functor Make(M : sig type t end) = struct sequence s table t : {Id : int, Client : client, Channel : channel M.t} PRIMARY KEY (Id, Client) type topic = int val inj : sql_injectable topic = _ val create = nextval s fun subscribe id = cli <- self; ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[cli]}); case ro of None => ch <- channel; dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[cli]}, {[ch]})); return ch | Some r => return r.T.Channel fun send id msg = queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]}) (fn r => Basis.send r.T.Channel msg) fun subscribers id = r <- oneRow (SELECT COUNT( * ) AS N FROM t WHERE t.Id = {[id]}); return r.N end