reserve a,x,y for object, A,B for set,
  l,m,n for Nat;
reserve X,Y for set, x for object,
  p,q for Function-yielding FinSequence,
  f,g,h for Function;
reserve m,n,k for Nat, R for Relation;

theorem
  for f being Function of X,X holds iter(iter(f,m),n) = iter(f,m*n)
proof
  let f be Function of X,X;
  rng f c= dom f by Lm1;
  hence thesis by Th78;
end;
