Re: Appending static arrays

[Jack Applegame via Digitalmars-d-learn]

On Monday, 17 July 2017 at 17:38:23 UTC, Nordlöw wrote:
I'm want to define a specialization of `append()` that takes 
only static arrays as inputs and returns a static array being 
the sum of the lengths of the inputs.

Have anybody already implemented this?

If not, I'm specifically interested in how to most conveniently 
infer the length (as an enum) of the returned static array from 
the `.length`s of inputs (which of course must be enum-values 
too).

My recursive version:

auto concat(T, size_t N, ARRS...)(auto ref T[N] a, auto ref ARRS 
arrs) {
    static if(arrs.length == 0) {
        return a;
    } else {
        T[N + arrs[0].length] r = void;
        r[0..N] = a[];
        r[N..$] = arrs[0][];
        return concat(r, arrs[1..$]);
    }
}

unittest {
    int[3] a1 = [1, 2, 3];
    int[3] a2 = [4, 5, 6];
    int[3] a3 = [7, 8, 9];

    static assert(is(typeof(concat(a1)) == int[3]));
    assert(concat(a1) == [1, 2, 3]);

    static assert(is(typeof(concat(a1, a2, a3)) == int[9]));
    assert(concat(a1, a2, a3) == [1, 2, 3, 4, 5, 6, 7, 8, 9]);
}