theorem Th70:
  for F being non empty SubStr of GPFuncs X
  for f,g being Element of F holds f [*] g = g (*) f
proof
  let F be non empty SubStr of GPFuncs X;
  let f,g be Element of F;
  carr(F) c= carr(GPFuncs X) by Th23;
  then reconsider f9 = f, g9 = g as Element of GPFuncs X;
  f[*]g = f9[*]g9 by Th25;
  hence thesis by Def37;
end;
