Tested each sample.

gem/ex7.lua

@@ -0,0 +1,16 @@
+function sink.table(t)
+  t = t or {}
+  local f = function(chunk, err)
+    if chunk then table.insert(t, chunk) end
+    return 1
+  end
+  return f, t
+end
+
+local function null()
+  return 1
+end
+
+function sink.null()
+  return null
+end