Tuple and tie?

[H. S. Teoh via Digitalmars-d-learn]

On Tue, Jul 08, 2014 at 07:02:17PM +0000, NCrashed via Digitalmars-d-learn wrote:
[...]
> auto tie(StoreElements...)(ref StoreElements stores)
[...]

Here's my take on it, that doesn't need to use pointers:

	import std.typecons;
	
	template TypesOf(T...)
	{
		static if (T.length == 1)
			alias TypesOf = typeof(T[0]);
		else
			alias TypesOf = TypeTuple!(typeof(T[0]), TypesOf!(T[1..$]));
	}
	
	@property void tie(T...)(Tuple!(TypesOf!T) t)
	{
		foreach (i, ref var; T)
		{
			T[i] = t[i];
		}
	}
	
	Tuple!(int, string) func() {
		return tuple(1, "a");
	}
	
	void main()
	{
		int x;
		string y;
	
		tie!(x,y) = func();
	
		import std.stdio;
		writefln("%d %s", x, y);
	}

It does involve some slightly more arcane template magic, though. ;-)
Basically, the TypesOf template transforms a list of alias arguments
into a list of the types of said arguments, so that we can match a list
of variables to the Tuple that is to be assigned to them.

This also (ab)uses the fact that assigning to a function call gets
interpreted in this context as setting a global @property, so there's no
need to overload opAssign at all. (Arguably, this makes it more an
insane hack than a clever solution!)


T

-- 
Once the bikeshed is up for painting, the rainbow won't suffice. -- Andrei Alexandrescu