function [v,alpha] = House(x)
% x is an n-vector
% v is a unit vector so that if y = (I - 2*v*v')x then y(2:n) = 0
% and y(1) = alpha. Returning alpha makes the implementation of SkewReduce
% a little simpler.
v = x;
if v(1)< 0
alpha = norm(x);
else
alpha = -norm(x);
end
v(1) = v(1)-alpha;
v = v/norm(v);