Binary search gem

bsearch.gemspec

# -*- encoding: utf-8 -*-
$:.unshift '.'
require 'bsearch'

Gem::Specification.new do |s|
  s.name = 'bsearch-ruby'
  s.version = BSearch::VERSION

  s.authors = ["Aaron Suggs"]
  s.description = "A binary search implementation in ruby"
  s.email = "aaron@ktheory.com"

  s.files = ['bsearch.rb']
  s.require_path = '.'
  s.homepage = 'https://gist.github.com/3219940'
  s.rdoc_options = ["--charset=UTF-8"]
  s.summary = %q{Binary search}
  s.test_files = ['test_bsearch.rb']

  s.required_ruby_version = '>= 1.9.3' # Maybe less?
end

bsearch.rb

# Binary search algorithm
module BSearch
  VERSION = '0.1.1'

  # Assume's haystack is an array of comparable objects
  def self.bsearch(needle, haystack, first=0, last=nil)
    last ||= haystack.size - 1
    return nil if last < first # not found, or empty haystack

    cur = first + (last - first)/2
    case needle <=> haystack[cur]
    when -1 # needle is smaller than cur value
      bsearch(needle, haystack, first, cur-1)
    when 1 # needle is larger than cur value
      bsearch(needle, haystack, cur+1, last)
    when 0
      cur
    end
  end
end

test_bsearch.rb

require 'test/unit'
require_relative 'bsearch'

class BSearchTest < Test::Unit::TestCase

  def test_bsearch_results
    ary = (0..9).to_a
    ary.each do |i|
      assert_equal i, BSearch.bsearch(i, ary)
    end
  end

  def test_empty_haystack
    assert_nil BSearch.bsearch(0, [])
  end

  def test_not_found
    needles = [1,3,5,7]
    haystack = [2,4,6]
    needles.each{|n| assert_nil BSearch.bsearch(n, haystack) }
  end
end