Consider the following class dictionary, propagation patterns
and main program.

Find the UNKNOWNs so that the program fits the documentation.


// ============================================================
// BusRoute.cd : Class dictionary for bus routes.
// Written by Ali Ozmez for the COM3360 project.
// Last update on Tue Nov 28 17:11:12 1995.
// ============================================================

BusRoute =
	"BusRoute:" <name> RouteName
	"total" "route" "length" ":" <totalLength> RouteLen
	"consisting" "of" "bus" "stops" ":" <busStops> List(BusStop)
	"with" "assigned" "busses" ":" <buses> List(Bus).

BusStop	=
	<id> StopId
	"at:" <location> RouteLoc  // clockwise dist. from origin
	"with" "waiting" "list" ":" <waitingList> List(Person).

Bus =
	<id> BusId
	"at:" <position> RouteLoc  // clockwise dist. from origin
	[ "currently" "at" "stop" ":"  <currentStop>  StopId]
	"capacity:" <capacity> BusCapac
	"speed:" <speed> BusSpeed
	"carrying" "passenger(s)" ":" <passengers> List(Person).

Person =
	<id> PersonId
	"destination:" <destination> StopId.   // id of the dest. stop

List(S) ~ "(" { S } ")".

RouteName = <v> DemString.
RouteLen  = <v> DemNumber "ft".
RouteLoc  = <v> DemNumber "ft".
BusCapac  = <v> DemNumber "passengers".
BusSpeed  = <v> DemNumber "ft/min".
StopId    = <v> DemIdent.
BusId     = <v> DemIdent.
PersonId  = <v> DemIdent.

// ============================================================
// simulate.pp : Propagation patterns for bus route simulation.
// Written by Ali Ozmez for COM3360 project.
// Last update on Tue Nov 28 21:51:23 1995.
// ============================================================


// Following PP does a unit time long (1 min) simulation.
*operation* void simulate()
  *traverse*
    *from* BusRoute *to* Bus
  *carry*
    *in* BusRoute *busRoute = (@ this @)
    *along* *from* BusRoute *to* Bus
  *wrapper* Bus
    (@
     StopId *stopId = this->get_currentStop();
     if (stopId != NULL) {
       // waiting at a stop
       this->drop_passengers(stopId);
       this->load_passengers( busRoute->find_stop(stopId) );
       this->set_currentStop(NULL);   // prepare to move
     }	
     else {
       // moving along the route
       int prevPos = this->get_loc();
       int nextPos = (prevPos + this->get_spd()) % busRoute->get_len();
       BusStop *stop = busRoute->any_stop_around(prevPos, nextPos);
       if (stop == NULL)
	 this->proceed_to(nextPos);
       else if (this->have_stop_request( stop->get_id() )) {
	 this->proceed_to( stop->get_loc() );
	 this->set_currentStop( stop->get_id() );   // stop here
       }
       else {
	 int have_room = this->get_cap() - this->count_passengers(); 
	 if ( have_room && stop->anybody_waiting() ) {
	   this->proceed_to( stop->get_loc() );
	   this->set_currentStop( stop->get_id() );   // stop here
	 }
	 else
	   this->proceed_to(nextPos);
       }
     }
    @)

// PP to drop the passengers who want to get off at the current stop.

// The propagation pattern updates the Bus-object with the new passenger
// list. All persons who have arrived at the destination are
// removed from the bus. The destination is an argument to
// the propagation pattern.

*operation* void drop_passengers(StopId *iStopId)
  *traverse*
    *from* Bus *to* Person
  *carry*
    *in* Person_List *newPasList = (@ new Person_List() @)
    *along* *from* Bus *to* Person
  *wrapper* Person
    (@
     if (!iStopId->g_equal( this->get_destination() )) 
       newPasList->append(this);
     @)
  *wrapper* Bus *suffix*
    (@ this->set_passengers(newPasList); @)

// PP to load some (or all) of the people waiting at the stop.
*operation* void load_passengers(BusStop *iStop)
  *traverse*
    *from* Bus *to* Person_List
  *carry*
    *in* Person_List *newPasList
    *along* *from* Bus *to* Person_List
  *wrapper* Bus
    (@
     int allowance = this->get_cap() - this->count_passengers();
     newPasList = iStop->give_passengers(allowance);
     @)
  *wrapper* Person_List
    (@ this->concatenate(newPasList); @)

// PP to find the stop from its id. 

// Finds for a given BusRoute-object and StopId-object,
// the BusStop-object with the given StopId-object.

*operation* BusStop *find_stop(StopId *iStopId) *init* (@ NULL @)
  *traverse*
    *from* BusRoute *to* BusStop
  *wrapper* BusStop
    (@
     if (iStopId->g_equal( this->get_id() ))
       return_val = this;
     @)
  *wrapper* ~> BusStop_List, BusStop
    (@ if (return_val) return; @)

// PP to count the passengers travelling on a bus.
*operation* int count_passengers()
  *traverse*
    *from* Bus *to* Person_List
  *wrapper* Person_List
    (@ return_val = this->list_length(); @)

// PP to transfer people from a stop (to a bus).

// The following pp transfers people from a stop to a bus.
// It returns the list of passengers which the stop "gives",
// and it updates the BusStop object to reflect the people
// who have entered the bus.

*operation* Person_List *give_passengers(int allowance)
  *init* (@ new Person_List() @)
  *traverse*
    *from* BusStop *to* Person
  *carry*
    *in* Person_List *newWaitList = (@ new Person_List() @)
    *along* *from* BusStop *to* Person
  *wrapper* Person
    (@ 
     if (return_val->list_length() < allowance)
       return_val->append(this);
     else
       newWaitList->append(this);
     @)
  *wrapper* BusStop *suffix*
    (@ this->set_waitingList(newWaitList); @)

// PP to search for a stop in the given interval of route.
*operation* BusStop *any_stop_around(int prevPos, int nextPos)
  *init* (@ NULL @)
  *traverse*
    *from* BusRoute *to* BusStop
  *wrapper* BusStop
    (@ 
     int stopLoc = this->get_loc();
     if (prevPos < nextPos) {
       if ((stopLoc > prevPos) && (stopLoc <= nextPos))
         return_val = this;
     }
     else if ((stopLoc > prevPos) || (stopLoc <= nextPos))
       return_val = this;
     @)
  *wrapper* ~> BusStop_List, BusStop
    (@ if (return_val) return; @)

// PP to move the bus to its new position.
*operation* void proceed_to(int newPos)
  *traverse*
    *from* Bus *to* RouteLoc
  *wrapper* RouteLoc
    (@ this->get_v()->set_val(newPos); @)

// PP to see if there is any passenger who wants to get off at
// the specified stop.
*operation* int have_stop_request(StopId *iStopId) *init* (@ 0 @)
  *traverse*
    *from* Bus *to* Person
  *wrapper* Person
    (@
     if (iStopId->g_equal( this->get_destination() ))
       return_val = 1;
     @)
  *wrapper* ~> Person_List, Person
    (@ if (return_val) return; @)

// PP to see if anybody waiting at the specified stop.
*operation* int anybody_waiting() *init* (@ 0 @)
  *traverse*
    *from* BusStop *to* Person_List
   *wrapper* Person_List
     (@ return_val = this->empty(); @)

// PP to get the get the length of a BusRoute object as an int.
*operation* int get_len()
  *traverse*
    *from* BusRoute *to* RouteLen
   *wrapper* RouteLen
     (@ return_val = this->get_v()->get_val(); @)

// PP to get the get the position of a Bus or BusStop object as an int.
*operation* int get_loc()
  *traverse*
    *from* {Bus, BusStop} *to* RouteLoc
   *wrapper* RouteLoc
     (@ return_val = this->get_v()->get_val(); @)

// PP to get the get the capacity of a Bus object as an int.
*operation* int get_cap()
  *traverse*
    *from* Bus *to* BusCapac
   *wrapper* BusCapac
     (@ return_val = this->get_v()->get_val(); @)

// PP to get the get the speed of a Bus object as an int.
*operation* int get_spd()
  *traverse*
    *from* Bus *to* BusSpeed
   *wrapper* BusSpeed
     (@ return_val = this->get_v()->get_val(); @)


//-----------------------------------------------------------------
// main.C : Main function for bus route simulation program.
// Written by Ali Ozmez for COM3360 project.
// Last update on Tue Nov 28 17:11:23 1995.
//-----------------------------------------------------------------

#include "proj.h"

void out_of_store()
{
  cerr << "proj: operator new failed, out of store\n";
  exit( 1 );
}

#ifndef __GNUC__
extern PF set_new_handler( PF );
#else
extern "C"  PF set_new_handler( PF );
#endif

/*
 * GEN_DIR is a global variable containing the path of the generation
 * environment. This path is used to find the cd-print and cd-parse
 * class dictionaries.
 * Do NOT delete the following statement.
 */

char* GEN_DIR = getenv( "GEN_DIR" );

int main( int argc, char* argv[], char* envp[] )
{
  // set new handler to catch out of memory exception
  set_new_handler( &out_of_store );

  //----------------------------------------
  // Parsing an object 
  //----------------------------------------
  // specify file to parse in 
  const int MAXPATH = 256;
  char Dem_input[MAXPATH];

  // Input file is first argument
  if( argc >= 2 )
     strcpy( Dem_input, argv[1] );
  else {
     strcpy( Dem_input, "demeter-input" );  // default input 
  }

  // parse it in 
  cout << "Parsing in object in: " << Dem_input << "." << endl;
  BusRoute* iBusRoute = new BusRoute();
  if ( ( BusRoute* ) iBusRoute -> g_parse( Dem_input ) == NULL )
  {
     cerr << "Parser error." << endl;
     exit(1);
  }
  cout << endl;

  //----------------------------------------
  // Your own code follows after this 
  //----------------------------------------
  int i, stime;

  // Simulation time is the second argument
  stime = (argc >= 3) ? atoi(argv[2]) : 30;

  // Display the initial state of the bus route
  cout << "Initial state of the input bus route : \n\n";
  iBusRoute->g_print();

  // Do the simulation here
  for (i=1; i < stime; i++) {
    cout << "\n\nNext state (after " << i << " minutes) : \n\n";
    iBusRoute->simulate();
    iBusRoute->g_print();
  }
    
  // Display the final state of the bus route
  cout << "\n\nFinal state of the input bus route (after ";
  cout << stime << " minutes) : \n\n";
  iBusRoute->simulate();
  iBusRoute->g_print();

  cout << "\n\n*** FINISHED ***" << endl;

  return ( 0 );
}
Question 2:
===========

Consider the class dictionary from question 1.
It only provides for one bus route.

Change the class dictionary so that it describes a bus system
consisting of several bus routes. Specifically, you class dictionary
should accept the following sentence describing a bus system.
Assume that a bus system contains at least one BusRoute-object.

(busroutes

BusRoute: "Ruggles / Harvard Square"
total route length : 5000 ft
consisting of bus stops : (
  Stop0 at: 0 ft
	with waiting list : (
	  Person1 destination: Stop1))
with assigned busses : (
  Bus1 	at: 0 ft
	currently at stop : Stop0
	capacity: 5 passengers
	speed: 700 ft/min
	carrying passenger(s) : ())

++++

BusRoute: "Alewife / Burlington Square"
total route length : 5000 ft
consisting of bus stops : (
  Stop0 at: 0 ft
	with waiting list : (
	  Person1 destination: Stop1))
with assigned busses : (
  Bus1 	at: 0 ft
	currently at stop : Stop0
	capacity: 5 passengers
	speed: 700 ft/min
	carrying passenger(s) : ())
)

Find the UNKNOWNs below.
Your new class dictionary should have the following form:

BusSystem = UNKNOWN
FourPlusList ~ UNKNOWN.
followed by the class dictionary from question 1.



Traversal directive:

*from* { BusRoute } *to* { Bus } 

Propagation graph for traversal:

      BusRoute = < buses > Bus_List . 
      Bus_List ~ { Bus }.
      Bus = .


================================
Traversal directive:

*from* { Bus , BusStop } *to* { RouteLoc } 

Propagation graph for traversal:

      BusStop = < location > RouteLoc . 
      Bus = < position > RouteLoc . 
      RouteLoc = . 


Consider the C++ program below which was produced from the
simulate propagation pattern from question 1.
Find the UNKNOWNs below:

void BusRoute::simulate(  )
{
  // variables for carrying in and out
  UNKNOWN
  // outgoing calls
  // construction edge prefix wrappers
  this->get_buses()->simulate( busRoute  );
}

void Bus::simulate( UNKNOWN )
{
  // prefix class wrappers
     StopId *stopId = this->get_currentStop();
     if (stopId != NULL) {
       // waiting at a stop
       this->drop_passengers(stopId);
       this->load_passengers( busRoute->find_stop(stopId) );
       this->set_currentStop(NULL);   // prepare to move
     }	
     else {
       // moving along the route
       int prevPos = this->get_loc();
       int nextPos = (prevPos + this->get_spd()) % busRoute->get_len();
       BusStop *stop = busRoute->any_stop_around(prevPos, nextPos);
       if (stop == NULL)
	 this->proceed_to(nextPos);
       else if (this->have_stop_request( stop->get_id() )) {
	 this->proceed_to( stop->get_loc() );
	 this->set_currentStop( stop->get_id() );   // stop here
       }
       else {
	 int have_room = this->get_cap() - this->count_passengers(); 
	 if ( have_room && stop->anybody_waiting() ) {
	   this->proceed_to( stop->get_loc() );
	   this->set_currentStop( stop->get_id() );   // stop here
	 }
	 else
	   this->proceed_to(nextPos);
       }
     }
}

void Bus_List::simulate( BusRoute*  busRoute )
{
  // outgoing calls
  Bus_list_iterator	next_Bus(*this);
  Bus*		each_Bus;

  while ( UNKNOWN = UNKNOWN() )
  {
    each_Bus->simulate( busRoute  );
  }
}



#include "proj.h"



//  BusRoute  = "BusRoute:" 
//           <name > RouteName 
//           "total" 
//           "route" 
//           "length" 
//           ":" 
//           <totalLength > RouteLen 
//           "consisting" 
//           "of" 
//           "bus" 
//           "stops" 
//           ":" 
//           <busStops > BusStop_List 
//           "with" 
//           "assigned" 
//           "busses" 
//           ":" 
//           <buses > Bus_List .
void BusRoute::simulate(  )
{
  DEM_TRACE("BusRoute","void BusRoute::simulate()");
  // variables for carrying in and out
  BusRoute*  busRoute =  this ;

  // assignments for carrying in

  // prefix class wrappers

  // outgoing calls
  // construction edge prefix wrappers
  this->get_buses()->simulate( busRoute  );
  // construction edge suffix wrappers

  // suffix class wrappers

  // assignments for carrying out
}

//  Bus  = <id > BusId 
//      "at:" 
//      <position > RouteLoc 
//       [ <currentStop > StopId  ] 
//      "capacity:" 
//      <capacity > BusCapac 
//      "speed:" 
//      <speed > BusSpeed 
//      "carrying" 
//      "passenger(s)" 
//      ":" 
//      <passengers > Person_List .
void Bus::simulate( BusRoute*  busRoute )
{
  DEM_TRACE("Bus","void Bus::simulate(BusRoute*  busRoute)");
  // variables for carrying in and out

  // assignments for carrying in

  // prefix class wrappers

     StopId *stopId = this->get_currentStop();
     if (stopId != NULL) {
       // waiting at a stop
       this->drop_passengers(stopId);
       this->load_passengers( busRoute->find_stop(stopId) );
       this->set_currentStop(NULL);   // prepare to move
     }	
     else {
       // moving along the route
       int prevPos = this->get_loc();
       int nextPos = (prevPos + this->get_spd()) % busRoute->get_len();
       BusStop *stop = busRoute->any_stop_around(prevPos, nextPos);
       if (stop == NULL)
	 this->proceed_to(nextPos);
       else if (this->have_stop_request( stop->get_id() )) {
	 this->proceed_to( stop->get_loc() );
	 this->set_currentStop( stop->get_id() );   // stop here
       }
       else {
	 int have_room = this->get_cap() - this->count_passengers(); 
	 if ( have_room && stop->anybody_waiting() ) {
	   this->proceed_to( stop->get_loc() );
	   this->set_currentStop( stop->get_id() );   // stop here
	 }
	 else
	   this->proceed_to(nextPos);
       }
     }
    

  // outgoing calls

  // suffix class wrappers

  // assignments for carrying out
}

//  Bus_List  ~  { Bus  }. .
void Bus_List::simulate( BusRoute*  busRoute )
{
  DEM_TRACE("Bus_List","void Bus_List::simulate(BusRoute*  busRoute)");
  // variables for carrying in and out

  // assignments for carrying in

  // prefix class wrappers

  // outgoing calls
  Bus_list_iterator	next_Bus(*this);
  Bus*		each_Bus;

  while ( each_Bus = next_Bus() )
  {
  // repetition edge prefix wrappers
    each_Bus->simulate( busRoute  );
  // repetition edge suffix wrappers
  }

  // suffix class wrappers

  // assignments for carrying out
}