Spent today bulding the Evil Splicer, a program that parses ghc -ddump-splices output, and uses it to expand Template Haskell splices in source code. I hope to use this crazy hack to get the webapp working on Android.

This was a good opportunity to use the Parsec library for parsing the ghc output. I've never really used it before, but found it quite nice to work with. The learning curve, if you already know monads and applicatives, is about 5 minutes. And instead of ugly regular expressions, you can work with nice code that's easily composable and refactorable. Even the ugly bits come out well:

 {- All lines of the splice result will start with the same
   - indent, which is stripped. Any other indentation is preserved. -}
    i <- lookAhead indent
    result <- unlines <$> many1 (string i >> restOfLine)

Anyway, it works.. sorta. The parser works great! The splices that ghc outputs are put into the right places in the source files, and formatted in a way that ghc is able to build. Often though, they contain code that doesn't actually build as-is. I'm working to fix up the code to get closer to buildable.

Meanwhile, guilhem has made ssh connection caching work for rsync special remotes! It's very nice to have another developer working on git-annex.