begin migrating tests to pure prolog, correct bug in toplevel

src/tests/facts.pl

@@ -0,0 +1,26 @@
+:- dynamic(p/2).
+:- dynamic(p/3).
+
+p(Z, Z).
+clouds(are, nice).
+p(Z, h(Z, W), f(W)).
+
+test_queries_on_facts :-
+    findall(Z, p(Z, Z), [Z]),
+    findall(Z, p(Z, z), [z]),
+    findall(Z, p(Z, w), [w]),
+    \+ p(z, w),
+    p(w, w),
+    \+ clouds(Z, Z),
+    findall(Z, clouds(are, Z), [nice]),
+    \+ p(z, h(z, z), f(w)),
+    p(z, h(z, w), f(w)),
+    findall(W, p(z, h(z, W), f(w)), [w]),
+    findall(Z, p(Z, h(Z, w), f(Z)), [w]),
+    \+ p(z, h(Z, w), f(Z)),
+    retract(p(_,_,_)),
+    assertz(p(Z, h(Z, W), f(W))),
+    p(f(f(a)), h(f(f(a)), f(a)), f(f(a))),
+    retract(p(Z, h(Z, W), f(W))).
+
+:- initialization(test_queries_on_facts).