A version of map that discards elements
mapMaybe f s passes all output from
s through the
function
f and discards elements for which
f s
evaluates to
Nothing.
Example:
ghci> Streams.fromList [Just 1, None, Just 3] >>=
Streams.mapMaybe id >>=
Streams.toList
[1,3]
Since: 1.2.1.0