[Haskell-cafe] [Maybe Int] sans Nothings
michael rice
nowgate at yahoo.com
Mon May 23 18:20:25 CEST 2011
What's the best way to end up with a list composed of only the Just values,no Nothings?
Michael
==========================
import Control.Monad.Stateimport Data.Maybe
type GeneratorState = State Int
tick :: GeneratorState (Maybe Int)tick = do n <- get if ((n `mod` 7) == 0) then return Nothing else do put (n+1) return (Just n)
{-*Main> evalState (sequence $ replicate 9 tick) 1[Just 1,Just 2,Just 3,Just 4,Just 5,Just 6,Nothing,Nothing,Nothing]-}
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