map -package:containers -package:base-compat -package:base -package:basement -package:invertible -package:ghc -package:amazonka-core -package:os-string -package:bytestring -is:exact -package:incipit-base -package:base-compat-batteries package:pipes
Apply a function to all values flowing downstream
map id = cat
map (g . f) = map f >-> map g
Apply a function to all values flowing downstream, and forward each
element of the result.
Apply a monadic function to all values flowing downstream
mapM return = cat
mapM (f >=> g) = mapM f >-> mapM g
Consume all values using a monadic function
(mapMaybe f) yields
Just results of
f.
Basic laws:
mapMaybe (f >=> g) = mapMaybe f >-> mapMaybe g
mapMaybe (pure @Maybe . f) = mapMaybe (Just . f) = map f
mapMaybe (const Nothing) = drain
As a result of the second law,
mapMaybe return = mapMaybe Just = cat