Frustrations with const

[H. S. Teoh]

On Thu, Mar 08, 2012 at 08:22:05PM +0100, Timon Gehr wrote:
> On 03/08/2012 08:09 PM, H. S. Teoh wrote:
[...]
> >The problem is, how to write this function so that it can be called from
> >*both* a const public method and a non-const public method? Since the
> >method itself doesn't actually modify anything, it *should* in theory be
> >possible to mark it as const:
> >
> >	const Slot *findSlot(Key key) { ... }
> >
> >However, because the const applies to 'this', the compiler insists that
> >referencing anything via 'this', including reading a pointer to a slot,
> >must also be const, so it refuses to let the return type be Slot*; it
> >has to be const(Slot)*.
> >
> >But this is silly, because now the caller isn't allowed to modify the
> >Slot either, so now I need to bloat the code with two identical copies
> >of findSlot, one with const, and one without (since if it wasn't marked
> >const, then a const method couldn't call it).
[...]
> inout(Slot)* findSlot(Key key) inout { ... }

Ahhh. Thanks!

But that still doesn't solve the problem:

	inout(Slot)* findSlot(Key key) inout {
		auto slot = slots[hash(key)];
		while (slot) {
			if (slot.hash == hash(key) && slot.key == key)
				return slot;

			// Error: cannot modify inout(Slot)*
--->			slot = slot.next;
		}
		return null;
	}



T

-- 
Help a man when he is in trouble and he will remember you when he is in trouble again.