[Haskell-cafe] [Haskell] ANNOUNCE: haskell-src-exts 1.14.0

AlanKim Zimmerman alan.zimm at gmail.com
Tue Aug 20 13:02:34 CEST 2013

This is not using haskell-src-exts, but the Haskell Refactorer has a
structure to keep a parallel tree of tokens indexed by SrcSpan, which
attempts to allocate comments to the appropriate point.

It does not make use of the AST itself, so may be usable with


On Tue, Aug 20, 2013 at 11:19 AM, Niklas Broberg
<niklas.broberg at gmail.com>wrote:

> Hi Niklas,
> 1) My most desired feature would be a syntax tree that does not pluck
>> pluck comments out and make me treat them separately. It looks much
>> easier to me to have a fully descriptive tree and (filter . concatMap) /
>> traverse them out in some way than getting a list of comments and having
>> to insert them back in the right places myself.
>> Is that possible?
> Sadly not - it's theoretically impossible. The fact that you can put
> comments literally wherever, means that it's impossible to treat them as
> nodes of the AST. E.g.
>   f {- WHERE -} x = -- WOULD
>       -- THESE
>       do -- COMMENTS
>          a {- END -} <- g x -- UP
>          return {- ? -} a
> What would be theoretically possible is to define a restricted language
> that allows comments only in certain well-defined places (cf haddock), and
> ignores any others. That's a lot of work though, and it's not clear how big
> the gain is. :-\
> A different solution could be to improve the support, through better
> helper functions, for handling a syntax tree and a list of comments
> together. That's something I think could be worthwhile.
>> 2) Have you considered downloading the all-of-Hackage tarball and
>> running haskell-src-exts over it to get a benchmark of how much HSE can
>> already parse of the Haskell code out there?
> Considered, yes. Done, no. Would love to see the results :-). The crew at
> OdHac (Roman, Erik, Simon) ensured that the current version handles all of
> 'base', which is a good start.
> Cheers, Niklas
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