[GHC] #2393: Text.PrettyPrint.HughesPJ: Bug fixes, performance improvement

[GHC]

#2393: Text.PrettyPrint.HughesPJ: Bug fixes, performance improvement
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        Reporter:  guest             |         Owner:
            Type:  bug               |        Status:  closed
        Priority:  normal            |     Milestone:  6.10.1
       Component:  libraries/pretty  |       Version:  6.8.3
      Resolution:  fixed             |      Keywords:
Operating System:  Unknown/Multiple  |  Architecture:  Unknown/Multiple
       Test Case:                    |
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Comment (by Thomas Miedema <thomasmiedema@…>):

 In [changeset:"67576ddc67f39bef43c473f30af0887d22011710/ghc"
 67576ddc/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="67576ddc67f39bef43c473f30af0887d22011710"
 Pretty: bugfix fillNB (#10735)

 This is a backport of a bug fix by Benedikt Huber (#2393), from commit
 1e50748beaa4bd2281d323b18ea51c786bba04a1 in the pretty library.

 From https://mail.haskell.org/pipermail/libraries/2008-June/009991.html:

     Law <l1> states that

     > sep (ps++[empty]++qs)   = sep (ps ++ qs)
     >         ...ditto hsep, hcat, vcat, fill...

     In the current implementation, this fails for the paragraph fill
     variants.

     > render' $ fsep [ text "c", text "c",empty, text "c", text "b"]
     >   where render' = renderStyle (Style PageMode 7 1.4)
     >> c c c
     >>     b
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2393#comment:8>
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