function eset = new_edges( cluster, graph )
% returns the set of new edges to be added to graph based on cluster
N = length(cluster);
eset = cell(1,N-1); % at most n-1 edges possible given n nodes
j = 1;
for i=1:N,
  thisn = cluster(i);
  others = setdiff( cluster, thisn );
  for o=others,
    if graph(thisn,o) == 1
      %disp(sprintf('already an edge between %d,%d',thisn,o));
      % already an edge
    else
      edge = [thisn, o];
      eset{j} = edge;
      j = j+1;
    end;
  end;
end;
% shrink eset
if j == 1, eset = [];
else
  cset = cell(1,j-1);
  for i=1:j-1,
    cset{i} = eset{i};
  end;
  eset = cset;
end;