Class: Range (Ruby 2.5.1)

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A Range represents an interval—a set of values with a beginning 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 beginning 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"]

Custom Objects in Ranges¶ ↑

Ranges can be constructed using any objects that can be compared using the <=> operator. Methods that treat the range as a sequence (each and methods inherited from Enumerable) expect the begin object to implement a succ method to return the next object in sequence. The step and include? methods require the begin object to implement succ or to be numeric.

In the Xs class below both <=> and succ are implemented so Xs can be used to construct ranges. Note that the Comparable module is included so the == method is defined in terms of <=>.

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) @length <=> other.length end def to_s sprintf "%2d #{inspect}", @length end def inspect 'x' * @length end end

An example of using Xs to construct a range:

r = Xs.new(3)..Xs.new(6) #=> xxx..xxxxxx r.to_a #=> [xxx, xxxx, xxxxx, xxxxxx] r.member?(Xs.new(5)) #=> true

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