Function exec_cmd

[exec_cmd cmd] executes the toplevel command [cmd]. Returns Some() when the computation succeeded and None when the command failed. */

(
    db: &mut Database,
    heap: &mut Heap,
    cmd: &ToplevelCmd,
    rl: &mut Editor<(), rustyline::history::DefaultHistory>,
    interrupted: &Arc<AtomicBool>,
    max_depth: i32,
)