Re: [Haskell-beginners] Maybe, Either

I think there is no such function in standard library. But you can also do the same by `maybe (Left err) Right (lookup key assoc)` without defining eitherLookup. HTH -nwn On Sun, Sep 13, 2009 at 12:14 AM, Michael Mossey wrote:

I want to use 'lookup' inside an Either String monad. So I want to write something like

eitherLookup :: Eq a => String -> a -> [(a,b)] -> Either String b eitherLookup s x ps = case lookup x ps of                         Just y -> Right y                         Nothing -> Left s

Is there such a function existing?

Thanks, Mike _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners