debugging a mpg calcuator

[j3tt]

I have trouble pinpointing the what causes an endless loop.

//Ch9AppE07.cpp
//Calculates and displays the miles per gallon
//Created/revised by <Jett Bailes> on <11.20.09>

#include <iostream>
#include <iomanip>

using std::cout;
using std::cin;
using std::endl;
using std::setprecision;
using std::fixed;

//function prototypes
double getMiles();
double getNumGallons();
double calcMpg(double);

int main()
{	
	//declare variables
	double miles       = 0.0;
	double gallons     = 0.0;
	double milesPerGal = 0.0;
	
	//enter input items
	miles = getMiles();
	gallons = getNumGallons();

	//calculate miles per gallon
	milesPerGal = calcMpg(miles);

	//display output item
	cout << fixed << setprecision(1);
	cout << "Miles per gallon: " << milesPerGal << endl;

    return 0;
}   //end of main function

//*****function definitions*****
double getMiles()
{
	double numMiles = 0.0;
	cout << "Enter the number of miles: ";
	cin >> numMiles;
	return numMiles;
}	//end of getMiles function

double getNumGallons()
{
	double numGals = 0.0;
	cout << "Enter number of gallons: ";
	cin >> numGals;
	return numGals;
}	//end of getNumGallons function

double calcMpg(double distance)
{
	double galUsed = 0.0;
	return distance / galUsed;
}	//end of calcMpg function

These endless loops always throw me for a loop. (haha, a little programming humor)

[helios]

There aren't any loops in that code.

[j3tt]

execute it and you'll see what I mean..

[Bazzy]

double calcMpg(double distance)
{
	double galUsed = 0.0;
	return distance / galUsed; // division by zero
}

[Lodger]

Something's not quite right here...

double calcMpg(double distance)
{
	double galUsed = 0.0;
	return distance / galUsed;
}	//end of calcMpg function

Edit: Beaten by a minute!

[j3tt]

hmmm. I'm not sure how to go about fixing it. I get the same results after declaring the galUsed variable in the main and passing it to the function. I'm confused.

//Ch9AppE07.cpp
//Calculates and displays the miles per gallon
//Created/revised by <Jett Bailes> on <11.20.09>

#include <iostream>
#include <iomanip>

using std::cout;
using std::cin;
using std::endl;
using std::setprecision;
using std::fixed;

//function prototypes
double getMiles();
double getNumGallons();
double calcMpg(double, double);

int main()
{	
	//declare variables
	double miles       = 0.0;
	double gallons     = 0.0;
	double milesPerGal = 0.0;
	double galUsed = 0.0;
	
	//enter input items
	miles = getMiles();
	gallons = getNumGallons();

	//calculate miles per gallon
	milesPerGal = calcMpg(miles, galUsed);

	//display output item
	cout << fixed << setprecision(1);
	cout << "Miles per gallon: " << milesPerGal << endl;

    return 0;
}   //end of main function

//*****function definitions*****
double getMiles()
{
	double numMiles = 0.0;
	cout << "Enter the number of miles: ";
	cin >> numMiles;
	return numMiles;
}	//end of getMiles function

double getNumGallons()
{
	double numGals = 0.0;
	cout << "Enter number of gallons: ";
	cin >> numGals;
	return numGals;
}	//end of getNumGallons function

double calcMpg(double distance, double galUsed)
{
	return distance / galUsed;
}	//end of calcMpg function

[Bazzy]

Since its value is still zero, the result would be the same.
If you read your code carefully, the variable you should pass is already declared and assigned to a value...

[firedraco]

It is still 0.0 when you pass it to the function, since you never actually get input into it.

EDIT: 遅かった・・・。