gistfile1.rs

            let len = xs.len();
            let end = uint::min(len, base + items_per_task);

            vec::unpack_slice::<A, ()>(xs) {|p, _len|
                let slice = (ptr::offset(p, base), end - base);
                let f = ptr::addr_of(f);
                futures += [future::spawn() {|copy base|
                    unsafe {
                        let slice : [const A]/& = 
                            unsafe::reinterpret_cast(slice);
                        (*f)(base, slice)
                    }
                }];
            };