On 12/24/2011 08:22 PM, Andrew Wiley wrote:
On Sat, Dec 24, 2011 at 1:08 PM, Timon Gehr<timon.g...@gmx.ch> wrote:
On 12/24/2011 07:00 PM, Andrew Wiley wrote:
On Sat, Dec 24, 2011 at 9:50 AM, Timon Gehr<timon.g...@gmx.ch> wrote:
On 12/24/2011 06:18 PM, Andrew Wiley wrote:
2011/12/24 Mr. Anonymous<mailnew4s...@gmail.com>:
On 24.12.2011 19:01, Denis Shelomovskij wrote:
23.12.2011 22:51, bearophile пишет:
++a[] works, but a[]++ doesn't.
Already known compiler bug.
Is it a joke? Array expression in D are for performance reasons to
generate x2-x100 faster code without any compiler optimisations. Link
to
one of these epic comments (even x100 more epic because of '%' use
instead of 'x###'):
https://github.com/D-Programming-Language/druntime/blob/master/src/rt/arraybyte.d#L1127
But `a[]++` should store a copy of `a`, increment elements and return
stored copy. It is hidden GC allocation. We already have a silent
allocation in closures, but here a _really large_ peace of data can be
allocated. Yes, this allocation sometimes can be optimized out but not
always.
IMHO, D should not have `a[]++` operator.
Why should it store a copy? o_O
I also don't see any allocations in the code on the URL above.
int a_orig = a++;
int[] arr_orig = arr[]++;
If ++ is going to be applied to an array, it needs to have the same
meaning as it does elsewhere. After this operation, arr_orig and arr
must refer to different arrays for that to be true.
Not necessarily.
class D{
int payload;
D opUnary(string op:"++")(){payload++; return this;}
}
void main() {
D d = new D;
assert(d.payload == 0);
assert(d++.payload == 1);
}
That doesn't match integer semantics:
int a = 0;
assert(a++ == 0);
assert(a == 1);
Yes, that was my point.
Then I'm not understanding what you're trying to prove.
I'm saying that if we implement a postfix ++ operator for arrays,
keeping the language consistent would require it to make a copy if the
user stores a copy of the original array.
And I said: "not necessarily"
That is because reference types have had semantics that go well with not
making a copy all along, so there is no danger of making things more
inconsistent.
I guess it could be argued
that since arrays have hybrid value/reference semantics, no copy
should be made and the original should change.
Actually, looking at it from that angle, a[]++ is fundamentally
ambiguous because it could have value semantics or reference
semantics, so I would argue that we shouldn't have it for that reason.
'++a' and 'a += 1' do not have such ambiguities.
I don't think a[]++ should necessarily be there either.
