On Wednesday, 11 July 2012 at 02:02:52 UTC, Andrei Alexandrescu
wrote:
On 7/10/12 9:45 PM, Timon Gehr wrote:
I do not desire logical const as a language feature. But
conservative type systems are not good for everything. The
root of the class hierarchy needs to be good for everything.
Object is not an adequate root any more.
How about we consider just stiffening that upper lip and
implement comparison and hashing without modifying their target?
I remember offering a suggested structure for cached hashing for
const/immutable data (mostly a test/example)... If you follow a
similar setup you could get the 'logical const' while following
the language rules; Namely the mutable state is separate from the
const state. Course it's sorta a wrapper, but that's better than
breaking the type system or trying to do something else equally
questionable.
It went something like...
struct CachedHash(T) {
T value;
uint hash;
alias value this;
uint toHash() {
if (!hash)
hash = value.toHash();
return hash;
}
}
