Error running concurrent process and storing results in array

[Steven Schveighoffer]

On 5/6/20 2:29 PM, drug wrote:
> 06.05.2020 16:57, Steven Schveighoffer пишет:
>>> ```
>>> foreach(i; 0..n) // instead of for(long i = 0; i < n;)
>>> ```
>>> I guess that `proc` delegate cant capture `i` var of `foreach` loop 
>>> so the range violation doesn't happen.
>>
>> foreach over a range of integers is lowered to an equivalent for loop, 
>> so that was not the problem.
> 
> I was surprised but `foreach` version do not have range violation, so 
> there is difference between `foreach` and `for` loops. I did not try 
> DerivedThread at all, only suggested them to avoid var capture. I just 
> changed `for` by `foreach` and range violation gone. Probably this is 
> implementation details.
> 

Ah yes, because foreach(i; 0 .. n) actually uses a hidden variable to 
iterate, and assigns it to i each time through the loop. It used to just 
use i for iteration, but then you could play tricks by adjusting i.

So the equivalent for loop would be:

for(int _i = 0; _i < n; ++_i)
{
    auto i = _i; // this won't be executed after _i is out of range
    ... // foreach body
}

So the problem would not be a range error, but just random i's coming 
through to the various threads ;)

Very interesting!

-Steve