C++ Area of a Rectangle

[jshm415]

1 and 2: Write a function RectArea that takes in lengths (double) of a rectangle and returns the area (double) + overload RectArea to take ints in place of doubles

3. ) Write a driver (main) that uses the file from question 1 & 2 (prototype with extern). The program should
take in the values from command line (./main one two) and prints the area in the driver program (File=main1.cpp).

Hello, I am trying to teach myself C++ and I came across these problems on the Internet. I was able to 1 and 2, but I am not quite sure about how to do 3.

My guess is that you have to make a new program, and in this new program, you put #include <iostream> and #include rectArea.cpp (That's the file of question 1 and 2) and using namespace std;

Am I right?????

Also, the problem said something about extern. What should I do with extern prototypes????

If this is the case, what do you do after using namespace std;?



Here's what I have so far

  #include <iostream>
using namespace std;

double rectArea(double, double);
int rectArea(int, int);

int main ()
{
	double length;
	double width;
	
	cout << "What is the length of the rectangle? " << endl;
	cin >> length;

	cout << "What is the width of the retangle? " << endl;
	cin >> width;

	rectArea(length, width);

	return 0;
}

double rectArea(double l, double w)
{
	double area;
	area = l * w; 
	return area;
}

int rectArea(int l, int w)
{
	int area;
	area = l * w;
	return area;
}

[TwilightSpectre]

I assume you write a file that contains just the rectArea functions, and then another file that contains just a main function. However, in the other file, you declare the other functions, using function prototypes (like in lines 4-5 of your program). I don't know what it means by extern, extern is only used for global variables...

[jshm415]

So I need to write a file that has the double rectArea and int rectArea function. Then, in the other file, you would call these two functions by #include rectArea.cpp and have function prototypes + main function. Am I right?

Also, how can I print the area? I thought by returning the area, it would automatically return the value

[TwilightSpectre]

No, do not include rectArea.cpp. You just have your compiler both files, and the linker will do the work. So, for example (with GCC), you would compile like this:

g++ -Wall -Wextra -pedantic-errors -c -o rectArea.o rectArea.cpp
g++ -Wall -Wextra -pedantic-errors -c -o main1.o main1.cpp
g++ -o main main1.o rectArea.o