[GHC] #12440: Strictness of span and break does not match documentation

[GHC]

#12440: Strictness of span and break does not match documentation
-------------------------------------+-------------------------------------
           Reporter:  rwbarton       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  8.0.1
  libraries/base                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The
 [http://hackage.haskell.org/package/base-4.9.0.0/docs/Prelude.html#v:span
 documentation] of `span` says

     `span p xs` is equivalent to `(takeWhile p xs, dropWhile p xs)`

 However, that's not literally true since `span p xs` is _|_ if either `xs`
 is _|_ or `xs = x :_` and `p x` is _|_.

 This same error is also present in the Haskell 98 report, which states the
 same property of `span` but gives a definition equivalent to the one used
 by GHC.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12440>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler