On 07/12/10 05:51, Steven Schveighoffer wrote:
On Mon, 06 Dec 2010 14:04:43 -0500, Jonathan M Davis
<jmdavisp...@gmx.com> wrote:
On Monday, December 06, 2010 07:37:27 Steven Schveighoffer wrote:
It should be relatively painless. Just change the signatures of the
base
functions, and fix any compile errors.
And watch all the code break... I'll definitely welcome the change
(it's probably
the first bug that I voted on in bugzilla), but there will be tons of
code broken
by it, since you just _know_ that a lot of user code doesn't bother
to make
toString() and its friends const. It's still a change that needs to
be made
though. Being unable to properly compare const and immutable objects is
crippling. Of course, it would be more of an issue if it were easier
to actually
create immutable objects which are classes rather than strcuts, but
that's a
separate issue.
Yes, one of the issues is that const has a viral effect. If you
ignore const, none of your functions are const. So if you use
functions inside opEquals, those have to be marked as const, and so on.
But there are very few circumstances where opEquals needs to be marked
as mutable. If that is the case, there is something broken with your
code (and you should fix it) or there's something wrong with code you
use (and you'll have to insert casts to deal with it for now). In a
very small number of circumstances, non-const opEquals can be
beneficial (such as caching data that is expensive to calculate). We
need to find another way to deal with that (I suggest having logical
const, but that's not a popular idea with Walter :). But it shouldn't
detract from the requirements. You can always circumvent if you need
special cases. I'd rather start from a solid const-supporting
position and add holes where they make sense then start from a base
that is full of holes and try to patch them slowly.
In many cases affixing const to your code is not just a simple 'slap a
const on here'. It can involve careful thought and possibly redesign.
But without these changes, const is very useless, the standard library
needs to eat its own dogfood if we want to peddle it to others.
-Steve
Vote++
--
Graham St Jack
