Logical const

[Walter Bright]

Steven Schveighoffer wrote:
> On Mon, 29 Nov 2010 15:58:10 -0500, Walter Bright 
> <newshound2 at digitalmars.com> wrote:
> 
>> Steven Schveighoffer wrote:
>>> Having a logical const feature in D would not be a convention, it 
>>> would be enforced, as much as const is enforced.  I don't understand 
>>> why issues with C++ const or C++'s mutable feature makes any 
>>> correlations on how a D logical const system would fare.  C++ const 
>>> is not D const, not even close.
>>
>>
>> Because people coming from C++ ask "why not do it like C++'s?"
> 
> I don't get it.  A way to make a field mutable in a transitively-const 
> system is syntactically similar to C++, but it's not the same.  Having a 
> logical-const feature in D does not devolve D's const into C++'s const.  
> If anything it's just a political problem.

Having mutable members destroys any guarantees that const provides. That's not 
political.

And, I repeat, having a mutable type qualifier DOES NOT make logical const a 
language feature. This is why discussion and understanding of C++'s const system 
is so important - people impute characteristics into it that it simply does not 
have.