From: Dominik Bathon <dbatml@...>
Date: 2005-07-31T23:40:38+09:00
Subject: Re: [Brainstorming Input] Ruby-Oniguruma interoperability on Named Groups

On Sat, 30 Jul 2005 20:31:03 +0200, Wolfgang N�dasi-Donner  
<wonado@donnerweb.de> wrote:

> Now the idea.
>
> Ruby and Onigurama should be extended somehow to allow Ruby-objects  
> (usually regular expressions) to be
> registered somehow to the class Regexp, so that they can be referenced  
> later in regular expressions.

I think I generally like the idea to compose regular expressions that way  
...

> In detail a regular expression that consists only of a named group  
> definition (starts with '(?<name>') kann be
> registered by something like 'Regex.register(/(?<example>a|b|c|d)/)',  
> and be deleted by
> Regex.remove('<example>'). If the regular expression is assigned to a  
> variable this can be used, how to manage
> this in the 'remove' case has to be clearified. I used class methods for  
> this example, but it may be better to
> introduce a named Regexp objects which will be created by something like  
> '/(?<example>a|b|c|d)/.create. Some
> possibility for explicit deletion should be there, because the regex  
> engine Oniguruma must know about the
> object to take care about.

... but I think registering all named groups in one global place is not a  
good idea (even if you can unregister): what if two libraries use the same  
group names? I think there would be many name clashes.

So here is another idea: Let the caller manage the named groups himself.  
Maybe in arrays or hashes. Something like:

groups = [/(?<example>a|b|c|d)/, /(?<example2>e|f|g)/]

or with hashes:

groups = { "example" => /a|b|c|d/, "example2" => /e|f|g/ }

or maybe in some specialized named groups library class.

> These Object can later on be referenced in regular expressions by  
> '\k<name>' or '\g<name>' as if they were
> defined there.

To use those groups I would suggest something like:

/\k<example>/.with(groups)

RegExp#with would return the "composed" RegExp that can be used like any  
other RegExp.

What do you think?

Dominik

Disclaimer: I do not really know how named groups work in Oniguruma, just  
wanted to point out that one global registry might be a bad idea.