| /*============================================================================= |
| Copyright (c) 2001-2007 Joel de Guzman |
| |
| 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 PHOENIX_OPERATOR_IF_ELSE_HPP |
| #define PHOENIX_OPERATOR_IF_ELSE_HPP |
| |
| #include <boost/mpl/and.hpp> |
| #include <boost/mpl/if.hpp> |
| #include <boost/type_traits/is_same.hpp> |
| #include <boost/type_traits/is_reference.hpp> |
| #include <boost/type_traits/remove_reference.hpp> |
| #include <boost/spirit/home/phoenix/core/composite.hpp> |
| #include <boost/spirit/home/phoenix/core/compose.hpp> |
| #include <boost/spirit/home/phoenix/detail/type_deduction.hpp> |
| |
| namespace boost { namespace phoenix |
| { |
| BOOST_BINARY_RESULT_OF(true ? x : y, result_of_if_else) |
| |
| struct if_else_op_eval |
| { |
| template < |
| typename Env |
| , typename Cond |
| , typename Then |
| , typename Else |
| > |
| struct result |
| { |
| typedef typename Then::template result<Env>::type then_type; |
| typedef typename Else::template result<Env>::type else_type; |
| |
| typedef typename |
| result_of_if_else<then_type, else_type>::type |
| ite_result; |
| |
| // Note: c ? x : y can return an lvalue! Allow if_else_op_eval |
| // to return an lvalue IFF then_type and else_type are both lvalues |
| // with the same type. |
| |
| typedef typename |
| mpl::if_< |
| mpl::and_< |
| is_same<then_type, else_type> |
| , is_reference<then_type> |
| > |
| , ite_result |
| , typename remove_reference<ite_result>::type |
| >::type |
| type; |
| }; |
| |
| template < |
| typename RT |
| , typename Env |
| , typename Cond |
| , typename Then |
| , typename Else |
| > |
| static RT |
| eval(Env const& env, Cond& cond, Then& then, Else& else_) |
| { |
| return cond.eval(env) ? then.eval(env) : else_.eval(env); |
| } |
| }; |
| |
| template <typename Cond, typename Then, typename Else> |
| inline actor<typename as_composite<if_else_op_eval, Cond, Then, Else>::type> |
| if_else(Cond const& cond, Then const& then, Else const& else_) |
| { |
| return compose<if_else_op_eval>(cond, then, else_); |
| } |
| }} |
| |
| #endif |