From: "David Allsopp" <dra-news@metastack.com>
To: "'Dario Teixeira'" <darioteixeira@yahoo.com>, <caml-list@yquem.inria.fr>
Subject: RE: [Caml-list] Parameterised lexer
Date: Tue, 16 Sep 2008 10:38:12 +0100 [thread overview]
Message-ID: <629B7CBAE27E4325B489E51B90F20E48@countertenor> (raw)
In-Reply-To: <698632.75695.qm@web54606.mail.re2.yahoo.com>
Definitely not possible (directly) with ocamllex - what you're suggesting
would involve recompiling the automaton on each call which isn't how
ocamllex works. Don't know about ulex.
But: do you know enough about the kind of expressions that param could be to
use one regexp that would cover them all (e.g. ['x'|'y'|'z'] for the example
below)? You could then have a lexer action of the form:
rule token param = parse
reg-exp-for-params {if Str.string_match param (Lexing.lexeme lexbuf) 0
then () (* Code *)
else failwith "lexing: empty token"}
| rest-of-the-lexer
David
-----Original Message-----
From: caml-list-bounces@yquem.inria.fr
[mailto:caml-list-bounces@yquem.inria.fr] On Behalf Of Dario Teixeira
Sent: 14 September 2008 21:53
To: caml-list@yquem.inria.fr
Subject: [Caml-list] Parameterised lexer
Hi,
Is it possible to write a ocamllex/ulex scanner where a regexp is a
parameter
to the lexer function? I'm looking for something like the (invalid) ulex
code below demonstrates ("param" is the parameter):
let regexp alpha = ['a'-'z' 'A'-'Z']
let regexp whitespace = [' ' '\t' '\n']
let regexp param1 = 'x'
let regexp param2 = 'y'
let regexp param3 = 'z'
let rec token param = lexer
| param -> Printf.print "*";
token param lexbuf
| alpha+ -> Printf.printf "%s" (Ulexing.utf8_lexeme
lexbuf);
token param lexbuf
| whitespace+ -> Printf.printf " ";
token param lexbuf
| eof -> Printf.printf "EOF\n"
let main () =
let lexbuf = Ulexing.from_utf8_channel stdin
in token param1 lexbuf
let _ = Printexc.print main ()
Thanks in advance for your help!
Kind regards,
Dario Teixeira
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prev parent reply other threads:[~2008-09-16 9:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-14 19:53 Dario Teixeira
2008-09-16 9:38 ` David Allsopp [this message]
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