On 06/01/2007 09:36 AM, Eric Niebler wrote:
Larry Evans wrote: [snip]
where the expression tree node argument remains "packaged":
(expr<Tag, Left, Right> const &expr)
[snip] different, though. You'll need something like:
struct my_context { template<typename Expr> struct eval { typedef ... result_type; result_type operator()(Expr &expr, my_context &ctx) const { return ...; } }; };
[snip] Great! I started coding and then thought about creating a "catchall" method to handle any node. I got to here: struct xmpl_context { explicit xmpl_context(unsigned& a_indent) : indent(a_indent) { } template<typename Expr, long Arity = Expr::arity::value> struct eval { typedef void result_type; result_type operator()(Expr &expr, xmpl_context &ctx) const { typedef proto::tagof<Expr>::type tag_type; const char*tag_name=std::typeid(tag_type).name() std::cout<<std::setw(indent) <<""<<tag_name<<".get_instance=" <<expr.get_instance()<<"\n"; indent+=2; for(long ichild=0; ichild<Arity; ++ichild) { proto::eval(proto::arg_c<Expr,ichild>(expr), *this); } indent-=2; } }; private: unsigned& indent; }; ...then realized I needed something like mpl's for_each. I noticed in boost/xpressive/proto/fusion.hpp there's children templates, but they don't look like they'd help. How do I do what's implied by the above for loop? Thanks again. -regards, Larry