theorem Th47:
  s1 = s +* S & A = a implies S.A = s1.a
proof
  assume that
A1: s1 = s +* S and
A2: A = a;
 dom S = SCM-Memory by PARTFUN1:def 2;
  hence s1.a = S.A by A1,A2,FUNCT_4:13;
end;
