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// 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;
}
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