Hi! I don't understand something in there : pj-lester-book : Implementing functional languages: a tutorial by Simon Peyton Jones and David Lester, available at http://research.microsoft.com/~simonpj/Papers/pj-lester-book/ eval/apply : Making a Fast Curry: Push/Enter vs. Eval/Apply for Higher-order Languages by Simon Marlow and Simon Peyton Jones, available at http://www.haskell.org/~simonmar/papers/ The introduction in eval/apply states the arity of a function and the number of arguments in a call can match or differs (and it should be dealt with). In pj-lester-book (bottom of page 46 and top of page 47), it is stated that if the program has been type-cheched, the underflow check is unnecessary. When continuing to the G-machine then to the TIM-machine chapters, I haven't found discussion of an arity-mismatch. What am I missing ? Thanks a lot, Thu