[Haskell-cafe] extracting a single declaration using haskell-src-ext

Michael Sloan mgsloan at gmail.com
Tue Mar 17 20:02:27 UTC 2015


I wrote some code to do this quite recently, as part of an internal
tool at FP Complete.  I've copied out the relevant functions and
written an example of using it here:

I hope that helps!

On Tue, Mar 17, 2015 at 9:12 AM, Maurizio Vitale <mrz.vtl at gmail.com> wrote:
> G'day!
> Is there an easy way to extract a single declaration from an Haskell source
> file and print it with the original formatting?
> [I could live with pretty printing, but the default prettyPrint gives me a
> very strange formatting where something like:
> main = do
>   putStrLn "Hello"
> becomes:
> main = do putStrLn "Hello"]
> The closest I've got is to parse the file with comments and then get inside
> Module ...decls and do printExact with an empty comment list for the decl
> I'm interested in. This gives me the original formatting and empty lines
> where comments were that I can then remove.
> But if there was anything already out there that just take a String for the
> toplevel I'm interested in and convert that only, I'd love to know.
> Thanks,
>   Maurizio
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