Static Length Propagation of Ranges

[ZombineDev via Digitalmars-d-learn]

On Thursday, 20 October 2016 at 16:25:53 UTC, Meta wrote:
> On Thursday, 20 October 2016 at 13:05:05 UTC, Nordlöw wrote:
>> On Thursday, 20 October 2016 at 12:38:40 UTC, Nordlöw wrote:
>>> ElementType!R[n] arrayN(size_t n, R)(R r)
>>> {
>>>     assert(r.length == n);
>>>     typeof(return) dst;
>>>     import std.algorithm.mutation : copy;
>>>     r.copy(dst[]);
>>>     return dst;
>>> }
>>
>> Is there a place for part of this logic in Phobos?
>>
>> I'm thinking perhaps array{N,Exactly} should be added to 
>> std.array.
>>
>> The idea came to me after learning about dependent types in 
>> Idris:
>>
>> http://www.idris-lang.org/
>
> There was a pull request awhile back for a small function that 
> creates fixed-length arrays, but I think it was only intended 
> to create them from dynamic arrays (such as `auto sarr = [1, 2, 
> 3].staticArray`). Personally I think it would be nice to have a 
> version of `array` that creates a static array, but I don't 
> know how often it would be used or what the pitfalls are, if 
> any.

I think you're talking about this PR: 
https://github.com/dlang/phobos/pull/4090. It handles range 
iteration, as well as opApply iteration.

I also think that the addition is worth having, though Andrei 
seemed to disagree. The (other?) major obstacle is safe usage, 
which currently is not enforced by the compiler, see:
https://issues.dlang.org/show_bug.cgi?id=8838
https://issues.dlang.org/show_bug.cgi?id=12625

On the bright side, it looks like one of Walter's PRs for DIP1000 
should address those issues: 
https://github.com/dlang/dmd/pull/5972/files?diff=unified#diff-33b3e2fefc5298c0b9de67897929e7ceR89