Curiouser and curiouser... expr :: Parser Int expr = do t <- term do symbol "+" e <- expr return (t + e) +++ return t solves the undefined variable problem but introduces a new 'Last operator in do {...} must be an expression' error, which then disappears if I explicitly return e expr :: Parser Int expr = do t <- term do symbol "+" e <- expr return e return (t + e) +++ return t to give me the original undefined variable t error at the line expr = do t <- term . It looks in scope to me... :( Thanks, Nik Dr Nik Freydís Whitehead University of Akureyri, Iceland ********************************************************************* Having the moral high ground is good. Having the moral high ground and an FGMP-15 is better. *********************************************************************