   function [c, s] = givensRot(A,i,j,col)
%% function [c, s] = givensRot(A,i,j,col)
%% givens rotation G=G(i,j,t) such that
%% [G A](j,col) == 0
%% Note: in complex case matrix G takes the form
%%       | c    s̄ |
%%   G = |        |   where c = real - see code
%%       |-s    c |
%%  
   c = A(i,col) ;
   s = A(j,col) ;
   t = norm([c;s]); 
   if (t == 0.0)
     c = 1.0;
     s = 0.0;
   else
     s = s*sign(conj(c))/t;
     c = abs(c)/t;
   end
