Re: Acceptable to "const" a parameter in the definition but not in
the declaration?
* Jorgen Grahn, on 12.06.2010 08:58:
On Tue, 2010-06-08, Alf P. Steinbach wrote:
* Jorgen Grahn, on 08.06.2010 22:09:
On Tue, 2010-06-08, Alf P. Steinbach wrote:
...
However, only top level 'const' is disregarded for forming
the function's type.
E.g. 'int const' -> 'int', but not 'int const*' -> 'int*'.
Which is a slightly convoluted way of saying "only the things that are
surely irrelevant to the interface are disregarded in the interface".
That turns out to be a circular argument, because (see below) the 'const' is
only irrelevant because of the current rules that it is disregarded...
I was a bit too lazy to read your longer text carefully, but I suppose
I'm relying on the traditional meaning of call-by-value here, the one
you're taught in CS classes. *That* is what makes the const irrelevant
to the caller.
Yes, the 'const' is irrelevant to the caller.
However, in your first posting you wrote "only the things that are surely
irrelevant to the interface are disregarded in the interface" as a way to
remember the rule to disregard a top level 'const': "Easy to remember, and makes
good sense".
But as I then showed one can not deduce the rule from that: it is only with the
current rules that the 'const' is irrelevant to the interface, not with other
rules that could have been chosen. And so it's a circular argument that the rule
to disregard the 'const' is a logical consequence of the 'const' being
irrelevant, which it is because of the rule to disregard to it. And so on.
I don't see C++ moving away from call-by-value any time soon.
That's probably correct. ;-)
However, the implication that anyone has argued for such a change, is incorrect.
Cheers & hth.,
- Alf
--
blog at <url: http://alfps.wordpress.com>