Re: [Caml-list] Question re: camlp4 parser

[Stephane Glondu <Stephane.Glondu@crans.org>]

On Tuesday 26 July 2005 09:43, Paul Snively wrote:
> One hopefully final question: is there a convenient shorthand for
> saying something like "all printable characters except '=' or '['?" I
> assume not--that is, we have ranges (' '..'~') or we have variants
> ('A' | 'B' | 'C'...) and that's it. I'm somewhat spoiled, I think, by
> Spirit in C++, and its notion of "character sets" and operations on
> them, so I can say, e.g. "print_p - '='" that that will match all
> printable characters other than '='.

I don't know whether there is a way to do this directly. You can split your 
range so that it avoids '=' and '[', or do something like this:

let printable s =
  let buf = Buffer.create 100 in
  let rec aux = parser
      [< '  ('=' | '[') >] -> Buffer.contents buf
    | [< '' '..'~' as c; x = (Buffer.add_char buf c; aux) >] -> x
    | [< >] -> Buffer.contents buf
  in aux s ;;

printable (Stream.of_string "path=/usr/src") ;;
--> - : string = "path"

Bear in mind that the '=' or '?' will be discarded by the parser. If you 
don't want so, you can use Stream.peek (but it's much more annoying).


-- 
Stephane Glondu.