help with getData function

[school7]

i'm trying to right the definition of a function that prints a prompt and returns the value that the user input. if the value entered is negative it will print a predefined error message, dump all characters left on the line following the input, and ask for another value until a valid one is entered.

this is what i have so far

double getInput(string prompt)
{
	double value;
	cout << "Enter the " << prompt << endl;
	cin >> value;
	if(value<0) {
		do {
		cout << ERROR_MESSAGE << endl;
		cout << "Enter the " << prompt << endl;
		cin >> value;
		}
		while(value<0);
		}
	return value;
}


double altitude, fuelSupply, tractorBeamStrength;
altitude=getInput("current altitude of the ship (km): ");
fuelSupply=getInput("current fuel supply of the ship (kg): ");
tractorBeamStrength=getInput("strength of the enemy tractor beam (km/min/min): ");

i don't think it seems to be working -- any suggestions?

[Billdozer]

You need to add another argument ERROR_MESSAGE if it was not already defined. Also, you can clear cin by adding a couple of ignore commands.

const char ERROR_MESSAGE[] = "Enter a value greater than 0.";
double getInput(string prompt)
{
	double value;
	cout << "Enter the " << prompt << endl;
	cin >> value;
                cin.ignore (BUFSIZ, '\n');
	if(value<0) {
		do {
		cout << ERROR_MESSAGE << endl;
		cout << "Enter the " << prompt << endl;
		cin >> value;
                                cin.ignore (BUFSIZ, '\n');
		}
		while(value<0);
		}
	return value;
}


double altitude, fuelSupply, tractorBeamStrength;
altitude=getInput("current altitude of the ship (km): ");
fuelSupply=getInput("current fuel supply of the ship (kg): ");
tractorBeamStrength=getInput("strength of the enemy tractor beam (km/min/min): ");