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//-----------------------------------------------------------------------------
// boost variant/visitor_ptr.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2002-2003
// Eric Friedman
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_VARIANT_VISITOR_PTR_HPP
#define BOOST_VARIANT_VISITOR_PTR_HPP
#include "boost/variant/bad_visit.hpp"
#include "boost/variant/static_visitor.hpp"
#include "boost/mpl/eval_if.hpp"
#include "boost/mpl/identity.hpp"
#include "boost/type_traits/add_reference.hpp"
#include "boost/type_traits/is_reference.hpp"
#include "boost/type_traits/is_void.hpp"
namespace boost {
//////////////////////////////////////////////////////////////////////////
// function template visitor_ptr
//
// Adapts a function pointer for use as visitor capable of handling
// values of a single type. Throws bad_visit if inappropriately applied.
//
template <typename T, typename R>
class visitor_ptr_t
: public static_visitor<R>
{
private: // representation
typedef R (*visitor_t)(T);
visitor_t visitor_;
public: // typedefs
typedef R result_type;
private: // private typedefs
typedef typename mpl::eval_if<
is_reference<T>
, mpl::identity<T>
, add_reference<const T>
>::type argument_fwd_type;
public: // structors
explicit visitor_ptr_t(visitor_t visitor)
: visitor_(visitor)
{
}
public: // static visitor interfaces
template <typename U>
result_type operator()(const U&) const
{
throw bad_visit();
}
#if !defined(BOOST_NO_VOID_RETURNS)
public: // static visitor interfaces, cont.
result_type operator()(argument_fwd_type operand) const
{
return visitor_(operand);
}
#else // defined(BOOST_NO_VOID_RETURNS)
private: // helpers, for static visitor interfaces (below)
result_type execute_impl(argument_fwd_type operand, mpl::false_) const
{
return visitor_(operand);
}
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
execute_impl(argument_fwd_type operand, mpl::true_) const
{
visitor_(operand);
BOOST_VARIANT_AUX_RETURN_VOID;
}
public: // static visitor interfaces, cont.
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
operator()(argument_fwd_type operand) const
{
typedef typename is_void<result_type>::type has_void_result;
return execute_impl(operand, has_void_result());
}
#endif // BOOST_NO_VOID_RETURNS workaround
};
template <typename R, typename T>
inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T))
{
return visitor_ptr_t<T,R>(visitor);
}
} // namespace boost
#endif// BOOST_VISITOR_VISITOR_PTR_HPP
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