Appending static arrays

[Nordlöw via Digitalmars-d-learn]

On Monday, 17 July 2017 at 20:01:41 UTC, H. S. Teoh wrote:
> OK, here's an actual, compilable, runnable version:
>
> 	import std.algorithm : sum;
> 	import std.meta : allSatisfy, staticMap;
> 	import std.range : only;
> 	import std.traits : CommonType, isStaticArray;
>
> 	alias Elem(A : E[n], E, size_t n) = E;
> 	enum Length(A) = A.length;
> 	enum sumLengths(A...) = sum(only(0, staticMap!(Length, A)));
>
> 	CommonType!(staticMap!(Elem, A))[sumLengths!A] append(A...)(A 
> arrays)
> 		if (allSatisfy!(isStaticArray, A))
> 	{
> 		typeof(return) result = void;
> 		foreach (i, a; arrays) {
> 			enum offset = sumLengths!(A[0 .. i]);
> 			result[offset .. offset + a.length] = a[];

This slice assignment doesn't support conversion between 
different element-types, for instance from `int[]` to `double[]`.

But I'm not convinced that we should allow `CommonType` when 
operator ~ doesn't.