(* File: a-b-in-computations   Author: Hongyou Wu   Date: 2002 Dec 12 *)
(*                                                                    *)
(* Input: ta, tb                                                      *)
(*                                                                    *)
(* Optional input: ed, a, b                                           *)
(*                                                                    *)
(* Output: printouts, aa, bb                                          *)


Clear[aa,bb];

If[ValueQ[ed]==False,ed=5];

If[ta==00,   {aa=a;bb=If[tb==00,b,
                      If[tb==01,b-(b-a)/10^ed,
                                a+Max[1,Abs[a]]*10^ed]];},
If[ta==01,
   If[tb==00,{aa=a+(b-a)/10^ed;bb=b;},
   If[tb==01,{aa=a+(b-a)/10^ed;bb=b-(b-a)/10^ed;},
             {aa=a+Max[1,Abs[a]]/10^ed;bb=a+Max[1,Abs[a]]*10^ed;}]],
   If[tb==00,{aa=b-Max[1,Abs[b]]*10^ed;bb=b;},
   If[tb==01,{aa=b-Max[1,Abs[b]]*10^ed;bb=b-Max[1,Abs[b]]/10^ed;},
             {aa=-10^ed;bb=10^ed;}]]
  ]
  ];

Print["aa=",aa//N," & bb=",bb//N];