On Sunday 01 July 2007 17:24, Eric Niebler wrote:
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_;
};
how do I match the new "else_ operator" and transform it?
Well, if you use the BOOST_PROTO_DEFINE_FUNCTION_TEMPLATE macro like I show above, the IfElseGrammar might look like this:
// matches if_(e1)[e2].else_[e3] struct IfElseGrammar
: subscript<
unary_expr< phoenix::tag::else_ , subscript< unary_expr< phoenix::tag::if_ , PhoenixBooleanGrammar
, PhoenixGrammar
, PhoenixGrammar
{};
All right, that makes good sense. Now the next obvious thing to do is try do_[e1].while_(e2). So here's my attempt: // A do_ "operator" boost::proto::terminal<tag::Do>::type const do_ = {{}}; // matches do[e1] struct DoGrammar : boost::proto::subscript< tag::Do, StatementGrammar > {}; // A while_ "operator" template<typename Expr> struct Expression< Expr , typename enable_if<proto::matches<Expr, DoGrammar> >::type > : proto::extends<Expr, Expression<Expr>, Domain> { Expression() : while_(proto::make_expr<tag::While>(*this)) {}; // Oops, don't know how to do this here BOOST_PROTO_DEFINE_FUNCTION_TEMPLATE( 1 , while_ , Domain , (tag::While) , BOOST_PP_SEQ_NIL ); }; // matches do[e1].while_(e2) struct DoWhileGrammar : boost::proto::unary_expr< DoGrammar, tag::While > {}; Other than the fact that I don't know how to declare the while_ member above, does this look correct? Of course, I want to do while_(e1)[e2] as well, so there already is BOOST_PROTO_DEFINE_FUNCTION_TEMPLATE( 1 , while_ , Domain , (tag::While) , BOOST_PP_SEQ_NIL ); at namespace scope. Is there some way to reuse this in the extension of expressions that match DoGrammar? -Dave