Re: Joining AliasSeq/TypeTuple s

[Adrian Matoga via Digitalmars-d-learn]

On Tuesday, 29 March 2016 at 09:33:40 UTC, Voitech wrote:
Hi, i want to join two or more tupples in to one, with mixing 
the indexes like roundRobin but in compile time.

unittest{
import std.meta;
alias first=AliasSeq!(int, string,bool);
alias second=AliasSeq!("abc","def","ghi");
alias third=...

static assert(third==AliasSeq!(int, "abc", string, "def", bool, 
"ghi"));
}


How to obtain this kind of functionality ? Is there maybe some 
builin template for this in phobos ? I couldn't find this.

Thank you
Voitech.

import std.meta : AliasSeq;

template RR(A...)
        if (!(A.length & 1))
{
        static if (A.length == 0)
                alias RR = AliasSeq!();
        else {
                alias Left = A[0 .. $ / 2];
                alias Right = A[$ / 2 .. $];
		alias RR = AliasSeq!(Left[0], Right[0], RR!(Left[1 .. $], 
Right[1 .. $]));
        }
}

struct S(A...) {} // needed to reliably compare AliasSeq's for 
equality

unittest {
        alias first = AliasSeq!(int, string, bool);
        alias second = AliasSeq!("abc", "def", "ghi");
        alias third = RR!(first, second);
	static assert(is(S!third == S!(int, "abc", string, "def", bool, 
"ghi")));
}