Flatten a range of static arrays

[nullptr]

On Friday, 7 February 2020 at 20:13:57 UTC, Dennis wrote:
> If I have an input range with element type `int[3]`, how do I 
> easily turn it into a range of `int` so I can map it?
> If it were an int[3][] I could simply cast it to an int[] 
> before mapping, but I don't want to eagerly turn it into an 
> array.
> I thought of doing this:
> ```
> range.map!(x => x[]).joiner.map!(x => x*2);
> ```
>
> But it gives:
> Error: returning x[] escapes a reference to parameter x, 
> perhaps annotate with return
>
> I tried doing:
> ```
> map!((return x) => x[]) // same error
> map!((return ref x) => x[]) // does not match, map.front is not 
> an lvalue
> ```
>
> I can easily work around it with some more code, but I wonder 
> if someone knows an easy solution.

Depending on how your range is structured, it might be possible 
to just mark front as returning by ref to make this work.