diff --git a/misc.go b/misc.go
index 0674718..5b89537 100644
--- a/misc.go
+++ b/misc.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"slices"
 	"unicode"
 )
 
@@ -13,3 +14,14 @@ func assert(cond bool) {
 		panic("Assertion Failed")
 	}
 }
+
+// Ensure that the given elements are only appended to the given slice if they
+// don't already exist.
+func unique_append[T comparable](slc []T, items ...T) []T {
+	for _, item := range items {
+		if !slices.Contains(slc, item) {
+			slc = append(slc, item)
+		}
+	}
+	return slc
+}