any news on const/invariant?

[Steven Schveighoffer]

"Walter Bright" wrote
> Janice Caron wrote:
>>> Also, C++ has const as both a storage class and a type constructor, and
>>> yes, they have subtly different meanings. This doesn't seem to cause any
>>> major problems.
>>
>> That's because C++ behaves as expected. If I declare
>>
>>     const int * f();
>>
>> then I get a function which returns a pointer to const int, /not/ a
>> const member function which returns a pointer to mutable int.
>
> What is expected, or what you are *used* to? Let me put it another way, 
> can you explain the difference between C++ const storage class and C++ 
> const type constructors? There's a big semantic difference.

Let me reword Walter's point, as I think he didn't really get it across 
completely :)

Let's say someone had never used C++ and it's const system.  Let's say that 
person is a virgin coder starting to dabble in D.  Let's explain how const 
works to him/her:

to declare that a type is constant, you do:

const(Type) x;

to declare that a method returns a const value, you do:

const(Type) f();

to declare that a method is constant, that is, it will not modify any 
members of a class the method resides in, you do:

const Type f();

If that method returns a const type, then the method is declared as:

const const(Type) f();

for compatibility with C++ and C, you can also do:

const Type x;
for a const type declaration, and

Type f() const
for a const method declaration.

To someone who never used const before in another language, this isn't any 
less or more intuitive than the way C++ does it.  It's like saying using 
semicolons at the end of statements is intuitive.  It's just a different way 
of expressing what you want to the compiler.

-Steve