From: ptkwt@... (Phil Tomson)
Date: 2004-09-12T14:54:57+09:00
Subject: Re: look-behind in oniguruma

In article <ABQ0d.397334$gE.56953@pd7tw3no>,
Andrew Johnson  <ajohnson@cpan.org> wrote:
                          ^^^^^^^^
                          hmmm...

>On 12 Sep 2004 03:44:24 GMT, Phil Tomson <ptkwt@aracnet.com> wrote:
>> Apparently oniguruma supports look-behind.  Is there any documentation on how 
>> to use this feature?
>
>Essentially, they are the same as look-aheads ... zero-width assertions,
>except that the look-behind expression must be a fixed width pattern (no
>indeterminate quantifiers), and no captures are allowed in a negative
>look-behind 
>
>> for example, if I had the string "~ABC~DE" and I want to return a list of 
>> letters in the string which are preceeded by '~' ( ['A','D'] in this case) how 
>> might I use the look-behind feature in oniguruma to achieve this? or, how 
>> would I get a list of letters in the string which are not preceeded by '~' 
>> (['B','C', 'E'] in this example.
>
>
>  str = "~ABC~DE"
>  p str.scan(/(?<=~)[A-Z]/)
>  p str.scan(/(?<!~)[A-Z]/)
>
>gives:
>
>  ["A", "D"]
>  ["B", "C", "E"]
>

Thanks.  That's what I was looking for.  Is this essentially the same way that 
it works in Perl?

Phil