#2659: Add sortOn and other *On functions
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Reporter: twanvl | Owner:
Type: proposal | Status: closed
Priority: normal | Milestone: Not GHC
Component: libraries/base | Version: 6.9
Resolution: wontfix | Keywords:
Operating System: Unknown/Multiple | Architecture: Unknown/Multiple
Type of failure: None/Unknown | Difficulty: Unknown
Test Case: |
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Comment (by Herbert Valerio Riedel ):
In [changeset:"44512e3c855d8fb36ab6580f4f97f842ebcf4c6c/ghc"]:
{{{
#!CommitTicketReference repository="ghc"
revision="44512e3c855d8fb36ab6580f4f97f842ebcf4c6c"
Add Data.List.sortOn function (re #9004 and #2659)
`sortOn` sorts a list by comparing the results of a key function applied
to each
element. `sortOn f` is equivalent to `sortBy . comparing f`, but has the
performance advantage of only evaluating `f` once for each element in the
input list.
Historical note: This was already proposed in 2008 as part of
http://www.haskell.org/pipermail/libraries/2008-October/010797.html
It was, however, the recent re-attempt
http://www.haskell.org/pipermail/libraries/2014-April/022489.html
that let `sortOn` make it into base at last. Maybe the other functions
mentioned in #2659 might be worth reconsidering as well.
}}}
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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/2659#comment:7
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The Glasgow Haskell Compiler
