Iterate over an array while mutating it?

[Anh Nhan]

On Thursday, 27 March 2014 at 22:26:37 UTC, Infiltrator wrote:
> On Thursday, 27 March 2014 at 22:23:41 UTC, Anh Nhan wrote:
>> I want to iterate over an array, while adding new entries, and 
>> have those in the iteration loop.
>
> Depending on what you're trying to do, perhaps you would be 
> better off just adding the entries all at once instead of 
> iterating the array?
>
>
>> See here: https://gist.github.com/AnhNhan/9820226
>>
>> The problem is that the foreach loop seemingly only iterates 
>> over the original array, not minding the newly added entries.
>
> That's correct.  foreach caches (which makes it faster) but 
> means that you cannot mutate the range whilst iterating it.
>
>
>> Does somebody have a solution or approach for the loop to pick 
>> up those new entries?
>
> Your best bet is probably a for loop:
>
> for(int i = 0; i < arr.length; i++) { arr ~= element; ... }

On Thursday, 27 March 2014 at 22:27:18 UTC, bearophile wrote:
> Anh Nhan:
>
>> I want to iterate over an array, while adding new entries, and 
>> have those in the iteration loop.
>
> Don't iterate an array with foreach while you mutate it, even 
> if you manage to make it work, the code is not clear.
> I suggest to use a C-style for loop with an index and specify 
> in the code exactly what you want to do with the array and the 
> index. The resulting code is clear and safe.
>
> Bye,
> bearophile

Ah, that the foreach caches the entries would make sense. I tried 
creating iterators Java-style, which did not pick up the new 
entries, too.

It works with for-loops. Thanks for the explanations, they helped 
a lot.

Anh Nhan