Trouble using hashq-get-handle in Guile

Question

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)

It relies on guile-curl and guile-json to talk to the webserver and to parse the response. Things seem pretty straight-forward until I run. I can see the response from the server in json (very long and not posted here) and from within Emacs (using geiser to poke around) I can see:

scheme@(guile-user)> (hash-table? queryResults)
$25 = #t

so I know that queryResults is indeed a hash-table. When I take a look at the keys and associated values using print-hash I see that:

scheme@(guile-user)> (print-hash queryResults)
totalNumRecords => 23318
documents => (#<hash-table 2ad7c60 17/31> #<hash-table 2afdbc0 17/31> #<hash-table 2b0ab60 17/31> #<hash-table 2b0eb00 17/31> #<hash-table 2b10aa0 17/31> #<hash-table 2b13a40 17/31> #<hash-table 2b189e0 17/31> #<hash-table 2b1b980 17/31> #<hash-table 2b1e920 17/31> #<hash-table 2b228c0 17/31> #<hash-table 2b25860 17/31> #<hash-table 2b29800 17/31> #<hash-table 2b2d7a0 17/31> #<hash-table 2b30740 17/31> #<hash-table 2b336e0 17/31> #<hash-table 2b38680 17/31> #<hash-table 2b3b620 17/31> #<hash-table 2b3f5c0 17/31> #<hash-table 2b44560 17/31> #<hash-table 2b48500 17/31> #<hash-table 2b4c4a0 17/31> #<hash-table 2b50440 17/31> #<hash-table 2b533e0 17/31> #<hash-table 2b57380 17/31> #<hash-table 2b5c320 17/31>)

so that's good and it's what I expected. But when I try to use hashq-get-handle to get a look at the value for totalNumRecords or documents I get:

scheme@(guile-user)> (hashq-get-handle queryResults 'totalNumRecords)
$24 = #f

scheme@(guile-user)> (hashq-get-handle queryResults 'documents)
$24 = #f

which seems to indicate the key doesn't exist in the hash-table queryResults. I've tried all night with quotes, w/o quotes, futzing with the SRFI-69 hash-table implementations (during which I discovered the difference between native guile hash-tables and the SRFI-69 hash-tables), and went through the hash table examples in the guile reference manual (they all worked just fine). I'm out of ideas.

If someone could help me understand why my calls to hashq-get-handle aren't working out as expected I'd be most grateful.

UPDATE: Following ttn's suggestion from the guile-user mailing list:

scheme@(guile-user)> (hash-get-handle queryResults 'totalNumRecords)
$27 = #f
scheme@(guile-user)> (hashv-get-handle queryResults 'totalNumRecords)
$28 = #f

So it seems like the result is the same. No love.

Answer 1

This discussion on the guile-user mailing list (from both Thien-Thi Nguyen and Mark H Weaver) yielded the solution summarized here:

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.

Which ends up working out:

scheme@(guile-user)> (hash-get-handle queryResults "documents")
$29 = ("documents" #<hash-table 297f820 17/31> #<hash-table 2982700
17/31> #<hash-table 29896a0 17/31> #<hash-table 298f640 17/31> #\
<hash-table 29915e0 17/31> #<hash-table 299d580 17/31> #<hash-table
29a1520 17/31> #<hash-table 29a34c0 17/31> #<hash-table 29a6460 \
17/31> #<hash-table 29f7400 17/31> #<hash-table 29fd3a0 17/31>
#<hash-table 2a08340 17/31> #<hash-table 2a1c2e0 17/31> #<hash-table \
2a4b280 17/31> #<hash-table 2a96220 17/31> #<hash-table 2aa31c0 17/31>
#<hash-table 2aa5160 17/31> #<hash-table 2aaa100 17/31> #<has\
h-table 2ab10a0 17/31> #<hash-table 2abb040 17/31> #<hash-table
2accfe0 17/31> #<hash-table 2acef80 17/31> #<hash-table 2ad1f20 17/3\
1> #<hash-table 2af1ec0 17/31> #<hash-table 2af4e60 17/31>)

And a futher suggestion Mark made that makes good sense:

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.