prepare to add project_attributes/2 and attribute_goals/2

src/prolog/machine/project_attributes.pl

@@ -0,0 +1,46 @@
+:- use_module(library(dcgs)).
+
+driver(QueryVars, AttrVars) :-
+    phrase(gather_modules(AttrVars), Modules0),
+    sort(Modules0, Modules),
+    call_project_attributes(Modules, QueryVars, AttrVars),
+    call_attribute_goals(QueryVars),
+    call_attribute_goals(AttrVars).
+
+call_project_attributes([], _, _).
+call_project_attributes([Module|Modules], QueryVars, AttrVars) :-
+    (   catch(Module:project_attributes(QueryVars, AttrVars),
+	      error(evaluation_error((Module:project_attributes/2), project_attributes/2)),
+	      true) -> true
+    ;   true
+    ),
+    call_project_attributes(Modules, QueryVars, AttrVars).
+
+call_attribute_goals([]).
+call_attribute_goals([AttrVar | AttrVars]) :-
+    (   '$get_attr_list'(AttrVar, Ls) -> call_goals(Ls, AttrVar)
+    ;   true
+    ),
+    call_attribute_goals(AttrVars).
+
+call_goals(Ls, _) :- var(Ls), !.
+call_goals([Attr|Attrs], X) :-
+    '$module_of'(Module, Attr),
+    (   catch(Module:attribute_goals(X, Goal),
+	      error(evaluation_error((Module:attribute_goals/2), attribute_goals/2)),
+	      writeq(Goal)) -> true
+    ;   true
+    ),
+    call_goals(Attrs, X).
+
+gather_modules([]) --> [].
+gather_modules([AttrVar|AttrVars]) -->
+    { '$get_attr_list'(AttrVar, Attrs) },
+    gather_modules_for_attrs(Attrs),
+    gather_modules(AttrVars).
+
+gather_modules_for_attrs(Attrs) --> { var(Attrs), ! }.
+gather_modules_for_attrs([Attr|Attrs]) -->
+    { '$module_of'(Module, Attr) },
+    [Module],
+    gather_modules_for_attrs(Attrs).