696: Mainline

To gain a more complete understanding of multiple-file programs, you need to learn how to distribute not only class definitions, but also function prototypes and ordinary function definitions among header files and source-code files.

As an illustration, consider again the three-function version of the rabbit-calculating program introduced in Chapter 23. Recall that the purpose of the program is to calculate the number of rabbits after n months, given one newborn female rabbit at time 0.

The program contains three key functions:

int rabbits (int n) { 
  if (n == 0 || n == 1) 
     return 1; 
   else return previous_month (n) + penultimate_month (n);} 
int previous_month (int n) {return rabbits ((n - 1));} 
int penultimate_month (int n) {return rabbits ((n - 2));}