diff --git a/code/typeclass-prolog/kb.pl b/code/typeclass-prolog/kb.pl
new file mode 100644
index 0000000..d8e4bdc
--- /dev/null
+++ b/code/typeclass-prolog/kb.pl
@@ -0,0 +1,7 @@
+show(unit).
+show(list(X)) :- show(X).
+show(pair(X,Y)) :- show(X), show(Y).
+
+eq(X) :- ord(X).
+eq(nat).
+ord(nat).