program subleq;
    if command_line(1) = om then
        print("error: no file given");
        stop;
    end if;

    mem := readprog(command_line(1));

    loop init ip := 0; while ip >= 0 do
        a := mem(ip) ? 0;
        b := mem(ip+1) ? 0;
        c := mem(ip+2) ? 0;
        ip +:= 3;
        if a = -1 then
            mem(b) := ichar (getchar ? "\0");
        elseif b = -1 then
            putchar(char ((mem(a) ? 0) mod 256));
        elseif (mem(b) +:= -(mem(a) ? 0)) <= 0 then
            ip := c;
        end if;
    end loop;

    proc readprog(fname);
        if (f := open(fname, "r")) = om then
            print("error: cannot open file");
            stop;
        end if;

        mem := {};
        mp := 0;
        loop doing getb(f, n); while n/=om do
            mem(mp) := n;
            mp +:= 1;
        end loop;
        close(f);
        return mem;
    end proc;
end program;