Re: [Haskell-cafe] List spine traversal

andrewhhunter:

On Mon, Jun 29, 2009 at 11:30 PM, Ryan Ingram wrote:

...

There can't be a way to do so that is pure, because such a function could distinguish between

...

xs1 = () : xs1 and xs2 = f () where f () = () : f ()

But doesn't seq and friends cause many of our normal referential transparency guarantees to be invalid?

Equational reasoning, in the presence of bottoms, anyway. -- Don