function outdeck = shuffle(indeck, reps)
%
% shuffle(indeck) performs a GSR-shuffle on the elements of
% the list indeck
%
% shuffle(indeck,reps) does this operation reps times
%

if nargin <=1
	reps = 1;
end;

n = length(indeck);
idx = 1:n;

for k=1:reps
	% get n random numbers in ascending order
	rlist = sort(rand(1,n));
	% perform shift map on each
	rlist = rem(2*rlist,1);	
	% sort the list into ascending order
	[rlist,perm] = sort(rlist);
	% rearrange index list according to that sort
	idx = idx(perm);
end;

% reorder indeck accoring to idx
outdeck = indeck(idx);