On 11/07/2012 02:20, Timon Gehr wrote:
On 07/11/2012 01:57 AM, Walter Bright wrote:
On 7/10/2012 4:16 PM, Timon Gehr wrote:
Const is stronger than what is required to bridge the gap between
mutable and immutable. It guarantees that a reference cannot be used to
mutate the receiver regardless of whether or not the receiver is
immutable underneath. That is unnecessary as far as immutable is
concerned. It only needs to guarantee that the receiver does not change
if it is immutable underneath.
If you have a const function that accepts both mutable and immutable
args, then that function *by definition* cannot tell if it received
mutable or immutable args.
I understand. The trick is to disallow creating immutable instances of a
class which is allowed to mutate the receiver in const methods.
This is essentially your proposal with the casts, but it is type safe.
This removes the 'const' guarantees, but 'immutable' stays
unaffected. Furthermore, functions with closures are type checked at
their creation site and may violate const-transitivity without affecting
'immutable'.
It is interesting. But is does transfers the constraint on const on
constraint of not being const for children.
This isn't a free win, and I'm not sure it worth it.
