From: bbiker <renard@...>
Date: 2007-02-21T11:45:09+09:00
Subject: Re: Range#overlap?

On Feb 20, 7:04 pm, dbl...@wobblini.net wrote:
> Hi --
>
>
>
>
>
> On Wed, 21 Feb 2007, Daniel Schierbeck wrote:
> > On Wed, 2007-02-21 at 08:00 +0900, Daniel Finnie wrote:
> >> I think your implementation is cleaner however the endpoints of a Range
> >> do not have to implement #succ.
>
> >> class Range
> >>    def span? other
> >>      include? other.first and
> >>        (other.exclude_end? ? other.last < last : other.last <= last )
> >>    end
> >> end
>
> > I've tried that implementation, but i doesn't work if you consider this
> > valid:
>
> >  (4..8).span? 6...9
>
> > Since 6...9 yields the same values as 6..8. Or am I wrong to expect the
> > above?
>
> I don't think ranges really yield values.  Some of them can be
> converted to arrays, but a range qua range is really just two
> endpoints, between which everything comparable to those endpoints
> either is or isn't.
>
> I'm not sure I have my head around what span? is supposed to be doing.
> Can you write some test cases?  I keep thinking of this:
>
>    include?(other.first) and include?(other.last)
>
> but I don't think that's what you're trying to do with span?.
>
> David
>
> --
> Q. What is THE Ruby book for Rails developers?
> A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
>     (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
> Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
> A. Ruby Power and Light, LLC (http://www.rubypal.com)- Hide quoted text -
>
> - Show quoted text -

Here is my entry for overlap?
<code>
require 'facets/core/range/within'

class Range

  # Uses the Range#within and Range#include methods to determine
  # if another Range _overlap_ this Range.
  # neither Range is within the other Range
  #   (1..3).overlap?(2..4)  #=> true
  #
  def overlap?(other)
    #   |---|      |---|   |-----|  |-----|  |-----|
    #   |-----|   |-----|  |-----|   |---|     |---|
    !self.within?(other) && !other.within?(self) &&
    #  |-------|    |------|
    #   |-------|          |-------|
    (self.include?(other.first) && other.include?(self.last) ||
    #   |-------|          |-------|
    #  |-------|    |------|
     other.include?(self.first) && self.include?(other.last))
  end
end


=begin test

  require 'test/unit'

  class TCRange < Test::Unit::TestCase

    def test_overlap?
      assert(!(3..6).overlap?(3..6) )
      assert(!(4..5).overlap?(3..6) )
      assert(!(2..7).overlap?(3..6) )
      assert( (2..5).overlap?(3..6) )
      assert( (2..3).overlap?(3..6) )
      assert( (7..10).overlap?(6..9) )
      assert( (9..12).overlap?(6..9) )
    end
  end
=end
</code>