Hi, I want to have a parser like: p = do eof return something <|> do patternA update_parser_state p <|> do patternB update_parser_state_in_another_way p <|> do anyToken p i.e., go through the content, if pattern A occurs, update my internal state, if pattern B occurs, update the state in another way. Also, the exact forms of pattern A and pattern B might be dependent on the internal state at that time (e.g., whenever I encount pattern A, I increase a counter in my internal state, and that counter is included in pattern B). Finally, when I reach the end, I will then return something based on the final internal state. I did it in the above recursive fashion, but when I ran it, it caused a stack overflow error. So what is the best way to do this kind of parsing? Thanks! Di, Yu 7.11 __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com