From: Robert Dober <robert.dober@...>
Date: 2007-06-07T20:29:46+09:00
Subject: Re: What about a 'series' type?

On 6/7/07, Peter Marsh <evil_grunger@hotmail.com> wrote:

Honestly I do not believe that the core is the place to put such
things, furthermore I believe it is too specific a feature, a more
general approach might have better chances to be fit for the core; Yet
I do not think what follows is fit for the core either, but maybe you
find it interesting or helpful:

class Lazy
  def initialize init, op, *args
    @init = init
    @op   = op
    @args = args.dup
  end

  def upto value
    return [] if value < 1
    (2..value).inject([@init]){ |acc,| acc << acc.last.send( @op, *@args ) }
  end
end # class Lazy

505/6 > irb -r lazy.rb
irb(main):001:0> l = Lazy.new 1, :+, 2
=> #<Lazy:0xb7ddfa60 @args=[2], @init=1, @op=:+>
irb(main):002:0> l.upto 5
=> [1, 3, 5, 7, 9]
irb(main):003:0> m = Lazy.new 2, :*, 3
=> #<Lazy:0xb7dd4908 @args=[3], @init=2, @op=:*>
irb(main):004:0> m.upto 4
=> [2, 6, 18, 54]
irb(main):005:0>

Cheers
Robert

P.S. Implementations without #inject are theoretically possible ;)
R.
-- 
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw