tl;dr : Why is the following an error?
#lang at-exp racket
(define a "this")
@pregexp{^@a} ;; Should produce #px"^this" but errors out
@pregexp{@(~a "^" a)} ;; This works but is clumsy
Long version:
The at-exp language
(http://www.greghendershott.com/2015/08/at-expressions.html and
https://docs.racket-lang.org/scribble/reader-internals.html) allows
for (among other things) more convenient construction of regexen, like
so:
(pregexp "\\d\\d\\.\\d\\d") ;; base racket. Ugh.
@pregexp{\d\d\.\d\d} ;; at-exp...ah, much better
I started to reply to Ken MacKenzie's recent post about string
prefixes with a suggestion that, although string-prefix was what he
wanted in this case, a regex would be a more general solution. When I
went to test the code I was suggesting, I was surprised to find it
didn't work as expected. I thought maybe "^@" was a function or
special form in Racket, but a quick search of the docs revealed
nothing. I tried various forms of quoting inside the at-exp but
nothing worked.
What am I missing?
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