rubylazy-evaluationenumerable

How to create an infinite enumerable of Times?

I want to be able to have an object extend Enumerable in Ruby to be an infinite list of Mondays (for example).

So it would yield: March 29, April 5, April 12...... etc

How can I implement this in Ruby?

Solution

  • In 1.9 (and probably previous versions using backports), you can easily create enumerator:

    require 'date'

def ndays_from(from, step=7)
  Enumerator.new {|y|
    loop {
      y.yield from
      from += step
    }
  }
end

e = ndays_from(Date.today)
p e.take(5)
#=> [#<Date: 2010-03-25 (4910561/2,0,2299161)>, #<Date: 2010-04-01 (4910575/2,0,2299161)>, #<Date: 2010-04-08 (4910589/2,0,2299161)>, #<Date: 2010-04-15 (4910603/2,0,2299161)>, #<Date: 2010-04-22 (4910617/2,0,2299161)>]