Reading about D: few questions
mailnew4ster at gmail.com
Sat Dec 24 13:48:50 PST 2011
On 24.12.2011 19:18, Andrew Wiley wrote:
> 2011/12/24 Mr. Anonymous<mailnew4ster at 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###'):
>>> 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
>>> 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;
int arr_orig = 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.
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