]> From: Remi Vanicat <vanicat@labri.u-bordeaux.fr> > this one is unsafe : the fact that a is a block with a tag > Obj.double_tag doesn't proof that the same is true for b even if a and > b have the same type : > > # let i1 = Lazy.lazy_from_val 0.0;; > val i1 : float Lazy.t = lazy 0. > # let o1 = Obj.repr i1;; > val o1 : Obj.t = <abstr> > # Obj.is_block o1;; > - : bool = true > # Obj.tag o1 = Obj.double_tag;; > - : bool = true > # let i2 = lazy 3;; > val i2 : int lazy_t = <lazy> > # let o2 = Obj.repr i2;; > val o2 : Obj.t = <abstr> > # Obj.is_block o2;; > - : bool = true > # Obj.tag o2 = Obj.double_tag;; > - : bool = false > > both i1 and i2 have the same type, but only the first one is a block of > tag Obj.double_tag. A verification have to be done for both argument. Very interesting: you have found an unsoundness in the ocaml compiler. Using your example combined with arrays we obtain: # let arr = [|Lazy.lazy_from_val 0.0; lazy 1.0|];; val arr : float Lazy.t array = [|lazy 0.; lazy 4.32681603021051e-311|] i.e., the second lazy is assumed to be a float value, and results in a wrong result (clearly 1.0 is not anything close to 4.32e-311) So my take on this is that the code suggested for min is correct, this is the compiler which is wrong: two values with the same type _must_ have the same representation. A new headache for implementers... 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