function [a]=rfrot(a,alph,bet,%type)
// Copyright (C) 2001 Michel Juillard
// 
// apply fast Givens rotation to a pair of rows
// 
if %type==1 then
  tau = bet*a(1,:)+a(2,:);
  a(2,:) = a(1,:)+alph*a(2,:);
  a(1,:) = tau;
else
  tau = a(1,:)+bet*a(2,:);
  a(2,:) = alph*a(1,:)+a(2,:);
  a(1,:) = tau;
end