Documentation

Replace the contents of a Maybe Int with a constant String:

>>> Nothing $> "foo" Nothing >>> Just 90210 $> "foo" Just "foo" 

Replace the contents of an Either Int Int with a constant String, resulting in an Either Int String:

>>> Left 8675309 $> "foo" Left 8675309 >>> Right 8675309 $> "foo" Right "foo" 

Replace each element of a list with a constant String:

>>> [1,2,3] $> "foo" ["foo","foo","foo"] 

Replace the second element of a pair with a constant String:

>>> (1,2) $> "foo" (1,"foo") 

Convert from a Maybe Int to a Maybe String using show:

>>> show <$> Nothing Nothing >>> show <$> Just 3 Just "3" 

Convert from an Either Int Int to an Either Int String using show:

>>> show <$> Left 17 Left 17 >>> show <$> Right 17 Right "17" 

Double each element of a list:

>>> (*2) <$> [1,2,3] [2,4,6] 

Apply even to the second element of a pair:

>>> even <$> (2,2) (2,True) 

Replace the contents of a Maybe Int with unit:

>>> void Nothing Nothing >>> void (Just 3) Just () 

Replace the contents of an Either Int Int with unit, resulting in an Either Int '()':

>>> void (Left 8675309) Left 8675309 >>> void (Right 8675309) Right () 

Replace every element of a list with unit:

>>> void [1,2,3] [(),(),()] 

Replace the second element of a pair with unit:

>>> void (1,2) (1,()) 

Discard the result of an IO action:

>>> mapM print [1,2] 1 2 [(),()] >>> void $ mapM print [1,2] 1 2