HughesPJ.vcat should behave like 'foldr ($$) empty', not like 'foldr ($+$) empty'

The performance tuning for libraries/pretty applied in June 2008

Tue Jun 24 12:37:15 BST 2008  benedikt.huber@gmail.com
  * fillNB bug, lazy vcat 

accidentally changed the behavior of vcat to foldr ($+$) empty, although it should be foldr ($$) empty, according to the documentation. Fixing this is simple (patch attached).

hunk ./Text/PrettyPrint/HughesPJ.hs 497
-vcat = reduceAB . foldr (above_' True) empty
+vcat = reduceAB . foldr (above_' False) empty

See:

http://www.haskell.org/pipermail/libraries/2008-December/011032.html http://www.haskell.org/pipermail/libraries/2010-March/013067.html

It would be nice to add a test case, but I'm not sure where to put it.

Trac metadata

Trac field	Value
Version	6.12.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/pretty
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