function  [ c, seed ] = c4_uniform_01 ( seed )

%% C4_UNIFORM_01 returns a unit pseudorandom C4.
%
%  Discussion:
%
%    The angle should be uniformly distributed between 0 and 2 * PI,
%    the square root of the radius uniformly distributed between 0 and 1.
%
%    This results in a uniform distribution of values in the unit circle.
%
%  Modified:
%
%    21 September 2006
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer SEED, a seed for the random number generator.
%
%    Output, complex C, the pseudorandom complex value.
%
%    Output, integer SEED, a seed for the random number generator.
%
  if ( seed == 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'C4_UNIFORM_01 - Fatal error!\n' );
    fprintf ( 1, '  Input SEED = 0!\n' );
    error ( 'C4_UNIFORM_01 - Fatal error!' );
  end

  k = floor ( seed / 127773 );

  seed = 16807 * ( seed - k * 127773 ) - k * 2836;

  if ( seed < 0 )
    seed = seed + 2147483647;
  end

  r = sqrt ( seed * 4.656612875E-10 );

  k = floor ( seed / 127773 );

  seed = 16807 * ( seed - k * 127773 ) - k * 2836;

  if ( seed < 0 )
    seed = seed + 2147483647;
  end

  theta = 2.0 * pi * seed * 4.656612875E-10;

  c = r * ( cos ( theta ) + i * sin ( theta ) );