class Range < Object

A Range represents an interval—a set of values with a start and an end. Ranges may be constructed using the s..e and s...e literals, or with Range.new. Ranges constructed using .. run from the start to the end inclusively. Those created using ... exclude the end value. When used as an iterator, ranges return each value in the sequence.

(-1..-5).to_a → []
(-5..-1).to_a → [-5, -4, -3, -2, -1]
('a'..'e').to_a → ["a", "b", "c", "d", "e"]
('a'...'e').to_a → ["a", "b", "c", "d"]

Ranges can be constructed using objects of any type, as long as the objects can be compared using their <=> operator and they support the succ method to return the next object in sequence.

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)
    raise TypeError unless other.kind_of? Xs
    @length <=> other.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

mixins

Enumerable: collect, detect, each_with_index, entries, find, find_all, grep, include?, map, max, member?, min, reject, select, sort, to_a

class methods

new: Range.new( start, end, exclusive=false ) → aRange; Constructs a range using the given start and end. If the third parameter is omitted or is false, the range will include the end object; otherwise, it will be excluded.

instance methods

===: rng === anObject → true or false; Returns true if anObject is an element of rng, false otherwise. Conveniently, === is the comparison operator used by case statements.
case 79 when 1..50 then print "low\n" when 51..75 then print "medium\n" when 76..100 then print "high\n" end

produces:

high
begin: rng.begin → anObject; Returns the first object of rng.
each: rng.each {| i | block } → rng; Iterates over the elements rng, passing each in turn to the block.
(10..15).each do |n| print n, ' ' end

produces:

10 11 12 13 14 15
end: rng.end → anObject; Returns the object that defines the end of rng. See also Range#length.
(1..10).end → 10 (1...10).end → 10
exclude_end?: rng.exclude_end? → true or false; Returns true if rng excludes its end value.
first: rng.first → anObject; Returns the first object in rng.
last: rng.last → anObject; Synonym for Range#end.
length: rng.length → anInteger; Returns the number of objects in rng.
(1..10).length → 10 (1...10).length → 9
size: rng.size → anInteger; Synonym for Range#length.

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"

Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/).

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