/* Example on while loop ( linear interpolation)
        Fall 1999
   _________________________________
   Jacob Y. Kazakia     jyk0
   September 21, 1999
   Recitation Instructor: J.Y. Kazakia
   Recitation Section 01
   ________________________________

Purpose:        This program calculates the temperature of a surface at a given elapsed
         time after the start of cooling

Algorithm:      The initial temperature is given  at  T1 = 160 oC
            The temperature T2 = 95 oC is reached 1.6 minutes later.  After an
            additional 5.1 minutes the temperature drops to 30 oC and remains
            constant thereafter.  Linear interpolation is to be used for other
            times.  The formulas are:

               temp = T1 + rate1 * (time - time1)    for  time1<=time<time2

               temp = T2 + rate2 * (time - time2)    for  time2<=time<time3

               temp = T3                                 for  time3<=time

               rate1 = ( T2 - T1 ) / ( time2 - time1 )
               rate2 = ( T3 - T2 ) / ( time3 - time2 )

*/
#include <iostream.h>   // header which contains the functions
                        // needed for input and output
void main( )
{
  double T1 = 160.0;
  double T2 =  95.0;
  double T3 =  30.0;
  double time1 = 0.0;
  double time2 = 1.6;
  double time3 = 6.7;

  double time, temp;
  double rate1, rate2;

  rate1 = ( T2-T1)/(time2-time1);
  rate2 = ( T3-T2)/(time3-time2);

  cout<<"\n\n  Enter the time elapsed since the start of cooling ( in minutes)-->";
  cin >> time;

  while ( time > 0.0 )
  {
  if ( time <= time2)
    temp = T1 + rate1 * (time - time1);
  else if ( time <= time3)
    temp = T2 + rate2 * (time - time2);
  else
    temp = T3;

  cout << "\n\n  At this time the temperature is : " <<temp;

  cout<<"\n\n  Enter another time elapsed  ( in minutes)..";
  cout <<" \n  ENTER -1 to TERMINATE \n ....>";
  cin >> time;

  }

  cout << " \n\n                 GOOD BYE";

   // hold the screen
   char hold;
   cout << " \n\n Enter a character to quit \n";
   cin >> hold;
}

/*

TYPICAL RUN



 Enter the time elapsed since the start of cooling ( in minutes)-->1.6


 At this time the temperature is : 95

 Enter another time elapsed  ( in minutes)..
 ENTER -1 to TERMINATE
....>6.7


 At this time the temperature is : 30

 Enter another time elapsed  ( in minutes)..
 ENTER -1 to TERMINATE
....>4.8


 At this time the temperature is : 54.2157

 Enter another time elapsed  ( in minutes)..
 ENTER -1 to TERMINATE
....>

  Enter another time elapsed  ( in minutes)..
  ENTER -1 to TERMINATE
 ....>-1


                 GOOD BYE

 Enter a character to quit



*/