function v = GAbvShape(nv,x,y)% GAbvShape(nv,x,y): Set the shape of the bivector for drawing.% If called with no arguments, will return the current shape.% nv may be 'default' (a disk)%           'American'%           'Canadian'%           'Dutch'%        or 'UserDefined'% If nv is 'UserDefined', you should also pass in x and y coordinates%  of the shape you wish to use.%%See also gable.% GABLE, Copyright (c) 1999, University of Amsterdam% Copying, use and development for non-commercial purposes permitted.%          All rights for commercial use reserved; for more information%          contact Leo Dorst (leo@wins.uva.nl).%%          This software is unsupported.persistent t;global GABVX GABVY;  if nargin == 0    if isa(t,'double')      t = 'default';    end  else    t = nv;  end  if nargin==3    GABVX=x;    GABVY=y;  end  v = t;