.array changes the order

[xtreak via Digitalmars-d-learn]

On Thursday, 12 May 2016 at 10:02:46 UTC, thedeemon wrote:
> On Thursday, 12 May 2016 at 09:44:39 UTC, xtreak wrote:
>> I came across the issue where using .array after .joiner 
>> caused the changes to the output. The program is at 
>> https://dpaste.dzfl.pl/0885ba2eddb4 . I tried to debug through 
>> the output but I couldn't get the exact issue. It will be 
>> helpful if someone confirms this as a bug.
>
> It's not a bug per se, just probably documentation being not 
> clear enough. Essentially it's the same issue as with 
> File.byLine: a range that mutates its state, so it's ok to 
> consume lazily but if you just store references (as array() 
> does) you get references to the same mutated value as result.
>
> Quick fix:
>
>   r.chunks(2).map!permutations.joiner.map!array.array.writeln;
>
> i.e. copy each permutation to separate array before it's gone.

Thanks a lot. Can you kindly elaborate a little more on 
File.byLine with an example of the scenario so that I don't get 
bitten by it. File.byLine.array works as expected for me. A 
little more explanation on the permutations will also be helpful 
since joiner.map!array converts the subranges to arrays, so does 
joiner work by mutating state if so how does it do.