theorem Th24:
  for f be Function holds Swap(f,x,y)|X = Swap(f|X,x,y)
proof
  let f be Function;
  thus Swap(f,x,y)|X = Swap(f,x,y)*(id X) by RELAT_1:65
  .=Swap(f*(id X),x,y) by Th23
  .=Swap(f|X,x,y) by RELAT_1:65;
end;
