#2717: Add nubWith, nubOrd
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Reporter: Bart Massey | Owner:
Type: proposal | Status: new
Priority: normal | Component: libraries/base
Version: | Severity: normal
Keywords: | Testcase:
Architecture: Unknown/Multiple | Os: Unknown/Multiple
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This is a followup to my proposal #2629, which had a much more ambitious
scheme. After much discussion, it was decided to put this smaller
proposal on the table.
I've implemented a new function Data.List.nubWith that takes a "stop list"
and "filtering function" as an argument, and filters its target list
against the stop list. I've then implemented Data.Set.nubOrd in terms of
nubWith. nubBy is left alone, since there's nothing obvious to be done
about it. All of the nubs are still fully lazy.
Basic QuickCheck tests have been written, and pass.
Performance benchmarking shows my nubOrd implementation to be quite
comparable to that of nub in cases where the latter performs well, and
dramatically faster when nub performs poorly. In particular, nubOrd can
work on long lists with long nubs, unlike the basic nub, which is
hopeless.
Patch against current Darcs head attached.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2717>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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