On Mon, May 23, 2011 at 9:20 AM, michael rice <nowg...@yahoo.com> wrote:
> What's the best way to end up with a list composed of only the Just values, > no Nothings? > > Michael > > ========================== > > import Control.Monad.State > import 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] > -} > > There's a library function for it, but also: > filter ((/=) Nothing) is readable enough.
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe