title: why is this factorial recursive function inefficient?
body: <p>In the book "Think like a programmer", the following recursive function is said to be "highly inefficient" and I can't figure out why (the book does not explain). It doesn't seem like there are any unnecessary calculations being done. Is it because of the overhead of calling so many functions (well the same function multiple times) and thus setting up environments for each call to the function?</p>
  
  <pre><code>int factorial(int n) {
    if (n == 1) return 1;
    else return n * factorial(n-1);
  }
  </code></pre>