From: Clifford Heath <no@...>
Date: 2008-02-15T14:59:55+09:00
Subject: Cute open range?

So I wanted to allow folk using my DSL to say "0..N",
"1..N", etc, to describe the cardinality of a relationship,
and I needed to find a useful way to define N without
making it a fixed integer maximum value.

Well, I came up with this, which I thought was cute:

class N
  def self.coerce(n)
    [ n, n+1 ]    # Anything you can do, I can do better
  end
end

Now when I ask (0..N) === m, for any m, it says "true",
and when I say the following, it never ends:

(0..N).each do |n|
  puts n
end

But more importantly, I can say:

do_something if range.last == N

Ruby is sweeet :-).

Clifford Heath.