:: a -> (a -> b) -> b -package:rio -package:ghc-lib-parser -package:vivid package:diagrams-lib

& is a reverse application operator. This provides notational convenience. Its precedence is one higher than that of the forward application operator $, which allows & to be nested in $. This is a version of flip id, where id is specialized from a -> a to (a -> b) -> (a -> b) which by the associativity of (->) is (a -> b) -> a -> b. flipping this yields a -> (a -> b) -> b which is the type signature of &

Examples

>>> 5 & (+1) & show
"6"

>>> sqrt $ [1 / n^2 | n <- [1..1000]] & sum & (*6)
3.1406380562059946

Postfix function application, for conveniently applying attributes. Unlike ($), (#) has a high precedence (8), so d # foo # bar can be combined with other things using operators like (|||) or (<>) without needing parentheses.