]> >>>>> "nf" == Nicolas FRANCOIS (AKA El Bofo) <nicolas.francois@free.fr> writes: nf> I define a polynom parser like this : let rec parse = let let rec parse = let parse_puissance = parser | [< ''^'; e = parse_int >] -> e | [< >] -> 1 in let parse_x = parser | [< ''X'; e = parse_puissance >] -> e | [< >] -> 0 in let parse_coeff = parser | [< n = R.parse >] -> n | [< >] -> R.one in let parse_monome = parser | [< n = R.parse; e = parse_x >] -> monome n e | [< e = parse_x >] -> monome R.one e in parser | [< ''+'; m = parse_monome; p = parse >] -> m ++ p | [< ''-'; m = parse_monome; p = parse >] -> (opp m) ++ p | [< m = parse_monome; p = parse >] -> m ++ p | [< >] -> zero nf> parse_int and the R.parse functions work OK, and I'll add all nf> the "_=parse_space" after. But : # let p1 = P.parse (Stream.of_string "1+X");; Stack overflow during evaluation (looping recursion?). nf> What's the problem ? Ahh. I didn't look closely enough. The problem can be seen by looking at what happens when you try to parse the empty stream: in parse: [< >] -> cases 1 and 2 fail, tries [< m = parse_monome; p = parse >] in m = parse_monome: [< >] -> I assume R.parse fails, so it tries [< e = parse_x >] in parse_x [< >] -> case 1 fails, case 2 [< >] succeeds parse_x returns 0 parse_monome returns monome R.one 0 [< m = parse_monome; ... >] succeeded, move to [< ...; p = parse >] And at this point, parse is called on [< >] again and it loops. Unfortunately, I can't remember how to explicitly check for the end of the stream--and it's been removed from the O'Caml manual. That's what you have to do to avoid this. A quick and dirty hack is to have a special symbol (";", for instance) at the end of every phrase. John. ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners