On Mar 5, 2004, at 12:41, Brandon Michael Moore wrote:
At the lower level of remimplementing your functions I can suggest a few things.
Brandon, Thanks for great suggestions! Following them, here is how I redone the code: ... import Data.Maybe import Data.Either import Data.Typeable ... data Flag = Verbose | Input String | Output String | Filter String deriving Show Data instance Eq Flag where x == y = toConstr x == toConstr y findFlag :: Flag -> [Flag] -> Flag findFlag f fs = fromMaybe f (find (==f) fs) The only problem is my GHC does not seems to find 'Data' class and I am getting following errors: Type constructor or class not in scope: `Data' Variable not in scope: `toConstr' Variable not in scope: `toConstr' Also I have style question: What is the best way to define equality test in this example: 1. Via instantiating EQ class 2. via standalone function (I can define sameConstr Flag -> Flag -> Bool) 3. inline lambda expression passed to find I am leaning towards #2 or #3. Vadim -- "La perfection est atteinte non quand il ne reste rien a ajouter, mais quand il ne reste rien a enlever." (Antoine de Saint-Exupery)