function b = Qadjb(W,b)
% QADJ computes the product Q*b (adjoint of Q  times b)
%
% see also: HOUSEHOLDER
%
% tire de: LN Trefethen & D Bau III, Numerical Linear Algebra, 1997 SIAM Philadelphia

[m,n]=size(W);

for k=1:n
    b(k:m)=b(k:m)-2*W(k:m,k)*W(k:m,k)'*b(k:m);
end
