thoughts on immutability in D

[Mehrdad]

On 9/23/2011 4:13 PM, Jonathan M Davis wrote:
> On Friday, September 23, 2011 15:58 Andrej Mitrovic wrote:
>> On 9/24/11, Peter Alexander<peter.alexander.au at gmail.com>  wrote:
>>> On 23/09/11 6:48 AM, Walter Bright wrote:
>>>> On 9/22/2011 4:39 AM, bearophile wrote:
>>>>> Walter:
>>>> "logical const" in C++ is faith-based programming.
>>> I think you're exaggerating it's uselessness.
>>>
>>> It's faith-based as much as 'walking down the street assuming that the
>>> next person won't stab you' is faith-based. There's no guarantee, but
>>> 99% of the time your "faith" is well placed.
>> So then don't use const if u need caching and use convention if your
>> faith is well placed!
> const in C++ really does help to catch bugs. It's definitely better than
> nothing. I do _not_ think that it is worthless like Walter at least gives the
> impression that he thinks.
>
> Now, I _do_ think that on the whole, D's const is better. The transitiveness
> of const is a major improvement IMHO, and the caching thing, while annoying,
> isn't that big a loss in my experience. I expect that with Peter's gaming
> background, it's much more of an issue for him. I think that it's at least
> theoretically possible to get a caching mechanism to work with const, which
> would overcome that portion of the logical const problem, but the question is
> how best to do it and whether the added complication is worth the cost.
> Certainly, it's the sort of thing that we should look into for D3 when we get
> that far. But for now, on the whole, D's const is a definite improvement over
> C++'s const, and you just don't use const in D in quite as many places as you
> would have in C++.
>
> But while C++'s const is not as good as D's const, it's still very worthwhile
> IMHO.
>
> - Jonathan M Davis
So far, the 5% of the code it breaks has made it 95% worthless for me, 
though I'm not sure about others (would love to hear otherwise)...