Merge branch 'master' into docs-builtins

diff --cc src/lib/builtins.pl
index 89270f6f8393b074ca9dc64d176442e903fe7905,d7f3c536b879141fbbd8282ae74ab338e346eaff..aef9b32bdb181dcda99d84b6b9ebc5197f8a69c4
--- 1/src/lib/builtins.pl
--- 2/src/lib/builtins.pl
+++ b/src/lib/builtins.pl
@@@ -256,38 -158,34 +256,45 @@@ G1 -> G2 :- control_entry_point((G1 -> 
  :- non_counted_backtracking staggered_if_then/2.
  
  staggered_if_then(G1, G2) :-
-     '$get_staggered_cp'(B),
      call(G1),
-     '$set_cp'(B),
+     !,
      call(G2).
  
 +%% ;(G1, G2)
 +%
 +% Disjunction (or)
  G1 ; G2 :- control_entry_point((G1 ; G2)).
  
  
  :- non_counted_backtracking staggered_sc/2.
  
- staggered_sc(G, _) :- call(G).
+ staggered_sc(G, _) :-
+     (  nonvar(G),
+        G = '$call'(builtins:staggered_if_then(G1, G2)) ->
+        call(G1),
+        !,
+        call(G2)
+     ;  call(G)
+     ).
  staggered_sc(_, G) :- call(G).
  
 +%% !.
 +%
 +% Cut operator. Discards the choicepoints created since entering the prediacate in which the operator appears.
 +% Using cut is not recommended as it introduces a non-declarative flow of programming and makes it more difficult
 +% to reason about the programs. Also restricts the ability to run the program with alternative execution strategies
  !.
  
  :- non_counted_backtracking set_cp/1.
  
  set_cp(B) :- '$set_cp'(B).
  
 +%% ,(G1, G2)
 +%
 +% Conjuction (and)
  ','(G1, G2) :- control_entry_point((G1, G2)).
  
+ 
  :- non_counted_backtracking control_entry_point/1.
  
  control_entry_point(G) :-
@@@ -941,30 -739,12 +938,29 @@@ findall_with_existential(Template, Goal
  
  :- non_counted_backtracking bagof/3.
  
 +%% bagof(Template, Goal, Solution).
 +%
 +% Unify Solution with a list of alternatives of the variables in Template coming from calling Goal.
 +% If Goal has no solutions, the predicate fails.
 +% If free variables that are not in Template appear in Goal, the predicate will backtrack over
 +% the alternatives of those free variables. However, you can use the syntax `Var^Goal` to not bind
 +% Var in Goal and prevent that.
 +%
 +% Example:
 +%
 +%     f(1, 3).
 +%     f(2, 4).
 +%     ?- bagof(X, f(X, Y), Bag).
 +%        Y = 3, Bag = [1],
 +%     ;  Y = 4, Bag = [2].
 +%     ?- bagof(X, Y^f(X, Y), Bag).
 +%        Bag = [1,2].
  bagof(Template, Goal, Solution) :-
      error:can_be(list, Solution),
-     term_variables(Template, TemplateVars0),
-     term_variables(Goal, GoalVars0),
-     sort(TemplateVars0, TemplateVars),
-     sort(GoalVars0, GoalVars),
-     set_difference(GoalVars, TemplateVars, Witnesses0),
+     term_variables(Template, TemplateVars),
+     term_variables(Goal, GoalVars),
+     term_variables(TemplateVars+GoalVars, TGVs),
+     lists:append(TemplateVars, Witnesses0, TGVs),
      findall_with_existential(Template, Goal, PairedSolutions0, Witnesses0, Witnesses),
      keysort(PairedSolutions0, PairedSolutions),
      group_by_variants(PairedSolutions, GroupedSolutions),
@@@ -986,22 -766,12 +982,21 @@@ iterate_variants_and_sort([_|GroupSolut
  
  :- non_counted_backtracking setof/3.
  
 +%% setof(Template, Goal, Solution).
 +%
 +% Similar to bagof/3 but Solution is sorted and duplicates are removed. Example:
 +%
 +%     f(1, 2).
 +%     f(1, 3).
 +%     f(2, 4).
 +%     ?- setof(X, Y^f(X, Y), Set).
 +%        Set = [1, 2].
  setof(Template, Goal, Solution) :-
      error:can_be(list, Solution),
-     term_variables(Template, TemplateVars0),
-     term_variables(Goal, GoalVars0),
-     sort(TemplateVars0, TemplateVars),
-     sort(GoalVars0, GoalVars),
-     set_difference(GoalVars, TemplateVars, Witnesses0),
+     term_variables(Template, TemplateVars),
+     term_variables(Goal, GoalVars),
+     term_variables(TemplateVars+GoalVars, TGVs),
+     lists:append(TemplateVars, Witnesses0, TGVs),
      findall_with_existential(Template, Goal, PairedSolutions0, Witnesses0, Witnesses),
      keysort(PairedSolutions0, PairedSolutions),
      group_by_variants(PairedSolutions, GroupedSolutions),