Fully transitive const is not necessary

[Michel Fortin]

On 2008-04-02 04:14:28 -0400, "Janice Caron" <caron800 at googlemail.com> said:

>> -= Pure function + invariant data is required for FP =-
> 
> That sounds reasonable, though it should really say /transitive/ 
> invariant data.

Hum, I'm wondering if an invariant class couldn't have a mutable 
member, but access to the mutable member from a const or invariant 
reference would require synchronized access to keep thread safety 
guaranties.

In other words:

	class X {
		mutable int a;
		
		const void foo() {
			writefln(a); // illegal, const this doesn't give access to mutable member.
			synchronized (this) {
				writefln(a); // legal, synchronization gives access to mutable member.
				++a;         // legal since a is mutable.
			}
		}
	}

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/