/*

  This program converts temperature values from Celsius,Rakine or Fahrenheit
  into K. It demonstrates the use of the Switch/Case construct. 

  Copyright C. S. Tritt, Ph.D.
  Created 10/6/02
  Last revised 10/6/02
  Version 1.1
  
*/

// 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.

      switch (tUnits)
      {
         case 'c':
         case 'C':
            tOutputK = tInput + 273.15; // Convert deg. C to K.
            break;
         case 'r':
         case 'R':
            tOutputK = tInput * 5. / 9.; // Convert deg. R to K.
            break;
         case 'F':
         case 'f':
            tOutputK = (tInput + 459.67) * 5. / 9.; // Convert deg. F to K.
            break;
         default:
            cout << "Temperature units must be c, C, r, R, f or F. Aborting.\n";
            return 1; // No break required here because of unconditional return.
      } // End of switch/case.

      // Display results.

      if (tOutputK < 0) // Valid input produces non-negative output.
      {
         cout << "Invalid input. Aborting.\n";
         return 2;
      }
      cout << "is " << tOutputK << " K.\n";
      cout << "Go again (\"y\" or \"n\")? ";
      cin >> again;
   }
   while (again == 'y' or again == 'Y');
   return 0;
}