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Going Shopping

The next task is to add the shop. The definition can go straight after the code listed above (so that the shop exterior is placed in the jetty room). If you haven't already tried defining your own shop interior, you could do so now, remembering to add a counter and maybe some items for sale (which could just be Decoration objects for now). You could also try adding a bell on the shop's counter, which Heidi can ring for service.

Here's our version
+ Enterable -> insideShop 'small shop/store' 'shop'
  "The small, timber-clad shop has an open door, above which is a sign 
   reading GENERAL STORE"

insideShop : Room 'Inside Shop'
 "The interior of the shop is lined with shelves containing all sorts of 
  items, including basic foodstuffs, sweets, snacks, stationery, batteries,
  soft drinks and tissues. Behind the counter is a door marked 'PRIVATE'. "
 out = jetty
 north asExit(out)
 south : OneWayRoomConnector
       destination = backRoom
       canTravelerPass(traveler) { return traveler != gPlayerChar; }
        { "The counter bars your way to the door. "; }    

+ Decoration 'private door*doors' 'door'
  "The door marked 'PRIVATE' is on the far side of the counter, and there 
  seems to be no way you can reach it. The other door out to the jetty is to 
  the north. "

+ Fixture, Surface 'counter' 'counter'
  "The counter is about four feet long and eighteen inches wide. "

++ bell : Thing 'small brass bell' 'small brass bell'
  "The bell comprises an inverted hemisphere with a small brass knob 
   protruding through the top. Attached to the bell is a small sign. "
    verify() {}
    check() {}
    action() {"TING!";}

+++ Component, Readable 'sign' 'sign'
 "The sign reads RING BELL FOR SERVICE. "

+++ Component 'knob/button' 'knob'
  "The knob protrudes through the top of the brass hemisphere of the bell. "
  dobjFor(Push) remapTo(Ring, bell)

backRoom: Room 
  north = insideShop
Only a few things need any explanation here. The definition of backRoom is minimal because the Player Character will never visit it - the location exists solely as somewhere for the shopkeeper to be when she's not in the shop. We thus define the OneWayRoomConnector south from the shop interior so that the Player Character can't pass but the shopkeeper can. Although two doors are mentioned (or at least implied) by the room description, we supply a Decoration object to represent them; a fuller implementation isn't necessary. The essential items are the counter and the bell on the counter that the customer must ring to attract attention. This introduces a new class, the Component class, which, as its name suggests, treats objects of that class as components of the object that contains them. The sign is also of class Readable, which makes it a more likely target for a read command; it would also allow read sign to produce a different description if we had overridden the readDesc property on the object, but that would be rather fussy here. We allow the player to ring the bell either with ring bell or push knob, the latter command remapping to the former. Since ring is not a verb defined in the library, we need to define it, which we can do by copying the definition of Row and making the few necessary changes:

  'ring' singleDobj
  : RingAction
  verbPhrase = 'ring/ring (what)'

modify Thing
    preCond = [touchObj]
    verify() { illogical('{You/he} can\'t ring {that dobj/him}'); }
If we were designing this game for real, we'd probably want to populate the shop with a few more decoration objects, e.g. for the shelves, the items on the shelves, and a cash register on the counter; we'll be adding some of these later, the rest can be left, yet again, as an exercise for the reader. Right now we need to attend to what happens when the bell is rung; obviously more than just displaying the string 'TING' is required; we need to summon the shopkeeper.

There are several ways this could be done; the way we shall use here probably isn't the simplest or the most elegant, it's simply one that lets us try out some features of the library we haven't met yet. In brief, we'll cause the ringing of the bell to trigger a
SoundEvent. We'll then add a SenseConnector between the inside of the shop and the back room so that the SoundEvent can be detected by the shopkeeper even when she's in the back room, but we also need to make the shopkeeper a SoundObserver so she'll be receptive to the sound. We'll then have the sound trigger a daemon on the shopkeeper to make her walk into the shop one turn later (a fuse would have done just as well, so it doesn't much matter which we use here.)

This probably sounds rather complicated, if not downright incomprehensible, so let's take it one step at a time. First, we need to define the
bellRing : SoundEvent
We have made the SoundEvent responsible for producing the "TING!" so we've had to override its triggerEvent(source) method, otherwise the definition of bellRing would have been even simpler. The call to inherited(source) within triggerEvent(source) is absolutely vital here, since it's the inherited method (i.e. the behaviour defined on the class) that does all the work of notifying interested parties that the sound event has just happened. The source parameter is the object from which the sound is supposed to emanate. This is the bell, whose dobjFor(Ring) now needs to its action method redefined thus:
action()       {      bellRing.triggerEvent(self);     }  
Where self, of course, refers to the bell object. The next task is to make sure that the bell ring can be heard in the back room as well as the shop. To do that we need to define a SenseConnector between the two:
SenseConnector, Intangible 'wall' 'wall'
  connectorMaterial = paper
  locationList = [backRoom, insideShop]
If everything works as it should, giving the SenseConnector the name 'wall' should be unnecessary, but if something works unexpectedly and the parser wants to refer to this object, it's as well that it should have a recognizable name so we can see what's happening. Since the sound does notionally travel through the wall, that's a sensible name to give it. On the other hand, the player does not need to interact with this object in any way, so we make it of class Intangible (as well as SenseConnector), so that it does not have any physical presence. The connectorMaterial defines the senses this SenseConnector will pass: paper is predefined to be transparent to sound and smell but opaque to sight and touch; in this case we don't care one way or the other about smell, and since it does what we want with the other three senses, this will do fine.

Now all we have to do is to define the shopkeeper. At this point we shan't program all her behaviour, just what's needed to get her to respond to the bell ring:
shopkeeper : SoundObserver, Person 'young shopkeeper/woman' 'young shopkeeper'
"The shopkeeper is a jolly woman with rosy cheeks and fluffy blonde curls. "
  isHer = true
  properName = 'Sally'
  notifySoundEvent(event, source, info)
    if(event == bellRing && daemonID == nil && isIn(backRoom))
daemonID = new Daemon(self, &daemon, 2);   
    else if(isIn(insideShop) && event==bellRing)
     "<q>All right, all right, here I am!</q> says {the 
  daemonID = nil
    "{The shopkeeper/she} comes through the door and stands behind the 
      counter. ";
    daemonID = nil;   
  globalParamName = 'shopkeeper'
The first new feature to note here is the addition of SoundObserver to the shopkeeper's class list. This allows us to define the notifySoundEvent method, which will be triggered by the bell ring. Since the bell ring is the only soundEvent in the game we hardly need to test for it, but to be on the safe side we do so anyway (if event == bellRing). At the same time we check that the shopkeeper is still in the back room and that the daemon is not yet operative. We also check to see if the bell is rung while she's in the shop so she can simply respond with a suitable remark.

The complicated part is setting up the daemon. A new daemon is created with a call to
new Daemon(obj, prop, interval), where obj is the object it refers to, prop is the method on that object that is called each time the daemon is invoked, and interval is the number of turns between each invocation of the daemon. Here we define the daemon to run the daemon method (note that the parameter is supplied as &daemon) on self (the shopkeeper) every second turn (this means she won't come into the shop until the turn after the bell is rung). Since we want to be able to stop the daemon again we need to store a reference to the daemon, which we do in the property daemonID (note that we could have called the daemon method and the reference property anything we liked).

The daemon method first moves the shopkeeper into the shop and displays a suitable message to announce her arrival. We use
moveIntoForTravel rather than moveInto to move the shopkeeper since with the latter the library code tries to find a path to move her through, and may well end up moving her through the SenseConnector with dire consequences (i.e. a runtime error); moveIntoForTravel avoids this problem. Once the shopkeeper has moved the daemon has done its work, so we get it to tidy up after itself, first by calling daemonID.removeEvent(), and finally by resetting daemonID back to nil so we can easily test for there no longer being an active daemon.

In this particular case we could have achieved the same effect slightly easier by using a fuse rather than a daemon. Instead of
daemonID = new Daemon(self, &daemon, 2);  
We could have written
daemonID = new Fuse(self, &daemon, 1);  
(Note the change in the number from 2 to 1 to produce the same effect of the shopkeeper moving on the next turn). The use of the fuse would have avoided the need for the line:
We should still need to keep track of whether we had an active fuse (using daemonID, which we might rename fuseID had we used a fuse) in order to make sure that a second ringing of the bell while the fuse was still active did not cause the creation of a second fuse.

Having reached this point, we can start expanding the definition of the shopkeeper using ActorStates and TopicEntries as with Joe the Charcoal Burner; you might like to try this out for yourself before reading this guide's version over the page.
+ sallyTalking : InConversationState
   specialDesc = "{The shopkeeper/she} is standing behind the counter 
    talking with you. "
   stateDesc = "She's standing behind the counter talking with you. "
   nextState = sallyWaiting

++ sallyWaiting : ConversationReadyState
  specialDesc = "{The shopkeeper/she} is standing behind the counter,
    checking the stock on the shelves. "
  stateDesc = "She's checking the stock on the shelves behind the counter. "
  isInitState = true  
    if(!gPlayerChar.isIn(insideShop) && shopkeeper.isIn(insideShop)) 

+++ HelloTopic
  "<q>Hello, <<getActor.isProperName ? properName : 'Mrs Shopkeeper'>>,</q>
      you say.<.p>
    <q>Hello, <<getActor.isProperName ? 'Heidi' : 'young lady'>>, what can
    I do for you?</q> asks {the shopkeeper/she}."

+++ ByeTopic
   "<q>'Bye, then!</q> you say.<.p>
    <q>Goodbye<<getActor.isProperName ? ', Heidi' : nil>>. 
    See you again soon!</q> {the shopkeeper/she} beams in return. "

+++ ImpByeTopic
  "{The shopkeeper/she} turns away and starts checking the stock on the 
There is scarcely anything new here. Note the use of the double angle-bracket construction in the HelloTopic and ByeTopic to vary what's said according to whether Sally and Heidi have exchanged names yet, and the separate ImpByeTopic to decide what should be displayed when the conversation is ended; if the conversation ends because Heidi stops conversing or walks out of the shop, Sally simply goes back to work. Heidi will be considered to have stopped talking if she fails to address a conversational command to Sally for the number of turns in the attentionSpan of Sally's current InCoversationState. By default this is four; it can be made effectively infinite by setting attentionSpan to nil.

takeTurn() method is called once every turn that this is Sally's current ActorState. Here we use it to check whether Heidi is still inside the shop; if she isn't, and Sally still is, then we send Sally back to her back room. It may occur to you that the takeTurn method is effectively a kind of daemon; to produce the effect of Sally coming into the shop the turn after the bell is rung, we could simply have added a few extra lines of code to this takeTurn method, perhaps in conjunction with a custom property. We could have dispensed with the whole mechanism of SoundEvent and SenseConnector, and simply have added a line of code in the dobjFor(Ring) method of the bell to change the value of the custom property which the additional code in the takeTurn() method could test for. But then we'd have lost the opportunity to look at sensory events, sense connectors, fuses and daemons. If you want to try to do it the simpler way, by all means experiment.
Since the shopkeeper has been summoned by the ringing of the bell, she is likely to initiate the conversation rather than waiting to be addressed by her customer. To handle this, add the following line after daemonID = nil; at the end of the shopkeeper's daemon method:
initiateConversation(sallyTalking, 'sally-1');  
And then add the definition of the appropriate conversation node; a good place for it would be between the definition of the shopkeeper and the definition of sallyTalking:
+ ConvNode 'sally-1'
  npcGreetingMsg = "<q>Right, what can I get you?</q> she asks. <.p>"
We don't need to put any topics under this conversation node; its only function is to display the npcGreetingMsg. Any topics can then be handled by the sallyTalking:InConversationState. Let's start by adding a few now (put them after the definition of sallyWaiting):
++ AskTellTopic [shopkeeper, gPlayerChar]
  "<q>I'm Heidi. What's your name?</q> you ask.<.p>
  <q>Hello, Heidi; I'm <<shopkeeper.properName>>,</q> she smiles.

+++ AltTopic
 "<q>I'm feeling really <i>very</i> well today; how are you?</q> you 
 <q>I'm feeling very well too, thanks.</q> she tells you. "
 isActive = (shopkeeper.isProperName)

++ AskTellTopic @burner
  "<q>Do you know {the burner/him}, the old fellow who works in the 
   forest?</q> you enquire innocently.<.p>
  <q>He's not <i>that</i> old,</q> she replies coyly. "

++ AskTellTopic @tWeather
  "<q>Lovely weather we're having, don't you think?</q> you remark.<.p>
  <q>Absolutely,</q> she agrees, <q>and with luck, it should stay fine 

++ DefaultAskTellTopic, ShuffledEventList
    '<q>What do you think about ' + gTopicText + '?</q> you ask.<.p>
    <q>Frankly, not a lot.</q> she replies. ',
    '<q>I think it\'s really interesting that...</q> you begin.<.p>
    <q>Oh yes, really interesting.</q> she agrees. ',
    'You make polite conversation about ' + gTopicText + ' and
    {the shopkeeper/she} makes polite conversation in return. '

Most of this should be fairly familiar. Note that placing a list in square brackets, as in the [shopkeeper, gPlayerChar] in the first AskTellTopic means that the topic can be triggered by any of the objects in the list; so this topic will work equally well for ask shopkeeper about herself or tell shopkeeper about yourself. Note also the use of string concatenation (joining strings together with the + operator) in the DefaultAskTellTopic to allow the use of a variable element (gTopicText) in an EventList. The other slight novelty (unless you already experimented with it at the end of the previous chapter) is the use of a Topic object to talk about the weather; since the weather is not a physical object defined anywhere in the game, we don't have a game object to match it to. To cope with this type of situation, where you want to be able to converse about things that are not game objects, there is a special Topic class. In this case all we need define is:
tWeather : Topic 'weather';
There's nothing magic about the 't' with which I started the object name here; that's just a convention I use to mark it as a Topic object as opposed to an ordinary game object. Note that, unlike game objects, Topic objects are assumed to be known by default, so that they are always available to ask about and tell about commands. This can be changed by setting defining the isKnown property of the topic to nil when it is defined, e.g. if a player is to be informed about a gruesome murder during a conversation, but does not know of it when the game begins, one might define the murder topic object thus:
tMurder : Topic 'gruesome murder'
    isKnown = nil

When the player then learns of the murder at a later point one could use the
gSetKnown(tMurder) macro to set tMurder.isKnown = true.

Getting Started in TADS 3
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