7 | |CENTER| *U was a usurer, a miserable elf;*
8 | |CENTER| *V was a vintner, who drank all himself.*
12 .. image:: /images/picV.png
15 |V|\iewed from the inside, Benny's café is warm and welcoming, and packed
16 with lunchtime customers. We'll try to conjure up some appropriate images,
17 but the main focus of the room isn't the decor: it's the door leading to
18 the toilet -- and, perhaps, privacy?
25 Benny's café is populated with customers enjoying their lunch, so it won't
26 be a good place to change identities. However, the toilet to the north
27 looks promising, though Benny has strict rules about its use and the door
30 .. admonition:: Cultural Note
31 :class: admonition note
33 Not for the first time, this guide betrays its origins. In European
34 countries the word "toilet" often refers not only to the white porcelain
35 artefact, but also to the room in which it can be found (also, a
36 "bathroom" is for taking a bath, a "restroom" for taking a rest). Bear
37 with us on this; the dual usage becomes important a little later on.
39 We define the café room in simple form:
41 .. code-block:: inform
43 Room cafe "Inside Benny's cafe"
45 "Benny's offers the FINEST selection of pastries and
46 sandwiches. Customers clog the counter, where Benny himself
47 manages to serve, cook and charge without missing a step. At
48 the north side of the cafe you can see a red door connecting
53 We'll elaborate on the last line (``n_to toilet_door``) later, when we
54 define the door object which lies between the café and the toilet.
56 We've mentioned a counter:
58 .. code-block:: inform
60 Appliance counter "counter" cafe
61 with name 'counter' 'bar',
64 "The counter is made of an astonishing ALLOY of metals,
65 STAIN-PROOF, SPILL-RESISTANT and VERY EASY to clean. Customers
66 enjoy their snacks with UTTER tranquillity, safe in the notion
67 that the counter can take it all.",
74 That :prop:`before` property, superficially normal, actually conceals a
75 little surprise. By now you should be entirely comfortable with using an
76 object's :prop:`before` property to intercept an action directed at that
77 object; for example, if the player types HIT COUNTER then the counter's
78 :prop:`before` property is potentially able to intercept the resulting
79 :act:`Attack` action. However, the command PUT KEY ON COUNTER generates
80 *two* actions. First, a :act:`PutOn` action is offered to the key
81 (effectively saying, do you want to be placed on top of the counter?);
82 that’s the normal bit. And then the surprise: a :act:`Receive` action is
83 offered to the counter (effectively saying, are you happy to have the key
84 placed on you?) Both actions have the same opportunity of returning
85 :const:`false` to let the action continue, :const:`true` to prevent it.
87 .. Generated by autoindex
89 pair: LetGo; library action
90 pair: Receive; library action
92 The :act:`Receive` action is generated by the library in the ``PutOnSub``
93 action handler, and also in ``InsertSub`` (so a command like PUT BIRD IN
94 NEST sends a Receive to the nest object). There’s a matching :act:`LetGo`,
95 generated by the library from commands like TAKE KEY OFF COUNTER and REMOVE
96 BIRD FROM NEST. :act:`Receive` and :act:`LetGo` are examples of what’s
97 called a :term:`fake action`.
101 In "William Tell" we defined the ``quiver``, way back in
102 :ref:`possessions`, as an ``open container``. As things stand, the
103 player can put *any* held object, however inappropriate, into it. We
104 could have trapped the :act:`Receive` action to ensure that arrows are
105 the only acceptable contents (recollect that ``~~``, to be read as "not",
106 turns true into false and vice versa):
108 .. code-block:: inform
112 print_ret "But it was a present from Hedwig, your wife.";
114 if (~~(noun ofclass Arrow))
115 print_ret "Only arrows -- clean arrows -- go in your quiver.";
118 Here, we intercept any attempt to place an item on the counter, and
119 translate it into an attempt to give that item to Benny. Part of the
120 game's plot depends on the player returning the toilet key to Benny, and
121 also paying him for his delicious cup of world-famous Cappuccino. Putting
122 the key and the money on the counter is a reasonable alternative way for
123 the player to accomplish this.
125 We've also mentioned some customers. These are treated as NPCs, reacting
126 to our hero’s performance.
128 .. code-block:: inform
130 Object customers "customers" cafe
131 with name 'customers' 'people' 'customer' 'men' 'women',
133 if (costume has worn)
134 "Most seem to be concentrating on their food, but some do
135 look at you quite blatantly. Must be the MIND-BEFUDDLING
136 colours of your costume.";
138 "A group of HELPLESS and UNSUSPECTING mortals, the kind
139 Captain FATE swore to DEFEND the day his parents choked on a
140 DEVIOUS slice of RASPBERRY PIE.";
144 if (costume has worn)
145 "People seem to MISTRUST the look of your FABULOUS costume.";
147 "As John Covarth, you attract LESS interest than Benny's
150 "There's no telling what sorts of MUTANT bacteria these
151 STRANGERS may be carrying around.";
153 "Mindless massacre of civilians is the qualification for
154 VILLAINS. You are SUPPOSED to protect the likes of these
158 "These people don't appear to be of the cooperative sort.";
160 number_of_comments 0, ! for counting the customer comments
162 if (location ~= cafe) return;
163 if (self.number_of_comments == 0) {
164 self.number_of_comments = 1;
165 print "^Nearby customers glance at your costume with open
168 if (random(2) == 1) { ! do this 50% of the time
169 self.number_of_comments = self.number_of_comments + 1;
170 switch (self.number_of_comments) {
171 2: "^~Didn't know there was a circus in town,~ comments one
172 customer to another. ~Seems like the clowns have the
174 3: "^~These fashion designers don't know what to do to show
175 off,~ snorts a fat gentleman, looking your way. Those
176 within earshot try to conceal their smiles.";
177 4: "^~Must be carnival again,~ says a man to his wife, who
178 giggles, stealing a peek at you. ~Time sure flies.~";
179 5: "^~Bad thing about big towns~, comments someone to his
180 table companion, ~is you get the damnedest bugs coming
182 6: "^~I sure WISH I could go to work in my pyjamas,~ says a
183 girl in an office suit to some colleagues. ~It looks SO
185 default: StopDaemon(self);
189 has scenery animate pluralname;
191 Let's go step by step. Our hero enters the café dressed as John Covarth,
192 but will eventually manage to change clothes in the toilet, and he'll have
193 to cross back through the café to reach the street and win the game. The
194 customers' :prop:`description` takes into consideration which outfit the
195 player character is wearing.
197 .. Generated by autoindex
199 pair: Answer; library action
200 pair: Ask; library action
201 pair: Attack; library action
202 pair: Kiss; library action
203 pair: Tell; library action
204 pair: life; library property
206 In "William Tell" we’ve seen a brief manifestation of the :prop:`life`
207 property, but here we'll extend it a little. As we explained, :prop:`life`
208 lets you intercept those actions particular to animate objects. Here we
209 trap :act:`Attack` and :act:`Kiss` to offer some customised messages for
210 these actions when applied to the customers. Also, we avoid conversation
211 by intercepting :act:`Ask`, :act:`Tell` and :act:`Answer` in order just to
212 produce a message which depends on the player character's attire.
214 .. Generated by autoindex
216 pair: animate; library attribute
217 pair: orders; library property
219 One other feature of :attr:`animate` objects is the possibility of giving
220 them orders: BILL, SHAKE THE SPEAR or ANNIE, GET YOUR GUN . These actions
221 are dealt with in the :prop:`orders` property and, as with the :prop:`life`
222 property, the embedded routine can become quite complex if you want your
223 NPCs to behave in an interesting way. In this case, we don't need the
224 customers to perform tasks for us, so instead we provide a simple rejection
225 message, just in case the player tries to order people around.
227 .. Generated by autoindex
229 pair: daemon; library property
231 Which leaves us with the :prop:`daemon` bit. A daemon is a property
232 normally used to perform some timed or repetitive action without the need
233 of the player’s direct interaction; for example, machines which work by
234 themselves, animals that move on their own, or people going about their
235 business. More powerfully, a daemon may take notice of the player’s
236 decisions at a particular moment, allowing for some interactive behaviour;
237 this is, however, an advanced feature that we won't use in this example. A
238 daemon gets a chance of doing something at the end of every turn, typically
239 to (or with) the object to which it’s associated. In our example, the
240 daemon triggers some sneers and nasty comments from the customers once our
241 hero comes out of the toilet dressed in Captain Fate’s costume.
243 To code a daemon, you need to do three things:
245 #. First, define a daemon property in the object’s body; the value of the
246 property is always an embedded routine.
248 #. However, daemons do nothing until you activate them. This is easily
249 achieved with the call :samp:`StartDaemon({obj_id})`, which may happen
250 anywhere (if you want some object's daemon to be active from the
251 beginning of the game,you can make the call in your Initialise routine).
253 #. Once the daemon has finished its mission (if ever) you may stop it with
254 the call :samp:`StopDaemon({obj_id})`.
256 How does our particular daemon work? The appearance of our hero in full
257 crime-fighting wear will make the customers stare at him and make snarky
258 remarks. This must happen in the café room – the place where the customers
259 are -- so we need to make certain that the daemon does something
260 interesting only while the player stays in the right place (and hasn’t
261 wandered, say, back into the toilet):
263 .. code-block:: inform
265 if (location ~= cafe) return;
267 So if the location is not the café room (remember ~= means "not equal to"),
268 return without doing anything else; on this turn, there’s nothing for the
269 daemon to do. We use a plain ``return`` statement because the value
270 returned from a daemon doesn’t matter.
272 We have defined a customised local property, ``number_of_comments``, to
273 control the sequence of customers' remarks. When the Captain enters the
274 café room from the toilet for the first time, the value of the property
275 should be zero, so the statement block under the test:
277 .. code-block:: inform
279 if (self.number_of_comments == 0) {
280 self.number_of_comments = 1;
281 print "^Nearby customers glance at your costume with open
285 will happen only this once. What we intend is to output the text "Nearby
286 customers..." right after the startling entrance of our hero, setting up
287 the scene for the comments which are about to happen. Since we assign a
288 value of 1 to the property, the message will not be printed again. Notice
289 how we use an explicit ``print`` statement; the execution of the daemon
290 will continue normally to the next line.
292 We want the customers to indulge in witticisms once they see the costumed
293 Captain, but not on a completely predictable basis.
295 .. code-block:: inform
297 if (random(2) == 1) ...
299 ``random`` is an Inform routine used to generate random numbers or to
300 choose randomly between given choices; in the form
301 :samp:`random({expression})` it returns a random number between 1 and
302 ``expression`` inclusive. So our condition is actually stating: if a
303 random choice between 1 and 2 happens to be 1 then perform some action.
304 Remember that a daemon is run once at the end of every turn, so the
305 condition is trying to squeeze a comment from a customer roughly once every
308 Next, we proceed as we have already seen in "William Tell", with a switch
309 statement to order the comments in a controlled sequence by cunning use of
310 our tailored local property, ``number_of_comments``. We have written just
311 five messages (could have been one or a hundred) and then we reach the
312 default case, which is a good place to stop the daemon, since we have no
313 more customers’ remarks to display.
315 .. Generated by autoindex
317 pair: after; library property
319 Ah, but when does the daemon *start* functioning? Well, as soon as our
320 protagonist comes out of the toilet dressed in his multicoloured super-hero
321 pyjamas. Since we want to minimise the possible game states, we’ll make
322 some general rules to avoid trouble: (a) players will be able to change
323 only in the toilet; (b) we won’t let players change back into street
324 clothes; and (c) once players manage to step into the street thus dressed,
325 the game is won. So, we can safely assume that if players enter the café
326 in their Captain’s outfit, they’ll be coming from the toilet. As a
327 consequence of all this, we add an :prop:`after` property to the café room
330 .. code-block:: inform
332 Room cafe "Inside Benny's cafe"
334 first_time_out false, ! Captain Fate's first appearance?
336 Go: ! The player has just arrived. Did he come from the toilet?
337 if (noun ~= s_obj) return false;
338 if (costume has worn && self.first_time_out == false) {
339 self.first_time_out = true;
340 StartDaemon(customers);
346 There are two useful techniques to detect when the player is entering or
347 leaving a room. We'll later see in detail how to deal with a player trying
348 to go away and how to avoid it if need be. For now, let’s just mention
349 that, in both cases, you have to intercept the :act:`Go` action in a room
350 object; if you trap it in a :prop:`before` property, you’re checking for
351 departure from the room; if you trap it in an :prop:`after` property,
352 you’re checking for arrivals into the room. Right now we wish to know if
353 the player just came from the toilet, so we use an :prop:`after` property.
357 .. code-block:: inform
359 if (noun ~= s_obj) return false;
361 is telling the interpreter that we want to do something if the player
362 entered the room by typing a GO SOUTH command (this would normally mean
363 "coming from the north", but remember that nothing stops you from
364 connecting rooms without cardinal logic); the interpreter will apply normal
365 rules for the other available directions.
367 .. Generated by autoindex
369 pair: daemon; library property
370 pair: true; library constant
372 Then we check whether the player character is wearing the costume, in which
373 case it starts the :prop:`daemon` of the ``customers`` object. The use of
374 the local ``first_time_out`` property ensures that the condition is
375 :const:`true` only once, so the statement block attached to it runs also
378 We've finished with the customers in the café. Now, we have the toilet to
379 the north which, for reasons of gameplay *and* decency, is protected by a
385 Door objects require some specific properties and attributes. Let's first
388 .. code-block:: inform
390 Object toilet_door "toilet door" cafe
391 name name 'red' 'toilet' 'door',
393 "A red door with the unequivocal black man-woman
394 silhouettes marking the entrance to hygienic facilities.
395 There is a scribbled note stuck on its surface.",
399 has scenery door openable lockable locked;
401 We find this door in the café. We must specify the direction in which the
402 door leads and, as we have mentioned in the café's description, that would
403 be to the north. That’s what the :prop:`door_dir` property is for, and in
404 this case it takes the value of the north direction property :prop:`n_to`.
405 Then we must tell Inform the identity of the room to be found behind the
406 door, hence the :prop:`door_to` property, which takes the value of the
407 toilet room -- to be defined later. Remember the café's connection to the
408 north, ``n_to toilet_door``? Thanks to it, Inform will know that the door
409 is in the way, and thanks to the :prop:`door_to` property, what lies
412 .. Generated by autoindex
414 pair: door; library attribute
415 pair: lockable; library attribute
416 pair: locked; library attribute
417 pair: open; library attribute
418 pair: openable; library attribute
419 pair: with_key; library property
421 Doors *must* have the attribute :attr:`door`, but beyond that we have a
422 stock of options to help us define exactly what kind of door we are dealing
423 with. As for containers, doors can be :attr:`openable` (which activates
424 the verbs OPEN and CLOSE so that they can be applied to this object) and,
425 since by default they are closed, you can give them the attribute
426 :attr:`open` if you wish otherwise. Additionally, doors can be
427 :attr:`lockable` (which sets up the LOCK/UNLOCK verbs) and you can make
428 them :attr:`locked` to override their default unlocked status. The verbs
429 LOCK and UNLOCK are expecting some kind of key object to operate the door.
430 This must be defined using the :prop:`with_key` property, whose value
431 should be the internal ID of the key; in our example, the
432 soon-to-be-defined ``toilet_key`` . If you don't supply this property,
433 players won't be able to lock or unlock the door.
435 This simple door definition has one problem, namely, that it exists only in
436 the café room. If you wish the door to be present also from the toilet
437 side, you can either (a) define another door to be found in the ``toilet
438 room``, or (b) make this one a two-sided door.
440 Solution (a) seems superficially straightforward, but then you have the
441 problem of keeping the states of the two doors – open/closed,
442 locked/unlocked -- in synch. In this scenario, where you can access the
443 toilet only through this door, that wouldn't be too complicated, since you
444 could leave the door object in the café room opened all the time,
445 regardless of what players do with the door object in the toilet room and
446 vice versa -- they are never going to see them at the same time. In
447 general terms, though, such inconsistencies lead to problems; solution
448 (a) is best ignored for most purposes.
450 Solution (b) is better, since you have only one door object to deal with
451 and its possible states affect both sides. However, the coding gets a
452 little bit complicated and you''ll have to define routines for most
455 .. code-block:: inform
457 Object toilet_door "toilet door"
458 with name 'red' 'toilet' 'door',
460 if (location == cafe)
461 "A red door with the unequivocal black man-woman silhouettes
462 marking the entrance to hygienic facilities. There is a
463 scribbled note stuck on its surface.";
465 "A red door with no OUTSTANDING features.";
467 found_in cafe toilet,
469 if (location == cafe) return n_to;
473 if (location == cafe) return toilet;
477 has scenery door openable lockable locked;
479 First of all, the door now needs a :prop:`found_in` property, since it's
480 going to be located both in the café and the toilet. The
481 :prop:`description` checks which side of the door we are looking at –
482 testing the current value of the variable :var:`location`, which holds the
483 room the player is in -- because we have a scribbled note stuck on one
484 side, but not on the other. And the :prop:`door_dir` and :prop:`door_to`
485 properties must use the same trick, because we travel north from the café
486 into the toilet, but south from the toilet into the café.
488 Right now, the game will display "the toilet door" every time it needs to
489 refer to this object. It would be nice if we could somehow get the game to
490 distinguish between "the door to the toilet" and "the door to the cafe",
491 depending on the side we are facing. For this, a ``short_name property``
492 is the thing. We have already talked about the external name defined as
493 part of an object's header information:
495 .. code-block:: inform
497 Object toilet_door "toilet door"
499 That ``toilet door`` will be the name displayed by the game at run-time to
500 refer to the door. With identical effect, this could also have been coded
503 .. code-block:: inform
506 with short_name "toilet door",
508 :prop:`short_name` is a property that supplies the external name of an
509 object, either as a string or an embedded routine. Normally, objects
510 retain the same external name throughout the game -- and the header
511 information method is perfect in that case -- but if it needs to change,
512 it's easy to write a routine as the value of :prop:`short_name`:
514 .. code-block:: inform
517 with name 'red' 'toilet' 'door'
519 if (location == cafe) print "door to the toilet";
520 else print "door to the cafe";
526 Notice the ``return true`` at the end of the routine. You''ll recall that
527 the standard rule says "return false to carry on, true to take over and
528 stop normal execution". In the case of :prop:`short_name`, "carry on"
529 means "and now display the external name from the header information",
530 which is sometimes handy; for instance, you could write a
531 :prop:`short_name` routine to prefix an object's external name with one of
532 a range of adjectives -- perhaps a shining/flickering/fading/useless
537 What's displayed if there isn't an external name in an object's header?
538 If you've read the section :ref:`compile-as-you-go`, you'll recall that
539 the interpreter simply uses the internal identifier within parentheses;
540 that is, with no external name and no :prop:`short_name` property, we
543 You open the (toilet_door).
545 And the same principle applies if we were mistakenly to ``return false``
546 from this short_name routine: we would get, first, the result of our
547 ``print`` statement, and then the standard rules would display the
550 You open the door to the toilet(toilet_door).
552 Doors can get more complicated than this (no, please, don't throw our guide
553 out of the window). Here comes some optional deluxe coding to make the
554 door object a bit friendlier in game play, so you can skip it if you
557 Our door now behaves nicely at run-time. It can be locked and unlocked if
558 the player character has the right key; it can be opened and closed. A
559 sequence of commands to go into the toilet and lock the door behind you
560 would be: UNLOCK DOOR WITH KEY, OPEN DOOR, GO NORTH, CLOSE DOOR, LOCK DOOR
561 WITH KEY. After we are finished, let's go back to the café: UNLOCK DOOR
562 WITH KEY, OPEN DOOR, SOUTH. If the player is of the fastidious kind: CLOSE
563 DOOR, LOCK DOOR WITH KEY. This game features only one door, but if it had
564 three or four of them, players would grow restless (at the very least) if
565 they needed to type so many commands just to go through a door. This is
566 the kind of thing reportedly considered as poor design, because the game is
567 suddenly slowed down to get over a simple action which involves no secrets
568 or surprises. How exciting can the crossing of an ordinary door be, after
571 .. Generated by autoindex
573 pair: after; library property
574 pair: before; library property
576 If a few lines of code can make the life of the player easier, it's worth a
577 shot. Let's provide a few improvements to our toilet door in
578 :prop:`before` and :prop:`after` properties:
580 .. code-block:: inform
584 if (self hasnt locked || toilet_key notin player)
586 ks = keep_silent; keep_silent = true;
587 <Unlock self toilet_key>; keep_silent = ks;
590 if (self hasnt open) return false;
591 print "(first closing ", (the) self, ")^";
592 ks = keep_silent; keep_silent = true;
593 <Close self>; keep_silent = ks;
598 if (self has locked) return false;
599 print "You unlock ", (the) self, " and open it.^";
600 ks = keep_silent; keep_silent = true;
601 <Open self>; keep_silent = ks;
605 The basic idea here is to let the player who holds the key perform just one
606 action to both unlock *and* open the door (and, conversely, to close *and*
607 lock it). The relevant actions are :act:`Unlock` and :act:`Open`, and
608 :act:`Lock` (:act:`Close` is not necessary; if players just close the door
609 we shouldn’t assume that they want to lock it as well).
611 * **Open**: if the door isn't locked or the player doesn't hold the key,
612 keep going with the default :act:`Open` action defined by the library.
613 That leaves a locked door and a player holding the key, so we redirect
614 processing to the :act:`Unlock` action, giving as arguments the door
615 (self) and the toilet key. Since we are using single angle-brackets
616 ``<...>``, the action resumes after the unlocking is done (note that the
617 :act:`Unlock` action also takes care of opening the door). Finally, we
618 ``return true`` to stop the library from trying to open the door by
621 * **Lock**: if the door is already closed, keep going with the standard
622 library :act:`Lock` action. If not, tell players that we are closing the
623 door for them, redirect the action briefly to actually close it, and then
624 ``return false`` to let the :act:`Lock` action proceed as before.
626 .. Generated by autoindex
628 pair: true; library constant
630 * **Unlock**: we place this action in the after property, so (let's hope)
631 the :act:`Unlock` action has already happened. If the door is still
632 locked, something went wrong, so we ``return false`` to display the
633 standard message for an unsuccessful unlocking. Otherwise, the door is
634 now unlocked, so we inform the player that we are opening the door and
635 redirect the action to actually open it, returning :const:`true` to
636 suppress the standard message.
638 .. Generated by autoindex
640 pair: false; library constant
641 pair: keep_silent; library variable
643 In all processes there is a library variable called :var:`keep_silent`,
644 which can be either :const:`false` (the normal state) or :const:`true`;
645 when :const:`true`, the interpreter does not display the associated message
646 of an action in progress, so we can avoid things like:
648 .. code-block:: transcript
651 You open the door to the toilet.
652 You unlock the door to the toilet and open it.
654 Although we want to set :var:`keep_silent` to :const:`true` for the
655 duration of our extra processing, we need to reset it afterwards. In a
656 case like this, good design practice is to preserve its initial value
657 (which was probably :const:`false`, but you should avoid risky
658 assumptions); we use a local variable ``ks`` to remember that initial
659 setting so that we can safely restore it afterwards. You’ll remember that
660 a local variable in a standalone routine is declared between the routine’s
661 name and the semicolon:
663 .. code-block:: inform
665 [ BeenToBefore this_room;
667 In exactly the same way, a local variable in an embedded routine is
668 declared between the ``[`` starting marker of the routine and the
671 .. code-block:: inform
675 You can declare up to fifteen variables this way -- just separated by
676 spaces -- which are usable only within the embedded routine. When we
679 .. code-block:: inform
683 we are actually making ``ks`` equal to whatever value :var:`keep_silent`
684 has (either :const:`true` or :const:`false`; we actually don't care). We
685 then set :var:`keep_silent` to :const:`true`, make the desired silent
686 actions, and we assign:
688 .. code-block:: inform
692 which restores the value originally stored in ``ks`` to :var:`keep_silent`.
693 The effect is that we manage to leave it as it was before we tampered with
696 Well, that's about everything about doors. Everything? Well, no, not
697 really; any object can grow as complex as your imagination allows, but
698 we’ll drop the subject here. If you care to see more sophisticated doors,
699 check Exercises :dm4:`3 and 4 <s6.html#ex3>` in the |DM4|, where an
700 obliging door opens and unlocks by itself if the player simply walks in its
703 So far, we have the player in front of a locked door leading to the toilet.
704 A dead end? No, the description mentions a scribbled note on its surface.
705 This one should offer no problem:
707 .. code-block:: inform
709 Object "scribbled note" cafe
710 with name 'scribbled' 'note',
712 if (self.read_once == false) {
713 self.read_once = true;
714 "You apply your ENHANCED ULTRAFREQUENCY vision to the note
715 and squint in concentration, giving up only when you see the
716 borders of the note begin to blacken under the incredible
717 intensity of your burning stare. You reflect once more how
718 helpful it would've been if you'd ever learnt to read.
719 ^^A kind old lady passes by and explains:
720 ~You have to ask Benny for the key, at the counter.~^^
721 You turn quickly and begin, ~Oh, I KNOW that, but...~^^
722 ~My pleasure, son,~ says the lady, as she exits the cafe.";
725 "The scorched undecipherable note holds no SECRETS from
728 read_once false, ! has the player read the note once?
731 "No reason to start collecting UNDECIPHERABLE notes.";
735 Just notice how we change the description after the first time the player
736 examines the note, using the local property ``read_once`` created just for
737 this purpose. We don’t want the player to walk off with the note, so we
738 intercept the :act:`Take` action and display something more in character
739 than the default message for scenery objects: "That's hardly portable".
741 We've talked a lot about the toilet key; it seems about time to code it.
742 Originally, the key is in Benny's possession, and the player will have to
743 ask for it, just as the note explains. Although we'll define Benny in
744 detail throughout the next chapter, here we present a basic definition,
745 largely so that the key has a parent object.
747 .. code-block:: inform
749 Object benny "Benny" cafe
752 "A deceptively FAT man of uncanny agility, Benny entertains his
753 customers crushing coconuts against his forehead when the mood
755 has scenery animate male proper transparent;
757 Object toilet_key "toilet key" benny
758 with name 'toilet' 'key',
761 if (clothes has worn) print "the CRUCIAL key";
762 else print "the used and IRRELEVANT key";
766 "Your SUPRA PERCEPTIVE senses detect nothing of consequence
767 about the toilet key.",
770 "You SCAN your surroundings with ENHANCED AWARENESS,
771 but fail to detect any key.";
773 "Benny is trusting you to look after that key.";
776 While Benny has the key, there's logically no way to examine it (or perform
777 any other action involving it), but we want to prevent the interpreter from
778 objecting that ``You can't see any such thing``. We've made the
779 ``toilet_key`` a child of the ``benny`` object, and you can see that
780 Benny's got a :attr:`transparent` attribute; this means that the key is in
781 scope, and enables the player to refer to it without the interpreter
782 complaining. Because Benny also has an :attr:`animate` attribute, the
783 interpreter would normally intercept a TAKE KEY action with "That seems to
784 belong to Benny"; however, the same wouldn't apply to other commands like
785 TOUCH KEY and TASTE KEY. So, to prevent any interaction with the key while
786 it’s in Benny’s pockets, we define a :prop:`before` property.
788 .. code-block:: inform
792 "You SCAN your surroundings with ENHANCED AWARENESS,
793 but fail to detect any key.";
795 "Benny is trusting you to look after that key.";
798 All of the :prop:`before` properties that we've so far created have
799 contained one or more labels specifying the actions which they are to
800 intercept; you'll remember that in "William Tell" we introduced the
801 ``default`` action (see :ref:`props-class`) to mean "any value not already
802 catered for". There's one of those labels here, for the Drop action, but
803 that's preceded by a piece of code that will be executed at the start of
804 *every* action directed at the key. If it's still in Benny’s possession,
805 we display a polite refusal; if the player has it then we prevent careless
806 disposal; otherwise, the action continues unhindered.
808 (In fact, the hat-on-a-pole ``Prop`` introduced in :ref:`south-side` had
809 this all-exclusive :prop:`before` property:
811 .. code-block:: inform
815 print_ret "You're too far away at the moment.";
818 It would have behaved exactly the same if we'd omitted the ``default``
819 label, as we do here for Benny's key.)
821 .. Generated by autoindex
823 pair: article; library property
825 Another small innovation here: the :prop:`invent` library property (we
826 didn’t make it up) which enables you to control how objects appear in
827 inventory listings, overriding the default. Left to itself, the
828 interpreter simply displays the object's external name, preceded either by
829 a standard article like "a" or "some", or one specifically defined in the
830 object's :prop:`article` property. Here we replace "the toilet key" with
831 one of two more helpful descriptions, making it a most valuable object in
832 the eyes of John Covarth, and something to be despised haughtily by Captain
833 Fate once it's of no further use to him.
835 When we had players in the street, we faced the problem that they might
836 choose to examine the café from the outside. While it's unlikely that
837 they'll try to examine the toilet room from the outside, it takes very
838 little effort to offer a sensible output just in case:
840 .. code-block:: inform
842 Object outside_of_toilet "toilet" cafe
843 with name 'toilet' 'bath' 'rest' 'room' 'bathroom' 'restroom',
846 if (toilet_door has open) {
851 "Your SUPERB deductive mind detects that the DOOR is
854 if (toilet_door has open)
855 "A brilliant thought flashes through your SUPERLATIVE
856 brain: detailed examination of the toilet would be
857 EXTREMELY facilitated if you entered it.";
859 "With a TREMENDOUS effort of will, you summon your
860 unfathomable ASTRAL VISION and project it FORWARD
861 towards the closed door... until you remember that it's
862 Dr Mystere who's the one with mystic powers.";
864 <<Open toilet_door>>;
866 <<Close toilet_door>>;
868 "That would be PART of the building.";
870 has scenery openable enterable;
872 As with the ``outside_of_cafe`` object, we intercept an :act:`Enter`
873 action, to teleport players into the toilet room if they type ENTER TOILET
874 (or to display a refusal if the toilet door is closed). Players may try to
875 EXAMINE TOILET; they'll get a different message if the door is open -- we
876 invite them to enter it -- or if it's closed. OPEN TOILET and CLOSE TOILET
877 inputs are redirected to :act:`Open` and :act:`Close` actions for the
878 toilet door; remember that the double angle-brackets imply a ``return
879 true``, so that the action stops there and the interpreter does not attempt
880 to :act:`Open` or :act:`Close` the ``outside_of_toilet`` object itself
881 after it has dealt with the door.
883 You're right: the toilet looms large in this game (we blame it on early
884 maternal influences). We’ve introduced an ambiguity problem with the
885 ``outside_of_toilet`` object, and we'll need some help in fixing it.