🚀 go-pugleaf

In article <23842@alice.att.com>, I wrote:

> Converting T** to const T** had better not be legal in C++, because if
> it were, it would open a hole in the type system that would allow modification
> of genuinely constant objects.

I suppose I should give an example:

	const char x = '*';
	char* p;

Now, if we could make p point at x, that would be bad news because we
could then change the value of x even though it is a const object.

Well, if we can do this:

	const char** q = &p;

(which is illegal, but would be legal if conversions from T** to const T**
existed), then we would be able to do this:

	*q = &x;

which would effectively make p point at x.  All the other operations here
are unquestionably legal, which means we must rule out the declaration of q.
-- 
				--Andrew Koenig
				  ark@europa.att.com