// ownership in practice: a list owns its boxes. nothing here calls free;
// everything is released at the end of the block that owns it.
fn box(v) -> .u { let b = new(1); b[0] = v; return u*b; }
fn mklist(cap) -> .u { let l = new(cap + 1); l[0] = 0; return u*l; }
// item m*arrives (it was given down), and goes d*on into the borrowed list
fn push(.m l, .d item) { l[l[0] + 1] = d*item; l[0] = l[0] + 1; return 0; }
fn show(.m l)
{
	let i = 1;
	putc('[');
	while (i <= l[0]) { if (i > 1) putc(' '); putn(l[i][0]); i++; }
	putc(']');
	return 0;
}
fn squares(n) -> .u
{
	let l = mklist(n), i = 0;
	while (i < n) {
		let b = box(i * i);
		push(l, d*b);
		i++;
	}
	return u*l;
}
fn main()
{
	let before = live_objects();
	{
		let l = squares(6);
		show(l); putc(10);
		puts("live: "); putn(live_objects() - before); putc(10);
	}
	puts("after the block: "); putn(live_objects() - before); putc(10);
	return 0;
}