[RESOLVED] I am trying to figure out why I am receiving "unresolved external symbol"

[Bankaijoey]

This message is appearing for each of my functions. Could someone explain what the issue is and how to fix it/ prevent it in the future?
Thank You. Here is my code:

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

struct airport
{
	float numLanded;
	float numDeparted;
	float greatestLanded;
	float leastLanded;
};

float averageDeparture(airport, int);
float averageLanded(airport, int);
int greatestLanded(airport, int);
int leastLanded(airport, int);


int main()
{
	string months[] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
	airport statistics[12];
	int totalLanded = 0;
	int totalDeparted = 0;
	int count;
	
		for (count = 9; count < 12; count++)
		{
			cout << "Please enter the number of planes that landed in " << months[count] << ": " << endl;
			cin >> statistics[count].numLanded;
			cout << "Please enter the number of planes that departed in " << months[count] << ": " << endl;
			cin >> statistics[count].numDeparted;
			cout << "Please enter the greatest number of planes that landed on a single day in " << months[count] << ": " << endl;
			cin >> statistics[count].greatestLanded;

			
			
			totalLanded += statistics[count].numLanded;
			totalDeparted += statistics[count].numDeparted;
		}
		
	

	cout << "The average monthly landings for the year is " << averageDeparture(statistics[count], count) << endl;
	cout << "The average monthly departures for the year is " << averageLanded(statistics[count], count) << endl;
	cout << "The total landings for the year is " << totalLanded << endl;
	cout << "The total departures for the year is " << totalDeparted << endl;
	cout << "The greatest number of planes that landed in a single day is " << greatestLanded(statistics[count], count) << " which occured in the month of " << months[count] << endl;
	cout << "The least number of planes that landed in a single day is " << leastLanded(statistics[count], count) << " which occured in the month of " << months[count] << endl;

	system("pause");
	return 0;
}

float averageDeparture(airport array[], int pos)
{
	float total = array[pos].numDeparted;
	
	return (total / 3);
	
}

float averageLanded(airport array[], int pos)
{
	float total = array[pos].numDeparted;
	

	return (total / 3);

}

int greatestLanded(airport array[], int pos)
{
	int max = 0;
	for (int i = 1; i < pos; i++)
	{
		if (array[i].numLanded > array[i + 1].numLanded)
		{
			max = array[i].numLanded;
			return max;
		}
	}
}

int leastLanded(airport array[], int pos)
{
	int min = 0;
	for (int i = 1; i < pos; i++)
	{
		if (array[i].numLanded < array[i + 1].numLanded)
		{
			min = array[i].numLanded;
			return min;
		}
	}
}

[ahoodin]

The prototypes should look more like this:

int greatestLanded(airport array[], int pos);

You have C Style prototypes, but also the first parameter is not right.

Your definition and your prototype should be the same.

[ahoodin]

The compiler is currently looking for a function definition that takes a single airport object. Not an array.

[Bankaijoey]

I have made the changes but now i am getting a message saying "cannot convert argument 1 from airport to airport[]" on each function now?

[ahoodin]

try

int greatestLanded(struct airport array[], int pos);

and make it the same in both places

[Bankaijoey]

Ok im still getting that message im pretty sure im changing the right things but here is the modified code:

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

struct airport
{
	float numLanded;
	float numDeparted;
	float greatestLanded;
	float leastLanded;
};

float averageDeparture(struct airport array[], int pos);
float averageLanded(struct airport array[], int pos);
int greatestLanded(struct airport array[], int pos);
int leastLanded(struct airport array[], int pos);


int main()
{
	string months[] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
	airport statistics[12];
	int totalLanded = 0;
	int totalDeparted = 0;
	int count;
	
		for (count = 9; count < 12; count++)
		{
			cout << "Please enter the number of planes that landed in " << months[count] << ": " << endl;
			cin >> statistics[count].numLanded;
			cout << "Please enter the number of planes that departed in " << months[count] << ": " << endl;
			cin >> statistics[count].numDeparted;
			cout << "Please enter the greatest number of planes that landed on a single day in " << months[count] << ": " << endl;
			cin >> statistics[count].greatestLanded;

			
			
			totalLanded += statistics[count].numLanded;
			totalDeparted += statistics[count].numDeparted;
		}
		
	

	cout << "The average monthly landings for the year is " << averageDeparture(statistics[count], count) << endl;
	cout << "The average monthly departures for the year is " << averageLanded(statistics[count], count) << endl;
	cout << "The total landings for the year is " << totalLanded << endl;
	cout << "The total departures for the year is " << totalDeparted << endl;
	cout << "The greatest number of planes that landed in a single day is " << greatestLanded(statistics[count], count) << " which occured in the month of " << months[count] << endl;
	cout << "The least number of planes that landed in a single day is " << leastLanded(statistics[count], count) << " which occured in the month of " << months[count] << endl;

	system("pause");
	return 0;
}

float averageDeparture(struct airport array[], int pos)
{
	float total = array[pos].numDeparted;
	
	return (total / 3);
	
}

float averageLanded(struct airport array[], int pos)
{
	float total = array[pos].numDeparted;
	

	return (total / 3);

}

int greatestLanded(struct airport array[], int pos)
{
	int max = 0;
	for (int i = 1; i < pos; i++)
	{
		if (array[i].numLanded > array[i + 1].numLanded)
		{
			max = array[i].numLanded;
			return max;
		}
	}
}

int leastLanded(struct airport array[], int pos)
{
	int min = 0;
	for (int i = 1; i < pos; i++)
	{
		if (array[i].numLanded < array[i + 1].numLanded)
		{
			min = array[i].numLanded;
			return min;
		}
	}
}

[2kaud]

In c++ you don't need to use the word struct when referring to a struct type (or class). So

float averageDeparture(airport array[], int pos);

and likewise for the function definition.

cout << "The average monthly landings for the year is " << averageDeparture(statistics[count], count) << endl;

statistics[count] references an element of the array statistics. However the function parameter requires the whole array to be passed so

cout << "The average monthly landings for the year is " << averageDeparture(statistics, count) << endl;

[Bankaijoey]

Thank You. That fixed the issue I was having.

[2kaud]

A couple of further comments.

When dealing with an array of a fixed size (statistics) it is usually considered good practice to set the size of the array as a const int variable at the start and use the variable whenever the size of the array is used (eg in a for loop).

const int NOMONTHS = 12;

string months[] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };

As the contents of this array don't change, it would usually be declared as const. Also as the size of months array is known from the const var it can be specified.

const string months[NOMONTHS] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };

for (count = 9; count < 12; count++)

becomes

for (count = 9; count < NOMONTHS; count++)

I'm assuming for test purposes that you are starting at 9 rather then 0?

return (total / 3);

Why 3? As your loop is only going from 9 to 11 then you only enter 3 sets of data, but hard coding a number like this in code leads to errors. What if you make the original for loop start at 6?

If you want code like this IMO I would use another const variable for number required. Something like this

const int REQ = 3;
...
for (count = NOMONTHS - REQ; count < NOMONTHS; count++)
...
return (total / REQ);

That way if you change REQ to be what is wanted then it is right all through the program.