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.
<=> to implement the conventional comparison operators (
>) and the method
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 → true s4.between?(s1, s3) → false s4.between?(s3, s5) → true [ s3, s2, s5, s4, s1 ].sort → [Z, YY, XXX, WWWW, VVVVV]
<=>min is less than zero or if anObject
<=>max is greater than zero,
3.between?(1, 5) → true 6.between?(1, 5) → false 'cat'.between?('ant', 'dog') → true 'gnu'.between?('ant', 'dog') → false
Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
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