Please apply the comparison function given to nubBy to elements of the list in the order in which they occur in the list.
Christian.Maeder at dfki.de
Wed Sep 21 10:00:52 CEST 2011
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
> 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
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