]> From: Oleg Trott <oleg_trott@columbia.edu> > Objective Caml version 3.07+2 > > # sin == sin;; > - : bool = false > # let f = sin;; > val f : float -> float = <fun> > # f == f;; > - : bool = true > > I don't like the fact that (sin == sin) returns false. This is coherent with the specification of (==), which says that it is fully specified only for mutable structures. (** [e1 == e2] tests for physical equality of [e1] and [e2]. On integers and characters, physical equality is identical to structural equality. On mutable structures, [e1 == e2] is true if and only if physical modification of [e1] also affects [e2]. On non-mutable structures, the behavior of [(==)] is implementation-dependent; however, it is guaranteed that [e1 == e2] implies [e1 = e2]. *) And note that: # sin = sin;; Exception: Invalid_argument "equal: functional value". so returning false in this case is valid. This is for the defensive part. Now the real explanation: primitives (appearing as "external" in the .mli) are not closures by themselves. A closure is built as needed. As a result, two different occurences of "sin" will create different closures. If this is a problem for you, you should just be careful of wrapping all your primitives. This is just what "let f = sin" does. (Note however that the specification doesn't say what should be (==) for closures either. It just happens to be reflexive in the current implementation.) Jacques Garrigue ------------------- 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