theorem
  x, w ==>* y, v^w, TS implies v = <%>E
proof
  assume x, w ==>* y, v^w, TS;
  then len(v^w) <= len w by Th89;
  then len v + len w <= 0 + len w by AFINSQ_1:17;
  hence thesis by XREAL_1:6;
end;
