[GHC] #13573: Add Foldable1 to base

[GHC]

#13573: Add Foldable1 to base
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10365, #15566    |  Differential Rev(s):  Phab:D4812
       Wiki Page:                    |
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Changes (by Iceland_jack):

 * related:  #10365 => #10365, #15566


Comment:

 Also

 {{{#!hs
 maximumBy :: Foldable1 f1 => (a -> a -> Ordering) -> (f1 a -> a)
 maximumBy cmp = foldl1_ max'
   where max' x y = case cmp x y of
                         GT -> x
                         _  -> y

 minimumBy :: Foldable1 f1 => (a -> a -> Ordering) -> (f1 a -> a)
 minimumBy cmp = foldl1_ min'
   where min' x y = case cmp x y of
                         GT -> y
                         _  -> x
 }}}

 and per #15566

 {{{#!hs
 maximumOn, minimumOn :: Foldable1 f1 => Ord cmp => (a -> cmp) -> (f1 a ->
 a)
 maximumOn = maximumBy . comparing
 minimumOn = minimumBy . comparing
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13573#comment:21>
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