a nonstate keyword

[Neil Vice]

"Steven Schveighoffer" <schveiguy at yahoo.com> wrote in message 
news:g1mmbh$ftq$1 at digitalmars.com...
> What if D2 were to introduce a keyword that allows you to decouple a class 
> member from the class state for the purposes of const?  This keyword 
> basically means that the member is stored with the class data but is 
> unaffected by the constancy of an instance.  In other words, a non-state 
> member variable is not cast to const when the class instance is cast to 
> const.  This is an implementation of the 'is associated with' OO 
> relationship.  This is similar to the 'mutable' keyword in C++, or the way 
> mutexes work in D.
>
> If this were to happen, would you consider this to be a positive, 
> negative, or inconsequential change?

This is certainly a feature I've felt the need for in the past, and caching 
to me is the obvious use-case.

Having said that, I recall arguments to the effect that there are better 
ways to implement such things that don't require the use of such a keyword 
and prevent the need to "break" the transitive-const model.

Given this, my current stance is that it should be left out unless it can be 
demonstrated that there is a useful design that cannot be implemented 
without it, and I will be interested to see if I continue to feel the need 
for it when optimising code in future.