Re: [Caml-list] Where are the AST specs?

["Nicolas Pouillard" <nicolas.pouillard@gmail.com>]

On 3/19/07, Loup Vaillant <loup.vaillant@gmail.com> wrote:
> > BTW camlp4 provides a simple macro system through a dynamic syntax
> > extension. It features DEFINE, IFDEF, INDEF, and INCLUDE.
>
> Actually, I didn't meant C macros.

Yes, but these are somewhat better than C ones.

> > However camlp4 is itself a powerful way to manage the OCaml syntax as
> > AST through it's quotation system.
>
> That is what I meant. However, I want it as simple as possible.
>
> > Have you a simple specification of what you want for OCaml (or some examples).
>
> For instance, I woud have wanted
> (defun f x y z (+ x (* y z)))

DEFINE F(x, y, z) = x + y * z;;

F(F(1, 2, 3), 4, 5);;

[...]

> another example:
> (+ x y z)
>
> (plus (plus x y) z)

Yes the macro extension is to weak for that.

Here is a camlp4 snippet todo it:

$ cat macros.ml
open Camlp4.PreCast;;
AstFilters.register_str_item_filter begin
  Ast.map_expr begin function
  | <:expr@loc< \!+ ($tup:e$) >> ->
      begin match Ast.list_of_expr e [] with
      | [] | [_] -> assert false
      | x :: xs -> List.fold_left (fun acc x -> <:expr@loc< $acc$ + $x$ >>) x xs
      end
  | <:expr< \!+ $e$ >> -> e
  | e -> e
  end
end#str_item;;

Can be used like that:

$ cat test_macros.ml
!+ (1, 2, 3, 4);;
$ camlp4o ./macros.cmo test_macros.ml
let _ = ((1 + 2) + 3) + 4

> I havent specified the macro system yet. I think I shoud wait untill i
> have written a reader. (And therefore specified an AST)

IMHO starting from the macro extension of camlp4 and write a new one
more powerful is a good way to go.

-- 
Nicolas Pouillard