どうやら関数合成をやるためのシロモノらしい。F#使いからの要望だそうな。
7.6.3
Prelude> import Data.Function Prelude Data.Function> [1,2,3] & map (+3) & filter even & Prelude.sum <interactive>:3:9: Not in scope: `&' <interactive>:3:20: Not in scope: `&' <interactive>:3:34: Not in scope: `&'
7.10.2
Prelude> import Data.Function Prelude Data.Function> [1,2,3] & map (+3) & filter even & Prelude.sum 10