Ranges in Ruby
The first and perhaps most natural use of ranges is to express a sequence. Sequences have a start point, an end point, and a way to produce successive values in the sequence. In Ruby, these sequences are created using the ".." and "..." range operators. The two dot form creates an inclusive range, and the three-dot form creates a range that excludes the specified high value. In Ruby ranges are not represented internally as lists: the sequence 1..100000 is held as a Range object containing references to two Fixnum objects. Refer program p021ranges.rb. If you need to, you can convert a range to a list using the to_a method.
Ranges implement methods that let you iterate over them and test their contents in a variety of ways.
Another use of the versatile range is as an interval test: seeing if some value falls within the interval represented by the range. We do this using ===, the case equality operator.
Note: The Ruby Logo is Copyright (c) 2006, Yukihiro Matsumoto. I have made extensive references to information, related to Ruby, available in the public domain (wikis and the blogs, articles of various Ruby Gurus), my acknowledgment and thanks to all of them. Much of the material on rubylearning.com and in the course at rubylearning.org is drawn primarily from the Programming Ruby book, available from The Pragmatic Bookshelf.