: mpl::true_
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{};
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}}
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#if defined(_MSC_VER)
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# pragma warning(pop)
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#endif
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#endif
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