On Thursday, 8 July 2021 16:37:09 CEST you wrote:
> Hi,
>
> I'm seeking advice for passing simple key-value pairs to a function and
> generate a string out of these values. Neither the names not the number
> of keys is known in advance.
>
> Background: This shall become a generic function for generating URI
> query-strings.
>
> My current approach please see below. Anyhow, I'm wondering whether the
> quite and quasiquote can be replaced by something simpler.
>
> (use-modules (ice-9 match))
>
> (define limit 100)
> (define evaluation "linux")
>
> (define* (api-uri base path #:rest query)
>
> (define (build-query-string kv)
> (match kv
> ((name #f) #f)
> ((name (? string? value))
> (string-append name "=" value)) ; FIXME: encode
> ((name (? number? value))
> (string-append name "=" (number->string value)))))
>
>
> (format #t "~%Query: ~a~%~%" query)
> (let ((query-string
> (when query
> (string-join
> (filter (lambda (x) x) (map build-query-string query))
> "&"))))
> (format #t "~%Query-String: ~a~%~%" query-string)
> ;; todo: build uri incl. query-string
> ))
>
>
> (api-uri "https://ci.guix.gnu.org"; "/api/jobs")
> (api-uri "https://ci.guix.gnu.org"; "/api/jobs"
> `("nr" ,limit)
> `("evaluation" ,evaluation)
> `("system" ,#f))
Hello,
personally I'd use key-value pairs rather than lists for passing in arguments
and simplify it a bit by using fold-right from SRFI-1, like this:
#+BEGIN_SRC scheme
(use-modules (srfi srfi-1))
(define (api-uri base path . query)
(string-join
(fold-right
(lambda (name-value-pair result)
(if (cdr name-value-pair)
(cons (string-append (car name-value-pair)
"="
(object->string (cdr name-value-pair)))
result)
result))
'()
query)
"&"))
(api-uri "https://ci.guix.gnu.org";
"/api/jobs"
(cons "nr" limit)
(cons "evaluation" evaluation)
(cons "system" #f))
#+END_SRC
Vale,
-Tim
