Re: #2309: containers: specialize functions that fail in a Monad to Maybe

Excerpts from Ross Paterson's message of Sat Jul 19 01:29:40 +0200 2008:

To summarize:

Several container classes have types like

lookup :: (Monad m, Ord k) => k -> Map k a -> m a

And what about keeping the monadic version under another name like lookupM? Cheers, -- Nicolas Pouillard aka Ertai