Signal(Sig_Val val, ckt_time time): The
Signal constructor accepts a signal value (which is simply
an enumerated type) and the time at which the signal occurred. The
corresponding private members of the Signal object are then
initialized with these values.
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friend ostream &operator <<(ostream &os, const Signal &sig):
This is an overloaded operator function which lets the
implementation use the standard insertion operator (<<) to
display the value and time of a Signal object on standard
output.
Sig_Val get_value(): This is a simple accessor
function which returns the value of the signal.
ckt_time get_time(). This is a simple accessor
function which returns the time at which the signal occurred.
void set_value(Sig_Val newval): This method
changes the value of the signal to the specified value. It is used only
by the replace() method of the Wire class and is
intended for future support of zero-delay component simulation.