add missing usings

diff --git a/core/classes/tuple/tuple-docs.factor b/core/classes/tuple/tuple-docs.factor
index cc670751686eee377512b9263f1abcacf8a39553..45d3931448f99037b88c62b31a2dcd9e0d3c2765 100644 (file)
--- a/core/classes/tuple/tuple-docs.factor
+++ b/core/classes/tuple/tuple-docs.factor
@@ -129,7 +129,7 @@ ARTICLE: "tuple-inheritance-example" "Tuple subclassing example"
 }
 "Rectangles and parallelograms use the same algorithm for computing the area, whereas they use different algorithms for computing perimiter. Also, rectangles and parallelograms both have " { $snippet "width" } " and " { $snippet "height" } " slots. We can exploit this with subclassing:"
 { $code
-    "USING: math.constants math.functions ;"
+    "USING: accessors kernel math math.constants math.functions ;"
     "GENERIC: area ( shape -- n )"
     "GENERIC: perimiter ( shape -- n )"
     ""