datasort stype = | psend of (vt@ype) | precv of (vt@ype) | pclose | pwait | pseq of (stype, stype) stadef :: = pseq absvtype channel (stype) extern fun send {s:stype} {a:vt@ype} (!channel (psend (a) :: s) >> channel (s), a): void extern fun recv {s:stype} {a:vt@ype} (!channel (precv (a) :: s) >> channel (s)): a extern fun close (channel (pclose)): void extern fun wait (channel (pwait)): void stadef proto_srv = precv (int) :: precv (int) :: psend (bool) :: pwait stadef proto_cli = psend (int) :: psend (int) :: precv (bool) :: pclose extern fun srv (channel (proto_srv)): void extern fun cli (channel (proto_cli)): void implement srv (ch) = let val a = recv ch val b = recv ch val _ = send (ch, a = b) in wait ch end implement cli (ch) = let val _ = $showtype ch val _ = send (ch, 1) val _ = $showtype ch val _ = send (ch, 2) val _ = $showtype ch val b = recv (ch) val _ = $showtype ch in close ch; end