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

Niklas Broberg niklas.broberg at gmail.com
Tue Aug 20 11:19:52 CEST 2013

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20130820/fc1513c2/attachment.htm>

More information about the Haskell-Cafe mailing list