Changing from variable to another

[stardust2552]

I am having some trouble, I am trying to change a nominal value to a new value.. I declared the nominal value but later I want to prompt the user to input a new value. but I don't wan to have to re write all my formulas for the nominal value... How do I do this.

double C_NewValue();
double C_NewTolerance();
double C_nominalValue;
double C_tolerance;


Capacitor:: Capacitor(void)
  {
	 C_nominalValue = 100;

       C_tolerance = 10;
  }
void Capacitor::setCapacitance ()
 {
	 C_nominalValue = C_NewValue;
	 C_tolerance = C_NewTolerance;
	 
 }

... it's telling me that = doesn't convert from double... But I don't know what else to use? I also tried float and int...

[Zhuge]

C_NewValue and C_NewTolerance are functions, you must call them and assign the results.

[stardust2552]

I understand that and I haven't got the main I was just trying to figure out my classes...

So When I get my new tolerance I am going to have to change or make all new code for.... because I use C_nominalValue in that equation....

void Capacitor::Calc_Cap()
 {
C_minimumValue = C_nominalValue*(1-C_tolerance/100);

C_maximumValue = C_nominalValue*(1+C_tolerance/100);
 }

?