function shortcut_all(p) =
let pp = p->p;
in if eql(p,pp) then pp else shortcut_all(pp) $

function compress_graph(P,E) =
let 
    % update edges to point to new parent %
    e1,e2 = unzip(e);
    e = {(i,j): i in p->e1; j in p->e2};

    % remove self edges and flip edges up %
    e = {if i > j then (j,i) else (i,j)
	 : (i,j) in e
	 | i /= j};

    % identify roots, relabel roots, and relabel edges %
    roots = {p == i : p in p ; i in [0:#p]};
    labels = enumerate(roots);
    e1,e2 = unzip(e);
    e =   {(li,lj): li in labels->e1; lj in labels->e2}

in (e,pack_index(roots)) $

function hybrid_connected_components(E,n) =
if #E == 0 then [0:n]
else
  let P = shortcut_all([0:n]<-E);
      (E,I) = compress_graph(P,E);
      R = hybrid_connected_components(E,#I);
      Ins = P <- zip(I, I->R);
  in Ins->Ins $

edges = [(1, 5), (5, 6), (1, 6), (6, 10), (4, 5), (13, 4), 
         (2, 13), (2, 11), (9, 2), (12, 9), (8, 9), (3, 7)];

hybrid_connected_components(edges,14);