# Approminately equals returns true when values are close enough, within some
# distance epsilon above or below the given value.

# Adds the approximately equals operation to Numeric and its progeny.
class Numeric
  
  # The initial default distance from a Numeric below which it is considered
  # to be approximately equal to a another Numeric.
  @@epsilon = 0.0000000001
  
  # The default distance from a Numeric below which it is considered to be
  # approximately equal to a another Numeric.
  def Numeric.epsilon
    @@epsilon
  end
  
  # Sets the default distance for approximately equals comparisons.
  def Numeric.epsilon=(epsilon)
    @@epsilon = epsilon.abs
  end

  # returns true if the difference between the instance and the given Numeric
  # is less than the given distance.
  def approximately_equals?(value,epsilon=@@epsilon)
    (self - value).abs < epsilon
  end
  
  alias =~ approximately_equals?
  
end