Hello, sorry for the delay in replying, I have been away from my computer during the last weeks. Simon Peyton-Jones wrote:
I've fixed GHC's pretty-printer to print do-notation using braces and semi-colons, which is much more robust. I hope that's useful
This is certainly useful, and it seems to fix the issues for me. Thank you very much! Thomas Schilling wrote:
That said, if you're trying to do source-to-source transformations you probably want to keep the original layout as much as possible. GHC's pretty-printer isn't designed for that. GHC's syntax tree has very accurate source locations, so you could start from there and build your own pretty printer.
Niklas Broberg wrote:
In general, unless you actually want to use any other components of the GHC API, e.g. evaluate your code, then I see no reason to use the GHC API for source manipulation. haskell-src-exts simply does that better (and definitely better than haskell-src). But I couldn't tell if that's enough for the original poster's needs. :-)
Well, the application is a debugger for Concurrent Haskell programs. It reads a program and replaces certain function calls with calls to location-aware wrappers that allow stepping the program and highlighting the original source location. The result of this transformation is then compiled and executed; it is not intended to be seen by the user (who is shown the original source). So I guess what we need is not a "pretty printer" but a "valid printer". We need accurate original source locations and we need to access the syntax tree after typechecking to be able to tell which functions to replace. The GHC API looked like the way to go and it does so even more with Simon's patch. Thanks for your input, Jan -- If you're happy and you know it, syntax error!