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0 pointszaptheimpaler10y ago0 comments

I don't understand one thing about this notation:

   fun :: A -> B -> C -> D

can be bracketed in a bunch of different ways -

   fun1 :: (A -> B) -> (C -> D)
   fun2 :: A -> (B -> C -> D)

etc. and don't these all mean different things?

fun1 would take a function and return a function, whereas fun2 takes an A and returns a curried function of B,C -> D.

0 comments

Muphrid10y ago

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.

dwenzek10y ago

Read:

   fun :: A -> (B -> (C ->D))

kryptiskt10y ago

Yes, functions need to be bracketed, as they are single arguments with a complex type.

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