Programming Ruby
The Pragmatic Programmer's Guide
module Comparable
Relies on:
<=>
Index:
Comparisons
between?
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
サ
true
s4.between?(s1, s3)
サ
false
s4.between?(s3, s5)
サ
true
[ s3, s2, s5, s4, s1 ].sort
サ
[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)
サ
true
6.between?(1, 5)
サ
false
'cat'.between?('ant', 'dog')
サ
true
'gnu'.between?('ant', 'dog')
サ
false
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/)).
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.