Compare/Slice/Get/Set to Container

Hello, it would be nice to add these functions to List so that vala is even easier to use! I tried contains, but I did not succeed

they are just ideas, maybe it is a very bad idea

in any case I find that slice is really a good idea!

public List<G> slice (long start, long end)
{
	unowned List<G>? l = this;
	var tmp = new List<G>();
	if (start < l.length())
	{
		while(start != end && start != l.length()){
			tmp.append(l.nth_data((uint)start));
			start++;
		}
	}
	return (tmp);
}

public G get(int index){
	unowned List<G>? l = this;
	return l.nth_data(index);
}

public void set(int index, G item){
	unowned List<G>? l = this;
	uint i = 0;
	if (index < l.length())
	{
		while (i < index && l != null){
			l = l.next;
			i++;
		}
		l.data = item;
	}
}

public bool contains(G needle){
    foreach(var i in this){    
        if (needle == i)       
            return true;       
    }                          
    return false;
}

public static List<G> from_tab(G []tab){
	var l = new List<G>();
	foreach (G i in tab){
		l.append(i);
	}
	return l;
}

Example output: 21

void main()
{
	var l = new List<int>();
	l.append(5);
	l.append(3);
	l.append(2);
	l.append(1);
	l.append(8);

	foreach(var i in l[2:4]){
		print(@"$i");
	}
}