[Haskell-cafe] Silly question

Joel Reymont joelr1 at gmail.com
Mon Oct 31 04:06:21 EST 2005

How do I run z "a" from ghci or the IO monad?

module Foo where

import qualified Data.Map as M
import Control.Monad
import Control.Monad.List
import Prelude hiding ((!!))

(!!) :: (Ord k, MonadPlus m) => [M.Map k v] -> k -> m v
(!!) maps key = msum $ map (M.lookup key) maps
x :: M.Map String Int = M.empty
y :: M.Map String Int = M.fromList [("a", 1)]
z m = [x, y] !! m

     Thanks, Joel


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