From: Sean Middleditch <elanthis@...>
Date: 2002-02-27T00:33:10+09:00
Subject: Re: Nested paired brackets in regexp

Assuming that all your're doing is looking for data inside of brackets,
you'd be better off using a custom search/parse engine.

Basically, keep a nest value.  On your first <, up the nest value by
one, and mark which position in the string you found it on.  Then,
continue scanning the string.  Up the nest value on each <, and decrease
it for each >.  When the next value gets back to zero, you've found the
last outer value.  Use the previously stored start position, and extract
the data.

You can then, of course, continue scanning the string, for more bracket
pairs.

On Tue, 2002-02-26 at 09:45, Yasuo Saito wrote:
> Hi.
> 
> Ruby's regular expression is very powerful.
> 
> But, I cannot express paired brackets(<...>), which
> might be nested, in a single regular expression.
> 
> How can I check nested paired brackets by a single/simple
> (extended) regular expression, if possible?
> 
> eg.
>  input            | expected
> ------------------+--------------
> "ab<cd>ef"        | "<cd>"
> "ab<cd>e<fg>"     | "<cd>"
> "ab<cd<e<>fg>h>i" | "<cd<e<>gh>i>"
> "ab<cd<e>f"       | not matched
> 
> 
> Y.Saito