newton's method for computing sqrt

newton.rb

PRECISION = 0.0001

def newtonian_guess( guess,fx,fdx )
  loop do 
    better_guess = guess - ( fx.call( guess ).to_f / fdx.call( guess ).to_f )
    return better_guess if ((better_guess - guess).abs <= PRECISION)
    guess = better_guess
  end
end

def sqrt( num )
  guess = num/2
  return newtonian_guess( guess, lambda {|x| (x**2)-num } ,lambda {|x| 2*x })
end


class Float
  def to_sqrt
    sqrt( self )
  end
end


p 2.0.to_sqrt
# => 1.41421356237469