diff --git a/racket/typed/spin-prelude.pml b/racket/typed/spin-prelude.pml
new file mode 100644
index 0000000..73c6593
--- /dev/null
+++ b/racket/typed/spin-prelude.pml
@@ -0,0 +1,9 @@
+/* Useful macros */
+
+#define ASSERTED(x) (x##_assertions > 0)
+#define RETRACTED(x) (x##_assertions == 0)
+#define ASSERT(x) x##_assertions = x##_assertions + 1
+#define RETRACT(x) x##_assertions = x##_assertions - 1
+
+/* Rest of Program */
+