[GHC] #15131: Speed up certain Foldable NonEmpty methods

[GHC]

#15131: Speed up certain Foldable NonEmpty methods
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Core Libraries    |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4677
       Wiki Page:                    |
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Comment (by YitzGale):

 Replying to [comment:3 dfeuer]:
 > Yours has to hold on to the "and then add one" while calculating the
 length of the list.

 Are you sure GHC doesn't inline the {{{+1}}}? In any case, this is
 slightly better:


 {{{#!hs
 length (_ :| as) = List.foldl' (\c _ -> c+1) 1 as
 }}}

 > Same goes for `max` and `min`.

 Yes, and also for {{{product}}} and {{{sum}}}, but I did that purposely. I
 want the semantics to be the same as for {{{List}}}, which is a bit weird
 because it uses {{{foldl}}}. And I don't want to hard-code a copy of the
 {{{foldl}}} here. I want it to be fixed automatically if we every get
 around to fixing it for List.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15131#comment:4>
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