
theorem
  for C,D be non empty set, b be Element of D, F be Function of [:D,C:],D
  ex g being Function of [:C,NAT:],D st for a being Element of C holds
  g.(a,0) = b & for n being Element of NAT holds g.(a,n+1) = F.(g.(a,n),a)
  by Lm2;
