TADS Programming - Ask/Tell - Part 2
   asktell.t: ASK/TELL-based conversation system for TADS
                            V1.0
            Suzanne Skinner, 1999, Public Domain
                        tril@igs.net

@~Concluded from last issue

ioTopicVerb: a verb which uses topics as indirect objects. Non-
topics will never show up in disambiguation questions. validIo and
validIoList are not used for scoping, nor are verIoAskAbout and
the like used. Instead, all disambiguation is done within
disambigIobj. If no topics match the player's input, that method
will return the special catchall topic catchallNonTopic. Since no
NPCs or infoSources know about this topic, it will simply cause a
"disavow" to be printed. Similarly, if topics match but no known
topics match, catchallUnknownTopic will be returned, which will
cause a reply of "you don't know about that" to any type of query
(ask, tell, consult, look up).

Important properties: none

class ioTopicVerb: deepverb
validIoList(actor, prep, dobj) = (nil)
validIo(actor, obj, seqno) = true
ioDefault(actor, prep) = (nil)

disambigIobj(actor, prep, dobj, verprop, wordlist, objlist,
flaglist, numberWanted, isAmbiguous, silent) = {
local i, len;
local newlist = [];
local unknownTopicsFound = nil;

len = length(objlist);
for (i=1; i <= len; i++) {
if (isclass(objlist[i], topic)) {
if (objlist[i].known)
newlist += objlist[i];
else
unknownTopicsFound = true;
}
}
if (length(newlist) < 1) {
if (unknownTopicsFound)
newlist += catchallUnknownTopic;
else
newlist += catchallNonTopic;
}
return newlist;
}
;

doTopicVerb: a verb which uses topics as direct objects.
disambigDobj simply calls disambigIobj on ioTopicVerb. See
ioTopicVerb for more details.

Important properties: none

class doTopicVerb: deepverb
validDoList(actor, prep, io) = (nil)
validDo(actor, obj, seqno) = true
doDefault(actor, prep, io) = (nil)

Allowing multiple objects can cause erroneous sdescs (e.g.
catchallNonTopic.sdesc) to get printed.

rejectMultiDobj(prep) = {
"You can't use multiple objects with that verb.";
return true;
}

disambigDobj(actor, prep, io, verprop, wordlist, objlist,
flaglist, numberWanted, isAmbiguous, silent) = {
    return ioTopicVerb.disambigIobj(actor, prep, io, verprop,
wordlist,
           objlist, flaglist, numberWanted, isAmbiguous, silent);
  }
;


********** adv.t Modifications ***********

Modifications to thing for default responses to ask, tell,
consult, look up, and redirections of ioConsultOn to doConsultOn,
ioAskFor to doAskFor.
Important properties: none, unless you want to change default
responses.

modify thing
  replace verDoAskAbout(actor, io) = {"There is no response.";}
  verIoAskFor(actor) = {}
  verDoAskFor(actor, io) = {"There is no response.";}
  ioAskFor(actor, dobj) = {dobj.doAskFor(actor, self);}

  replace verDoTellAbout(actor, io)= {"There is no response.";}

  verIoConsultOn(actor) = {}
  verDoConsultOn(actor, io) = {"That's not an information
source.";}
  ioConsultOn(actor, dobj) = {dobj.doConsultOn(actor, self);}
  verIoLookupIn(actor) = {"That's not an information source.";}
  verDoLookupIn(actor, io) = {}
;

Modifications to movableActor (parent class for all actors)

Important properties:
+ askTopics(topic, words): This method should output text and
return true for a valid topic, otherwise return nil, in which case
disavow will be printed by doAskAbout. The specific vocabulary
words used to refer to the topic are passed in the "words"
parameter.
+ tellTopics(topic, words): works almost identically to askTopics.
+ doAskFor(actor, io): You should override this method if you want
to allow the player to ask this NPC *for* something. Like "ask
about", it takes topics only. By default, it simply outputs
self.disavow.
+ disavow: default changed to "There is no response.". This
method will be called if askTopics returns nil.

+ tellDisavow: calls disavow by default. This method will be
called if tellTopics returns nil.

modify movableActor
  askTopics(topic, words) = {return nil;}
  tellTopics(topic, words) = {return nil;}
  doAskFor(actor, io) = {self.disavow;}
  replace disavow = "There is no response."
  tellDisavow = {self.disavow;}

  replace doAskAbout(actor, io) = {
    if (!self.askTopics(io, objwords(2)))
      self.disavow;
  }

  verDoTellAbout(actor, io) = {}
  doTellAbout(actor, io) = {
    if (!self.tellTopics(io, objwords(2)))
      self.tellDisavow;
  }

  verDoAskFor(actor, io) = {}
;

************** Special Objects *************

catchallNonTopic: If the game is expecting a topic, and the player
enters vocabulary that does not match any objects of the topic
class (known or unknown), then the disambiguation function on
ioTopicVerb or doTopicVerb will return a single-item list
consisting of catchallNonTopic. Since no NPC or infoSource will
have a response/entry for this topic, it will simply cause a
"disavow" statement to be printed.

Important properties: none

catchallNonTopic: knownTopic
  sdesc = "non-topic (you should never see this)"
;


catchallUnknownTopic: Similar to catchallNonTopic, this topic will
be returned by disambiguation functions if the player's vocabulary
matches no *known* topics, but at least one unknowntopic.  Default
messages are set here so that ask, tell, and consult will all
output topic.unknownMsg in response. The default message for "look
up" must be handled in infoSource itself, in ioLookupIn.

Important properties: none

catchallUnknownTopic: knownTopic
  sdesc = "unknown topic (you should never see this)"
  ioAskAbout(actor, dobj) = {topic.unknownMsg;}
  ioAskFor(actor, dobj) = {topic.unknownMsg;}
  ioTellAbout(actor, dobj) = {topic.unknownMsg;}
  ioConsultOn(actor, dobj) = {topic.unknownMsg;}
;



********* New and Replaced Verbs *******

replace askVerb: ioTopicVerb, darkVerb
  verb = 'ask'
  sdesc = "ask"
  prepDefault = aboutPrep
  ioAction(aboutPrep) = 'AskAbout'
  ioAction(forPrep) = 'AskFor'
;

replace tellVerb: ioTopicVerb, darkVerb
  verb = 'tell'
  sdesc = "tell"
  prepDefault = aboutPrep
  ioAction(aboutPrep) = 'TellAbout'
;

consultVerb: ioTopicVerb
  verb = 'consult'
  sdesc = "consult"
  prepDefault = onPrep
  ioAction(onPrep) = 'ConsultOn'
  ioAction(aboutPrep) = 'ConsultOn'
;

lookupVerb: doTopicVerb
  verb = 'look up' 'read about'
  sdesc = "look up"
  prepDefault = inPrep
  ioAction(inPrep) = 'LookupIn'
;

************ New Prepositions *************

forPrep: Prep
  preposition = 'for'
  sdesc = "for"
;
#pragma C-
                              - o -