method rdtable : signal_type -> signal_type -> signal_type
method select2 : signal_type -> signal_type -> signal_type
method select3 : signal_type -> signal_type -> signal_type -> signal_type
method rdtable : signal_type -> signal_type -> signal_type
method select2 : signal_type -> signal_type -> signal_type
method select3 : signal_type -> signal_type -> signal_type -> signal_type