On Wed, May 2, 2012 at 7:20 PM, Tony Morris wrote:

Is there a library to traverse a source AST keeping state?

Hi Tony, I was able to do this [1] using haskell-src-exts and a state monad. AST traversal is possible due to HSE deriving instances for Data in all its datatype declarations, but the traversals were of a generic variety, rather than zippers. I read Scrap Your Zippers [2] and looked at various other generic zipper libs, but in the end I managed without zippers. Note that most zipper libs require instance declarations for all the syntax datatypes -- Scrap Your Zippers only requires the Data instances that HSE comes with, not sure why I was unable to use it, probably just inexperience. Note that the "Annotated" version of the HSE parser/AST will probably not provide enough generality for the sorts of attributes you want to store (it's for source locations, unless something changed in the most recent release). Best of luck, and I'll be interested to hear other responses! -Andrew [1] http://hackage.haskell.org/freesect (in particular FreeSect*.hs) [2] https://www.cs.indiana.edu/~adamsmd/papers/scrap_your_zippers/