Transitive const sucks

[Sean Kelly]

Bruno Medeiros wrote:
> Sean Kelly wrote:
>> read operations.  But for better or worse, D const has a different 
>> aim.  The goal is largely to produce a system which allows for 
>> compiler optimization rather than to enforce some sort of logical 
>> restrictions on behavior.  I suspect this means that D apps won't look 
>> very much like C++ apps in terms of how const is used, and the overall 
>> utility for the average programmer may well be somewhat small.
> 
> I'm don't think that's entirely true. 'invariant' the keyword is indeed 
> made to allow several compiler and program optimizations, but 'const' 
> the keyword is really for enforcing program contracts and restrictions, 
> thus improving safety. I don't even think 'const' the keyword has any 
> use whatsoever for optimization.

True enough.  But the current design (ie. transitive and lacking 
'mutable') is such that 'const' may have limited utility for UDTs where 
logical state is not equivalent to physical state.  I still think this 
is fine, as I'd prefer something simple and understandable, but I wonder 
whether this will be sufficient for enterprise programmers looking to 
switch from C++ to D.  Only time will tell, I suppose.


Sean