Another Transitive const solution

[Craig Black]

> Goals of transitive const
> 1. To make the compiler able to perform optimisations based on const.
> 2. To make a documenting const system that is checked by the compiler and 
> useful to the programmer.
>
> Goal 1 is not achievable as has been shown previously in this group :

Correct me if I'm wrong, but I read in an article that there are simple 
optimizations that can be performed by C++ compilers using const.  For 
example this is preferred:

const int size = container.size();
for(int i = 0; i < size; i++) { ... }

rather than this:

int size = container.size();
for(int i = 0; i < size; i++) { ... }

Because it gives the compiler assurance to know that the size will not 
change during the loop.

-Craig