Pass by reference

[melgunn6]

I need to change this code from a return function to a pass by reference, but its not a math problem so I'm not sure what i need to do:

// File: Lab 22P1.cpp

#include <cstdlib>
#include <iostream>
using namespace std;

string getProductCode();

int main()
{
string productCode = "";

productCode = getProductCode();
cout << "Product code read from keyboard: " << productCode << endl;

system("pause");
return 0;
}

string getProductCode()
{
string code = "";
bool valid = false;
while (valid == false )
{
cout << "Enter the orange's 4-digit code. " << endl;
cout << "The last digit must be either 4 or 7." << endl;
cout << "Enter code here: ";
cin >> code;
if (code.length() == 4 && (code[3] == '4' || code[3] == '7'))
{
valid = true;
}
else
{
cout << "Invalid code. Please try again." << endl;
}
}
return code;
}

[LB]

Although it does not make sense to do so, this is how you would do it:

void getProductCode(std::string &code)
{
    //...
    //no return statement
}

[melgunn6]

and would that go in place of the "return" statement listed? not sure where to put it...

[LB]

You need to change your function declaration and definition. Since you did not put your code [code]between code tags[/code] I cannot tell you which line numbers to look at. You can edit your post and fix it if you want.

[melgunn6]

Im not sure if i understand what you are saying, this code doesn't run, but just to show you to see if im on the right path.


// File: Lab 22P1.cpp

#include <cstdlib>
#include <iostream>
using namespace std;

void getProductCode();

int main()
{
double productCode = 0;

productCode = getProductCode(string, code);
cout << "Product code read from keyboard: " << productCode << endl;

system("pause");
return 0;
}

void getProductCode(std::string &code)
{
string code = "";
bool valid = false;
while (valid == false )
{
cout << "Enter the orange's 4-digit code. " << endl;
cout << "The last digit must be either 4 or 7." << endl;
cout << "Enter code here: ";
cin >> code;

if (code.length() == 4 && (code[3] == '4' || code[3] == '7'))
{
valid = true;
}
else
{
cout << "Invalid code. Please try again." << endl;
}
}
}

[LB]

Please edit your post so that your code is [code]between code tags[/code] so I can reference line numbers.

[melgunn6]

// File: Lab 22P1.cpp


#include <cstdlib>
#include <iostream>
using namespace std;

void getProductCode();

int main()
{
	double productCode = 0;
	
	productCode = getProductCode(string, code);	
	cout << "Product code read from keyboard: " << productCode << endl;

    system("pause");
    return 0;
}

void getProductCode(std::string &code)
{
	string code = "";
	bool valid = false;
	while (valid == false )
	{
		cout << "Enter the orange's 4-digit code. " << endl;
		cout << "The last digit must be either 4 or 7." << endl;
		cout << "Enter code here: ";
		cin >> code;
		
		if (code.length() == 4 && (code[3] == '4' || code[3] == '7'))
		{
			valid = true;
		}
		else
		{
			cout << "Invalid code.  Please try again." << endl;
		}
	}
}

[giblit]

Line 24 should pass a variable not a type and non-existant variable actually I'm not sure the line I'm on phone but when u call it and prototype are wrong

[melgunn6]

line 5?

[LB]

You need to change line 8 the same way you changed line 21.

@giblit: I think you mean line 14, not 24

[melgunn6]

/ File: Lab 22P1.cpp

#include <cstdlib>
#include <iostream>
using namespace std;

void getProductCode(std::string &code)

int main()
{
	double productCode = 0;
	
	productCode = getProductCode(string, code);	
	cout << "Product code read from keyboard: " << productCode << endl;
	
	getProductCode(string, code)

    system("pause");
    return 0;
}

void getProductCode(std::string &code)
{
	string code = "";
	bool valid = false;
	while (valid == false )
	{
		cout << "Enter the orange's 4-digit code. " << endl;
		cout << "The last digit must be either 4 or 7." << endl;
		cout << "Enter code here: ";
		cin >> code;
		
		if (code.length() == 4 && (code[3] == '4' || code[3] == '7'))
		{
			valid = true;
		}
		else
		{
			cout << "Invalid code.  Please try again." << endl;
		}
	}
}

/
ok i changed line 8 like line 21, now i get error of the following: 26 9 E:\CIS 115\Lab22P1.cpp [Error] declaration of 'std::string code' shadows a parameter

[melgunn6]

Ok i finally see what you all were saying, but now I am still getting the same error, for line 23 :(

// File: Lab 22P1.cpp

#include <cstdlib>
#include <iostream>
using namespace std;

void getProductCode(string &);

int main()
{
	string productCode = 0;
	
	getProductCode(productCode);	
	cout << "Product code read from keyboard: " << productCode << endl;
	

    system("pause");
    return 0;
}

void getProductCode(string &code)
{
	string code = "";
	bool valid = false;
	while (valid == false )
	{
		cout << "Enter the orange's 4-digit code. " << endl;
		cout << "The last digit must be either 4 or 7." << endl;
		cout << "Enter code here: ";
		cin >> code;
		
		if (code.length() == 4 && (code[3] == '4' || code[3] == '7'))
		{
			valid = true;
		}
		else
		{
			cout << "Invalid code.  Please try again." << endl;
		}
	}
}

[LB]

Remove "string" from the start of line 23 - the variable already exists (it is the parameter).

[melgunn6]

ok so i removed it, the program compiles, but it runs an error of termination...

[mutexe]

hint...

string productCode = 0;

You've defined a string, but initialised it with an integer..

also do this at the top:

#include <string> 

Also, you get the user to enter the code and do the validation in the same function, so why are you even passing the code into that function?

[LB]

mutexe wrote:

Also, you get the user to enter the code and do the validation in the same function, so why are you even passing the code into that function?

Read OP - professor requires it.

[mutexe]

ah right.

[melgunn6]

thanks for your help! I finally think i have it correct!