/*
 * CISC102-12 
 * 06.06.05
 * conversion.2.c
 * This program converts Celsius temperatures to Fahrenheit.
 * - modified 06.13.05 to accept user input
 * - modified 06.20.05 to use a function
 */

#include<stdio.h>
/* STOP_VALUE is the sentinel for our input loop */
#define STOP_VALUE -99

/*
 * Converts Fahrenheit to Celsius.
 * Input is the temperature in Fahrenheit.
 * The returned value is the temperature in Celsius.
 */
double convertFtoC( double fahr ) {
    double celsius = (5/9.0) * ( fahr - 32 );  
    return celsius;
    // alternative implementation: 
    // return  (5/9.0) * ( fahr - 32 );  
}

int main() {
  double celsius;
  double fahrenheit;

  printf("Welcome!\n");
 
  printf("Enter a temperature in F (Enter %d to stop): ",
	 STOP_VALUE);
  scanf("%lf", &fahrenheit);

  /* Keep prompting for user input as long as the input
   * is not equal to the STOP_VALUE.
   */
  while( fahrenheit != STOP_VALUE ) {
    celsius = convertFtoC(fahrenheit);

    printf("%.2lf degrees F is %.2lf degrees C.\n", fahrenheit,
	   celsius);

    printf("Enter a temperature in F (Enter %d to stop): ",
	   STOP_VALUE);
    scanf("%lf", &fahrenheit);
  }

  printf("Thank you for using my program.\n");

  return 0;
}