From: Pete Hodgson <phodgson@...>
Date: 2008-11-07T02:39:28+09:00
Subject: Finding gaps in a sorted sequence

Hi Folks,

Given a sorted enumeration I need to find the first gap in a sequence.

e.g.
3 == find_gap [1,2,4,5]
nil == find_gap [1,2,3,4]

Here's the best I can come up with

def first_gap( seq )
  seq.each_cons(2) do |l,r|
    _next = l.next
    return _next if r!= _next
  end
  nil
end

but it seems rather ugly. Anyone have a more elegant implementation?

Cheers,
Pete