Inventory

struct Item { name: str.utf8, grams: int32[min 1, max 50_000] }

fn heaviest [...'items': Item] -> Item or fail[none] {
    if list.length[lend 'items'] equal_to 0 { fail none; }
    let mut 'best' := list.remove[lend.mut 'items', pos 1];
    for 'it' in lend 'items' {
        if 'it'.grams > 'best'.grams { change 'best' = copy 'it'; }
    }
    return give 'best';
}

fn kilos ['grams': int32] -> int32 or fail[not_whole, out_of_range] {
    let 'k': bin64 = to.bin64['grams'] div.near 1000.0;
    return to.int32['k'] otherwise fail;
}

fn initial [lent 'name': str.utf8] -> char.point {
    let 'first' := std::str.at.point[lend 'name', pos 1] otherwise `?`;
    let 'code' := char.code['first'];
    if 'code' at_least 97 and 'code' at_most 122 {
        return char.point.from_code['code' minus 32] otherwise `?`;
    }
    return 'first';
}

MAIN {
    let mut 'shelf': list[Item][min 0, max 4] = list.empty;
    list.append[lend.mut 'shelf', value Item[name = "rope", grams = 1_250]];
    list.append[lend.mut 'shelf', value Item[name = "helmet", grams = 900]];
    list.append[lend.mut 'shelf', value Item[name = "tent", grams = 4_000]];

    let 'count' := list.length[lend 'shelf'];
    let 'left': int8 = 4 minus 'count';
    std::print.useful['count', " items, room for ", 'left', " more", newln];

    let 'top' := heaviest[...copy 'shelf'] otherwise { none { std::print.useful["empty shelf", newln]; std::exit[0]; } };
    std::print.useful["heaviest: ", initial[lend 'top'.name], " ", 'top'.name, newln];

    let 'kg' := kilos['top'.grams] otherwise -1;
    std::print.useful['top'.name, " is ", 'kg', " kg", newln];

    let 'gone' := list.remove[lend.mut 'shelf', pos 2];
    std::print.useful["removed ", 'gone'.name, ", ", list.length[lend 'shelf'], " left", newln];
}