Re: Trouble using hashq-get-handle in Guile

[Mark H Weaver]

jamil egdemir <address@hidden> writes:

> I'm having trouble getting the value associated with a key in a
> hash-table and I'm totally confused as to what I'm doing wrong.  The
> code I'm using is shown below:
>
>     (use-modules (curl))
>     (use-modules (json))
>
>     ;; use curl to hit the site's api to get results of query as json:
>     (define handle (curl-easy-init))
>     (curl-easy-setopt handle 'url
>
> "http://api.data.gov:80/regulations/v3/documents.json?api_key=mySecKey&countsOnly=0&encoded=1&dktid=EPA-HQ-OAR-2013-0602&dkt=R&cp=C&rpp=25&po=0";)
>     (define s (curl-easy-perform handle))
>
>     ;; parse the json in the string into guile scheme:
>     (define queryResults (json-string->scm s))
>
>     ;; use this to see the keys and values in the resulting hash
> table:
>     (define print-hash (lambda (my-hash)
>                          (hash-for-each (lambda (key value)
>                                           (format #t "~a => ~a~%" key value))
>                                         my-hash)))
>
>     ;; now let's take a look at the keys and values:
>     (print-hash queryResults)
>
>     ;; now let's get the value associated with the documents key:
>     (hashq-get-handle queryResults 'documents)

Based on a quick glance at the json code, I suspect you want this:

  (hash-get-handle queryResults "documents")

i.e. change 'hashq-get-handle' to 'hash-get-handle', and pass a string
as the key, not a symbol.

If you use "~s" instead of "~a" in 'print-hash', it will be clear
whether the keys are strings or symbols because strings will print
within double quotes.

     Regards,
       Mark