Manual:Alias Engine

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React on input - Mudlets Alias Engine

Note Note: A screencast is available on getting started with aliases - watch it!

Mudlet has a feature called "aliases" that allows you to set up certain phrases or commands that will automatically trigger certain actions or responses. These actions are defined using a specific type of language called "Perl regex expressions." Aliases only work on the input that the user types into the command line, while a separate feature called "triggers" works on the output that the game sends back. When you type a command and press enter, it is sent to the alias feature to see if it matches any of the phrases or commands that have been set up. If it does match, the alias will take over and either send a different command to the game or run a script (a set of instructions) that you have defined. This system is powerful because it gives you control over what happens when a certain phrase or command is entered. You can even change the user's input as it is being processed, allowing you to manipulate the command before it is sent to the game.

Alias-diagram.png

The example in the diagram above shows 2 matching aliases, but only one of them sends commands to the game - and only if the player is healthy enough to attack the opponent. The other alias that matched the user input (enemy) choses a fitting opponent and sets the variable enemy accordingly, otherwise it issues a warning that attacking one of the available enemies would be too dangerous.

For an alias to match the command text the same rules as explained above in the trigger section apply. However, to simplify matters there is only one alias type. As alias are not performance critical we could reduce the amount of trigger types to just Perl regex as this type can do it all and performance is no issue with alias as the amount of data is much less. Even if you type like a madman you’ll never get close to sending the same amount of text to the game than the amount of text the game sends back to you.

What does it mean that a regex is true or "matched"? A trigger or an alias fires - or executes its commands/script - when the text matches the pattern of the trigger or alias. In most cases this means that the text contains the trigger/alias pattern. If the regex pattern is reen then a text "The green house" will match because "reen" is contained in the text. More complex regex patterns can also hold information on where in the text a certain pattern must occur in order to match. ^tj only matches when the letters "tj" occur at the beginning of the text. Consequently, a text like "go tj" would not match. Regex patterns can also capture data like numbers, sequences of letters, words etc. at certain positions in the text. This is very useful for game related scripting and this is why it is explained below.

Let’s get back to alias. We start with a simple example.

We want Mudlet to send "put weapon in bag" whenever we type "pwb". Consequently, the pattern is pwb and as the task is so simple it’s enough to enter "put weapon in bag" in the send field. Then we click on save to save the changes and activate the alias by clicking on the padlock icon. Then we leave the trigger editor and test our new alias. After typing "pwb" and pressing return Mudlet will send the command "put weapon in bag" to the game.

Let’s move on to a more complicated example that is needed very often.

We want our script to automatically put the weapon in the correct bag as we have many bags and many weapons. The pattern stays the same. ^pwb The ^ at the beginning of the line means that the command starts with pwd and no other letter in front of this. If we define our pattern more clearly, the pattern will match less often. Without the ^ the alias will match and the alias script will always be run whenever there is the sequence of letters "pwb" in your commands. This may not always be what you want. This is why it’s usually a good idea to make the pattern definition as exact as needed by being less general. The more general the pattern, the more often it will match.

Back to our task: The pattern is ^pwb. Let’s assume that we have defined 2 variables in some other script. The variable "weapon" is the weapon we use and the variable "bag" is the name of the bag. NOTE: In Mudlet global variables can be accessed anywhere from within Mudlet scripts - no matter if they have been defined in a trigger script, in an alias script or in a key or button script. As soon as it’s been defined it somewhere it is usable. To make sure that a variable is local only, i. e. cannot be referenced from other scripts, you have to use the keyword local in front of your variable definition. Back to our alias: Pattern is: ^pwb

Script is:

send(f"put {weapon} in {bag}")

Depending on the values of our variables weapon and bag the command "pwb" will be substituted with an appropriate command. To set your weapon and bag variables we use 2 more aliases: Alias to set the weapon: uw (\w)+

Script:

weapon = matches[2]
send( "wield " .. weapon )

To set our bag variable: Pattern:^set bag (.*)

bag = matches[2]

Now let’s go back to our initial problem. We want an alias to put our current weapon into our current bag. But what happens if we are in the middle of a fight and absolutely need to sip a healing potions because we are close to death and cannot take the risk that the bag may be too full to take the weapon? We want to upgrade out little alias to take into account that the bag may be full and chose an empty bag instead. To do this we set up a trigger that detects messages that indicate that the attempt to put the weapon in the bag failed. In this trigger we execute this little bag-is-full-detection-trigger Trigger Pattern: (type substring) Your bag is full.

Script:

bagIsFull = true;

This detection trigger will set the variable bagIsFull to true as soon as it sees the message "Your bag is full.". Then you know that you have to use your spare bag to take the weapon.

Now we have the tools to write an improved version of our little alias script:

if bagIsFull then
    send(f"put {weapon} in {spareBag}")
else
    send(f"put {weapon} in {bag}")
end

The next example is one of the most common aliases a tell alias: Pattern:^tj (.*)

Script:

send("tell Jane " .. matches[2])

Sadly, Jane is your fiancée and the one thing she is a vegetarian and absolutely hates all words that relate to meat. Luckily, you know enough about aliases by now to make her believe that you’d never ever even think about meat. So you head to your global function script (any script item will do as long as you define your variables outside of your function definitions. See the scripts chapter below for more information. In your script "my global functions" you add a Lua table containing a list of all of all words that a vegetarian might hate. For example:

happyJaneTable = {"meat", "burger", "steak", "hamburger", "chickenburger"}

Now you can upgrade your tell-jane script to automatically search our tell for all words that Jane might not like. In case such a word is found we substitute the entire tell with "How is the weather?".

for key, value in ipairs(happyJaneTable) do       -- looking at each element of the list
    badWord = happyJaneTable[key]                 -- check out the Lua table chapter below for more info
    begin, end = string.find(command, badWord)    -- begin holds the start position of the word, end* the end-position
    if begin ~= nil then                          -- we have found a bad word
        send("tell Jane How is the weather?")
        return
    end
end

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