//an example of C++ functions
//csci107, Laura Toma

#include <iostream.h>


const float PI = 3.1412; 


//describes the program to the user
void describeProgram() {
  
  cout << "This program will ask for a radius and will compute "
       << "the circumference or the area of a circle with that radius. "
       << "Then it will repeat.." << endl;
  return;
}


//returns the circumference of a circle of radius rad
float compute_circum(float rad) {

  float circum = 2 * PI * rad;
  return circum; 
}


//returns the area of a circle of radius rad
float compute_area(float rad) {
  
  float area =  PI * rad * rad;  
  return area; 
}
 

int main() {

  char answer = 'y', option; 
  float r;

  //describe the program to the user
  describeProgram();

  while (answer == 'y') {
    cout << "enter a radius: ";
    cin >> r; 
    
    //read option
    cout <<"what would you like to compute? ";
    cout << "(press a for area, c for circumference): "; 
    cin >> option;

    if (option == 'c') {
      cout << "The circumference is: " << compute_circum(r) << endl;
    } else if  (option == 'a') {
      cout << "The area is: " << compute_area(r) << endl;
    } else {
      cout << "not a valid option..\n";
    }
    
    //again?
    cout << "again? (y/n): ";
    cin >> answer;
  }
  
}