On 26-09-2012 19:23, Jonathan M Davis wrote:
On Wednesday, September 26, 2012 17:12:49 Alex Rønne Petersen wrote:
On 26-09-2012 15:34, monarch_dodra wrote:
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.
I'd still consider it to be bad practice to do anything which relies on the
order of evaluation of function arguments, because the order is undefined in
other languages, and if you get into the habit of doing stuff like func(++i,
++i, ++i) in D, you're going to be screwed when you have to program in other
languages. It's just cleaner to avoid that kind of stuff, and I'd love it if it
were illegal (a single ++i is fine - it's using i in multiple arguments _and_
modifying it in one of them which is the problem). That being said, defining
the order will at least reduce bugs, even if it's considered bad practice to
do anything in a function call which would rely on the arguments being
evaluated in a particular order.
- Jonathan M Davis
I do not know any other languages than C and C++ that leave it undefined.
--
Alex Rønne Petersen
a...@lycus.org
http://lycus.org
