function o = vsum(A)
%
% Implements MATLAB standard function SUM on varying matrices.
% 22/9-1995, Kjetil Havre.
%
   [mt,nr,nc,n] = minfo(A);
   if strcmp( mt, 'syst' ) == 1
       disp( 'Only implemented for varying and constant matrices.' );
       return;      
   end
   
   o = veval('sum',A);
end
