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)
@length <=> other.length
end
def to_s
sprintf "%2d #{inspect}", @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
In the previous code example, class Xs includes the Comparable module. This is because Enumerable#member? checks for equality using ==. Including Comparable ensures that the == method is defined in terms of the <=> method implemented in Xs.
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.
Returns true only if obj is a Range, has equivalent beginning and end items (by comparing them with ==), and has the same exclude_end? setting as <i>rng</t>.
(0..2) == (0..2) #=> true (0..2) == Range.new(0,2) #=> true (0..2) == (0...2) #=> false
Returns true if obj 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
Iterates over the elements rng, passing each in turn to the block. You can only iterate if the start object of the range supports the succ method (which means that you can’t iterate over ranges of Float objects).
(10..15).each do |n|
print n, ' '
end
produces:
10 11 12 13 14 15
Returns true only if obj is a Range, has equivalent beginning and end items (by comparing them with eql?), and has the same exclude_end? setting as rng.
(0..2) == (0..2) #=> true (0..2) == Range.new(0,2) #=> true (0..2) == (0...2) #=> false
Generate a hash value such that two ranges with the same start and end points, and the same value for the "exclude end" flag, generate the same hash value.
Returns true if obj 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
Returns true if obj 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
Iterates over rng, passing each nth element to the block. If the range contains numbers or strings, natural ordering is used. Otherwise step invokes succ to iterate through range elements. The following code uses class Xs, which is defined in the class-level documentation.
range = Xs.new(1)..Xs.new(10)
range.step(2) {|x| puts x}
range.step(3) {|x| puts x}
produces:
1 x
3 xxx
5 xxxxx
7 xxxxxxx
9 xxxxxxxxx
1 x
4 xxxx
7 xxxxxxx
10 xxxxxxxxxx