Ur/Web: demo/broadcast.ur annotate

Allow type class instances with hypotheses via local ('let') definitions

author	Adam Chlipala <adam@chlipala.net>
date	Wed, 25 Jul 2012 14:04:59 -0400
parents	0406e9cccb72
children

rev	line source
adamc@699	1 functor Make(M : sig type t end) = struct
adamc@699	2 sequence s
adamc@699	3 table t : {Id : int, Client : client, Channel : channel M.t}
adamc@709	4 PRIMARY KEY (Id, Client)
adamc@699	5
adamc@699	6 type topic = int
adamc@699	7
adamc@699	8 val inj : sql_injectable topic = _
adamc@699	9
adamc@699	10 val create = nextval s
adamc@699	11
adamc@699	12 fun subscribe id =
adamc@699	13 cli <- self;
adamc@699	14 ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[cli]});
adamc@699	15 case ro of
adamc@699	16 None =>
adamc@699	17 ch <- channel;
adamc@699	18 dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[cli]}, {[ch]}));
adamc@699	19 return ch
adamc@699	20 \| Some r => return r.T.Channel
adamc@699	21
adamc@699	22 fun send id msg =
adamc@699	23 queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]})
adamc@699	24 (fn r => Basis.send r.T.Channel msg)
adamc@699	25
adamc@699	26 fun subscribers id =
adamc@699	27 r <- oneRow (SELECT COUNT( * ) AS N FROM t WHERE t.Id = {[id]});
adamc@699	28 return r.N
adamc@699	29 end

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