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
____________________
Racket Users list:
http://lists.racket-lang.org/users
