In a future version of what I am working on I see regex being an excellent
solution. My search is against a file I load into a list at program
initialization. However for other parts of this to load a list based on a
partial file filtered with regex may be a better solution.
There is also the case that I eventually switch to a DB backend, but at
prototype stage I have been skipping that.
Sorry not an answer to your query, but I think I could make use of the answer
so inserting myself into the thread.
Ken
On Friday, October 28, 2016 at 3:18:14 PM UTC-4, David K. Storrs wrote:
> 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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