Programmering i Ruby

Den Pragmatiske Programmerers Veiledning
Forrige < Innhold ^
Neste >
klassen Range
Forelder: Object
Versjon: 1.6

Indeks:

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

klassemetoder
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.

instansmetoder
=== 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 .

Forrige < Innhold ^
Neste >

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide".
Translation to norwegian by Norway Ruby User Group.
Copyright for the english original authored by David Thomas and Andrew Hunt:
Copyright © 2001 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/).

(Please note that the license for the original has changed from the above. The above is the license of the original version that was used as a foundation for the translation efforts.)

Copyright for the norwegian translation:
Copyright © 2002 Norway Ruby User Group.
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/).
Distribution of substantively modified versions of this document is prohibited without the explicit permission of the copyright holder.
Distribution of the work or derivative of the work in any standard (paper) book form is prohibited unless prior permission is obtained from the copyright holder.