On 26-09-2012 15:34, monarch_dodra wrote:
On Wednesday, 26 September 2012 at 12:48:19 UTC, Timon Gehr wrote:
On 09/26/2012 02:07 PM, monarch_dodra wrote:
On Tuesday, 25 September 2012 at 22:58:11 UTC, Iain Buclaw wrote:
Pop quiz!
Without cheating, I invite people to have a good guess what 'abc' is
equal to, but just to narrow it down.
1) It isn't "ABC".
2) On x86/x86_64, it isn't "ACB".
3) On everything else, it's the reverse of what you'd expect on
x86/x86_64.
I'd say abc's value is "unspecified", and any attempt at predicting it
would be bogus. That's my answer anyways
...
Why? This is not useful behaviour.
What do you mean "why"? Because order of evaluation is not specified, so
the value of abc is not specified. That was my answer. The question
wasn't really "what would useful behavior be".
IMO: useful behavior would be if it was explicitly illegal to modify (or
modify + read) the same value twice in the same expression. I'd rather
expressions such as:
A()[] = B()[] + C()[];
x[i] = ++i + 1;
Be illegal rather than have (an arbitrarily defined) specified behavior.
Trying to specify a specific behavior in such cases is opening a can of
worms.
No it isn't. There's a perfectly sensible, sane, and intuitive fix for
this: always evaluate arguments left-to-right. No exceptions.
It's not that complicated.
--
Alex Rønne Petersen
[email protected]
http://lycus.org
