function length = circle01_length ( )

%*****************************************************************************80
%
%% circle01_length(): length of the circumference of the unit circle in 2D.
%
%  Licensing:
%
%    This code is distributed under the MIT license. 
%
%  Modified:
%
%    11 January 2014
%
%  Author:
%
%    John Burkardt
%
%  Output:
%
%    real LENGTH, the length.
%
  r = 1.0;
  length = 2.0 * pi * r;

  return
end
