The Prettyprint library you can download from:
http://www.cs.uu.nl/wiki/HUT/Download
and is described on:
http://www.cs.uu.nl/wiki/HUT/PrettyPrintingCombinators
contains amongst others the following code:
data Doc = Empty
| Char Char -- invariant: char is not '\n'
| Text !Int String -- invariant: text doesn't
contain '\n'
| Line !Bool -- True <=> when undone by
group, do not insert a space
| Cat Doc Doc
| Nest !Int Doc
| Union Doc Doc -- invariant: first lines of
first doc longer than the first lines of the second doc
| Column (Int -> Doc)
| Nesting (Int -> Doc)
text "" = Empty
text s = Text (length s) s
so if you define now:
wrap l t r = Text 0 l <|> text t <|> Text 0 r
you should be set and done,
Doaitse Swierstra
On Dec 13, 2006, at 10:31 PM, Tomasz Zielonka wrote:
On Wed, Dec 13, 2006 at 08:58:25PM +0000, Neil Mitchell wrote:
I've been using the HughesPJ pretty printing library, but I need a
new
combinator:
wrap :: String -> Doc -> String -> Doc
wrap prepend doc append = ...
The semantics of this would be that the text is prepended and
appended
to the doc when rendered, but does not alter the pretty printing at
all. The idea of this is to support printing with HTML rendering:
wrap "<span class='keyword'>" (text "case") "</span>"
The HughesPJ library is 1000 lines long, so will be quite a lot of
work to change this to get it working properly.
I am not sure it will work, but it's sufficiently easy to try.
Look at the innards of HughesPJ, especially the TextBeside data
constructor. Its second parameter is an Int holding the length
of the text. Perhaps if you created TextBeside with your HTML
markup, but with 0 length field, things would be laid out properly.
Something like:
wrap prepend doc append =
zeroText prepend <> doc <> zeroText append
zeroText s = textBeside_ (Str s) 0 Empty
Best regards
Tomasz
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