I find myself using this all the time; it seems it'd be handy to have built in.
(define (shuffled list)
(sort list #:key (lambda (_) (random)) #:cache-keys? #t))
Thanks.
_
For list-related administrative tasks:
Eric Hanchrow wrote:
I find myself using this all the time; it seems it'd be handy to have built in.
(define (shuffled list)
(sort list #:key (lambda (_) (random)) #:cache-keys? #t))
Is the distribution of shuffled lists uniform? That'd be hard to
analyze, since it would depend on the
On Thu, Nov 11, 2010 at 12:18 PM, Neil Toronto neil.toro...@gmail.com wrote:
Eric Hanchrow wrote:
I find myself using this all the time; it seems it'd be handy to have
built in.
(define (shuffled list)
(sort list #:key (lambda (_) (random)) #:cache-keys? #t))
Is the distribution of
I think that if random doesn't pick the same number twice you're
guaranteed to be independent of the sorting algorithm, at least.
Robby
On Thu, Nov 11, 2010 at 11:18 AM, Neil Toronto neil.toro...@gmail.com wrote:
Eric Hanchrow wrote:
I find myself using this all the time; it seems it'd be
On Thu, Nov 11, 2010 at 12:40 PM, Neil Toronto neil.toro...@gmail.com wrote:
I don't know. I know that the run through the list and swap with another
random element algorithms are usually non-uniform, and so are a lot of
other things that seem like they'd work. I wouldn't use something that
On Thu, Nov 11, 2010 at 11:40 AM, Carl Eastlund c...@ccs.neu.edu wrote:
On Thu, Nov 11, 2010 at 12:40 PM, Neil Toronto neil.toro...@gmail.com wrote:
I don't know. I know that the run through the list and swap with another
random element algorithms are usually non-uniform, and so are a lot of
5 minutes ago, Neil Toronto wrote:
Carl Eastlund wrote:
It's pick a random, uniform ordering, and then sort based on it.
The random keys are chosen per element and cached (hence
#:cache-keys? #t), not per comparison.
Spanking good point, my good man. I think you're right.
It's a very
When truly picking uniformally shuffled lists from a given list, see:
http://telefonica.net/web2/koot/natural-to-permutation.scm
and try
(require srfi/27) ; for random-integer
(require natural-to-permutation.scm)
(let*
((lst (build-list 1000 (lambda (k) (round (quotient k 10)
I think it is a good idea. Any objectors?
Jay
On Wed, Nov 10, 2010 at 12:40 PM, David Van Horn dvanh...@ccs.neu.edu wrote:
The set library is missing a convenient way of selecting an element from a
set, making it hard to write recursive functions matching the inductive
structure of a set.
I've written a version of `set-choose', and also `set-first' and
`set-rest' (with the obvious meanings) a few times. They can be useful.
(I always waffled about whether to use just `set-choose', or `set-first'
along with `set-rest'. Mathematically, `set-first' and `set-rest' don't
make sense,
The check-within in the follow program (in BSL/ISL) seems to hang.
This is sort of the simplest example I can reproduce, but my students
have been running into this with some more complicated test cases. I
thought it might have to do with the inexact numbers, but even if you
change the #i0.501 to
On 11/11/10 7:34 PM, Nadeem Abdul Hamid wrote:
The check-within in the follow program (in BSL/ISL) seems to hang.
I see DrRacket (5.0.1, 5.0.99) loop on this:
(check-within (make-posn (list 0)
(list 0))
(make-posn (list 0)
(list
submitted as bug report
On Nov 11, 2010, at 7:54 PM, David Van Horn wrote:
On 11/11/10 7:34 PM, Nadeem Abdul Hamid wrote:
The check-within in the follow program (in BSL/ISL) seems to hang.
I see DrRacket (5.0.1, 5.0.99) loop on this:
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