
theorem Th31:
  for x,b being non pair set holds the carrier of IncrementStr(x,b
  ) = {x,b} \/ {[<*x,b*>,and2a]}
proof
  let x,b be non pair set;
  set p = <*x,b*>;
  rng p = {x,b} by FINSEQ_2:127;
  hence thesis by CIRCCOMB:def 6;
end;
