On 05/28/2013 06:04 PM, Peter Williams wrote:
> I'm implementing sets and the concept is sets of objects not sets of the
> values in the objects. I want to be able to initialize sets using
> arrays and I'm promising that I won't change the array or its contents.
> I'm also trying to promise that I won't (inside the set
> implementation) make any changes to individual objects. But I'm not
> promising that they won't be changed by other code that has access to
> them.
Then I still think that it is related to the fact that a const class
variable (not object) cannot refer to another object, which I think
should be possible. Others think so too:
http://forum.dlang.org/thread/bug-532...@http.d.puremagic.com/issues/
I remember the discussions on that topic and various syntax proposals
but I don't remember why class variable assignment syntax would not work:
// C is a class
const(C) c = new const(C);
// c promises that it won't mutate the object.
// Why can't it promise to not mutate another object?
c = new const(C); // <-- compilation error
I don't see the rationale for disallowing the last line. I think it
should work without any syntax change. Merely the class handle is being
changed.
In this case it looks like "turtles all the way *up*" because just
because the object is const, the handle is treated as const as well.
Ali
My head is thick today. :p
