On Fri, 2009-12-04 at 01:19 +0000, Malcolm Wallace wrote:
No non-bottoming program has changed, but fewer programs fail now. I find it hard to imagine that anyone could have been relying on getting a crash here.
Making something more lazy can cause a memory leak.
To come back to the specifics of partitionEithers, is anyone arguing that, in this case, the original over-strictness is either intentional, or useful?
I don't think anyone is complaining about this specific case. I think we agree that the general principle is to make things lazy except where there are compelling reasons to do otherwise. As another example, intersperse (and intercalate) could be made slightly more lazy with no loss of efficiency (indeed it looks like it could be an improvement): intersperse :: a -> [a] -> [a] intersperse _ [] = [] intersperse sep (x0:xs0) = x0 : go xs0 where go [] = [] go (x:xs) = sep : x : go xs vs the standard def: intersperse :: a -> [a] -> [a] intersperse sep [] = [] intersperse sep [x] = [x] intersperse sep (x:xs) = x : sep : intersperse sep xs intersperse '_' ('x' : undefined) = 'x' : undefined vs List.intersperse '_' ('x' : undefined) = undefined Duncan