Operator section
= Operator section
A partially applied infix operator: `(a op)` means `\x -> a op x`, and `(op b)` means `\x -> x op b`, subject to <Haskell>'s syntax rules. In particular, `(f .)` maps a <function> `g` to the <function composition> `f . g`. Composing such a section with a curried binary <function> composes at two argument levels: `((f .) . g) x y = f (g x y)` on total inputs.<Haskell 2010 Language Report>[§3.5, Sections]{ref}