Logical const

[Steven Schveighoffer]

On Mon, 29 Nov 2010 14:52:54 -0500, Walter Bright  
<newshound2 at digitalmars.com> wrote:

> Steven Schveighoffer wrote:
>> But in any case, const (even the non-logical variety) does not  
>> guarantee purity.  Only pure functions do that (always return the same  
>> value for the same input)
>
> Right, but C++ doesn't have purity either. I was trying to make the  
> point that C++ does not have a "logical const" language feature. It's  
> only a convention.

Yeah, but saying because a const function in C++ might return a different  
value because of logical const is, well, completely wrong :)  Nobody is  
expecting const to guarantee purity.  Even a D const function cannot make  
any assumptions about data that is const, because another alias could  
change it.

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.

-Steve