Unexpected behavior of cond about lisp HOT 4 CLOSED

Thanks for the feedback. The cond special form doesn't have a default when all conditions fail. Lisp isn't really standardized, so its up to the implementor to decide.

As you can see, the loop runs until a condition is not () or if the remaining list is (). If the remaining list t = () then f_begin(cdr(car(t)), e) fails because t = ().

L f_cond(L t, L *e) {
  while (T(t) != NIL && not(eval(car(car(t)), *e)))
    t = cdr(t);
  return f_begin(cdr(car(t)), e);
}

If you want cond to return () if no condition succeeds, then change this to

return T(t) != NIL ? f_begin(cdr(car(t)), e) : nil;

from lisp.

Perhaps this is worth an update.

from lisp.

Fixed.

from lisp.

Makes sense, thank you!

from lisp.