-John
On 11/1/06, Stefan Holdermans <[EMAIL PROTECTED]> wrote:
John,
> My question is, how do I preserve the ordering of entities in my
> list and still be able to assign the proper order values to each
> entity? Is there an efficient way to do this? How else might I
> improve my orderByPriority algorithm.
Straightforwardly, you could do it like this:
import List (sortBy)
type Priority = Int
type Order = Int
order :: [Priority] -> [(Priority, Order)]
order = unlabel . sortOnLab . assignOrder . sortOnPrio . label
where
label = zip [0 ..]
unlabel = map snd
sortOnLab = sortBy (\(l, _) (m, _) -> compare l m)
sortOnPrio = sortBy (\(_, p) (_, q) -> compare p q)
assignOrder = \xs -> zipWith (\(l, p) o -> (l, (p, o))) xs [0 ..]
For instance:
> order [5, 2, 3, 7]
[(5,2),(2,0),(3,1),(7,3)]
HTH,
Stefan
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