[GHC] #15521: Provide a strict version of sum

[GHC]

#15521: Provide a strict version of sum
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        Reporter:  dnadales          |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Prelude           |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ulysses4ever):

 Replying to [comment:1 f-a]:
 > Is there any occourrence when using a lazy `sum` is more appropriate
 than using its stricter version?

 One might go with a usual non-termination argument: if you have divergent
 computation inside your list AND you don't actually use the result of
 `sum`, then you get a different behaviour. Similar argument applies for
 “expensive” computation inside the list.

 Also, Haskell Report (the Haskell standard) says that `sum` should behave
 lazily (AFAIK). So, changing the behavior of `sum` seems a bit of extreme
 to me. I'd rather argue for adding `sum' / product'` to `Prelude`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15521#comment:2>
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