error5.cpp

// error5.cpp -- unwinding the stack
#include <iostream>
#include <cmath>
#include <string>
#include "exe_mean.h"

class demo{
private:
  std::string word;
public:
  demo(const std::string & str){
    word=str;
    std::cout<<"demo "<<word<<" created\n";
  }
  ~demo(){
    std::cout<<"demo "<<word<<" destroyed\n";
  }
  void show(){
    std::cout<<"demo "<<word<<" lives!\n";
  }
};

// function prototypes
double hmean(double a, double b);
double gmean(double a, double b);
double means(double a, double b);

int main(){
  using std::cout;
  using std::cin;
  using std::endl;

  double x, y, z;
  {
    demo d1("found in block in main()");
    cout<<"Enter two numbers: ";
    while(cin>>x>>y){
      try{
        z=means(x, y);
        cout<<"The mean of "<<x<<" and "<<y
            <<" is "<<z<<endl;
        cout<<"Enter next pair: ";
      }
      catch(bad_hmean & bg){
        bg.mesg();
        cout<<"Try again.\n";
        continue;
      }
      catch(bad_gmean & hg){
        cout<<hg.mesg();
        cout<<"Values used: "<<hg.v1<<", "
            <<hg.v2<<endl;
        cout<<"Sorry, you don't get to play any more.\n";
        break;
      }
    }
    d1.show();
  }
  cout<<"Bye!\n";
  cin.get();
  cin.get();
  return 0;
}

double hmean(double a, double b){
  if(a == -b)
    throw bad_hmean(a, b);
  return 2.0*a*b/(a+b);
}
double gmean(double a, double b){
  if(a<0 || b<0)
    throw bad_gmean(a, b);
  return std::sqrt(a*b);
}
double means(double a, double b){
  double am,hm,gm;
  demo d2("found in means()");
  am=(a+b)/2.0;
  try{
    hm=hmean(a, b);
    gm=gmean(a, b);
  }
  catch(bad_hmean & bg){
    bg.mesg();
    std::cout<<"Cauth in means()\n";
    throw;
  }
  d2.show();
  return (am+hm+gm)/3.0;
}