Question regarding ranges

[Xavius]

I'm in the process of trying to understand how to generate ranges, and I'm having trouble understanding what each method does within the following class (Source):

class Xs                # represent a string of 'x's
     include Comparable
     attr :length
     def initialize(n)
       @length = n
     end
     def succ
       Xs.new(@length + 1)
     end
     def <=>(other)
       @length <=> other.length
     end
     def to_s
       sprintf "%2d #{inspect}", @length
     end
     def inspect
       'x' * @length
     end
   end
 
   r = Xs.new(3)..Xs.new(6)   #=> xxx..xxxxxx
   r.to_a                     #=> [xxx, xxxx, xxxxx, xxxxxx]
   r.member?(Xs.new(5))       #=> true

The two I'm having particular trouble understanding are the succ & inspect methods.

[ruby-lang]

I don't know how familiar with Ruby you are, but the first thing to remember is that methods don't need an explicit return statement. They naturally return the value of the last statement executed. That means that:

• succ will return the "next" X in the sequence. It instantiates a new X object with a @length value equal to the current @length plus one. The succ method is the ++ operator of Ruby (with the difference that it returns a new object, instead of incrementing the original)
• inspect will return a string formed by "x", repeated @length times. If you check the documentation for String, you'll see the * (multiplication) method overriden there. The inspect method is used by the debugger (and when you print an object with p, that's the method it calls)

[Xavius]

I guess what I'm having trouble understanding is how succ does its thing without being explicitly called. I understand that initialize is automatically called upon during the formation of a new instance of a class (in this case Xs); is the same true for succ?

[stereofrog]

succ is called implicitly by the Range.to_a method

[Xavius]

Great Thanks guys!