[Haskell-cafe] Functions that return functions
nowgate at yahoo.com
Sun Apr 12 19:11:28 EDT 2009
You're getting ahead of me again.
--- On Sun, 4/12/09, Jake McArthur <jake.mcarthur at gmail.com> wrote:
From: Jake McArthur <jake.mcarthur at gmail.com>
Subject: Re: [Haskell-cafe] Functions that return functions
To: "michael rice" <nowgate at yahoo.com>
Cc: haskell-cafe at haskell.org
Date: Sunday, April 12, 2009, 5:45 PM
michael rice wrote:
> Admittedly, functions that return functions are Lispy, but perhaps there a Haskelly way to accomplish the same thing?
Actually, I think you will come to find that this way of thinking is more Haskelly than it is Lispy!
import Control.Applicative ((<$), (<*>))
import Control.Arrow ((&&&))
import Control.Monad (guard)
import Data.List (unfoldr)
makeVerifier f m = (==0) . (`mod` m) . sum . zipWith f [1..] . unfoldr nextDigit
where nextDigit = (<$) . (snd &&& fst) . (`divMod` 10) <*> guard . (/= 0)
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