Re: Left-bias and non-structural equality.

On 1/5/06, Christian Maeder wrote:

Jean-Philippe Bernardy wrote:

...

On 1/4/06, Christian Maeder wrote:

...

I would not like to drop biasing distinction, as I don't think this costs too much. With biasing, maps could be implemented via "biased sets" (Set (MapEntry a b)):

data MapEntry a b = a := b

instance Eq/Ord a => Eq/Ord (MapEntry a b) where compare (a1 := _) (a2 := _) = compare a1 a2

I would discourage such a use. This is exaclty why we provide Maps, after all.

I still agree, but it might be nice to have for testing, comparison, and property specification purposes.

Christian

Indeed, that's what I did to write the left-bias testing code. As it is, we can choose to enable or disable ill-defined Eq it when testing any given specific collection data-type. Cheers, JP.