[Haskell-cafe] Re: All equations must have the same arity - why?

"Neil Mitchell" wrote:

Hi,

It's nice to write functions in point free style:

f = sort . nub

But sometimes I have to add an extra case, on a certain value:

f [] = [1] f = sort . nub

But now these equations have different arities, and its rejected by Haskell. Why does this not simply desugar to:

f [] = [1] f x = (sort . nub) x

i.e. lift the arities to the longest argument list.

Is there a reason this isn't done?

Answer #2: Because you can't write f x = case x of [] -> [1] -> sort.nub -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited.