Thread: Using STRUCT and FUNCTION

Originally Posted by noobkiddo

Code:

#include <iostream>

using namespace std;

struct Carpet
{
    float lengthInFeet, widthInFeet;
};

float displayArea(float length, float width)
{
	float area;
	area = length * width; //need to access lengthInFeet and widthInFeet from Carpet object.
	return area;
}

int main()
{
	float length, width; //length and width are floats
	cout << "Enter length: ";
	cin >> length;
	cout << "Enter width: ";
	cin >> width;
	cout << "The square feet of carpet is: " <<displayArea <<endl;
}

is this correct?

Ok, let me put it this way. Struct is a collection of variables. And you can also treat a struct like you treat a variable (mostly). Like Mostly Harmless said, you need to instantiate the struct and then make it as a parameter for your "displayArea()" function.

For the function's definition is correct, however you're using it wrong. You didn't put any parameter at all into the function.

Please re-read the links I gave you until you've understood the basics of functions and structs. And then I'm sure you can solve your problem yourself.

BTW, your main() function is missing a return value.

Ok, I'm gonna help you more. Consider this struct:

Code:

struct employee {
  int id_number;
  char[255] name;
  int age;
  float salary;
};

So an employee is an entity has other entities (or attributes if you will) like an id, name, age, and salary.

And if I want to make an instance of employee named "noobkiddo" and insert the attributes in it, I'll make it like so:

Code:

int main()
{
  struct employee noobkiddo; 

  strcpy(noobkiddo.name, "Noob Kiddo");

  noobkiddo.id_number = 1;
  noobkiddo.age = 18;
  noobkiddo.salary = 10000.00;

  return 0;
}

Now there's an employee instantiated as "noobkiddo" that has an id_number = 1, name = "Noob Kiddo", age = 18, and salary = 10000.00.

For the function, like I said you've defined it right. However, you can't use it like this:

Code:

	cout << "Tdhe square feet of carpet is: " <<displayArea <<endl;

A function needs a parameter(s). Even "function()" actually use a parameter, a NULL one. If you said that you've read it over & over but still can't understand the concept of it, I think you should read more.

If you've understand the concept of

Originally Posted by g4j31a5

Code:

struct employee {
  int id_number;
  char[255] name;
  int age;
  float salary;
};

Surely you mean:

Code:

struct employee
{
     int id_number;
     char name[255];
     int age;
     float salary;
};

Originally Posted by IceDane

Surely you mean:

Code:

struct employee
{
     int id_number;
     char name[255];
     int age;
     float salary;
};

Hahaha... Yeah sorry. My bad. :P

Yes that's how you use a structure.

Here's a generous example.

Code:

// <iostream> inscluded for std::cout
#include <iostream>

// Here we declare a structure, named rectangle
// It has two elements: width and height (floats)
struct rectangle {
	float width;
	float height;
};

// Here we declare our Area function
// It returns a float, and takes a rectangle structure
// as its only argument
float Area(const struct rectangle& rect);

int main(int argc, char* argv[]) {
	// Create a variable, named myrect, of type rectangle
	struct rectangle myrect;
	
	// Initialize the rectangles elements
	myrect.width = 5.62;
	myrect.height = 2.21;
	
	std::cout << "The rectangle's width is " << myrect.width << std::endl;
	std::cout << "The rectangle's height is " << myrect.height << std::endl;
	// Pass the rectangle to the Area() function
	// It will multiply the rectangles width and height together
	// and return the resulting float
	std::cout << "The rectangle's area is " << Area(myrect) << std::endl;
	
	// main returns an integer
	return 0;
}

// Here's the actual implementation of the function defined above	
float Area(const struct rectangle& rect) {
	return (rect.width * rect.height);
}

Note that const struct rectangle& rect might look a little foreign to you. Break it down:

const: constant: the function will not alter the variable.
struct: structure: the variable being passed is a structure.
rectangle: the type of structure (user-defined)
&: by reference: I'll let someone else explain this one.
rect: the name of the variable for use in this specific function (user-defined).