(*  Title:      HOLCF/IOA/ABP/Sender.thy
    ID:         $Id: Sender.thy,v 1.6 2005/09/03 14:50:23 wenzelm Exp $
    Author:     Olaf Müller
*)

header {* The implementation: sender *}

theory Sender
imports IOA Action Lemmas
begin

types
  'm sender_state = "'m list  *  bool"  -- {* messages, Alternating Bit *}

constdefs
sq            :: "'m sender_state => 'm list"
"sq == fst"

sbit          :: "'m sender_state => bool"
"sbit == snd"

sender_asig   :: "'m action signature"
"sender_asig == ((UN m. {S_msg(m)}) Un (UN b. {R_ack(b)}),
                  UN pkt. {S_pkt(pkt)},
                  {})"

sender_trans  :: "('m action, 'm sender_state)transition set"
"sender_trans ==
 {tr. let s = fst(tr);
          t = snd(snd(tr))
      in case fst(snd(tr))
      of
      Next     => if sq(s)=[] then t=s else False |
      S_msg(m) => sq(t)=sq(s)@[m]   &
                  sbit(t)=sbit(s)  |
      R_msg(m) => False |
      S_pkt(pkt) => sq(s) ~= []  &
                     hdr(pkt) = sbit(s)      &
                    msg(pkt) = hd(sq(s))    &
                    sq(t) = sq(s)           &
                    sbit(t) = sbit(s) |
      R_pkt(pkt) => False |
      S_ack(b)   => False |
      R_ack(b)   => if b = sbit(s) then
                     sq(t)=tl(sq(s)) & sbit(t)=(~sbit(s)) else
                     sq(t)=sq(s) & sbit(t)=sbit(s)}"

sender_ioa    :: "('m action, 'm sender_state)ioa"
"sender_ioa ==
 (sender_asig, {([],True)}, sender_trans,{},{})"

ML {* use_legacy_bindings (the_context ()) *}

end
