> this should look like, even more than what it should do. For some reason,
> I kind of like writing this:
>
> *Math.Prime> is Prime 42
> False
>
> instead of this:
>
> *Math.Prime> isPrime 42
> False
Great! I like this a LOT.
Im working on a framework for ranking and unranking things where primes are just a tiny part:
> data DCountable > = Countable Integer > | Uncountable > deriving (Eq,Show) > > class CRankable a b where > rank :: a -> b -> Maybe Integer > unrank :: a -> Integer -> Maybe b > count :: a -> b -> DCountable
So using the instance for Prime on Integer looks like:
Cafe> unrank Prime 23 ::Maybe Integer Just 89 Cafe> rank Prime (89::Integer) Just 23
I have also for trees and lists and other things with defined parameters like length, or not.
Using my framework they are made quite simple.
RankIL is for IntegerList with any length (the bool is if the integers start on 1 or not, might look irrelevant here):
Cafe> map (unrank (RankIL True)) [0..10] ::[Maybe [Integer]]
[Just [1],Just [2],Just [1,1],Just [3],Just [1,2],Just [2,1],Just [1,1,1],Just [4],Just [1,3],Just [2,2],Just [3,1]]
RankIL is for IntegerTree
Cafe> map (unrank RankIT) [0..3] ::[Maybe (Tree Integer)]
[Just Node {rootLabel = 1, subForest = []},Just Node {rootLabel = 1, subForest = [Node {rootLabel = 1, subForest = []}]}...
..and so on..
Its not very pretty yet since ive only been a Haskeller for some weeks now, and I dont know about darcs (i run cvs as i have the book), but maybe my framework could be included once a Haskell-guru brushes it up a bit?
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