function x1 = xtstep(XX,q,ord)
%
%  Validated evaluation of one step with the Taylor method.
%
%  input:
% 	XX(N,4,ord+1)	(intval) Taylor coefficients of solution
% 	q		stepsize correction factor
% 	ord		order of Taylor expansion
%
%  output:
% 	x1(N,4)		(intval) solution
%

N=size(XX,1);
if isintval(q),
  qq=cumpotenz(q,ord);
else
  qq=q.^(0:ord)';
end
XX=reshape(XX,N*4,ord+1);
x1=reshape(XX*qq,N,4);

return

%
% written   Sept/10/02   D.Stoffer
%



