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115: Mainline

Still another virtue of procedure abstraction is that you easily can augment repetitive computations. For example, you have seen doubling_time defined this way:

double doubling_time (double r) { 
  return 72.0 / r; } 

You can easily decide to add a line to doubling_time that displays the doubling time:

double doubling_time (double r) { 
  printf ("The doubling time for rate %f is approximately %f years.\n", 
                                      r,                  72.0 / r); 
  return 72.0 / r; 
} 

Thus, to arrange for display, you do not need even to bother to find all the places where a doubling time is computed; you need only to change the doubling_time function's definition.