Optimizing Immutable and Purity

[Walter Bright]

Andrei Alexandrescu wrote:
> Walter Bright wrote:
>> Andrei Alexandrescu wrote:
>>> 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.
>>>>
>>>> --bb
>>>
>>> Const is still useful because inside a function you know for sure 
>>> that another thread can't modify the data.
>>
>> I think you meant immutable.
> 
> I meant const.


In the future, of course, "shared const" means another thread can modify 
it, but "const" means it cannot. Is that what you meant?