Re: [Caml-list] PCRE

[Markus Mottl <markus@oefai.at>]

On Sun, 29 Dec 2002, Oleg wrote:
> I'm new to PCRE. Can anyone explain to me why the output of
> 
> # open Pcre;;
> # version;;
> - : string = "3.4 22-Aug-2000"
> # full_split ~pat:"^(\\w+)(,(\\w+))*$" "a,b,c,d";;
> - : Pcre.split_result list =
> [Delim "a,b,c,d"; Group (1, "a"); Group (2, ",d"); Group (3, "d")]
> 
> does not contain Group(3, "b") and Group(3, "c") ?

Note that using "split" instead of "full_split" produces this list:

  - : string list = [""; "a"; ",d"; "d"]

This is absolutely correct Perl-behaviour.

"full_split" is actually the same, but it also allows you to access
matched substrings. Grouped subpatterns can only capture substrings once
(i.e. the last one if several are possible)!

> Similarly, I expected 
> 
> # full_split ~pat:"S(a\\d)+" "Sa1a2";;
> - : Pcre.split_result list = [Delim "Sa1a2"; Group (1, "a2")]
> 
> to produce [Delim "Sa1a2"; Group(1, "a1"); Group (1, "a2")]
> 
> The above uses the latest pcre-ocaml-4.31.0.

The same applies here: the behaviour of PCRE-OCaml is correct
wrt. Perl-semantics.

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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