/*

  This program converts temperature values from Celsius,Rakine or Fahrenheit
  into K. It demonstrates the alternative to the Switch/Case construct using
  If/Else. 

  Copyright C. S. Tritt, Ph.D.
  Created 10/6/02
  Last revised 10/7/02
  Version 1.0
  
*/

// Provide ANSI logical operator names.

#define and &&
#define or ||
#define not !

#include <iostream>
using namespace std;

int main()
{
   // Declare variables.

   double tInput; // Entered temperature in deg. C, R or F.
   double tOutputK; // Converted temperature in K.
   char tUnits; // Temperature units (c, C, r, R, f or F).
   char again; // Repeat indicator.

   do
   {

      // Prompt user and get input.

      cout << "Enter temperature to convert with units (c, C, r, R, f or F): ";
      cin >> tInput >> tUnits;

      // Process input using a switch/case construct. Handle both upper and lower
      // case letters.

      if (tUnits == 'c' or tUnits == 'C') 
         tOutputK = tInput + 273.15; // Convert C to K.
      else if (tUnits == 'r' or tUnits == 'R') 
         tOutputK = tInput * 5. / 9.; // Convert R to K.
      else if (tUnits == 'f' or tUnits == 'F') 
         tOutputK = (tInput + 459.67) * 5. / 9.; // Convert F to K.
      else 
      {
         cout << "Temperature units must be c, C, r, R, f or F. Aborting.\n";
         return 1;
      }

      // Display results.

      if (tOutputK < 0) // Valid input produces non-negative output.
      {
         cout << "Invalid input. Aborting.\n";
         return 2;
      }
      cout << "is " << tOutputK << " K.\n";

      // Check if user wants to go again.
      
      cout << "Go again (\"y\" or \"n\")? ";
      // cin >> again;
      again = 'y';
   }
   while (again == 'y' or again == 'Y');
   return 0;
}