[Haskell-cafe] All equations must have the same arity - why?
ndmitchell at gmail.com
Sun Jan 13 20:21:47 EST 2008
On 1/13/08, Conal Elliott <conal at conal.net> wrote:
> That eta-expansion desugaring would lose sharing.
Ah, that will be it.
> 1. Equations with different arities more often signal bugs than
> correct intentions.
I don't believe that. I suspect the type system will mop these up.
> 2. It's highly misleading.
Again, I don't believe that. Your argument holds for why we shouldn't
have multiple equations for definition, not that they should all be
the same arity.
> Offhand, I don't know of
> a desugaring that would do the trick and preserve sharing. Any ideas? -
> f = let body = sort . nub
> in \xs -> case xs of
>  -> 
> (_:_) -> body
Compared to other desugarings in Haskell, this one is positively tame!
I quite like the idea of permitting equations to have different
arities. It removes restrictions, makes things more regular etc.
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