Ruby v1.6 Class and Library Reference: <head> <body bgcolor="white">

module Comparable

Relies on:

<=>

Index:

The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning -1, 0, or +1 depending on whether the receiver is less than, equal to, or greater than the other object. Comparable uses <=> to implement the conventional comparison operators (<, <=, ==, >=, and >) and the method between?.

class SizeMatters

  include Comparable

  attr :str

  def <=>(anOther)

    str.size <=> anOther.str.size

  end

  def initialize(str)

    @str = str

  end

  def inspect

    @str

  end

end

s1 = SizeMatters.new("Z")

s2 = SizeMatters.new("YY")

s3 = SizeMatters.new("XXX")

s4 = SizeMatters.new("WWWW")

s5 = SizeMatters.new("VVVVV")

s1 < s2 -> true

s4.between?(s1, s3) -> false

s4.between?(s3, s5) -> true

[ s3, s2, s5, s4, s1 ].sort -> [Z, YY, XXX, WWWW, VVVVV]

instance methods

Comparisons anObject < otherObject -> true or false
anObject <= otherObject -> true or false
anObject == otherObject -> true or false
anObject >= otherObject -> true or false
anObject > otherObject -> true or false

Compares two objects based on the receiver's <=> method.

between? anObject.between?( min, max ) -> true or false

Returns false if anObject <=> min is less than zero or if anObject <=> max is greater than zero, true otherwise.

3.between?(1, 5) -> true

6.between?(1, 5) -> false

'cat'.between?('ant', 'dog') -> true

'gnu'.between?('ant', 'dog') -> false

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2000 Addison Wesley Longman, Inc. Released under the terms of the Open Publication License V1.0.
This reference is available for download.