An infix synonym for
fmap.
The name of this operator is an allusion to
$. Note the
similarities between their types:
($) :: (a -> b) -> a -> b
(<$>) :: Functor f => (a -> b) -> f a -> f b
Whereas
$ is function application,
<$> is function
application lifted over a
Functor.
Examples
Convert from a
Maybe Int to a
Maybe
String using
show:
>>> show <$> 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)