Am 20.09.2011 20:21, schrieb Edward Kmett: [...]

I would suggest you rephrase this as a formal proposal, then I can happily vote +1.

Seeing the "wonderful" interrelation between elem, nub, nubBy and i.e. unionBy eq xs ys = xs ++ foldl (flip (deleteBy eq)) (nubBy eq ys) xs intersectBy eq xs ys = [x | x <- xs, any (eq x) ys] (note that "any (eq x)" could be "elemBy eq") I see hardly a chance to make a sensible proposal. I think, it is wrong to change the implementation of "elem" and "notElem" since I expect the "key" to be the first argument of the eq-comparison (in contrast to the REPORT_PRELUDE!). But this all would not matter if the eq-function are always symmetric, which may be not the case in practise. So a change could break existing code.

I'd also suggest rephrasing rhe mapAccumR as a formal proposal. I'm not sure yet of whether or not I'd be behind that one, but make both proposals separately, so they can pass individually.

I also don't see a relation to mapAccumR, so why don't you make such a separate proposal? C.