any news on const/invariant?

[Bill Baxter]

Walter Bright wrote:
> Janice Caron wrote:

>> My objection to the existing syntax is more or less solely that
>>     const int f();
>>
>> does not declare that f returns a const int, and I think that all
>> newcomers to D will find that /hugely/ confusing.
> 
> Const is different in D than in C++, and it will take some getting used 
> to for refugees from C++. Anyone who expects it to behave exactly like 
> C++ will have difficulty. But if they spend a little time looking at it 
> and give it a chance, I think they'll find that it is more consistent, 
> intuitive, and usable than C++ const.
> 
> Just remember, the const storage class applies to the declaration, not 
> the type, and it will make sense.

Here's a class that compiles fine and will probably mostly work.

class Klass {

     this() {
         array.length = 10;
     }
     const int elem(int i) {
         return array[i];
     }

     int[] array;

}

But someday when someone tries to call elem() with a const Klass it will 
fail to compile.



Also in case anyone else wasn't sure, this is how you declare the common 
idiom of const method returning a const reference in the latest D2.008:

    const const(int*) get_elem_ptr(int i) {...}

Without the parens it gives "Redundant storage class".  (However 
declaring it "public public public" still does not create an error...)

Also const int* get_elem_ptr(int i) fails to compile because it tries to 
return a mutable pointer from a const method.  So that case is ok, but 
the one in Klass above seems like trouble brewing to me.

--bb