// Lab 9 Lecture

// comment the examples and run individually or several at once
// by commenting out the indicated sections of code. 
// (Eclipse: ctrl+/ to comment and uncomment)
// (Code Blocks: ctrl+shift+C to comment and ctrl+shift+x to uncomment)


// ---------------------------- Intro to Functions -----------------------------

//// This is a hello world program that uses a function.
//// hello_world function will print "Hello World" when called.
//
//// Note that 'main' is also a function. You have been using functions
//// all along and may not have even realized it.
//
//// this is the syntax for a function definition (with no parameters).
//// type name () 
//// { 
//// 	statements 
//// }
//
//// Where will this program start? At hello_world or main?
//
//#include <iostream>
//using namespace std;
//
//// this is a function definition
//void hello_world ()
//{
//	cout << "Hello World";
//}
//
//int main()
//{
//	// this is a function call
//	hello_world();
//
//	return 0;
//}


// --------------------------- Function Prototype -----------------------------

//// This program is the same other than it uses a prototype. A prototype
//// lets the compiler know that the function definition can be found
//// after when it is first called for.
//
//// Remember, the compiler goes through your program sequentially, so if it
//// comes to a function call but has not found the definition yet it will
//// get confused. The prototype simply lets the compiler know it will be
//// defined later.
//
//
//#include <iostream>
//using namespace std;
//
//// this is a prototype. Make sure to note the semicolon at the end.
//// type name ( parameter1, parameter2, ...) ;
//void hello_world();
//
//int main()
//{
//	// Function call
//	hello_world();
//
//	return 0;
//}
//
//// Function definition
//void hello_world ()
//{
//	cout << "Hello World";
//}


// ---------------------------- Function Returns ------------------------------

//// C++ Syntax requires that the declaration of a program begins with a type.
//// This is the data type that is returned by the function. If the function
//// does not need to return a value 'void' can be used to indicate that the
//// function will not return anything.
//
//// Note that main has an 'int' type, while our hello_world functions have
//// a 'void' type. At the end of our main function we have 'return 0'. This
//// means that when our main function ends, it will return the value '0' to
//// the function that called it. Our hello_world function has no 'return'
//// because its type is void.
//
//// Here are several more examples of functions with different return types 
//// and how they return values.
//
//#include <iostream>
//using namespace std;
//
//// prototypes
//int int_func();
//double double_func();
//bool bool_func();
//void void_func();
//
//int main()
//{
//	cout << "At top of main. calling functions: " << endl;
//
//	int i;
//	double d;
//	bool b;
//
//	// the value that is returned can be stored in a variable or used as a literal
//	i = int_func();
//	d = double_func();
//	b = bool_func();
//
//	// Why will you get an error if you uncomment this code?
////	int v = void_func();
//
//	void_func();
//
//	cout << "At bottom of main:" << endl;
//	cout << "i is : " << i << "  d is : " << d << "  b is : " << b << endl;
//
//	return 0;
//}
//
//// int_func definition
//int int_func()
//{
//	cout << "Inside int_func, will return value of 100"<< endl;
//	return 100;
//}
//
//// double_func definition
//double double_func()
//{
//	cout << "Inside double_func, will return value of 2.414"<< endl;
//	return 2.414;
//}
//
//// bool_func definition
//bool bool_func()
//{
//	cout << "inside bool_func, will return 'true'"<< endl;
//	return true;
//}
//
//void void_func()
//{
//	cout << "inside void_func, will not return anything" << endl;
//	// you can use a return with no value, or nothing at all.
//	return;
//}


// ---------------------------- Functions Example -----------------------------

//
//#include <iostream>
//using namespace std;
//
//// prototypes
//int get_sum ();
//
//int main()
//{
//	int sum;
//
//	sum = get_sum();
//
//	cout << "sum is :" << sum;
//	return 0;
//}
//
//// get_sum function takes 2 numbers from a user and returns the sum
//int get_sum ()
//{
//	// Note that we need to declare variables inside the function
//	// because variables in main do not exist here. We will learn
//	// more about this in the later lessons.
//	int num1, num2, total;
//
//	cout << "enter two numbers to be added" << endl;
//	cin >> num1 >> num2;
//
//	total = num1 + num2;
//
//	return total;
//}