symbols_and_ranges/range_cover_and_include.rb

tests/_examples/symbols_and_ranges/range_cover_and_include.rb in the metorex repository.

# `cover?` with a Range asks whether every value of it falls inside.
p (0..10).cover?(4...11)
p (0...10).cover?(4..10)
p (0..).cover?(4..)
p (nil...nil).cover?(4..)
p (0..10).cover?(5..3)
p (0..).cover?(4..6)
# A range ending on a Float it leaves out names no largest value.
p (0..10).cover?(4.0...11.0)
# `===` with a Range compares the Range itself, which no Integer range holds.
p (1..10) === (2..3)

# `include?` compares against the ends for numbers, walks a String range as
# `upto` does, and cannot decide for a range missing an end.
p ("a".."ab").include?("b")
p ("a".."ab").include?("ac")
p (nil..nil).include?(5)
p ("a".."ab").include?(nil)
p ("a".."ab").include?(Object.new)
spelled = Object.new
def spelled.to_str
  "b"
end
p ("a".."ab").include?(spelled)
wrong = Object.new
def wrong.to_str
  1
end
begin
  ("a".."ab").include?(wrong)
rescue TypeError => problem
  p problem.message
end
p (Rational(1, 2)..Rational(5, 2)).include?(2)
p (:aa..:ac).to_a
# A range of objects with `succ` walks its values to find one.
class Rung
  include Comparable
  attr_reader :height

  def initialize(height)
    @height = height
  end

  def succ
    Rung.new(height + 2)
  end

  def <=>(other)
    height <=> other.height
  end
end
p (Rung.new(0)..Rung.new(6)).include?(Rung.new(4))
p (Rung.new(0)..Rung.new(6)).include?(Rung.new(3))
[("aa"..), (.."aa")].each do |range|
  begin
    range.include?("a")
  rescue TypeError => problem
    p problem.message
  end
end

# `step` refuses to walk from a missing beginning.
begin
  (..10).step(1) { break }
rescue ArgumentError => problem
  p problem.message
end
begin
  (..10).step("a")
rescue ArgumentError => problem
  p problem.message
end

Output:

true
false
true
false
false
true
false
false
true
false
true
false
false
true
"can't convert Object to String (Object#to_str gives Integer)"
true
[:aa, :ab, :ac]
true
false
"cannot determine inclusion in beginless/endless ranges"
"cannot determine inclusion in beginless/endless ranges"
"#step iteration for beginless ranges is meaningless"
"#step for non-numeric beginless ranges is meaningless"