// Zeinalipour-Yazti Demetrios
// csyiazti
// cs10xx -
// Lab Sec#24
// lab5

/* Simple "carbon-14 Age calculation Program"
   The program computes the approximate age of an artifact using carbon-14 dating.
   It allows the user to continue doing this as many times as they want.
   The carbon-14 dating formula is the following :

   Age = -5700 * (ln(percentage_of_carbon14_remaining)/ ln(2) )

   where age is the approximate age in years and the percentage of carbon14
   remaining is a fraction of 1.0.
*/
#include <iostream>
#include <cmath>
using namespace std;

void main()
{

    /* declaration of variables */
   float pct_carbon;  // the percentage of carbon14 remaining
   float age;             // the approximation of the age calculated
   char answer;       // the users answer to the question if he wants to continue or not

   do
   {
      // the idea is to keep user's entry validation locally. We will insist on ansking him
     // the same que
     while (true)
     {
        cout << "Please enter percentage of carbon14 remaining [0.0-1.0] : ";
        cin  >> pct_carbon;
        // stop only if  pct_carbon ranges from 0.0-1.0
        if (pct_carbon>0.0 &&  pct_carbon<=1.0)
        { break; }
        cout << "Warning! - Percentage of carbon14 can only be between (0.0,1.0]\n";
     }

      // calculating age based on the given formula
     age = -5700 * ( log(pct_carbon) / log(2.0) );

     // output answer
     cout << "The approximation of the age (based on the carbon14 formula is : " << age << endl;

     // check users answer on question whether to continue or not
     do
     { cout << "\n\nDo you want to do the calculation again (y/n) :";
       cin  >> answer;
      } while (answer!='y' && answer!='n');

   } while (answer=='y' || answer=='Y'); // main loop

}