* Andrey Chudnov
* Does any generic traversal/transformation (uniplate-style) library support GADTs?
Any syb-style library works with GADTs, by the virtue of dealing with value representations instead of type representations.
* What is the best choice, performance- and memory-wise, for a parser combinator library with support for arbitrary look-ahead? Parsec is considered slow by some [1], but is it only in comparison with attoparsec (which, unfortunately, doesn't support arbitrary look-ahead)? Is there any parser library that performs better than Parsec while still supporting arbitrary look-ahead.
Not sure what you mean here — attoparsec does support unlimited lookahead, in the sense that a parser may fail arbitrarily late in the input stream, and backtrack to any previous state. Although attoparsec is a poor choice for programming language parsing, primarily because of the error messages. Roman