Array hacks

class Array
 
  # order the elements of this array by the values of the specified attribute of
  # each element
  #
  def sort_by_attribute! atb
 
    sort! {|a,b| a.send(atb) <=> b.send(atb)}
  end
 
 
  # provides the first element of this array for which the block provides "true"
  #
  def first_where
 
    each do |element|
 
      return element if yield element
    end
 
    nil
  end
 
 
  def index_of_first_where
 
    each_with_index do |element,i|
 
      return i if yield element
    end
  end
 
end