A new version of scsh-regexp, the SCSH regular expression API port to Chicken and SISC, is available. All API functions (except regexp manipulation such as uncase) are implemented, and there are a few bugfixes (including one that prevented compilation under SISC); there is still no SRE support.

For the moment, you will have to download this release from Google Code; the Chicken egg should be updated to release 0.2 in a day or two.

If you'd like to see a port of scsh-regexp to your favorite Scheme, feel free to let me know (or contribute some code), as I am unlikely to make any further changes otherwise (save fixing potential bugs, should any surface). A Guile port would be the easiest.

And now, a fun exercise: scsh-regexp can handle pretty URLs in SISCweb applications. More specifically, we are going to sidestep the publish method by passing all requests to a single handler, which will discriminate between various URLs using the match-cond macro; here's what a CMS application's entry point might look like:

(publish "/*" url-dispatcher)
(define (url-dispatcher request)
  (define path (request/get-path-info))
  (define (m url)
    (regexp-search (posix-string->regexp (string-append "^" url "$") path)))
  (match-cond 
   ((m "/archives/([0-9]+)/([0-9]+)") (_ year month)
    (list-stories year month))
   ((m "/story/([^/]*)") (_ story-slug)
    (send-story story-slug))
   ...
   (else (send-404))))

match-cond is described in the SCSH manual, but briefly it goes through a list of clauses (just like cond), and when a match is found, it binds variables to the specified sub-matches (which correspond to paranthesized chunks in the regexp). Note that the URLs now contain regexp-style wildcards, instead of SISCweb's usual servlet-style wildcards.

This approach can be made cleaner with macros, or, as I will describe in a future post, by using an upcoming feature of SISCweb 0.5 — (publish "/some/url/.*" handler 'regexp)