[Haskell-beginners] program not running lazily

Rein Henrichs rein.henrichs at gmail.com
Thu Jan 21 19:05:17 UTC 2016


s/not/note, sorry

On Thu, Jan 21, 2016 at 10:42 AM Rein Henrichs <rein.henrichs at gmail.com>
wrote:

> But not that doing so will cause the program to have an exponential
> runtime as each new ys must be repeatedly traversed to append a [y].. The
> alternative is to *unfold* your list by recursing on the right hand side of
> the (:) to add new elements.
>
> On Thu, Jan 21, 2016 at 5:43 AM Doug McIlroy <doug at cs.dartmouth.edu>
> wrote:
>
>> Each time you find another good 9-mer, you add it to
>> the head of the list. This means that the ultimate
>> list will be in reverse order of discovery: the first element
>> to be printed is the last one to be found.  To get
>> output in the order it was discovered, build the
>> output by ys++[y] rather than y:ys.
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>
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