Hello Mark
[ Literate haskell follows... ]
> module Verb where
> import qualified Data.Map as Map
> import Data.Char
> data Verb = Go | Get | Jump | Climb | Give deriving (Show, Read)
I wouldn't use read instead something either a simple function:
> verb :: String -> Maybe Verb
> verb "Go" = Just Go
> verb "Get" = Just Get
> verb _ = Nothing
Or possible a Map:
> verb2 :: String -> Maybe Verb
> verb2 s = Map.lookup s verb_map
> verb_map :: Map.Map String Verb
> verb_map = Map.fromAscList [ ("Go", Go), ("Get", Get) {- .. -} ]
You could then do more about say case sensitivity - e.g. add ("get",Get) etc
or always convert to upper before querying the map.
> verb3 :: String -> Maybe Verb
> verb3 s = Map.lookup (map toUpper s) verb_map2
> verb_map2 :: Map.Map String Verb
> verb_map2 = Map.fromAscList [ ("GO", Go), ("GET", Get) {- .. -} ]
Best wishes
Stephen
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