On Mar 17, 2016, at 2:05 PM, Andrew Gwozdziewycz <apg...@gmail.com> wrote:
> I am imagining an API that utilizes SCSH style regexes but allows you to do
> something like this (fictional):
>
> (define-values (area prefix line) (sre-match (: (= digits 3) (_? "-") (=
> digits 3) (_? "-") (= digits 3))))
Racket's `match` is not far from this. In fact maybe I shouldn't be thinking in
terms of hacking regexps, but rather making a new match expander. For instance,
you can destructure a list like so:
(match '("foo" "-42.3" "bar")
[(list a (? string->number b) c) 'yay]
[else 'boo])
So it would extend logically to this pseudocode:
(match "foo-42.3bar"
[(string-append a (? string->number b) c) 'yay]
[else 'boo])
On Mar 17, 2016, at 2:35 PM, Daniel Prager <daniel.a.pra...@gmail.com> wrote:
> Do you want the leftmost, longest substring matching the predicate?
>
Sometimes, but that's not hard to figure out. More often, I want to match
multiple predicates within one string.
#lang racket
(define (substring/p pred str)
(for*/first ([strlen (in-value (string-length str))]
[left-pos (in-range strlen)]
[right-pos (in-range strlen left-pos -1)]
[this-substring (in-value (substring str left-pos right-pos))]
#:when (pred this-substring))
this-substring))
(equal? (substring/p string->number "foo-46.3bar12789") "-46.3")
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