1 files changed, 11 insertions, 0 deletions
diff --git a/tex/context/base/util-sto.lua b/tex/context/base/util-sto.lua
index 34787be9b..19b8093c9 100644
--- a/tex/context/base/util-sto.lua
+++ b/tex/context/base/util-sto.lua
@@ -98,3 +98,14 @@ function storage.setinitializer(data,initialize)
     end
     setmetatable(data, m)
 end
+
+local keyisvalue = { __index = function(t,k)
+    t[k] = k
+    return k
+end }
+
+function storage.sparse(t)
+    t = t or { }
+    setmetatable(t,keyisvalue)
+    return t
+end