Eric Niebler wrote:
dan marsden wrote:
As phoenix expressions have operator(), I'm already using an expression wrapper around all my proto expressions, so I presume that is where I would add any special member support?
Yep. You could be to put all such members into the Phoenix expression wrapper and use a grammar to flag or disallow invalid uses. The members would just be Proto terminals, like "terminal<phoenix::tag::else_>::type const else_".
Oh wait, that's not quite what you want, because then if_[e1].else_[e2] will chop off the if_ part of the tree. What you need instead is a member like (untested): template<typename Expr ...> struct phoenix_expr : proto::extends<Expr ...> { phoenix_expr(...) : else_(proto::make_expr<phoenix::tag::else_>(*this)) {} // ... proto::result_of::make_expr< pheonix::tag::else_ // else is now an "operator" , phoenix_expr const
::type const else_; };
Then, if_/else_ statements would conform to the following grammar: subscript< unary_expr< phoenix::tag::else_ ,subscript<terminal<phoenix::tag::if_>,_>
,_
-- Eric Niebler Boost Consulting www.boost-consulting.com