anchor.diff:  %% match arguments are novars
   %% case arguments are novars
   %% receive timeouts are novars
  +%% binaries and maps are novars
   %% let/set arguments are expressions
   %% fun is not a safe
   
  
positive.code: force_novars(#icall{}=Call, St) -> {Call,[],St};
  force_novars(#ifun{}=Fun, St) -> {Fun,[],St};	%These are novars too
  force_novars(#ibinary{}=Bin, St) -> {Bin,[],St};
  force_novars(Ce, St) ->
      force_safe(Ce, St).
  
  
negative.code: 	false -> throw({bad_map,bad_map})
      end.
  
  map_build_pairs(Map, Es0, Ann, St0) ->
      {Es,Pre,St1} = map_build_pairs_1(Es0, St0),
      {ann_c_map(Ann, Map, Es),Pre,St1}.
  
  map_build_pairs_1([{Op0,L,K0,V0}|Es], St0) ->
      {K,Pre0,St1} = safe(K0, St0),
  