var forest := {}, encTab := {};

plaintext := 'this is an example for huffman encoding';

ft := {};
(for c in plaintext)
  ft(c) +:= 1;
end;

forest := {[f, c]: [c, f] in ft};
(while 1 < #forest)
  [f1, n1] := getLFN();
  [f2, n2] := getLFN();
  forest with:= [f1+f2, [n1,n2]];
end;
addToTable('', arb range forest);

(for e = encTab(c))
  print(c, ft(c), e);
end;

print(+/ [encTab(c): c in plaintext]);

proc addToTable(prefix, node);
  if is_tuple node then
    addToTable(prefix + '0', node(1));
    addToTable(prefix + '1', node(2));
  else
    encTab(node) := prefix;
  end;
end proc;

proc getLFN();
  f := min/ domain forest;
  n := arb forest{f};
  forest less:= [f, n];
  return [f, n];
end proc;