function A=area_ellipse(a, b)
% area_ellipse computes the area of an ellipse.
% Arguments a and b correspond to half the
% short and long axes.
% If only one argument is passed, then a and b
% are assumed to be equal to that argument,
% and effectively the area of a circle is
% computed.

error(nargchk(1, 2, nargin))

if (nargin == 1)
  b=a;
end

if ((a < 0) || (b < 0))
  A=0;
else
  A=pi*a*b;
end