add tabling library, update README, make Cargo.toml non-local

src/prolog/lib/tabling/global_worklist.pl

@@ -0,0 +1,40 @@
+/*    Ported to Scryer Prolog by Mark Thom (2019/2020). 
+ */
+
+:- module(global_worklist,
+	  [ put_new_global_worklist/0,
+	    add_to_global_worklist/1,
+	    worklist_empty/0,
+	    pop_worklist/1
+	  ]).
+
+:- use_module(library(atts)).
+:- use_module(library(non_iso)).
+
+:- attribute table_global_worklist/1.
+
+put_new_global_worklist :-
+  (  bb_get(table_global_worklist_initialized, _) ->
+     true
+  ;  put_atts(Worklist, table_global_worklist([])),
+     bb_put(table_global_worklist, Worklist),
+     bb_b_put(table_global_worklist_initialized, [])
+  ).
+
+add_to_global_worklist(TableIdentifier) :-  
+  bb_get(table_global_worklist, TableGlobalWorklistFlag),
+  get_atts(TableGlobalWorklistFlag, table_global_worklist(L1)),
+  put_atts(TableGlobalWorklistFlag, table_global_worklist([TableIdentifier|L1])),
+  bb_put(table_global_worklist, TableGlobalWorklistFlag).
+
+worklist_empty :-
+  bb_get(table_global_worklist,TableGlobalWorklistFlag),
+  get_atts(TableGlobalWorklistFlag, table_global_worklist(L)),
+  L == [].
+
+pop_worklist(TableIdentifier) :-
+  bb_get(table_global_worklist,TableGlobalWorklistFlag),
+  get_atts(TableGlobalWorklistFlag, table_global_worklist(L1)),  
+  L1 = [TableIdentifier|L2],
+  put_atts(TableGlobalWorklistFlag, table_global_worklist(L2)),
+  bb_put(table_global_worklist, TableGlobalWorklistFlag).