Optimizing Immutable and Purity

[Walter Bright]

Bill Baxter wrote:
> On Tue, Dec 23, 2008 at 11:30 AM, Jerry Quinn <jlquinn at optonline.net>
> wrote:
>> This was an interesting read.  It would be nice to see a discussion
>> of how const is going to fit in in terms of optimization potential,
>> since you can always cast it away.
> 
> It's basically useless for optimizations I think. Even if the view of
> the data you have is const, someone else might have a non-const view
> of the same data. So for instance, if you call any function, your
> "const" data could have been changed via non-const global pointers to
> the same data.

Right. It's useless.

Casting away const and immutable also puts one into undefined behavior 
territory.