Call by reference

[bozz51]

Hello,
I have a file data.txt that has these set of numbers:
126534 9 8 10
321345 7 3 5
324341 9 9 9
I'm trying to create a call by reference that will use a function called ProcessARow to calculate Min,Max and Average in a table like this
Std-Id A1 A2 A3 Min Max Average
----------------------------------S-------------------------------------
126534 9 8 10 8 10 9.0
321345 7 3 5 3 7 5.0
324341 9 9 9 9 9 9.0

I keep getting errors
Error 2 error LNK2019: unresolved external symbol
Error 3 error LNK1120: 1 unresolved externals
Not sure what I'm doing wrong as the forum suggests I'm a newbie.

  #include <fstream>
#include <iostream>

using namespace std;



void ProcessARow(int x, int y, float z);



int main()
{
	ifstream fin;
	fin.open("data.txt");
	int id, A1, A2, A3;

	cout << "Std-Id \tA1 \tA2 \tA3 \t Min \t Max \t Avg\n";
	cout << "---------------------S-------------------------------\n";
	while (fin >> id >> A1 >> A2 >> A3){
			
		int max = A1;
		int min = A1;
		float avg = A1 + A2 + A3 / 3.0;

		
			if (A2 > max)
				max = A2;
			if (A3 > max)
				max = A3;
			if (A2 < min)
				min = A2;
			if (A3 < min)
				min = A3;
			ProcessARow(min, max, avg);
			cout << id << "\t" << A1 << "\t" << A2 << "\t" << A3 << "\t" << min << "\t" << max << "\t" << avg << endl;
			system("pause");
		}

}

[giblit]

1) You are passing by copy.
2) You never told the compiler what the function does.

[bozz51]

Not sure what you mean?

[giblit]

void ProcessARow(int &x, int &y, float &z); This is passing by reference.
void ProcessARow(int x, int y, float z); What does this do??

[bozz51]

like this?

int ProcessARow(int &max, int &min, int &avg);

int main()
{
	ifstream fin;
	fin.open("data.txt");
	int id, A1, A2, A3;

	cout << "Std-Id \tA1 \tA2 \tA3 \t Min \t Max \t Avg\n";
	cout << "---------------------S-------------------------------\n";

	while (fin >> id >> A1 >> A2 >> A3)
 {
		int max = A1;
		int min = A1;
		if (A2 > max)
			max = A2;
		if (A3 > max)
			max = A3;
		if (A2 < min)
			min = A2;
		if (A3 < min)
			min = A3;
		float avg = A1 + A2 + A3 / 3.0;
		cout << id << "\t" << A1 << "\t" << A2 << "\t" << A3 << "\t" << min << "\t" << max << "\t" << avg << endl;
		
		
		
	}

	

	system("pause");
}

[giblit]

You need to read up on functions I think. You are not understanding how to setup them. Basically you want something like:

int function(/*parameters type & name(suggested not required)*/); //prototype

int main()
{
    function(/*parameter variables/values*/); //calling the function
}

int function(/*parameters type & name(required)*/ ) //declaration
{
    //do something
    //you can use the parameter variables
}

http://www.cplusplus.com/doc/tutorial/functions/

[AbstractionAnon]

You've removed the call to ProcessARow which has probably eliminated the undefined external. Since you're not calling it, you don't need the function prototype at line 1.

giblit wrote:

You never told the compiler what the function does.

What giblit meant is that you provided a function declaration, but your never wrote the function. That is what the linker tried to tell you with the "undefined external" message. i.e. Where is the implementation for ProcessARow?

[bozz51]

This is my latest however I'm getting new errors

redefinition of formal parameter max,min???

#include <fstream>
#include <iostream>

using namespace std;



void ProcessARow(int id,int A1,int A2,int A3,int& max, int& min, float& avg);
int main()
{
	ifstream fin;
	fin.open("data.txt");
	int id, A1, A2, A3, max, min;
	float avg;
	cout << "Std-Id \tA1 \tA2 \tA3 \tMin \tMax \tAvg\n";
	cout << "--------------------S------------------------------\n";
	while (fin >> id >> A1 >> A2 >> A3)
	{
		ProcessARow(id, A1, A2, A3, max, min, avg);
	}
}
	void ProcessARow(int id, int A1, int A2, int A3, int &max, int &min, float &avg)
	{
		int max = A1;
		int min = A1;
		if (A2 > max)
			max = A2;
		if (A3 > max)
			max = A3;
		if (A2 < min)
			min = A2;
		if (A3 < min)
			min = A3;
		avg = (A1 + A2 + A3) / 3.0;
		cout << id << "\t" << A1 << "\t" << A2 << "\t" << A3 << "\t" << min << "\t" << max << "\t" << avg << endl;
		return;

		system("pause");
	}

[giblit]

		int max = A1;
		int min = A1;

You should remove the int from both and use the ones passed via the parameters.

[bozz51]

I fixed it needed to fix line 24,25

[bozz51]

Thanks so much giblit