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class Range
Parent: Object
Version: 1.6

Index:

new === begin each end exclude_end? first last length size

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 © 2000 Addison Wesley Longman, Inc. Released under the terms of the Open Publication License V1.0.
This reference is available for download.