ok i've got a function with a prototype that takes in a char value and checks for a match, if it matches returns bool true. The error comes in how i'm referencing. I need to be able to change the value of the original variable depending on the return of true/false. i'm using the & by ref but not sure if i'm doing it right.

this is the error:
error C2664: 'checkpackage' : cannot convert parameter 1 from 'char *' to 'char &'
A reference that is not to 'const' cannot be bound to a non-lvalue

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

bool checkpackage(char &);

int main()
{
	
	fstream infile;
	fstream outfile;

	char file[9];
	char file2[9];

	
	cout << "Please enter the name of the file to read in: "; 
	cin.getline(file,10);

	cout << "Please enter in the name of the file to save to: ";
	cin.getline(file2, 10);

	infile.open(file, ios::in);
	outfile.open(file2, ios::out | ios::trunc);
	if (!infile)
	{
		cout << "No file found.";
		return 0;
	}
	else 
	{
	
		int Maxhours[13] = {0,744,672,744,720,744,720,744,744,720,744,720,744};
		float tot_bill, savings_A, savings_B, savings_C, Tot_hours, overage, over_hours;
		const double A_MONTHY = 9.95;
		const double B_MONTHY = 14.95;
		const double C_MONTHY = 19.95;
		const float A_OVERAGE_CHARGE = 2.00;
		const float B_OVERAGE_CHARGE = 1.00;
		char package, Date4, Date5;
		int Date, Date2, Date3;
		string cus_No;

		

		infile >> Date >> Date4;
		infile >> Date2 >> Date5;
		infile >> Date3;

		outfile << Date << Date4 << Date2 << Date5 << Date3 << endl << endl << endl;
		

		if (Date >= 1 && Date <= 12)
		{
			while (!infile.eof())
			{
			
				infile >> cus_No; 
				infile >> package;
				infile >> Tot_hours;

				if (checkpackage(&package))
				{

					if (Tot_hours > Maxhours[Date])
					{
						outfile << "Invalid number reached in Used hours at customer number: " << cus_No << endl;
					}
					else
					{
						if (package == 'A' || package == 'a')
						{
							
							over_hours = Tot_hours - 10;

							if (over_hours > 0)
							{
								overage = A_OVERAGE_CHARGE * over_hours;
							}
							else 
							{
								overage = 0;
							}
							

							tot_bill = A_MONTHY + overage;

							if ((Tot_hours - 20) > 0)
							{

								savings_B = tot_bill - (B_MONTHY + (B_OVERAGE_CHARGE * (Tot_hours - 20)));
							}
							else 
							{
								savings_B = tot_bill - B_MONTHY;
							}


							savings_C = tot_bill - C_MONTHY;

							outfile << "Customer number: " << cus_No << endl;
							outfile << "Current Package: " << package << endl;
							outfile << "Total hours used: " << Tot_hours; 
							outfile << endl << endl << endl;
							outfile << "Monthly charge: \t\t\t\t" << A_MONTHY << endl;
							if (over_hours > 0 )
							{
								outfile << "Overage charge: \t" << over_hours << "*" << A_OVERAGE_CHARGE << "\t\t\t" << overage << endl;
							}
							outfile << "				\t\t\t\t----------" << endl;
							outfile << "Total bill:	 \t\t\t\t" << tot_bill << endl << endl;

							if (savings_B > 0)
							{
								outfile << "You could have saved: $" << savings_B << " by switching to package B" << endl;
							}
							if (savings_C > 0)
							{
								outfile << "You could have saved: $" << savings_C << " by switching to package C" << endl;
							}
							outfile << endl << endl;
							outfile << & quot;___________________________________________________________________________
____" << endl;

							}
							else if (package == 'B' || package == 'b')
							{
								over_hours = Tot_hours - 20;

							

								if (over_hours > 0)
								{
									overage = B_OVERAGE_CHARGE * over_hours;
								}
								else 
								{
									overage = 0;
								}

								tot_bill = B_MONTHY + overage;
								
								if ((Tot_hours - 10) > 0)
								{
									savings_A = tot_bill - (A_MONTHY + ((Tot_hours - 10) * A_OVERAGE_CHARGE));
								}
								else
								{
									savings_A = tot_bill - A_MONTHY;
								}
								
								savings_C = tot_bill - C_MONTHY;
										
								
	
								
								outfile << "Customer number: " << cus_No << endl;
								outfile << "Current Package: " << package << endl;
								outfile << "Total hours used: " << Tot_hours; 
								outfile << endl << endl << endl;
								outfile << "Monthly charge: \t\t\t\t" << B_MONTHY << endl;
								if (over_hours > 0 )
								{
									outfile << "Overage charge: \t" << over_hours << "*" << B_OVERAGE_CHARGE << "\t\t\t" << overage << endl;
								}
								outfile << "				\t\t\t\t----------" << endl;
								outfile << "Total bill:	 \t\t\t\t" << tot_bill << endl << endl;

							
								if (savings_A > 0)
								{
									outfile << "You could have saved: $" << savings_A << " by switching to package A" <<endl;
								}
								if (savings_C > 0)
								{
									outfile << "You could have saved: $" << savings_C << " by switching to package C" << endl;
								}
								outfile << endl << endl;
								outfile << & quot;___________________________________________________________________________
____" << endl;
								
							}	
							else if (package == 'C' || package == 'c')
							{
								tot_bill = C_MONTHY;
														
								outfile << "Customer number: " << cus_No << endl;
								outfile << "Current Package: " << package << endl;
								outfile << "Total hours used: " << Tot_hours; 
								outfile << endl << endl << endl;
								outfile << "Monthly charge: \t\t\t\t" << C_MONTHY << endl;
								outfile << "				\t\t\t\t----------" << endl;
								outfile << "Total bill:	 \t\t\t\t" << tot_bill << endl << endl;
	
								
	
								if (Tot_hours <= 15)
								{
									if (Tot_hours <= 10)
									{
										savings_A = tot_bill- A_MONTHY;
										outfile << "You could have saved: $" << savings_A << " by switching to package A" << endl;
									}
									else 
									{
										savings_A = tot_bill - (A_MONTHY + (Tot_hours - 10 * A_OVERAGE_CHARGE));
										outfile << "You could have saved: $" << savings_A << " by switching to package A" << endl;
									}
								}
								else if (Tot_hours > 12 && Tot_hours <= 25)
								{
									if (Tot_hours <= 20)
									{
										savings_B = tot_bill - B_MONTHY;
										outfile << "You could have saved: $" << savings_B << " by switching to package B" << endl;
									}
									else 
									{
										savings_B = tot_bill - (B_MONTHY + (Tot_hours - 20 * B_OVERAGE_CHARGE));
										outfile << "You could have saved: $" << savings_B << " by switching to package B" << endl;
									}
									
								}
								outfile << endl << endl;
								outfile << & quot;___________________________________________________________________________
____" << endl;
							}
						}
					}
				}
			}
			else 
			{
				cout << "Invalid date specified please check numbers and try again" << endl;
				outfile << "Invalid date specified please check numbers and try again" << endl;
				return 0;
			}

		}
	return 0;
}

bool checkpackage(char &pckge) <-- error here
{
	if (pckge == 'A' || pckge == 'a' || pckge == 'b' || pckge == 'B' || pckge == 'c' || pckge == 'C')
	{
		if (pckge == 'a')
		{
			pckge = 'A';
		}
		else if (pckge == 'b')
		{
			pckge = 'B';
		}
		else if (pckge == 'c')
		{
			pckge = 'C';
		}
	}
		return true;
}

This post has been edited by born2c0de: 1 Sep, 2008 - 05:48 AM

You've declared checkpackage as taking a reference. This means that the compiler will internally convert the passed argument to a pointer, so that it can be changed within the function; there is no need to pass the address of package to checkpackage. Just call it like this: if (checkpackage(package)) {}

Also, stylistically, I don't like the fact that checkpackage modifies the value passed in, as this is a side effect and not readily obvious. I would prefer to use the toupper(char c) function in the ctype library (#include <cctype>) to convert it as you pass it in. I'd do it something like this:

if (checkpackage(package = toupper(package))) { ... }

bool checkpackage(const char package)
{
    static const char validPackages[] = { 'A', 'B', 'C' };
    int i;
    for (i = 0; i < sizeof(validPackages) / sizeof(validPackages[0]); ++i)
        if (package == validPackages[i])
            return true;
    return false;
}

that would work, but i have to change the original value inside the function, its required by the teacher and it has to be done using &

Well Jack is right for the most part, just pass the variable name to your function, no appending of the & on the front. if (checkpackage(package)) {} after the call "package" will be altered by the function. You are passing by reference here since your function takes it in as char &.

If you don't believe us, print out the value of "package" variable before you call your function "checkpackage" and then afterwards. Make sure you pass it a lowercase value like 'a' and you will see that after your call the "package" variable will be 'A'.

ohh, i believe you guys, but the way that jack did it made it seem to me that he was having me make the change before sending it to the function. BTW, thanks taking off the & in the function call worked.