Getting started – our sample library

This chapter's example code has two pieces: a library that defines a public function and a console application that calls this function. Libraries are a great way to break up your applications, and while this example is simple, it also lets me show you how to create a library and include it in your application.

I'm going to stretch your imagination a bit; let's pretend that you're responsible for setting up a library of math functions. In this example, we'll only write one function, factorial. You should be able to recollect the factorial function from introductory programming; it's represented by a ! and is defined as follows:

• 0! is 0

• 1! is 1

• n! is n × (n - 1)!

This is a recursive definition and we can code it in the following way:

unsigned long factorial(unsigned int n)
{
    switch(n) 
    {
        case 0: return 0;
        case 1: return 1;
        default: return n * factorial(n-1);
    }
}

An alternate definition that avoids the cost of function calls...