Proposal: add Control.Monad.whenJust ∷ (Monad m) ⇒ Maybe α→(α→ m ()) → m ()
haskell.org at liyang.hu
Wed Nov 30 08:11:32 CET 2011
This particular pattern crops up a lot for me. Does it for anyone else?
I (half-heartedly) propose adding to Control.Monad the following:
> -- | A variation of 'when' for 'Maybe a'.
> whenJust :: (Monad m) => Maybe a -> (a -> m ()) -> m ()
> whenJust = flip (maybe (return ()))
so that I can write:
> whenJust (Map.lookup k m) $ \ a -> do
instead of say:
> case Map.lookup k m of
> Nothing -> return ()
> Just a -> do
which is not only nicer on the eyes, but also saves me a valuable level of
Discussion period: 2 weeks.
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