anchor.diff:      Src = mk_val(Src0),
       Dst = mk_val(Dst0),
       emit([Dst," = ",Src," - ",Int]);
  +enc_cg({set,{var,Src},{var,Dst}}) ->
  +    emit([Dst," = ",Src]);
   enc_cg({'try',Try,{P,Succ},Else,Dst}) ->
       emit([mk_val(Dst)," = try "]),
       enc_cg(Try),
  
positive.code:     Else = enc_pre_cg_1(Else0, StL, outside_seq),
      {'try',Try,{P,Succ},Else,Dst};
  enc_pre_cg_nonbuilding(Imm, _) -> Imm.
  
  
  %%%
  %%% Code generation for encoding.
  
negative.code:     [{lc,per_fixup(B),V,L}|per_fixup(T)];
  per_fixup([{lc,B,V,L,Dst}|T]) ->
      [{lc,per_fixup(B),V,L,Dst}|per_fixup(T)];
  per_fixup([{set,_,_}=H|T]) ->
      [H|per_fixup(T)];
  per_fixup([{sub,_,_,_}=H|T]) ->
      [H|per_fixup(T)];
  per_fixup([{'try',Try0,{P,Succ0},Else0,Dst}|T]) ->
  