J. Garrett Morris wrote: > Maybe has a Monad instance, so you can write this as follows (untested): > > exists str wmap = boolFromMaybe exists' > where exists' = > do x <- Map.lookup (sort str) wmap > find (== str) (snd x) > boolFromMaybe (Just _) = True > boolFromMaybe Nothing = False
Small improvement (Data.Maybe is underappreciated): > exists str wmap = isJust exists' > where exists' = > do x <- Map.lookup (sort str) wmap > find (== str) (snd x) and maybe another improvement, though this is dependent on your tastes: > exists s wmap = isJust $ Map.lookup (sort s) wmap >>= find (== s) . snd -Udo -- Catproof is an oxymoron, childproof nearly so.
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