The order of operations here is "right associative". So A -> B -> C -> D is equivalent to any of the following A -> (B -> C -> D) A -> (B -> (C -> D))

The order of operations here is "right associative". So A -> B -> C -> D is equivalent to any of the following A -> (B -> C -> D) A -> (B -> (C -> D)) A -> B -> (C -> D) They're equivalent through currying. But you can only add or remove parentheses for stuff that is on the right of a function arrow. (A -> B) -> (C -> D) is a different thing.