I write this kind of code all the darn time:
;; take (listof (list a b)) into (hashof a (listof b))
(define (gather l)
(for/fold ([ht (make-hash)])
([pr l])
(hash-set ht (first pr) (cons (second pr)
(hash-ref ht (first pr) empty)
;; gather
Would any of the functions in unstable/list help? For example,
#lang racket
(require unstable/list)
(define (gather lst)
(for/hash ([g (group-by car lst)])
(values (caar g) (append-map cdr g
(gather '((a c) (a d) (b e) (b f)))
; = '#hash((a . (c d)) (b . (e f)))
On Thu, Jun 11, 2015
IIUC in SQL this would simply be:
SELECT student, AVG(rating)
FROM scores
GROUP BY student
Apparently a DSL for querying tables can be handy. :)
The Racket equivalent for the special case of a 2-column table (a
hash-table) could be something like:
(define (sql-ish-aggregate-group-by f xs)
On Jun 11, 2015, at 10:19 AM, Stephen Chang stch...@ccs.neu.edu wrote:
Would any of the functions in unstable/list help? For example,
Ah, ‘group-by’ is very nice, yes. Looks like that was Vincent’s? Many thanks,
Vincent!
John
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I understand it may be too far to come for just one day for many, but
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Robby
On Thu, Jun 11, 2015 at 2:29 PM, 'John Clements' via users-redirect
us...@plt-scheme.org wrote:
Golly, that was fast. So much for RacketCon this year.
Golly, that was fast. So much for RacketCon this year.
My fault, I know.
John
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How do you include a racket module in an R6RS program?
I have remote.rkt in the same directory as test.scm.
With R5RS I could do (#%require remote.rkt), but that doesn't work, and I
tried various things in the (import) statement without success.
Are there any plans for an R7RS lang in Racket?
On Thursday, June 11, 2015 at 4:22:19 PM UTC-4, John Carmack wrote:
How do you include a racket module in an R6RS program?
I have remote.rkt in the same directory as test.scm.
With R5RS I could do (#%require remote.rkt), but that doesn’t work, and I
tried various things in the
At Thu, 11 Jun 2015 20:22:16 +, John Carmack wrote:
How do you include a racket module in an R6RS program?
I have remote.rkt in the same directory as test.scm.
With R5RS I could do (#%require remote.rkt), but that doesn't work, and I
tried various things in the (import) statement
At Wed, 10 Jun 2015 18:44:15 +0200, Michael Titke wrote:
On 10/06/2015 12:33, Michael Titke wrote:
I changed from one OS to another and I was missing a simple feature:
automatic password generation. To fill the gap with a Scheme I
implemented such a generator as a command line tool
Let me rephrase Matthew. Racket is only related to Scheme. See
http://racket-lang.org/new-name.html for an explanation of our move. Our
understanding is that the Scheme community wants to move back to a world where
the language is small while Racket wants to move to a world where programmers
As Greg points out, it was directly inspired by SQL's `group-by`. I've
found it really handy when thinking about data in a relational way.
Anyone opposed to moving it to `racket/list`? That would make it more
discoverable?
Vincent
At Thu, 11 Jun 2015 11:17:26 -0700,
'John Clements' via
Matthew Flatt wrote on 06/11/2015 10:00 PM:
Android via NDK is a supported platform.
Matthew, that's great. Thank you.
Anyone implemented `racket/gui` for Android with this, or otherwise
hooked up things so that the Racket program can drive a UI on Android?
Neil V.
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I appreciate the position, but I do think there is still value in being able to
optionally carve off all the extra goodness and act like a more primitive
Scheme to provide compatibility with various embedded options where full Racket
isn't practical.
DrRacket is a key element of my strategy
Short: What I am trying to say is that after R6RS, we moved on from Scheme.
Don't expect us to support it, don't expect us to stand it its way. We are
moving in an orthogonal direction.
Long: We appreciate small kernel language and we inherited this from Scheme.
We do not appreciate it keep
Has anyone tried to build Racket 6.x for the Android NDK (or whatever is
the current way to do native code)? That might be the fastest path,
rather than targeting Dalvik, Java, or JS.
Encouraging: I did find that Racket 6.x builds pretty easily as a
possibly-viably-sized OpenWrt package,
Android via NDK is a supported platform. The src/README file has information
on cross-compilation and specific hints for Android. I'm not in a position to
double check just now, but it built the last time I tried a few months ago.
Embedding should be as easy as on any platform. I wouldn't
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