A standard way of formatting numbers is to present them with commas (or some other delimiter) separating each group of thousands. Our next script does that by adding a method called
commify to all numbers. You might think that we could do this by opening the Integer class and adding a new method to it, as we did in
power_of.rb. This is certainly a reasonable approach, except that we may want to use
commify on floating-point numbers as well. What’s the solution?
The answer deals with an object-oriented concept called inheritance. We discussed this earlier in Chapter 3 when we added methods to the Object class. Inheritance is what allows all other classes to use methods of the Object class, because ...