Is there some reason the following methods on Array aren't included as 
standard?

class Array
  def and?
    # return true if the provided block returns true for every element
    each {|x| return false unless yield x} if block_given?
    return true
  end
  def or?
    # return true if the provided block returns true for at least one 
element
    each {|x| return true if yield x} if block_given?
    return false
  end
end

I find these to be very useful, and was suprised to not see them.  Is 
there another way to get the same effect (including short circuit of 
evaluation as soon as a condition fails)?