reserve n,i,j,k for Nat;
reserve T for TuringStr,
  s for All-State of T;

theorem Th26:
  for T being TuringStr,t be Tape of T, h be Integer, s be Symbol of T,
  i be object holds Tape-Chg(t,h,s).h=s &
  (i <> h implies Tape-Chg(t,h,s).i=t.i)
proof
  let tm be TuringStr,t be Tape of tm,h be Integer, s be Symbol of tm,
  i be object;
  set t1=Tape-Chg(t,h,s), p=h .--> s;
  thus t1.h=s by FUNCT_7:94;
  assume i <> h;
  then not i in dom p by TARSKI:def 1;
  hence thesis by FUNCT_4:11;
end;
