--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/demo/more/versioned.ur	Tue Oct 06 15:39:27 2009 -0400
@@ -0,0 +1,114 @@
+functor Make(M : sig
+                 con key :: {Type}
+                 con data :: {Type}
+                 constraint key ~ data
+                 constraint [When] ~ (key ++ data)
+
+                 val key : $(map sql_injectable key)
+                 val data : $(map (fn t => {Inj : sql_injectable_prim t,
+                                            Eq : eq t}) data)
+
+                 val keyFolder : folder key
+                 val dataFolder : folder data
+             end) = struct
+    con all = [When = time] ++ M.key ++ map option M.data
+    table t : all
+
+    val keys = List.mapQuery (SELECT DISTINCT t.{{M.key}} FROM t) (fn r => r.T)
+
+    con dmeta = fn t => {Inj : sql_injectable_prim t,
+                         Eq : eq t}
+
+    fun keyRecd (r : $(M.key ++ M.data)) =
+        map2 [sql_injectable] [id] [sql_exp [] [] []]
+             (fn [t] => @sql_inject)
+             [_] M.keyFolder M.key (r --- M.data)
+
+    fun insert r = dml (Basis.insert t
+                                     ({When = (SQL CURRENT_TIMESTAMP)}
+                                          ++ keyRecd r
+                                          ++ map2 [dmeta] [id]
+                                          [fn t => sql_exp [] [] [] (option t)]
+                                          (fn [t] x v => @sql_inject (@sql_option_prim x.Inj)
+                                                          (Some v))
+                                          [_] M.dataFolder M.data (r --- M.key)))
+
+    fun keyExp (r : $M.key) : sql_exp [T = all] [] [] bool =
+        foldR2 [sql_injectable] [id] [fn before => after :: {Type} -> [before ~ after]
+                                         => sql_exp [T = before ++ after] [] [] bool]
+               (fn [nm :: Name] [t :: Type] [before :: {Type}] [[nm] ~ before]
+                                (inj : sql_injectable t) (v : t)
+                   (e : after :: {Type} -> [before ~ after]
+                    => sql_exp [T = before ++ after] [] [] bool)
+                   [after :: {Type}] [[nm = t] ++ before ~ after] =>
+                   (SQL t.{nm} = {[v]} AND {e [[nm = t] ++ after] !}))
+               (fn [after :: {Type}] [[] ~ after] => (SQL TRUE))
+               [_] M.keyFolder M.key r
+               [_] !
+
+    fun current k =
+        let
+            fun current' timeOpt r =
+                let
+                    val complete = foldR [option] [fn ts => option $ts]
+                                   (fn [nm :: Name] [v :: Type] [r :: {Type}] [[nm] ~ r]
+                                                    v r =>
+                                       case (v, r) of
+                                           (Some v, Some r) => Some ({nm = v} ++ r)
+                                         | _ => None)
+                                   (Some {}) [_] M.dataFolder r
+                in
+                    case complete of
+                        Some r => return (Some r)
+                      | None =>
+                        let
+                            val filter = case timeOpt of
+                                             None => (WHERE TRUE)
+                                           | Some time => (WHERE t.When < {[time]})
+                        in
+                            ro <- oneOrNoRows (SELECT t.When, t.{{map option M.data}}
+                                               FROM t
+                                               WHERE {filter}
+                                                 AND {keyExp k}
+                                               ORDER BY t.When DESC
+                                               LIMIT 1);
+                            case ro of
+                                None => return None
+                              | Some r' =>
+                                let
+                                    val r = map2 [option] [option] [option]
+                                            (fn [t ::: Type] old new =>
+                                                case old of
+                                                    None => new
+                                                  | Some _ => old)
+                                            [_] M.dataFolder r (r'.T -- #When)
+                                in
+                                    current' (Some r'.T.When) r
+                                end
+                        end
+                end
+        in
+            current' None (map0 [option] (fn [t :: Type] => None : option t) [_] M.dataFolder)
+        end
+
+    fun update r =
+        cur <- current (r --- M.data);
+        case cur of
+            None => error <xml>Tried to update nonexistent key</xml>
+          | Some cur =>
+            let
+                val r' = map3 [dmeta] [id] [id] [fn t => sql_exp [] [] [] (option t)]
+                              (fn [t] (meta : dmeta t) old new =>
+                                  @sql_inject (@sql_option_prim meta.Inj)
+                                   (if @@eq [_] meta.Eq old new then
+                                        None
+                                    else
+                                        Some new))
+                              [_] M.dataFolder M.data cur (r --- M.key)
+                val r' = {When = (SQL CURRENT_TIMESTAMP)}
+                             ++ keyRecd r
+                             ++ r'
+            in
+                dml (Basis.insert t r')
+            end
+end