Checkpoint

examples/scratchpad.pl

@@ -1 +1,23 @@
-choice(X) :- X = 1, !; X = 2.
+% choice(X) :- X = 1, !; X = 2.
+grade(alice, a).
+grade(bob, b).
+grade(carol, a).
+grade(dave, c).
+
+got_an_a(Student) :-
+    grade(Student, Grade),
+    Grade = a.
+
+did_not_get_an_a(Student) :-
+    grade(Student, Grade),
+    Grade \= a.
+
+:- initialization(main).
+
+main :-
+    write("While "),
+    got_an_a(X),
+    write(X), write(" got an A, "), fail;
+    write("but "),
+    did_not_get_an_a(Y),
+    write(Y), write(" did not get an A, "), fail; write("unfortunately."), nl.