const?? When and why? This is ugly!

[Walter Bright]

Derek Parnell wrote:
> Walter, you have side-stepped the problem in question by talking about a
> totally different problem.

It's the same issue. When you use a cast, you are subverting the type 
system. That means you have to be sure you are doing it right. The 
compiler cannot help you.

> Burtons code says "b is invariant", but the program allows it to be
> changed. Your code does NOT say that any of those variables is invariant.
> The problem is NOT with the cast (although that is a totally different
> issue). The problem is that the code says "invariant" but the data gets
> changed anyhow. The method of changing the data is not the issue. The issue
> is that is gets changed at all.

When you cast something to immutable, you can no longer change it. It's 
a one-way ticket.