#ece244

Function prototype: the return type of the function, plus the function name and input arguments

function that calculates the factorial of a number

// c++ program that calculates the factorial of a number

#include <iostream>
using namespace std;

int factorial(int n) {
	int fact = 1;
	for (int i = 1; i <= n; i++) {
		fact *= i;
	}
	return fact;
}

int main(void) {
	int num = 4;
	cout << "num: " << num << ", factorial value: " << factorial(num) << endl;
	return 0;
}

Pass-by-value: the arguments that you pass into a function when calling it.

swapping two variables locally within a function

// function that swaps two variables, but only in the function, not in main

#include <iostream>
using namespace std;

void swap(int x, int y) {
	int temp = x;
	x = y;
	y = temp;
	cout << "swapped values: x = " << x << ", y = " << y << endl;
}

int main(void) {
	int x = 7, y = 13;
	swap(x,y);
	return 0;
}

pointers

same as in C; variable that holds the location (address in memory) of another variable.

• uses data type int*
• when creating a pointer, you can use &pointer_name to get the address
• *pointer_name is dereferences the pointer, which returns the value at that address
  e.g. px = &x; creates pointer pointing to address of variable x

pass-by-pointers

pass addresses of variables to functions so that they can affect variables globally.

function that swaps the values of variables globally

#include <iostream>
using namespace std;

void swap(int* px, int* py) {
	int temp = *px;
	*px = *py;
	*py = temp;
}

int main(void) {
	int x = 7, y = 13;
	swap (&x, &y);
	cout << "swapped: x = " << x << ", y = " << y << endl;
}

pass-by-reference

Pass-by-reference will make the same program less complex!
A reference is an alias, an alternate name, to a variable

int a = 7;
int &ra = a; (reference to an integer a)

• Does NOT create any special space in memory, it's JUST a reference, same location as the variable it's referencing.
• Also, pass-by-references cannot be reassigned!
• References must be initialized at the time of declaration.

So, we can rewrite the [[#function that swaps the values of variables globally]] so that it's nicer to read.

#include <iostream>
using namespace std;

void swap(int& rx, int& ry) { // something is wrong here i need to debug
	int& temp = rx; // reference to x
	rx = ry;
	ry = temp;
}

int main(void) {
	int x = 7, y = 13;
	int& rx = x, ry = y;
	swap (rx, ry);
	cout << "swapped: x = " << x << ", y = " << y << endl;
}