Pass the Parcel

1
Pass the Parcel

• specification gamepreparetopass12,pass12,preparet
  opass23,pass23,
  preparetopass34,pass34,preparetopass41,pass41,
  musicstop,musicstart,present
  exit( Pass the Parcel Game )( M.
  Calder 1999 )( represent passing by two
  eventspreparetopass and pass )( if music
  stops during passing, i.e. after prepare but
  before pass )( the intended recipient unwraps
  the parcel )library boolean endlib(
  )( The Parcel ADT
  )()type Parcel is
  booleansorts Parcelopns wrappers Parcel -gt
  bool new -gt Parcel add Parcel -gt
  Parcel unwrap Parcel -gtParcel
  initial Parceleqns forall pParcelofsort
  boolwrappers(new) falsewrappers(add(p))
  trueofsort ParcelUuwrap(add(p))
  punwrap(new) newinitial
  wrap(wrap(wrap(new))) endtype(
  )( Basic Player Process)(
  )process Playerpreparetoreceive,recei
  ve,preparetopass,pass,
  musicstop,musicstart,present(parcel?bool) exit
  parcel? -gt HasParcelpreparetorece
  ive,receive,preparetopass,pass,
  musicstop,musicstart,present(initial)
  not (parcel?) -gt (present exit
  HasnoParcelpreparetoreceive,receive,prepareto
  pass,pass, musicstop,musicstart,
  present)endproc

2

• ()( Player Has Parcel
  )()process
  HasParcelprepr,receive,prepp,pass,stop,start,win
  (pParcel) exit ( p is the parcel )(
  music is playing, player is about to pass the
  parcel )( pass the parcel 3 possibilities
  )( i) pass the parcel interrupted by music
  stop )( ii) pass the parcel, no interruptions
  )( iii) music stops before parcel passing
  commences ) (prepp (stop pass!p
  ((win exit)
  (start HasnoParcelprepr,r
  eceive,prepp,pass,stop,start,win))
  (pass!p HasnoParcelprepr,receive,pre
  pp,pass,stop,start,win)))
  ( music stops before beginning to pass
  )( unwrap the parcel and win if no wrappers
  left ) (let newpParcel unwrap(p) in
  (stop i (not(wrappers(newp)) -gt
  (win exit) (start
  HasParcelprepr,receive,prepp,pass,stop,start,win
  (newp)))))endproc

3

• ()( Player Does
  Not Have Parcel )(
  )process HasnoParcelprepr,receive,prepp,pass,st
  op,start,winexit ( music is playing,
  player is about receive the parcel )( receive
  the parcel 3 possibilities )( i) parcel
  passing interrupted by music stop, )(
  unwrap the parcel after receipt and exit if no
  wrappers left)( ii) receive the parcel, no
  interruptions )( iii) music stops before
  parcel passing commences) (prepr
  ((stop receive?pParcel i (let
  newpParcel unwrap(p) in
  (not(wrappers(newp)) -gt (win exit)
  (start HasParcelprepr,receive,pre
  pp,pass,stop,start,win(newp)))))
  (receive?pParcel HasParcelprepr,receive,
  prepp,pass,stop,start,win(p))))( music
  stops before parcel received )( don't actually
  receive anything ) (stop ((win exit)
  (start HasnoParcelprepr,re
  ceive,prepp,pass,stop,start,win)))endproc(
  )( Music
  )()proces
  s Musicstart,stop exit stop (exit
  start Musicstart,stop)endproc

4

• ()( A Game
  with 4 Players )(
  )process FourPlayerpreparetopass12,pass12,
  preparetopass23,pass23,
  preparetopass34,pass34,preparetopass41,pass41,
  musicstop,musicstart,present
  exit (((Playerpreparetopass41,pass41
  ,preparetopass12,pass12,
  musicstop,musicstart,present(true)
  preparetopass12,pass12,musicstop,musicstart,pres
  entPlayerpreparetopass12,pass12,preparetopass
  23,pass23, musicstop,musicstart,present(fa
  lse)) preparetopass23,pass23,musicstop,musi
  cstart,presentPlayerpreparetopass23,pass23,pr
  eparetopass34,pass34, musicstop,musicstart,
  present(false))preparetopass34,pass34,perpare
  topass41,pass41,musicstop,musicstart,presentPl
  ayerpreparetopass34,pass34,preparetopass41,pass41
  , musicstop,musicstart,present(false)
  )musicstart,musicstop(musicstart
  Musicmusicstart,musicstop)endprocendspec