> De: "John Rose" <john.r.r...@oracle.com> > À: "Remi Forax" <fo...@univ-mlv.fr> > Cc: "Karen Kinnear" <karen.kinn...@oracle.com>, "valhalla-spec-experts" > <valhalla-spec-experts@openjdk.java.net> > Envoyé: Jeudi 31 Janvier 2019 19:03:13 > Objet: Re: An example of substituability test that is recursive
> On Jan 31, 2019, at 3:19 AM, Remi Forax < [ mailto:fo...@univ-mlv.fr | > fo...@univ-mlv.fr ] > wrote: >> here is an example that recurse to its death with the current prototype > Fun fact: Change the Link to a Tree and you go from > linear to exponential in the depth. *Just* a fun fact; > it doesn't change Remi's point, which is that we can > construct value object instances that have large > "interiors". you mean like this: static value class Link { private final int value; private final Object next; private final Object next2; public Link(int value, Object next) { this.value = value; this.next = next; this.next2 = next; } } yes, i creates a DAG that will be too long to traverse :( you basically, DDOS yourself if you do a ==. > (Definition of the day: The "interior" of a value > object instance is the set of variables that determine > its substitutability equality and substitutability hash.) > To me this takes on a different shade of urgency > when I think about turning arrays into values. > Suppose we had Arrays.valueCopyOf to take an > immutable value-typed snapshot of an array. > Very useful! (Sort of like frozen arrays.) You > can make a size 1_000 value-array very quickly > and easily, and its interior would be as large > as Remi's laboriously constructed list. Facebook skip [1] has an operation like this, data structure are mutable (for the runtime, from the user POV everything is non mutable) inside a function and frozen when publish outside. [1] [ http://www.skiplang.com/ | http://www.skiplang.com/ ] Rémi
