Do you mean that if you operated on a list it would look like this:
#lang racket
(define (running-average-of-3 l2)
(define-values (_1 _2)
(for/fold ((current (second l2)) (prior (first l2))) ((next (rest (rest
l2))))
(displayln (/ (+ prior current next)))
(values next current)))
(void))
(running-average-of-3 '(1 2 3 4 5 6 7 8 9 0))
On May 26, 2012, at 12:56 AM, Harry Spier wrote:
> I can use for/fold to loop through a sequence while having the current
> element and the previous element of the sequence still available by
> doing something like this.
>
> (for/fold ([previous-element-in-sequence '()][list-being-created '()])
> ( [current-element-in-sequence sequence])
> (do some stuff)
> ....
> (values current-element-in-sequence
> (cons something list-being-created)))
>
> But what I want is to be able to loop through a sequence while having
> the prior, the current and the next element available.
>
> I'm sequencing through a representation of lines of a black and white
> page of text showing where the black pixels are and from that
> producing a graph showing the connectivity of the black pixel strips
> on each line to the ones on the lines above and below it.
>
> Using for/fold I'm able to code the graph of connectedness of the
> black strips on each line to the prior line in a very straightforward
> way, but I'd like to graph in both directions both to the prior line
> and to the next line at the same time.
>
> Is there a simple way to loop through a sequence and have the prior,
> current and next element available at the same time.
>
> Thanks,
> Harry
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