computation of conformal maps to polygonally bounded regions

				function Md = diff(M)
				%DIFF   Differentiated SC map object.
				%   DIFF(M) returns an object formally representing the derivative of
				%   the map M.
				
				%   Copyright 1998 by Toby Driscoll.
				%   $Id: diff.m 7 1998-05-10 04:37:19Z tad $
				
				Md = scmapdiff(M);