Hi, nubOrd: Seems good. Useful function to have. Shame its not in Data.List, but I understand the reasons for that, and think this is a perfectly sensible choice. nubWith: Seems bad. A not particularly useful function (other than to write nubOrd), with a fairly confusing name. I have previously used nubWith to mean nubOn (nubOn f = nubBy ((==) `on` f)) with cacheing of the function f. As a name, "with" only means "with additional stuff" - it gives no hint what the additional stuff is. The concept of stop-lists is a little confusing, and then you tell the user they almost certainly want to pass [] every single time - in that case why do they get an option? Also stop-lists have type "b", so stop-unconstrainted-type-variable seems a more appropriate name :-) The type signature is fairly complex. I'm not even convinced that nubWith really is a nub function, and not just some generalised filter - filterState perhaps. In which case you'd want to generalise Maybe b to (Bool,b). Can you ever imagine anyone other than nubOrd using nubWith? Is it a genuine utility function people have been crying out for? It seems perfectly good to include as a local function in Data.Set to be used to implement nubOrd, but I don't see its value as a standalone export from a very commonly used library full of very useful stuff. So, in summary I think nubOrd is great, and nubWith isn't nub, and isn't great. Thanks Neil
-----Original Message----- From: libraries-bounces@haskell.org [mailto:libraries-bounces@haskell.org] On Behalf Of Bart Massey Sent: 21 October 2008 10:04 am To: libraries@haskell.org Subject: Proposal #2717: Add nubWith, nubOrd
Ok, I've killed the overly ambitious proposal #2629, and replaced it with the more modest proposal #2717 http://hackage.haskell.org/trac/ghc/ticket/2717 which just adds Data.List.nubWith and Data.Set.nubOrd as previously discussed ad nauseam.
I know at least one person thought that adding these was a bad idea, but some others thought it was a fine thing to do. Hence the discussion on this list.
Bart Massey bart@cs.pdx.edu
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