On 11/26/2013 10:28 AM, John Cowan wrote:
> Michael Montague scripsit:
>
>> I propose breaking SREs completely free of PCREs.
> SREs are not new to this SRFI: they have been around since 1998.
> See <http://www.scsh.net/docu/post/sre.html>.  Gratuitously breaking
> other people's code is not nice.
>
Briefly looking through the first 16 or so implementations listed on
http://trac.sacrideo.us/wg/wiki/SchemeImplementationReleases, it
appeared to me that only Chicken and Chibi provide SRE regular
expressions. Most of the others provide something like PCRE regular
expressions with a different API than this SRFI. For example, Bigloo,
Racket, and Dorai Sitaram's pregexp don't use a <regexp-match> object,
but return the matches directly.

This SRFI is going to break people's code no matter how it comes out,
particularly if it becomes part of R7RS-large.

My opinion: SREs are a mutant love child of Scheme and Perl. To
understand them you need to understand Scheme and PCREs. You need to
remember what a bunch of characters like *+?= mean. Not fun. Too much
PCREs and not enough Scheme.

I think SREs are cool. I don't think that Olin Shivers went far enough
into the world of Scheme with the syntax. My proposed syntax would make
SREs easier to learn without knowing PCREs first and it would make it
easier for casual users of SREs to remember the syntax.

I don't think that I am trying to gratuitously break other people's
code. That is certainly not my goal.