chainable_compare

This provides a module which you can mix into any class to get chainable compare properties:

class String
  include ChainablyComparable
end

def pick_line(name)
  if "A" < name < "M"
    "Line a"
  else
    "Line b"
  end
end

puts pick_line("Yehuda")
puts pick_line("Evan")

This works by overriding the <, >, <=, and >= operators on the class in question, as well as in FalseClass. I probably wouldn't override built-in classes this way without thinking pretty hard about the consequences.

This works if you don't need to define your own comparison methods (i.e. your class inherits from a superclass that defines them). Otherwise, you can define <=> as usual:

class Version
  include ChainablyComparable

  attr_accessor :version

  def initialize(version)
    @version = version.split(".").map {|segment| segment.to_i }
  end

  def <=>(other)
    a, b = normalize(@version, other.version)
    a <=> b
  end

private
  def normalize(a, b)
    if a.size > b.size
      [a.dup, b.dup.fill(0, a.size - 1, a.size - b.size)]
    else
      [a.dup.fill(0, b.size - 1, b.size - a.size), b.dup]
    end
  end
end

version = Version.new("2.0")
Version.new("1.0.0") < version < Version.new("3")