Loop Problem

[HectorBerlioz]

Ok, I'm still new at this, so bear with me...
I have a question with regards to the code below:

# include <iostream>
# include <string>

using namespace std;

double test;

int main()
{

do
{
cout << "Test to see if a number is between 0 and 1000:" << endl;
cin >> test;
if (test >= 1000)
{
cout << "NUMBER IS GREATER THAN 1000!!!" << endl;
}
else if (test <= 0)
{
cout << "THE NUMBER IS LESS THAN 0!!!" << endl;
}
}
while ((test >= 1000) || (test <= 0));
cout << "The following number is between 0 and 1000: " << test << endl;
cout << endl;
cout << "Done" << endl;
return 0;

}


If the user "accidental ly" enters a letter instead of a number, the program goes nuts!!!

How do I account this possible user entry error?

Thanks,

Terence

[sjsn]

I'm dying on this one too... I've built a program that will contain the user in a loop if they enter an invalid value (any number less than 0), to get out of the loop they have to enter the correct value, or a letter... the letter will make my program go nuts too..!

Good question!

[momotaro]

Man read how to post and learn to INDENT your code!!!
its realy hard to understand

[momotaro]

plz explain clearly what u r expecting from ur prog!

[momotaro]

HINT! use this to handel the input errors
PS: its a hint u have to undes=rstand it then u can play with it...;)

int err=1;
err=scanf("%d" &input);
if err<=0 (here u can use a loop statement to ask the user to re enter his value!)

[sjsn]

Run this and for the startingMiles value enter a letter, the program then continues to the end return 0; this is the incorrect response.
Then run the program again and for the startingMiles value enter a negative number. This is the correct response to the error...

The question is, how do you include characters in the invalid response?

#include <iostream>
#include <iomanip>

using std::cout ;
using std::cin ;
using std::setprecision ;
using std::ios;

int main()
{

char cont	= ' ';	

do
	{	
	double startingMiles	=0;
	double endingMiles		=0;
	double milesDriven		=0;
	double gallonsOfGas		=0;
	double milesPerGallon	=0;
	
cout << "\n\n--------------- Gas Mileage Calculator -----------------\n\n" ;

	do
	{
		cout << "Enter the starting miles          : " ;
		cin  >> startingMiles ;

			if ( startingMiles < 0 )
			{
				cout << "\n" << startingMiles << " is an invalid value for starting miles. \n\n" ;
			}
	}while (startingMiles < 0);

	do
	{
		cout << "Enter the ending miles            : " ;
		cin  >> endingMiles ;

			if ( endingMiles < 0 )
			{
				cout << "\n" << endingMiles << " is an invalid value for ending miles. \n\n" ;
			}

			if ( endingMiles < startingMiles )
			{
				cout << "\nEnding miles " << endingMiles << " cannot be less than starting miles " << startingMiles << ". \n\n" ;
			}

	}while (startingMiles < 0 || endingMiles < startingMiles);

cout << "Enter the gallons of gas purchased: " ;
cin  >> gallonsOfGas ;

	if ( gallonsOfGas <= 0 )
	{
		cout << "\n" << gallonsOfGas << " is an invalid value for gallons of gas purchased. \n\n" ;
		return 0 ;
	}

milesDriven = endingMiles - startingMiles ;

milesPerGallon = milesDriven / gallonsOfGas ;

cout << setprecision( 2 ) << setiosflags(ios::fixed) << setiosflags( ios::showpoint ) ;

	cout << "\nBased on " << milesDriven << " miles driven and " 
		 << gallonsOfGas << " gallons of gas purchased, \nthe miles per gallon is " 
		 << milesPerGallon << "\n\n" ;
	
cout << "\nWould you like to do another calculation? (y/n): ";
cin >> cont;
cont = toupper (cont);

}while (cont == 'Y');

	return 0 ;
}