You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: reorth.m
    path of file: ./repos/lrslibrary/algorithms/mc/SVP/private
    
    the code of the file until where you have to start completion: function [r,normr,nre,s] = reorth(Q,r,normr,index,alpha,method)

%REORTH   Reorthogonalize a vector using iterated Gram-Schmidt
%
%   [R_NEW,NORMR_NEW,NRE] = reorth(Q,R,NORMR,INDEX,ALPHA,METHOD)
%   reorthogonalizes R against the subset of columns of Q given by INDEX. 
%   If INDEX==[] then R is reorthogonalized all columns of Q.
%   If the result R_NEW has a small norm, i.e. if norm(R_NEW) < ALPHA*NORMR,
%   then a second reorthogonalization is performed. If the norm of R_NEW
%   is once more decreased by  more than a factor of ALPHA then R is 
%   numerically in span(Q(:,INDEX)) and a zero-vector is returned for R_NEW.
%
%   If method==0 then iterated modified Gram-Schmidt is used.
%   If method==1 then iterated classical Gram-Schmidt is used.
%

    
function [r,normr,nre,s] = reorth(Q,r,normr,index,alpha,method)

%REORTH   Reorthogonalize a vector using iterated Gram-Schmidt
%
%   [R_NEW,NORMR_NEW,NRE] = reorth(Q,R,NORMR,INDEX,ALPHA,METHOD)
%   reorthogonalizes R against the subset of columns of Q given by INDEX. 
%   If INDEX==[] then R is reorthogonalized all columns of Q.
%   If the result R_NEW has a small norm, i.e. if norm(R_NEW) < ALPHA*NORMR,
%   then a second reorthogonalization is performed. If the norm of R_NEW
%   is once more decreased by  more than a factor of ALPHA then R is 
%   numerically in span(Q(:,INDEX)) and a zero-vector is returned for R_NEW.
%
%   If method==0 then iterated modified Gram-Schmidt is used.
%   If method==1 then iterated classical Gram-Schmidt is used.
%
%   The default value for ALPHA is 0.5. 
%   NRE is the number of reorthogonalizations performed (1 or 2).

% References: 
%  Aake Bjorck, "Numerical Methods for Least Squares Problems",
%  SIAM, Philadelphia, 1996, pp. 68-69.
%
%  J.~W. Daniel, W.~B. Gragg, L. Kaufman and G.~W. Stewart, 
%  ``Reorthogonalization and Stable Algorithms Updating the
%  Gram-Schmidt QR Factorization'', Math. Comp.,  30 (1976), no.
%  136, pp. 772-795.
%
%  B. N. Parlett, ``The Symmetric Eigenvalue Problem'', 
%  Prentice-Hall, Englewood Cliffs, NJ, 1980. pp. 105-109

%  Rasmus Munk Larsen, DAIMI, 1998.

% Check input arguments.
warning('PROPACK:NotUsingMex','Using slow matlab code for reorth.')
if nargin<2
  error('Not enough input arguments.')
end