Question

I’d like to create a subclass of Range in order to specify a step size other than 1 so I can do things like:

>> a = RangeWithStepSize.new(-1, 2, 0.5).each {|x| puts(x)}
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
=> -1..2

My first attempt at an implementation doesn’t work:

 class RangeWithStepSize < Range

  attr_reader :step_size

  def initialize(start_v, end_v, step_size, exclusive = false)
    super(start_v, end_v, exclusive)
    @step_size = step_size
  end

  def each
    self.step(step_size).each
  end

end

>> a = RangeWithStepSize.new(-1, 2, 0.5).each {|x| puts(x)}
=> #<Enumerator: [-1.0, -0.5, 0.0, 0.5, 1.0, 1.5, 2.0]:each>

It appears that RangeWithStepSize#each is returning a valid enumerator, but it doesn’t enumerate. Any idea why?

<aside>This may be related, but I notice is that Range#step without a block does NOT return an enumerator as specified in the documentation; it returns an array instead:

>> Range.new(-1, 2).step(0.5).class
=> Array

An Array is enumerable, but it is not an Enumerator. Is this a documentation bug?</aside>

clarification

I’d like to make a version of Range that encapsulates a step size, so I can do:

a = RangeWithStepSize(-1, 2, 0.5)
b = RangeWithStepSize(-1, 2, 0.25)

… so enumerating on a produces a step size of 0.5 and b produces 0.25.

Answer 1

You know you can do this, right? Inheritance isn’t necessary here.

(-1..2).step(0.5) do |x|
    puts x
end

Your code will work with a few small adjustments:

class RangeWithStepSize < Range

  attr_reader :step_size

  def initialize(start_v, end_v, step_size, exclusive = false)
    super(start_v, end_v, exclusive)
    @step_size = step_size
  end

  def each (&block)
    self.step(step_size).each(&block)
  end

end