Help appreciated - Pass by reference

[jmag91]

Hey fun2code, this is my current code below. Everything is working great, but I am not sure why it is printing the Main Menu twice after using the Input function. Why is it doing that?

#include <iostream>
using namespace std;

const double TAXPERMILE = .05;
const double TAXPERGAL = .529;

void Input(double& MilesDriven, double& GalsUsed);
void CalcAndDisplay(double& MilesDriven, double& GalsUsed);

int main()
{
	double MilesDriven = 0;
	double GalsUsed = 0;
	
	char loop = 'y';
	char menu;

	while (loop == 'y')
	{
		cout << "Main Menu" << endl;
		cout << "(E)nter the miles driven and number of gals used." << endl;
		cout << "(C)alculate the two tax rates and display them." << endl;
		cout << "(Q)uit the program." << endl;
		cout << "Enter a (E), (C) or (Q) only." << endl;
		cin.get(menu);

		switch (menu)
		{
		case 'e':
		case 'E':
			Input(MilesDriven, GalsUsed);
			break;
		case 'c':
		case 'C':
			CalcAndDisplay(MilesDriven, GalsUsed);
			break;
		case 'q':
		case 'Q':
			loop = 'n';
			break;
		}
	}

	system("cls");
	return 0;
}

void CalcAndDisplay(double& MilesDriven, double &GalsUsed)
{
	double TotalTaxDrivingMiles = 0;
	double TotalTaxFuel = 0;

	cout << "Enter the number of miles driven:" << endl;
	cin >> MilesDriven;
	cin.ignore();
	cout << "Enter the number of gallons used:" << endl;
	cin >> GalsUsed;
	cin.ignore();

	cout.setf(ios::fixed);
	cout.setf(ios::showpoint);
	cout.precision(2);

	TotalTaxDrivingMiles = TAXPERMILE * MilesDriven;
	TotalTaxFuel = TAXPERGAL * GalsUsed;

	cout << "The total of tax per mile is= " << TotalTaxDrivingMiles << endl;
	cout << "The total of tax per gallon is= " << TotalTaxFuel << endl;
	
	system("pause");
	system("cls");
}



void Input(double &MilesDriven, double &GalsUsed)
{
	bool invalid = false;

	do
	{
		invalid = false;
		cout << "Enter the amount of miles driven: " << endl;
		cin >> MilesDriven;
		cout << "Enter the number of gallons used: " << endl;
		cin >> GalsUsed;
		if (cin.fail())
		{
			invalid = true;
			cin.clear();
			cin.ignore();
		}
	} while (invalid);

	cout << "The values for miles driven and gallons of fuel used has been entered! " << endl;
	cout << "Miles driven = " << MilesDriven << endl;
	cout << "Gallons of fuel used = " << GalsUsed << endl;

	system("pause");
	system("cls");
}

[coder777]

The problem is on line 25: operator>> leaves the new line character in the stream which is extracted the next time you call get(...)

replace line 25 with cin >> menu;