gistfile1.txt

require 'benchmark'
require 'andand'

class Hash
  def except(*blacklist)
    {}.tap do |h|
      (keys - blacklist).each { |k| h[k] = self[k] }
    end
  end

  def except2(*blacklist)
    self.reject { |k, v| blacklist.include? k }
  end

  def only(*whitelist)
    {}.tap do |h|
      (keys & whitelist).each { |k| h[k] = self[k] }
    end
  end

  def only2(*whitelist)
    self.reject { |k, v| !whitelist.include? k }
  end
end

h = {}
1000000.times do |i|
  h[i] = i
end

a = (10..10000).to_a

puts Benchmark.measure {
  h.only *a
  h.except *a
}

puts Benchmark.measure {
  h.only2 *a
  h.except2 *a
}