7 | |CENTER| *W was a watchman, and guarded the door;*
8 | |CENTER| *X was expensive, and so became poor.*
12 .. image:: /images/picW.png
15 |W|\e've given ourselves an interesting challenge by overusing that
16 convenient word "toilet", and here we show you how we resolve the
17 ambiguities that have been introduced. Also, it's time for the eponymous
18 owner of Benny's café to be developed in full.
23 If you check the ``name`` properties of the toilet door, the toilet key
24 and the toilet room, you’ll see that the dictionary word ``'toilet'``
25 occurs in all of them. There won't be any problems if players mention
26 the words DOOR or KEY, but we reach a strange impasse should they try to
27 perform some action with just the word TOILET. The interpreter has to
28 think fast: is the player talking about the key? About the door? Or
29 about the toilet? Unable to decide, it asks: "Which do you mean, the
30 door to the toilet, the toilet key or the toilet?"
32 And guess what? Players will never be able to refer to the toilet object
33 (unless they type BATH ROOM or REST ROOM, not an obvious choice since we
34 haven't used those phrases anywhere visible). If the player answers
35 TOILET the parser will still have three objects with that dictionary
36 word as a possible name, so it will ask again, and again -- until we
37 give it some dictionary word which is not ambiguous. A human reader
38 would be able to understand that the word TOILET alone refers to the
39 room, but the interpreter won't -- unless we help it a little.
41 We could work around this problem in more than one way, but we'll take
42 this opportunity of demonstrating the use of a third-party library
45 When experienced designers find a problem which is not easily solvable,
46 they may come up with a smart solution and then consider that others
47 could benefit from the effort. The product of this generosity takes the
48 form of a library extension: the solution neatly packaged as a file that
49 other designers can incorporate into their source code. These files can
50 be found in the IF Archive: go to
51 http://mirror.ifarchive.org/indexes/if-archive.html and then select
52 "``.../infocom``", "``.../compilers``", "``.../inform6``",
53 "``.../library``", and "``.../contributions``". All of these files
54 contain Inform code. To use a library extension (also known as a library
55 contribution), you should download it and read the instructions (usually
56 embedded as comments in the file, but occasionally supplied separately)
57 to discover what to do next. Normally, you ``Include`` it (as we have
58 already done with ``Parser``, ``VerbLib`` and ``Grammar``), but often
59 there are rules about where exactly this Include should be placed in
60 your source code. It is not unusual to find other suggestions and
63 To help us out of the disambiguation problem with the word TOILET, we are
64 going to use Neil Cerutti's extension ``pname.h``, which is designed for
65 situations precisely like this. First, we follow the link to the IF archive
66 and download the compressed file ``pname.zip``, which contains two more
67 files: ``pname.h`` and ``pname.txt``. We place these files in the folder
68 where we are currently developing our game or, if using the environment we
69 proposed in :doc:`02`, in the ``Inform\Lib\Contrib`` folder. The text file
70 offers instructions about installation and usage. Here we find a warning:
72 This version of pname.h is recommended for use only with version 6/10
73 of the Inform Library.
75 We're actually using a later version, but this doesn't seem to cause a
76 problem. Most extensions aren't so fussy, but ``pname.h`` fiddles with
77 some routines at the heart of the standard library; these may not be
78 identical in other Inform versions.
80 The introduction explains what ``pname.h`` does for you; namely, it lets
81 you avoid using complicated ``parse_name`` routines to disambiguate the
82 player's input when the same dictionary word refers to more than one
83 item. A ``parse_name`` routine would have been the solution to our
84 problem before the existence of this file, and it qualifies as an
85 advanced programming topic, difficult to master on a first approach.
86 Fortunately, we don't need to worry. Neil Cerutti explains:
88 The ``pname.h`` package defines a new object property, ``pname``
89 (short for phrase name), with a similar look and feel to the standard
90 ``name`` property: both contain a list of dictionary words. However,
91 in a ``pname`` property the order of the words is significant, and
92 special operators ``'.p'`` ``'.or'`` and ``'.x'`` enable you to embed
93 some intelligence into the list. In most cases where the standard
94 ``name`` property isn't enough, you can now just replace it with a
95 ``pname`` property, rather than write a ``parse_name`` property
98 We'll soon see how it works. Let's take a look at the installation
101 To incorporate this package into your program, do three things:
103 #. Add four lines near the head of the program (before you include
106 .. code-block:: inform
111 Replace TryGivenObject;
113 #. Include the ``pname.h`` header just after you include ``Parser.h``.
115 .. code-block:: inform
120 #. Add ``pname`` properties to those objects which require phrase
123 It seems simple enough. So, following steps one and two, we add those
124 ``Replace...`` lines before the inclusion of ``Parser``, and we include
125 ``pname.h`` right after it. ``Replace`` tells the compiler that we're
126 providing replacements for some standard routines.
128 .. code-block:: inform
130 Constant Story "Captain Fate";
132 "^A simple Inform example
133 ^by Roger Firth and Sonja Kesserich.^";
134 Release 3; Serial "040804"; ! for keeping track of public releases
136 Constant MANUAL_PRONOUNS;
138 Replace MakeMatch; ! requited by pname.h
141 Replace TryGivenObject;
147 Now our source code is ready to benefit from the library package. How
148 does it work? We have acquired a new property -- ``pname`` -- which can
149 be added to some of our objects, and which works pretty much like a
150 ``name`` property. In fact, it should be used *instead* of a ``name``
151 property where we have a disambiguation problem. Let’s change the
152 relevant lines for the toilet door and the toilet key:
154 .. code-block:: inform
157 with pname '.x' 'red' '.x' 'toilet' 'door',
161 Object toilet_key "toilet key" benny
162 with pname '.x' 'toilet' 'key',
166 while leaving the ``outside_of_toilet`` unchanged:
168 .. code-block:: inform
170 Object outside_of_toilet "toilet" cafe
171 with name 'toilet' 'bath' 'rest' 'room' 'bathroom' 'restroom',
175 We are now using a new operator -- ``'.x'`` -- in our ``pname`` word
178 The first dictionary word to the right of a ``'.x'`` operator is
179 interpreted as optional.
181 and this makes the dictionary word ``'toilet'`` of lesser importance for
182 these objects, so that at run-time players could refer to the DOOR or
183 TOILET DOOR or the KEY or TOILET KEY -- but not simply to the TOILET --
184 when referring to either the door or the key. And, by leaving unchanged
185 the name property of the ``outside_of_toilet`` object – where there is also
186 another ``'toilet'`` entry -- the ``pname`` properties will tell the
187 interpreter to discard the key and the door as possible objects to be
188 considered when players refer just to TOILET. Looking at it in terms of
189 the English language, we've effectively said that "TOILET" is an
190 adjective in the phrases "TOILET DOOR" and "TOILET KEY", but a noun when
191 used on its own to refer to the room.
193 The ``pname.h`` package has additional functionality to deal with more
194 complex phrases, but we don't need it in our example game. Feel free,
195 however, to read ``pname.txt`` and discover what this fine library
196 extension can do for you: it's an easy answer to many a disambiguation
200 Don't shoot! I'm only the barman
201 ================================
203 A lot of the action of the game happens around Benny, and his definition
204 needs a little care. Let's explain what we want to happen.
206 So the door is locked and the player, after discovering what the note
207 stuck on the toilet door said, will eventually ask Benny for the key.
208 Sadly, Benny allows use of the toilet only to customers, a remark
209 he'll make looking pointedly at the menu board behind him. The player
210 will have to ask for a coffee first, thereby qualifying as a customer
211 in Benny's eyes and thus entitled to make use of the toilet. At last!
212 Rush inside, change into Captain Fate’s costume and fly away to save
215 Except that the player neither paid for the coffee, nor returned the
216 toilet key. Benny will have to stop the player from leaving the café in
217 these circumstances. To prevent unnecessary complication, there will be
218 a coin near the lavatory, enough cash to pay for the coffee. And that
219 about sums it all up; pretty simple to describe -- not so simple to
220 code. Remember Benny's basic definition from the previous chapter:
222 .. code-block:: inform
224 Object benny "Benny" cafe
227 "A deceptively FAT man of uncanny agility, Benny entertains his
228 customers crushing coconuts against his forehead when the mood
230 has scenery animate male proper transparent;
232 We can now add some complexity, beginning with a ``life`` property. In
235 .. code-block:: inform
238 Give: !... code for giving objects to Benny
239 Attack: !... code to deal with player's aggressive moves
240 Kiss: !... code about the player getting tender on Benny
241 Ask,Tell,Answer: !... code to handle conversation
244 We have seen some of these actions before. We'll take care of the easier
247 .. code-block:: inform
250 if (costume has worn) {
252 print "Before the horror-stricken eyes of the surrounding
253 people, you MAGNIFICENTLY jump OVER the counter and
254 attack Benny with REMARKABLE, albeit NOT sufficient,
255 speed. Benny receives you with a TREACHEROUS upper-cut
256 that sends your GRANITE JAW flying through the cafe.^^
257 ~These guys in pyjamas think they can bully innocent
258 folk,~ snorts Benny, as the EERIE hands of DARKNESS
259 engulf your vision and you lose consciousness.";
262 "That would be an unlikely act for MEEK John Covarth.";
265 "This is no time for MINDLESS infatuation.";
268 "Benny is too busy for idle chit-chat.";
270 Attacking Benny is not wise. If the player is still dressed as John
271 Covarth, the game displays a message refusing to use violence by reason
272 of staying in character as a worthless wimp. However, if Captain Fate
273 attempts the action, we'll find that there is more to Benny than meets
274 the eye, and the game is lost. Kissing and conversation are disallowed
275 by a couple of tailored responses.
277 The Give action is a bit more complicated, since Benny reacts to certain
278 objects in a special and significant way. Bear in mind that Benny's
279 definition needs to keep track of whether the player has asked for a
280 coffee (thereby becoming a customer and thus worthy of the key), whether
281 the coffee has been paid for, and whether the toilet key has been
282 returned. The solution, yet again (this really is a most useful
283 capability), is more local property variables:
285 .. code-block:: inform
287 Object benny "Benny" cafe
290 "A deceptively FAT man of uncanny agility, Benny entertains his
291 customers crushing coconuts against his forehead when the mood
293 coffee_asked_for false, ! has player asked for a coffee?
294 coffee_not_paid false, ! is Benny waiting to be paid?
295 key_not_returned false, ! is Benny waiting for the key?
299 Now we are ready to tackle the ``Give`` action of the ``life`` property,
300 which deals with commands like GIVE THE KEY TO BENNY (in a moment, we'll
301 come to the ``Give`` action of the ``orders`` property, which deals with
302 commands like BENNY, GIVE ME THE KEY):
304 .. code-block:: inform
309 "You NEED your unpretentious John Covarth clothes.";
311 "You NEED your stupendous ACID-PROTECTIVE suit.";
313 self.key_not_returned = false;
314 move toilet_key to benny;
315 "Benny nods as you ADMIRABLY return his key.";
318 self.coffee_not_paid = false;
319 print "With marvellous ILLUSIONIST gestures, you produce the
320 coin from the depths of your ";
321 if (costume has worn) print "BULLET-PROOF costume";
322 else print "ordinary street clothes";
323 " as if it had dropped on the counter from Benny's ear!
324 People around you clap politely. Benny takes the coin
325 and gives it a SUSPICIOUS bite. ~Thank you, sir. Come
326 back anytime,~ he says.";
329 The Give action in the ``life`` property holds the variable ``noun`` as
330 the object offered to the NPC. Remember that we can use the ``switch``
331 statement as shorthand for:
333 .. code-block:: inform
335 if (noun == costume) { whatever };
336 if (noun == clothes) { whatever };
339 We won't let players give away their clothes or their costume (yes, an
340 improbable action, but you never know). The toilet key and the coin are
341 successfully transferred. The property ``key_not_returned`` will be set to
342 true when we receive the toilet key from Benny (we have not coded that bit
343 yet), and now, when we give it back, it's reset to ``false``. The ``move``
344 statement is in charge of the actual transfer of the object from the
345 player's inventory to Benny, and we finally display a confirmation
346 message. With the coin, we find a new statement: ``remove``. This extracts
347 the object from the object tree, so that it now has no parent. The effect
348 is to make it disappear from the game (though you are not destroying the
349 object permanently -- and indeed you could return it to the object tree
350 using the ``move`` statement); as far as the player is concerned, there
351 isn’t a COIN to be found anywhere. The ``coffee_not_paid`` property will be
352 set to true when Benny serves us the cup of coffee (again, we’ll see that
353 in a moment); now we reset it to ``false``, which liberates the player from
354 debt. This culminates with the ``"..."`` print-and-return statement,
355 telling the player that the action was successful. In passing, remember
356 that in :ref:`homely-atmos` we defined the counter such that PUT KEY ON
357 COUNTER is automatically translated into GIVE KEY TO BENNY .
359 Why move the key to Benny but remove the coin instead? Once players
360 qualify as customers by ordering a coffee, they will be able to ask for
361 the key and return it as many times as they like, so it seems sensible
362 to keep the key around. The coin, however, will be a one-shot. We won't
363 let players ask for more than one coffee, to prevent their debt from
364 growing ad infinitum -- besides, they came in here to change, not to
365 indulge in caffeine. Once the coin is paid, it disappears for good,
366 supposedly into Benny's greedy pockets. No need to worry about it any
369 The benny object needs also an ``orders`` property, just to take care of
370 the player's requests for coffee and the key, and to fend off any other
371 demands. The ``Give`` action in an ``orders`` property deals with inputs
372 like ASK BENNY FOR THE KEY or BENNY, GIVE ME THE KEY. The syntax is
373 similar to that of the ``life`` property:
375 .. code-block:: inform
377 orders [; ! handles ASK BENNY FOR X and BENNY, GIVE ME XXX
379 if (second ~= player or nothing) "Benny looks at you strangely.";
382 if (toilet_key in player) "But you DO have the key already.";
383 if (self.coffee_asked_for == true)
384 if (toilet_key in self) {
385 move toilet_key to player;
386 self.key_not_returned = true;
387 "Benny tosses the key to the rest rooms on the
388 counter, where you grab it with a dextrous and
389 precise movement of your HYPER-AGILE hand.";
392 "~Last place I saw that key, it was in YOUR
393 possession,~ grumbles Benny. ~Be sure to return it
396 "~Toilet is only fer customers,~ he grumbles, looking
397 pointedly at a menu board behind him.";
399 if (self.coffee_asked_for == true)
400 "One coffee should be enough.";
401 move coffee to counter;
402 self.coffee_asked_for = self.coffee_not_paid = true;
403 "With two gracious steps, Benny places his world-famous
404 Cappuccino in front of you.";
406 "Food will take too much time, and you must change NOW.";
408 "With only the smallest sigh, Benny nods towards the menu
409 on the wall behind him.";
411 "~I don't think that's on the menu, sir.~";
415 * We test the value of ``second`` in order to trap over-generous
416 gestures such as BENNY, GIVE COFFEE TO CUSTOMERS . Then we consider
419 * **Toilet key:** first, we check whether players already have the key
420 or not, and complain if they do, stopping execution thanks to the
421 implicit ``return true`` of the ``"..."`` statement. If players don’t
422 have the key, we proceed to check whether they've asked for a coffee
423 yet, by testing the ``coffee_asked_for`` property. If this is true ,
424 we should also check if the key is actually one of Benny’s
425 possessions -- a perverse player could get the key, then drop it
426 somewhere and ask for it again; if this should happen, we indicate
427 that Benny is nobody's fool with the message ``"~Last place I saw
428 that key..."``. Once all these fitting conditions are ``true``,
429 players will get the key, which means that they have to return it --
430 the ``key_not_returned`` property becomes ``true`` -- and we display
431 a suitable message. However, if the player didn't ask for a coffee,
432 Benny refuses to oblige, mentioning for the first time the menu board
433 where players will be able to see a picture of a cup of coffee when
434 they EXAMINE it. Take care to see how all the ``else`` clauses pair
435 up with the appropriate if statements, triggering responses for each
436 of the conditions that wasn't met.
438 * **Coffee:** we check whether players have already asked for a coffee,
439 by testing the ``coffee_asked_for`` property, and refuse to serve
440 another one if ``true``. If ``false``, we place the coffee on the
441 counter, and set the properties ``coffee_asked_for`` and
442 ``coffee_not_paid`` to ``true``. The message bit you know about.
444 * **Food:** we'll provide an object to deal with all of the delicious
445 comestibles to be found in the café, specifically those (such as
446 "pastries and sandwiches") mentioned in our descriptions. Although
447 that object is not yet defined, we code ahead to thwart player's
448 gluttony in case they choose to ask Benny for food.
450 * **Menu:** our default response -- "I don’t think that’s on the menu,
451 sir" -- isn’t very appropriate if the player asks for a menu, so we
452 provide a better one.
454 * **Default:** this takes care of anything else that the player asks
455 Benny for, displaying his curt response.
457 And before you know it, Benny's object is out of the way; however, don't
458 celebrate too soon. There’s still some Benny-related behaviour that,
459 curiously enough, doesn’t happen in Benny's object; we're talking about
460 Benny's reaction if the player tries to leave without paying or
461 returning the key. We promised you that Benny would stop the player, and
462 indeed he will. But where?
464 We must revisit the café room object:
466 .. code-block:: inform
468 Room cafe "Inside Benny's cafe"
470 "Benny's offers the FINEST selection of pastries and sandwiches.
471 Customers clog the counter, where Benny himself manages to
472 serve, cook and charge without missing a step. At the north side
473 of the cafe you can see a red door connecting with the toilet.",
475 Go: ! The player is about to depart. Is he making for the street?
476 if (noun ~= s_obj) return false;
477 if (benny.coffee_not_paid == true ||
478 benny.key_not_returned == true) {
479 print "Just as you are stepping into the street, the big hand
480 of Benny falls on your shoulder.";
481 if (benny.coffee_not_paid == true &&
482 benny.key_not_returned == true)
483 "^^~Hey! You've got my key and haven't paid for the
484 coffee. Do I look like a chump?~ You apologise as only a
485 HERO knows how to do and return inside.";
486 if (benny.coffee_not_paid == true)
487 "^^~Just waidda minute here, Mister,~ he says.
488 ~Sneaking out without paying, are you?~ You quickly
489 mumble an excuse and go back into the cafe. Benny
490 returns to his chores with a mistrusting eye.";
491 if (benny.key_not_returned == true)
492 "^^~Just where you think you're going with the toilet
493 key?~ he says. ~You a thief?~ As Benny forces you back
494 into the cafe, you quickly assure him that it was only
495 a STUPEFYING mistake.";
497 if (costume has worn) {
498 deadflag = 5; ! you win!
499 "You step onto the sidewalk, where the passing pedestrians
500 recognise the rainbow EXTRAVAGANZA of Captain FATE's costume
501 and cry your name in awe as you JUMP with sensational
502 momentum into the BLUE morning skies!";
505 first_time_out false, ! Captain Fate's first appearance?
507 Go: ! The player has just arrived. Did he come from the toilet?
508 if (noun ~= s_obj) return false;
509 if (costume has worn && self.first_time_out == false) {
510 self.first_time_out = true;
511 StartDaemon(customers);
517 Once again, we find that the solution to a design problem is not
518 necessarily unique. Remember what we saw when dealing with the player's
519 description: we could have assigned a new value to the
520 ``player.description`` variable, but opted to use the
521 ``LibraryMessages`` object instead. This is a similar case. The code
522 causing Benny to intercept the forgetful player could have been added,
523 perhaps, to a ``daemon`` property in Benny’s definition. However, since
524 the action to be intercepted is always the same one and happens to be a
525 movement action when the player tries to leave the café room, it is also
526 possible to code it by trapping the ``Go`` action of the room object.
527 Both would have been right, but this is somewhat simpler.
529 We have added a ``before`` property to the room object (albeit a longish
530 one), just dealing with the ``Go`` action. As we mentioned in an earlier
531 chapter, this technique lets you trap the player who is about to exit a
532 room before the movement actually takes place, a good moment to
533 interfere if we want to prevent escape. The first line:
535 .. code-block:: inform
537 if (noun ~= s_obj) return false;
539 is telling the interpreter that we want to tamper only with southwards
540 movement, allowing the interpreter to apply normal rules for the other
541 available directions.
543 From here on, it's only conditions and more conditions. The player may
546 * without paying for the coffee and without returning the key,
548 * having paid for the coffee, but without returning the key,
550 * having returned the key, but not paid for the coffee, or
552 * free of sin and accountable for nothing in the eyes of all men (well,
553 in the eye of Benny, at least).
555 The first three are covered by the test:
557 .. code-block:: inform
559 if (benny.coffee_not_paid == true || benny.key_not_returned == true) ...
561 that is, if either the coffee is not paid for *or* if the key is not
562 returned. When this condition is ``false``, it means that both
563 misdemeanours have been avoided and that the player is free to go.
564 However, when this condition is ``true``, the hand of Benny falls on the
565 player's shoulder and then the game displays a different message
566 according to which fault or faults the player has committed.
568 If the player is free to go, and is wearing the crime-fighting costume,
569 the game is won. We tell you how that's reported in the next chapter,
570 where we finish off the design.