On Thursday 06 April 2006 06:44 pm, John Meacham wrote: > On Thu, Apr 06, 2006 at 10:52:52PM +0100, Brian Hulley wrote:
[snip a question about Eq and Ord classes] > well, there are a few reasons you would want to use inheritance in > haskell, some good, some bad. > > 1. one really does logically derive from the other, Eq and Ord are like > this, the rules of Eq says it must be an equivalance relation and that > Ord defines a total order over that equivalance relation. this is a good > thing, as it lets you write code that depends on these properties. <PUBLIC SERVICE ANNOUNCEMENT> Many of you probably know this already, but for those who might not know: Prelude> let x = read "NaN" :: Float Prelude> x == x False Prelude> x == 0 False Prelude> 0 < x False Prelude> x < 0 False Ewwwwww! Be careful how far you depend on properties of typeclasses, and make sure you document it when you do. <we now return to you regularly scheduled discussion> Rob Dockins _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
