[Haskell-cafe] monadic parser with Happy and Alex

Hi. I have completed a draft of a CSS lexer, using Alex. http://hg.mperillo.ath.cx/haskell/webtools/file/tip/src/CSS/Lexer.x The lexer use the posn wrapper. Now I'm starting to write the parser with Happy, however for the final product I would like to: 1) Be able to do I/O in the lexer, for stylesheets inclusion (@import rule) 2) be able to keep state in the parser (or lexer?), for character transcoding (@charset rule) This should be possible with Happy (and there are some example), however I don't find examples that make use of a lexer written with Alex. Should I write a lexer using only the Alex basic interface (without wrappers)? Thanks Manlio Perillo