How to avoid trailing whitespace generated by Text.PrettyPrint.HughesPJ?
Hi guys, it seems to me like the HughesPJ pretty printer has trouble dealing with empty lines in a nested environment. Consider the following example:
import Text.PrettyPrint.HughesPJ test1 = putStrLn $ render $ nest 4 $ vcat $ map text [ "line 1", "", "line 2" ]
The 'test1' function prints the following output, where blanks have been replaced by underscores to make them visible: *Main> test1 ____line_1 ____ ____line_2 Now, I would like to avoid this kind of trailing whitespace in the document I'm generated -- but how? My first thought was to replace text "" by empty, but that change effectively removes the empty line altogether:
test2 = putStrLn $ render $ nest 4 $ vcat $ [ text "line 1", empty , text "line 2" ]
*Main> test2 ____line_1 ____line_2 Is there another way to accomplish what I want? Take care, Peter
On 8 March 2013 23:10, Peter Simons
Hi guys,
it seems to me like the HughesPJ pretty printer has trouble dealing with empty lines in a nested environment. Consider the following example:
import Text.PrettyPrint.HughesPJ test1 = putStrLn $ render $ nest 4 $ vcat $ map text [ "line 1", "", "line 2" ]
The 'test1' function prints the following output, where blanks have been replaced by underscores to make them visible:
*Main> test1 ____line_1 ____ ____line_2
Now, I would like to avoid this kind of trailing whitespace in the document I'm generated -- but how? My first thought was to replace text "" by empty, but that change effectively removes the empty line altogether:
test2 = putStrLn $ render $ nest 4 $ vcat $ [ text "line 1", empty , text "line 2" ]
*Main> test2 ____line_1 ____line_2
Is there another way to accomplish what I want?
The pretty-printer is doing what it _should_ be doing here (namely indenting everything in that block); to get rid of unneeded trailing whitespace the only thing I can think of is to post-process the output (e.g.: unlines . reverse . dropWhile isSpace . reverse . lines).
Take care, Peter
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-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com
On Sat, 9 Mar 2013, Ivan Lazar Miljenovic wrote:
The pretty-printer is doing what it _should_ be doing here (namely indenting everything in that block); to get rid of unneeded trailing whitespace the only thing I can think of is to post-process the output (e.g.: unlines . reverse . dropWhile isSpace . reverse . lines).
You certainly mean unlines . map (reverse . dropWhile isSpace . reverse) . lines Btw. (dropWhileRev isSpace) would be lazier: http://hackage.haskell.org/packages/archive/utility-ht/0.0.8/doc/html/Data-L...
Hi Ivan,
*Main> test1 ____line_1 ____ ____line_2
The pretty-printer is doing what it _should_ be doing here (namely indenting everything in that block).
when you say "everything" you really mean "nothing", right? Notice that the line is empty. There is nothing to indent and these blanks are quite unnecessary. It's a bit of a stretch to say that the pretty printer should be adding them despite the fact that they serve no purpose.
to get rid of unneeded trailing whitespace the only thing I can think of is to post-process the output (e.g.: unlines . reverse . dropWhile isSpace . reverse . lines).
Well, if there is no other choice, then I'll do that. Take care, Peter
participants (3)
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Henning Thielemann -
Ivan Lazar Miljenovic -
Peter Simons