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

Jonathan Cast wrote:

On 13 Jan 2008, at 5:49 PM, Achim Schneider wrote:

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Jonathan Cast wrote:

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On 13 Jan 2008, at 5:27 PM, Achim Schneider wrote:

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Answer #2:

Because you can't write

f x = case x of [] -> [1] -> sort.nub

But why not?

Because arities aren't lifted to the longest argument list.

I think you lost the point of my question...

I'm glad you are capable of ever so nobly assigning the purest imaginable motives to me. You are a true inspiration.

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Treating case as syntax sugar for a higher-order function, so that all binding occurrences of lambdas in the unsugared code are associated with lambdas, is a good thing, and offers a natural way of desugaring the above, one case at a time.

What about

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

?

You could also do things like

f - x = (foo x).bar

with it. No more rewriting of pointfree code because of added arguments...

So `-' as a pattern means `implicitly apply the RHS to whatever this pattern matches'? I like it.

Yes. I suppose _> is a better idea, or something else beginning with _, as the rest of the characters could be functions. -- (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.