Thanks Niklas, in fact this produced a source with comments: import Language.Haskell.Exts.Annotated main = do (ParseOk (mod,comments)) <- parseFileWithComments defaultParseMode "Test.hs" let pretty = exactPrint mod comments writeFile "Test_PRETTY.hs" pretty However: - The source code produced was incorrect: class Dir d where was rewritten as: class Dir dwhere{ And: instance Dir Directory where localDir (Local f) = return f type URL= String was rewritten as: instance Dir Directory where localDir (Local f) = return f typeURL= String Are these known bugs? - Also, the printing is a bit too exact :-), I would like to keep my comments AND get the code nicely reformatted. Is there a way? What people use to keep their haskell source files in tip-top shape? Thanks titto 2009/10/20 Niklas Broberg :

Hi Pasqualino,

...

I am looking at the haskell-src-ext library.

It can parse files with comments and it can pretty print but, for what I can see it cannot do both :-)  (prettyPrint won't work on the structure returned by parseFileWithComments).

What you want is exactPrint, defined in Language.Haskell.Exts.Annotated.ExactPrint. :-)

Cheers,

/Niklas

Hi again,

However: - The source code produced was incorrect:

class Dir d where

was rewritten as:

class Dir dwhere{

That's weird, I'll look into it, thanks.

instance Dir Directory where  localDir (Local f) = return f

type URL= String

was rewritten as:

instance Dir Directory where  localDir (Local f) = return f

 typeURL= String

Sorry, I don't see the difference between these two. Did you write the correct one twice by mistake?

Are these known bugs?

No, there are no known bugs so please report everything you find! exactPrint is new and most likely sparsely used as of yet. I'd expect there to be a few bugs lying around here and there, and I appreciate all reports!

- Also, the printing is a bit too exact :-), I would like to keep my comments AND get the code nicely reformatted.

Is there a way?

No. Like Lennart points out that's a really difficult problem, not to say impossible, where do you place the comments after reformatting? Cheers, /Niklas

...

...

instance Dir Directory where  localDir (Local f) = return f

 typeURL= String

Sorry, I don't see the difference between these two. Did you write the correct one twice by mistake?

In case Pasqualino doesn't see your mail real soon... Maybe the difference is the missing space between "type" and "URL".

Ah, of course, I see it now, thanks! Cheers, /Niklas

Hi, there is also another difference: type URL= String was a top level definition but it has been moved under the previous instance declaration. I attach a source fragment and another file with the pretty printed output containing these three errors. Regarding the problem of pretty printing while keeping the comments I imagine that you would like the comments to be associated with the previous syntactical element (module, top level declaration or expression) and be rendered in the same relative position in the pretty printed output. I agree that it doesn't sound like an easy task. However, similar systems exists for most languages (I loved my Java reformatter in Eclipse) and it would be very handy in Haskell as well. Best, titto 2009/10/20 Niklas Broberg :

...

...

...

instance Dir Directory where  localDir (Local f) = return f

 typeURL= String

Sorry, I don't see the difference between these two. Did you write the correct one twice by mistake?

In case Pasqualino doesn't see your mail real soon... Maybe the difference is the missing space between "type" and "URL".

Ah, of course, I see it now, thanks!

Cheers,

/Niklas

-- Pasqualino "Titto" Assini, Ph.D. http://quicquid.org/

I'll see when I can get to fixing it, hopefully it won't be long.

Two fairly easy bugs to fix, darcs repo is updated. It's probably high time I did another release, stay tuned. I just can't believe I didn't have a single class declaration in my test suite to catch the first one! Or that no one else triggered it before (I guess no one has actually started using exactPrint in their code yet). Thanks again for reporting! :-) Cheers, /Niklas