On 24.12.2011 19:18, Andrew Wiley wrote:
2011/12/24 Mr. Anonymous<[email protected]>:
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.
Actually, when I think of it:
int a_orig = a++;
int[] arr_orig = arr[]++;
Should be read as:
int a_orig = a;
++a;
int[] arr_orig = arr[];
++arr[];
(If I'm not mistaken, it was written in the TDPL book)
Which means no copy of arr is made, and both arrays (which reference to
the same block) are affected.
