Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

On Tue, Mar 11, 2008 at 01:43:36AM -0400, Brandon S. Allbery KF8NH wrote:

On Mar 11, 2008, at 0:20 , Chaddaï Fouché wrote:

...

2008/3/11, David Menendez :

...

I think Adrian is just arguing that a == b should imply f a == f b, for all definable f, in which case it doesn't *matter* which of two equal elements you choose, because there's no semantic difference.

I completely agree that this propriety should be true for all Eq instance exported by a public module. I don't care if it is not the case in a isolated code, but libraries shouldn't break expected invariant (or at least be very cautious and warn the user). Even Eq Double respects this propriety as far as I know.

I wouldn't want to bet on that (Eq Double, that is). Floating point's just *evil*.

I wouldn't bet on it either: Prelude> 0.0 == -0.0 True Prelude> isNegativeZero 0.0 == isNegativeZero (-0.0) False Although isNegativeZero might be considered a ``private, "internal" interface that exposes implementation details.'' Groeten, Remi