[racket] (procedure? (hash)) -> true

As to (@ data 'COMPANY),  I've considered and used exactly that simply by (define @ hash-ref).   And it's not bad because it's shorter.   It's just not as good as (data 'COMPANY).    

I do notice that the Clojure folks decided that dictionaries were functions such that 

(def talk { "cow" "moo" "dog" "bark" })

can be treated in function position.

(talk "cow")

I'll be looking at the #%app idea in a bit.

------
John Griffin, CTO
IT Talent Team, LLC
www.ittalentteam.com
855-488-8326






On Aug 5, 2013, at 12:00 PM, users-request at racket-lang.org wrote:

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> Today's Topics:
> 
>   1. Re: (procedure? (hash)) -> true (Tony Garnock-Jones)
>   2. Re: (procedure? (hash)) -> true (Matthias Felleisen)
>   3. issue with Dr Racket in linux platform. (Vikas Sood)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 05 Aug 2013 11:39:06 -0400
> From: Tony Garnock-Jones <tonyg at ccs.neu.edu>
> To: John Griffin <jg at ittalentteam.com>, racket-users
> 	<users at racket-lang.org>
> Subject: Re: [racket] (procedure? (hash)) -> true
> Message-ID: <51FFC71A.8080205 at ccs.neu.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> On 08/05/2013 11:30 AM, John Griffin wrote:
>> Thanks in advance for any advice leading to more succinct hash access.
> 
> Had you considered something along the lines of
> 
> (define (handier-style data)
>   (when (@ data 'COMPANY)
>     (db-exec ... (@ data 'COMPANY))))
> 
> ?
> 
> You might start from
> 
> (define (@ base . path)
>   (match path
>     ['() base]
>     [(cons (? number? n) rest)
>      (apply @ (list-ref base n) rest)]
>     [(cons (? symbol? k) rest)
>      (apply @ (hash-ref base k) rest)]
>     [... maybe other things ...]))
> 
> to give yourself a not-quite-XPath-like means of projecting JSON values.
> 
> Interesting design decisions include: what to do when a list index is 
> out of range, or a hash key is not present? (Error? Terminate early 
> returning some kind of "undefined" value?)
> 
> Cheers,
>   Tony
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Mon, 5 Aug 2013 11:52:49 -0400
> From: Matthias Felleisen <matthias at ccs.neu.edu>
> To: John Griffin <jg at ittalentteam.com>
> Cc: users at racket-lang.org
> Subject: Re: [racket] (procedure? (hash)) -> true
> Message-ID: <B4E00C63-E999-46A0-8478-9DC9786980BC at ccs.neu.edu>
> Content-Type: text/plain; charset="windows-1252"
> 
> 
> Consider overriding #%app for your modules. And 
> 
> (define (curt-style-receiver data)
> (cond 
>  [(data 'COMPANY) => (curry db-exec ...)]  
>  [else .. what are you doing in the #f case? nothing? ...]))
> 
> 
> On Aug 5, 2013, at 11:30 AM, John Griffin wrote:
> 
>> I do a lot of work with hash as the result of JSON-RPC calls, with considerable use of hash-ref.   In most places, I've replaced the hash with a local result of transforming the hash to a procedure so that I can:
>> 
>> (stuff 'COMPANY)
>> 
>> rather than
>> 
>> (hash-ref stuff 'COMPANY)
>> 
>> Of course, the setup call to exchange the hash for the procedure takes another line, such that I only bother on longer functions with repeated benefit.
>> 
>> It certainly would be handy from a succinctness standpoint if a hash acted like a procedure (Any -> Any).  Noticing that struct can be a procedure? via a property , I wonder if there's a way for hash? and procedure? to both hold true.
>> 
>> It's more than simply saving the 9 letters of hash-ref followed by a space.  Performance is not an issue and given a curt enough representation, I'd prefer calling it twice rather than making a local define.  My current choices are:
>> 
>> ; current STYLE #1
>> (define (current-rpc-receiver data)
>>    (define company (hash-ref data 'COMPANY #f))
>>    (when company
>>        (db-exec ? company))
>> 
>> ; current STYLE #2
>> (define (curt-style-rpc-receiver data)
>>   (define HF (hash->procedure data))
>>    (when (HF 'COMPANY)
>>        (db-exec ?. (HF 'COMPANY))
>> 
>> ; what would be handier?.
>> 
>> (define (handy-style data)
>>    (when (data 'COMPANY)
>>       (db-exec ? (data 'COMPANY))
>> 
>> Thanks in advance for any advice leading to more succinct hash access.
>> 
>> ------
>> John Griffin, CTO
>> IT Talent Team, LLC
>> www.ittalentteam.com
>> 855-488-8326
>> 
>> 
>> 
>> 
>> 
>> 
>> ____________________
>> Racket Users list:
>> http://lists.racket-lang.org/users
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> ------------------------------
> 
> Message: 3
> Date: Mon, 5 Aug 2013 21:27:46 +0530
> From: Vikas Sood <vikaspragy at gmail.com>
> To: users at racket-lang.org
> Subject: [racket] issue with Dr Racket in linux platform.
> Message-ID:
> 	<CAPsG1M0RY3gUQyaGYGCGMiL8_d-H25JqbM0nhs8-9PjCEhnnbA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hi
> 
> When i  am running any program in DR Racket following message is
> being displayed.
> 
> 
> #%module-begin: illegal use (not a module body) in: (#%module-begin).
> 
> I am not able to run even the first sample code in racket in linux.
> 
> I am not facing any problem while running the same code in windows.
> 
> Kindly provide me with the cause and work around for linux.
> 
> regards
> 
> Vikas
> 
> 
> End of users Digest, Vol 96, Issue 10
> *************************************

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