any news on const/invariant?

[Janice Caron]

On Nov 29, 2007 8:50 AM, Bruce Adams <tortoise_74 at yeah.who.co.uk> wrote:
> What would be the point of an invariant method? A const method promises not
> to change any contents of the object. An invariant method makes the same
> promise.
> So there is no difference to the caller of such a method.
> I can't see that it make any difference inside the method either.

It makes a difference. Watch...

    class A
    {
        int x;
        const int f() { return x; }
        invariant int g() { return x; }
    }

    A ma = A(3);
    writefln(ma.f()); /* error */
    writefln(ma.g()); /* error */

    const A ca = A(3);
    writefln(ca.f()); /* OK */
    wriitefln(ca.g()); /* error */

    invariant A ia = A(3);
    writefln(ca.f()); /* OK */
    writefln(ia.g()); /* OK */