add use_module/{1,2} as full fledged predicates

src/prolog/toplevel.pl

@@ -1,3 +1,20 @@
+/* 
+ *  inserting the modules should not result in the insertion of
+ *  code. this is because they're already loaded by this point -- see
+ *  Machine::new.
+*/
+
+:- use_module(library(lists)).
+:- use_module(library(si)).
+
+'$repl'(ListOfModules) :-
+    maplist('$use_list_of_modules', ListOfModules),
+    false.
+'$repl'(_) :- '$repl'.
+
+'$use_list_of_modules'(Module) :-
+    catch(use_module(Module), E, '$print_exception'(E)).
+
 '$repl' :-
     catch('$read_and_match', E, '$print_exception'(E)),
     false. %% this is for GC, until we get actual GC.
@@ -17,3 +34,41 @@
     write_term('caught: ', [quoted(false)]),
     writeq(E),
     nl.
+
+'$predicate_indicator'(Source, PI) :-
+    (  nonvar(PI) ->
+       (  PI = Name / Arity ->
+	  (  var(Name) -> throw(error(instantiation_error, Source))
+	  ;  integer(Arity) ->
+	     (  \+ atom(Name) -> throw(error(type_error(atom, Name), Source))
+	     ;  Arity < 0 -> throw(error(domain_error(not_less_than_zero, Arity), Source))
+	     ;  true
+	     )
+	  ;  throw(error(type_error(integer, Arity), Source))
+	  )
+       ;  throw(error(type_error(predicate_indicator, PI), Source))
+       )
+    ;  throw(error(instantiation_error, Source))
+    ).
+
+use_module(Module) :-
+    (  nonvar(Module) ->
+       (  Module = library(Filename) -> '$use_module'(Filename)
+       ;  atom(Module) -> '$use_module_from_file'(Module)
+       ;  throw(error(invalid_module_specifier, use_module/1))
+       )
+    ;  throw(error(instantiation_error, use_module/1))
+    ).
+
+use_module(Module, QualifiedExports) :-
+    (  nonvar(Module) ->
+       (  list_si(QualifiedExports) ->
+	  maplist('$predicate_indicator'(use_module/2), QualifiedExports), !,
+	  (  Module = library(Filename) -> '$use_qualified_module'(Filename, QualifiedExports)
+	  ;  atom(Module) -> '$use_qualified_module_from_file'(Module, QualifiedExports)
+	  ;  throw(error(invalid_module_specifier, use_module/2))
+	  )
+       ;  throw(error(type_error(list, QualifiedExports), use_module/2))
+       )
+    ;  throw(error(instantiation_error, use_module/2))
+    ).