PID loop

#include <iostream>
using namespace std;

class PID{
  //scale factors
  double pScale = 0.0;
  double iScale = 0.0;
  double dScale = 0.0;
  
  //holding values
  double iTemp = 0;
  double dTemp = 0;
   
  //integrator max and min
  double iMax = 300;
  double iMin = -300;
  
  //Variable terms
  double pTerm = 0;
  double iTerm = 0;
  double dTerm = 0;
  double pid = 0;                     //these terms and above need to be inisalized outside the loop
  
  // Constructor
  //PID();  // Constructor, does nothing now
 
  // Class methods
  public:
  double update(double currVal, double idealVal);
  void print() {cout << pid << endl;}
};


double PID::update(double currVal, double idealVal){
  //finding error
  double errorValue = currVal - idealVal;         //currentValue is from sensors, idealValue is the wanted position
  
  pTerm = pScale * errorValue;
   
  dTerm = errorValue - dTemp;
  dTemp = errorValue;
  
  iTemp = iTemp + errorValue;
  if (iTemp > iMax)
    iTemp = iMax;
  if (iTemp < iMin)
    iTemp = iMin;
  iTerm = iScale * iTemp;
 
  pid = pTerm + iTerm + dTerm;
  return pid;
}


int main(){
    PID myPid;
    
    //need to insert error value and desired valur into these arguments
    double arg1 = 0.5;
    double arg2 = 0.0;
    
    myPid.update(arg1, arg2);
    myPid.print();

    return 0;
}