Re: Match-result submatch extraction is weird

[Alex Shinn <alexshinn@xxxxxxxxx>]

On Wed, Oct 16, 2013 at 4:23 AM, Peter Bex <Peter.Bex@xxxxxxxxx> wrote:

Hi all,

After clearing the initial roadblocks, I tried to use the library.
Being used to irregex I naively typed away and got this:

(define m (regexp-match '(seq ($ "x") "y") "xy"))
(rx-match-submatch m 1) => ERROR!

So, I looked up the syntax again and was confused:  why does the
rx-match-submatch procedure require the input string again?

Actually I can't remember why I made this change.

The advantage is that it uses one word less memory

for each match (and while running for each active

state in the search).  It's also nicer on GC if you have

a long-lived match object but don't actually need to

extract any substrings (unlikely).

On the other hand it's less convenient, and can give

weird results if passed the wrong string as you point

out.  It's also a bad design if you want a chunked

string API like in IrRegex.

Unless anyone has any other objections, I'll change the

rx-match-submatch API to omit the string input.

-- 

Alex