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<HTML><HEAD><TITLE>Answer to Exercise 66</TITLE></HEAD>
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<BODY BGCOLOR="#FFFFFF">
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<TABLE><TR><TD Valign="top"><IMG SRC="../icons/exercise.gif" ALT="??"><TD bgcolor="#FAA89B"><B>ANSWER TO EXERCISE 66</B><TR><TD><TD>
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The scheme will work like this: any room that ought to have a name
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should have a <TT>place_name</TT> property set to a dictionary word;
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say, the Bedquilt cave could be called <TT>'bedquilt'</TT>. Clearly
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you should only be allowed to type this from adjacent rooms.
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So we'll implement the following: you can only move by name to
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those rooms listed in the current room's <TT>to_places</TT> property.
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For instance, the Soft Room might have <TT>to_places</TT> set to
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to_places Bedquilt Slab_Room Twopit_Room;
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Now the code: if the player's verb is not otherwise understood,
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we'll check it to see if it's a place name of a nearby room,
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and if so store that room's object number in <TT>goto_room</TT>, converting
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the verb to <TT>'go#room'</TT> (which we'll deal with below).
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[ UnknownVerb word p i;
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p = location.&to_places; if (p==0) rfalse;
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for (i=0:(2*i)<location.#to_places:i++)
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if (word==(p-->i).place_name)
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{ goto_room = p-->i; return 'go#room';
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{ print "go to ", (name) goto_room; rtrue; }
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(The supplied <TT>PrintVerb</TT> is icing on the cake: so the parser can
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say something like "I only understood you as far as wanting to go to
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Bedquilt.'' in reply to, say, "bedquilt the nugget''.) It remains
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only to create the dummy verb:
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if (goto_room hasnt visited) "But you have never been there.";
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Verb "go#room" * -> GoRoom;
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Note that if you don't know the way, you can't go there! A purist might
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prefer instead to not recognise the name of an unvisited room, back at
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the <TT>UnknownVerb</TT> stage, to avoid the player being able to deduce names
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of nearby rooms from this 'error message'.}
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<HR>Back to <A HREF="../section26.html#ex66">the exercise in section 26</A><HR>
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