fix catch and throw: make sure we have an environment.

use $notrace consistently: note that it only matters if ran from the
debugger, otherwise it is just a meta-call.

pl/boot.yap

@@ -849,7 +849,7 @@ not(G) :-    \+ '$execute'(G).
 '$call'(G, CP, G0, CurMod) :-
 	( '$is_expand_goal_or_meta_predicate'(G,CurMod) ->
 	   (
-	     '$oncenotrace'(user:goal_expansion(G, CurMod, NG)) ->
+	     '$notrace'(user:goal_expansion(G, CurMod, NG)) ->
 	       '$call'(NG, CP, G0,CurMod)
 	     ;
 	       % repeat other code.
@@ -1076,7 +1076,7 @@ access_file(F,Mode) :-
 
 expand_term(Term,Expanded) :-
 	( \+ '$undefined'(term_expansion(_,_), user),
-	  once(user:term_expansion(Term,Expanded))
+	  '$notrace'(user:term_expansion(Term,Expanded))
         ;
 	  '$expand_term_grammar'(Term,Expanded)
 	),
@@ -1116,7 +1116,11 @@ expand_term(Term,Expanded) :-
 % where was the previous catch	
 catch(G, C, A) :-
 	'$catch'(C,A,_),
-	'$execute'(G).
+	'$execute'(G),
+	'$true'.
+
+% makes sure we have an environment.
+'$true'.
 
 
 % system_catch is like catch, but it avoids the overhead of a full
@@ -1127,7 +1131,8 @@ catch(G, C, A) :-
 '$system_catch'(G, M, C, A) :-
 	% check current trail
 	'$catch'(C,A,_),
-	'$execute_nonstop'(G, M).
+	'$execute_nonstop'(G, M),
+	'$true'.
 
 %
 % throw has to be *exactly* after system catch!
@@ -1164,8 +1169,11 @@ throw(Ball) :-
 '$exit_system_mode' :-
 	nb_setval('$system_mode',off),
 	( nb_getval('$trace',on) -> '$creep' ; true).
-	
-'$donotrace'(G) :-
+
+%
+% just leave this around to show  the debugger.
+%
+'$notrace'(G) :-
 	'$execute'(G).
 
 '$oncenotrace'(G) :-

pl/consult.yap

@@ -778,7 +778,7 @@ absolute_file_name(File,Opts,TrueFileName) :-
 
 
 '$extend_path_directory'(Name, D, File, Opts, NewFile, Call) :-
-	user:file_search_path(Name, Dir),	
+	'$notrace'(user:file_search_path(Name, Dir)),
 	'$extend_pathd'(Dir, D, File, Opts, NewFile, Call).
 
 '$extend_pathd'(Dir, A, File, Opts, NewFile, Call) :-

pl/errors.yap

@@ -240,16 +240,16 @@ print_message(Severity, Msg) :-
 print_message(Severity, Term) :-
 	(
 	 (
-	  '$notrace'(user:generate_message_hook(Term, [], Lines)) ->
+	  '$oncenotrace'(user:generate_message_hook(Term, [], Lines)) ->
 	  true
 	 ;
-	  '$notrace'(prolog:message(Term, Lines, [])) ->
+	  '$oncenotrace'(prolog:message(Term, Lines, [])) ->
 	  true
 	 ;
 	 '$message':generate_message(Term, Lines, [])
 	 )
 	->  (   nonvar(Term),
-		'$notrace'(user:message_hook(Term, Severity, Lines))
+		'$oncenotrace'(user:message_hook(Term, Severity, Lines))
 	    ->  !
 	    ;   !, '$print_system_message'(Term, Severity, Lines)
 	    )

pl/preds.yap

@@ -964,26 +964,6 @@ current_key(A,K) :-
 % do nothing for now.
 '$noprofile'(_, _).
 
-'$notrace'(G) :-
-	var(G), !,
-	'$do_error'(instantiation_error,G).	
-'$notrace'(G) :- number(G), !,
-	'$do_error'(type_error(callable,G),G).
-'$notrace'(G) :- db_reference(G), !,
-	'$do_error'(type_error(callable,G),G).
-'$notrace'(M:G) :-
-	\+ atom(M),
-	'$do_error'(type_error(atom,Na), Msg).
-'$notrace'(M:G) :- !,
-	'$notrace'(G, M).
-'$notrace'(G) :- !,
-	'$notrace'(G, prolog).
-
-
-'$notrace'(G, Mod) :-
-	\+ '$undefined'(G, Mod),
-	'$donotrace'(Mod:G).
-
 '$ifunctor'(Pred,Na,Ar) :-
 	(Ar > 0 ->
 	    functor(Pred, Na, Ar)

pl/signals.yap

@@ -99,7 +99,7 @@
 	'$execute_nonstop'('$call'(G, CP, G0, M),M0).
 % donotrace: means do not trace! So,
 % ignore and then put creep back for the continuation.
-'$start_creep'([M0|'$donotrace'(G)]) :-
+'$start_creep'([M0|'$notrace'(G)]) :-
 	!,
 	(
 	 CP0 is '$last_choice_pt',