#669: negative indentation in Text.PrettyPrint.HughesPJ
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Reporter: [EMAIL PROTECTED] | Owner: thorkilnaur
Type: bug | Status: new
Priority: normal | Milestone: 6.10 branch
Component: libraries/pretty | Version: 6.4.1
Severity: minor | Resolution:
Keywords: | Difficulty: Unknown
Testcase: pp1 | Architecture: Unknown
Os: Unknown |
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Comment (by benedikt):
Thanks thorkil
I'll document another example using $$ (not present in the paper), which
might be reported as a bug.
The negative indentation causes what I would call
"surprising behavior from the client's point of view".
{{{
show$ text "a" <> (nest 4 (text "b") $+$ text "c")) $$ text "d" ==>
|ab|
|c..d|
(text "a" <> (nest 4 (text "b") $+$ text "c")) $$ text "d" =
l1: ....|ab...|
l2: .c..|.....|
`overlap`
l3: ....|d.....|
==
l1: ....|ab...|
l2: .c..|d....|
}}}
The library behaves in a consistent way, but the client is probably
surprised that
(a $$ text "d") puts `d' in column 4.
The cleanest solution would be to make negative indentation a hard error -
but
this might break existing code, so I won't suggest it (maybe emit a
warning ?)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/669#comment:15>
GHC <http://www.haskell.org/ghc/>
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