// Program Gauge inputs pressure readings from file Gauge.dat
// and writes appropriate messages.  

#include <iostream>
#include <fstream>
using namespace std;

enum  DecisionType {ERROR, NORMAL, HIGH, EVACUATE}; 

void  GetPressure(ifstream&, DecisionType&);

int main ()
{
    ifstream  readings;
    DecisionType  pressure;        
    readings.open("gauge.dat");
    do
    {
        GetPressure(readings, pressure);
        switch (pressure)
        {
            case ERROR    : cout  << "Error in input."  
                            << endl;
                            break;
	    case NORMAL   : cout  << "Pressure in normal range."
			    << endl;
			    break;
	    case HIGH     : cout  << "Pressure on the high side."
			    << endl;
			    break;
	    case EVACUATE : cout  << "Evacuate plant!!!!"
                            << endl;
                            break;
        }
    }  while (pressure != EVACUATE);
    return 0;
}

/**************************************************/        
                                                            

void GetPressure(ifstream& readings, DecisionType& pressure)
// Pre:  File readings has been opened.                     
// Post: An integer pressure is read from file readings.      
//       pressure is ERROR if a negative pressure is read.        
//       pressure is NORMAL if the value is between 0 and 49.   
//       pressure is HIGH if the value is between 50 and 99.        
//       pressure is EVACUATE if the value is 100 or above.       

{                                                            
    int  reading;
    readings  >> reading;
    if (reading < 0)
        pressure = ERROR;
    else if (reading < 50)
        pressure = NORMAL;
    else if (reading < 100)
        pressure = HIGH;
    else 
        pressure = EVACUATE;
}