D const design rationale

[Sean Kelly]

Walter Bright wrote:
> Sean Kelly wrote:
> 
>> Perhaps I misunderstood the "must be known at compile-time" clause.
> 
> That's only when you use invariant as a storage class. It doesn't apply 
> when you use it as a type constructor.
> 
>>  Can 'invariant' apply to dynamic arrays that will remain unchanged 
>> once initialized?
> 
> Yes.

Ah, now it's coming clear.  For some reason I thought 'invariant' only 
worked as a storage class.  I guess my only real issue with the design 
now is the use of the word 'invariant' -- it's rather long :-)  In some 
respects I'd almost prefer using 'const' for 'invariant' and 'view' for 
'const'.  But I think this suggestion has come up before and 'view' was 
shot down because it's both a noun and a verb?

>   In my work I use almost no static data--it's all generated
>> on the fly or loaded from some data source.  Will 'invariant' help to 
>> make my code more optimal?
> 
> Not with the current compiler, because the back end hasn't been modified 
> to take advantage of it. But the potential is there.

Yeah, I don't care if the compiler does it now, only that the potential 
is there.  After all, this discussion is about the design, not the 
implementation.

Thanks for explaining things.  I'm coming to understand the reasoning 
behind the design you've chosen.


Sean