Discworld Documentation:
LPC for Dummies
Written by Drakkos Wyrmstalker
N.B - This is a work in progress... a living document if you like. If it appears to be dead when you view it, don't worry. It's most likely just playing possum.
Comments on these chapters and tutorials can be e-mailed to Drakkos.
Tutorial Answers
QUESTION ONE:
"A plural for objects is automatically created when the object is setup. We've already looked at how set_main_plural() can be used to change the default way the mud pluralises our object. Using add_plural(), demonstrate how we can add further plurals to an NPC."
Add plural can be used in the same way we've already seen with add_adjective. We simply pass in the plural, or an array containing multiple plurals, in the setup of our npc. So if we wanted to add, say, porridges and greys as plurals (which we wouldn't, unless we speak like Gollum, my preciousss), we would use the line:
add_plural(({"greys", "porridges"})).
We would mainly use add_plural when we're coding an item that may have several correct pluralisations. Since the MUD will only add one plural as standard, we use add_plural() to make sure all the bases are covered.
QUESTION TWO:
"It's possible to make an NPC auto attack any players who enter the room. Using set_aggressive(), how would we do this?"
Set_aggressive takes a single integer argument of one, two or zero. If we pass in one as an argument, then the NPC becomes aggressive and will attack all players who enter its environment. If we pass it in as two, then the NPC will attack all players, and all NPCs who enter the environment. Passing in zero as an argument will make the NPC passive. So to make our NPC attack players, we use the line:
set_aggressive(1);
In the setup of the NPC.
QUESTION THREE:
"We can provide our NPC with some cash by using the adjust_money() command. How would we do this to provide our NPC with two Ankh-Morpork dollars and fifty Ankh-Morpork pence?"
Adjust money allows us to modify the NPC's purse. It takes two arguments, the first being the number of coins, and the second being the type of coins. We can get a list of valid types of coin by doing 'call query_valid_types() /obj/handlers/money_handler'. Somewhere in the list that appears are the two types of coin we're interested in: "Ankh-Morpork pence", "Ankh-Morpork dollar", So, we want to give our NPC two dollars:
adjust_money(2, "Ankh-Morpork dollar");
And fifty pence:
adjust_money(50, "Ankh-Morpork pence");
We put this wherever we want our NPC to get the money. In most cases, we'll put it into the setup() of our NPC.
QUESTION FOUR:
"Discworld being a magical place, it's not unusual for areas to have high levels of background magic. How would you use the set_background_enchant() function to give a room some ambient, residual magic?"
The function set_background_enchant takes a single integer as an argument, and sets the ambient background magic of the room as that value. The line in setup would look like:
set_background_enchant (100);
Which would give the background magic level to those who can sense octarine as: There is the residual taste of magic in this place Higher values, obviously, mean a greater level of background magic.
QUESTION FIVE:
"Add_alias() can also be used on rooms to add additional labels for exits. Demonstrate how you can alias exits to synonyms using this function."
Add_alias takes two arguments. The first being the alias, or aliases to apply to an exit, the second being the exit itself. For example:
add_exit ("north", "/oh/some/room", "road");
We can then allow people to go north by typing 'Bing' or 'Bong' by using:
add_alias ("bing", "north");
add_alias ("bong", "north");
Or combining the two into one call by passing in an array as the first argument:
add_alias (({"bing", "bong"}), "north");
We can use add_alias to make odd exits somewhat more forgiving, as well as to be flexible with regards to conventional exits.
QUESTION SIX:
"Some rooms are, obviously, larger than others. Demonstrate how we can make a room larger or smaller using the set_room_size() function."
Inside rooms have a default size of ten cubic units, a unit being roughly equivalent to a foot. So a normal inside room will be 10' by 10' by 10'.
We can change the size of a room by using the set_room_size() function. This takes a single argument, which may either be an integer specifying the size of the room, or an array consisting of the three dimensions.
If the argument is a single value, then the dimensions are assumed to be equal in all directions... in other words, the room is cubic. If we pass in an array, it takes the form ({north-south radius, east-west radius, up-down radius}). So we could use:
set_room_size (20);
To make a room of twenty cubic units, or:
set_room_size (({20, 10, 10}));
To make a room that has a radius of 20 going north to south, a radius of 10 going from east to west, and a radius of 10 going up and down.
QUESTION SEVEN:
"load_chat() allows for special character strings to be passed in which are later expanded. The help file for expand_string() details the codes for this. If passing in a command as 'emote swings $mposs$ hips.' will be expanded as 'The grey blob swings his hips.', what would we pass in to get:
a) The capitalised name of a random living object in the room
b) The pronoun (he/she/it) of an object attacking our NPC
c) The short description of a random object in the NPC's inventory."
We enclose our special case string between two $ symbols. This indicates to the output processing code that we want to treat the text between the symbols as special. The first character after the first dollar determines which object we're referring to:
m - The NPC itself
l - A random living object in the NPC's room
o - A random object in the inventory of the NPC
a - A random object in the NPC's attacker list, if one exists.
We then follow this immediately with the information we want to access about the object: name - We want the name of the object
cname - We want the capitalised name
gender - We want the gender string
poss - We want the possessive string
obj - We want the objective string
pronoun - We want the pronoun string
gtitle - We want the guild title
We also have ashort, possshort, theshort, and oneshort, and these call the relevant short() function on the NPC.
So, for the cases we have above, we want:
a) $lcname$ (l - random living, cname - capitalised name)
b) $apronoun$ (a - random attacker, pronoun - pronoun string)
c) $ooneshort$ (o - random object, oneshort - the short of the object)
These functions can be used in load_chat and load_a_chat in place of a specific reference, for example:
load_chat(20,({
1 , ": fiddles with $ooneshort$.",
}));
QUESTION EIGHT:
"If we pass in an array as action to be executed as a part of add_respond_to_with(), the NPC will randomly perform one of the commands. How would you write an add_respond_to_with to make an NPC say either 'bing' or 'bong' when the player says hello?"
When the action to be performed as a result of an add_respond_to_with is an array, then the NPC will randomly pick one of the elements of the array to execute. Again, these elements take the form of commands to be executed by the NPC, so we'd have:
add_respond_to_with(({ "@say",({"hello"}), }),
({"say Bing.", "say Bong"}));
Which would give two random reactions to a player saying hello.
QUESTION NINE:
"An NPC will execute a story of sorts it a load_chat action is passed in as an array. How would we define a load_chat to make our NPC perform three actions, one after the other, in order?"
Again, we can achieve this simply by passing in the command as an array. Unlike add_respond_to_with, the load_chat() will execute each of these commands in turn, at intervals dictated by the chat frequency. So if we had:
load_chat(20,({ 2, ({"' Hello.",
"' There.",
"' I'm talking in.",
"'Slow.",
"'Motion"}),
1, "' Bwah-ha-ha!", }) );
And our leetle NPC executed the first action (the story array), we'd get:
Our NPC says: Hello.
Our NPC says: There.
Our NPC says: I'm talking in.
Our NPC says: Slow.
Our NPC says: Motion.
Each element of the story array would be executed before the NPC performed any other random chats.
QUESTION TEN:
"We've shown above how to move an object into a room. If we had a physical object, such as a sword or a chest, how would it be possible to add the object to a room without it appearing in the inventory line? Add_hidden_object() may prove useful."
Add_hidden_object() adds an object as hidden to a room. Pretty obvious stuff, yes! But it still bears some further explanation. It takes a single object argument, the argument being the object reference we want to add to the room. It moves the object to the room and makes it invisible with regards to the inventory line of the room. It can still be looked at, touched, smelled, kissed, fondled, etc, etc, as normal. Any commands associated with the item can still be used as if the item was there normally. The only difference is that the item will not be shown along with any other physical objects in the room.
To take an example, let's say we have an item located at /w/your_name/clever_item. We want to move this into our room, so we do:
object ob = clone_object ("/w/your_name/clever_item");
ob->move (this_object());
And then we enter our room, to see:
This is a very cool room, with lots of cool things. More cool things than you could shake a particularly cool stick at!
There are two obvious exits: east and southwest.
A clever item is here.
> look clever item
It's very clever!
But say we don't want that... we want our item to be invisible. So instead, we do:
object ob = clone_object ("/w/your_name/clever_item");
add_hidden_object (ob);
And we get:
This is a very cool room, with lots of cool things. More cool things than you could shake a particularly cool stick at!
There are two obvious exits: east and southwest.
>look clever item
It's very clever!
So although our item does not appear in the inventory line, it is still in the room.
QUESTION ELEVEN
"Modify exit is an extremely useful function in room coding, Have a read of the helpfile and see if you can work out the code to
a) Change the exit message of a player so that it would appear as "<name> staggers off to the <direction>".
b) Change an exit so that it does not appear in the list of obvious exits in a room."
We've already discussed modify exit a little in tutorial four. This is just an expansion of what we discussed there. In this case, for the first we use the "exit mess" type. The value we pass in after that uses the special character code $N, which is replaced by the name of the object taking the exit. $F and $T are replaced with the from direction, and the to direction respectively. So we'd use a modify exit that looks like:
modify_exit("east", ({"exit mess",
"$N stagger$s off to the $T."}));
Remember the stagger$s thing is a pluralisation code... it will appear as 'staggers' for one object taking the exit, and 'stagger' if two objects take the exit:
Drakkos Wyrmstalker staggers off to the east.
Drakkos Wyrmstalker and Draktest stagger off to the east.
The second part of this exercise is achieved by using the "obvious" type. Again, we use it as above. We pass in a 1 if we want the exit to be obvious... in other words, we want it to appear in the list of obvious exits. We pass in a 0 if we want it to be hidden:
modify_exit("east", ({"obvious", 0}));
Remember that we can combine all of our modify_exit statements into a single line of code, like so:
modify_exit("east", ({"exit mess", "$N stagger$s off to the $T.", "obvious", 0}));
Which is equivalent to both of the previous modify_exits.
QUESTION TWELVE
"We can give NPCs access to guild commands using the add_known_command function. Using this and an add_combat_action, show how we can make an NPC crush and strike at an enemy, should they have an appropriate weapon."
Add_known_command takes a single string as an argument, and that string is the name of the command. The command must exist as a part of /cmds/guild-race, however, or it will not be added. In our setup(), we would have the following lines to provide our NPC with access to the crush and strike commands:
add_known_command ("crush");
add_known_command ("strike");
Then, we add a combat action to our NPC as we've done before:
add_combat_action(25, "beat_them",(: do_whack :));
And then a function to handle the actual crushing or striking:
void do_whack(object attacker, object target) {
if (target == this_object()) {
return;
}
if (sizeof (this_object()->query_holding())) {
switch (random (2)) {
case 0:
do_command ("crush " + file_name (target)
+ " with weapon");
break;
default:
do_command ("strike " + file_name (target)
+ " with weapon");
break;
}
}
}
Then, we give our NPC an appropriate weapon in its setup(), and tell it to hold it:
ARMOURY->request_item ("sledgehammer", 100);
init_equip();
And voila! We have an NPC ready to beat some excrement out of its foes wif a big hammer. Whee!
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