Advanced Lua

Lua tables

A good overview of tables is available on Lua's wiki in the TablesTutorial. Nick Gammon has also written a nice overview on how to deal with Lua tables.

How to use multimatches[n][m]

multimatches[n][m] is the complement of matches[n] when matching multi-line triggers. multimatches[n][m] stores its matches by lines, inside each line are the relevant matches to it. The following example can be tested on the MUD batmud.bat.org:

In the case of a multiline trigger with these 2 Perl regex as conditions:

^You have (\w+) (\w+) (\w+) (\w+)

^You are (\w+).*(\w+).*

The command "score" generates the following output on batMUD:

 You have an almost non-existent ability for avoiding hits.
 You are irreproachably kind.
 You have not completed any quests.
 You are refreshed, hungry, very young and brave.
 Conquer leads the human race.
 Hp:295/295 Sp:132/132 Ep:182/181 Exp:269 >

If you add this script to the trigger:

showMultimatches()

The script, i.e. the call to the function showMultimatches() generates this output:

 -------------------------------------------------------
 The table multimatches[n][m] contains:
 -------------------------------------------------------
 regex 1 captured: (multimatches[1][1-n])
           key=1 value=You have not completed any quests
           key=2 value=not
           key=3 value=completed
           key=4 value=any
           key=5 value=quests
 regex 2 captured: (multimatches[2][1-n])
           key=1 value=You are refreshed, hungry, very young and brave
           key=2 value=refreshed
           key=3 value=young
           key=4 value=and
           key=5 value=brave
 -------------------------------------------------------

The function showMultimatches() prints out the content of the table multimatches[n][m]. You can now see what the table multimatches[][] contains in this case. The first trigger condition (=regex 1) got as the first full match "You have not completed any quests". This is stored in multimatches[1][1] as the value of key=1 in the sub-table matches[1] which, in turn, is the value of key=1 of the table multimatches[n][m].

The structure of the table multimatches:

multimatches {
                1 = {
                       matches[1] of regex 1
                       matches[2] of regex 1
                       matches[3] of regex 1
                              ...
                       matches[m] of regex 1 },
                2 = {
                       matches[1] of regex 2
                       matches[2] of regex 2
                             ...
                       matches[m] of regex 2 },
                 ...         ...
                n = {
                       matches[1] of regex n
                       matches[2] of regex n
                             ...
                       matches[m] of regex n }
}

The sub-table matches[n] is the same table matches[n] you get when you have a standard non-multiline trigger. The value of the first key, i. e. matches[1], holds the first complete match of the regex. Subsequent keys hold the respective capture groups. For example: Let regex = "You have (\d+) gold and (\d+) silver" and the text from the MUD = "You have 5 gold and 7 silver coins in your bag." Then matches[1] contains "You have 5 gold and 7 silver", matches[2] = "5" and matches[3] = "7". In your script you could do:

myGold = myGold + tonumber( matches[2] )
mySilver = mySilver + tonumber( matches[3] )

However, if you’d like to use this script in the context of a multiline trigger, matches[] would not be defined as there are more than one regex. You need to use multimatches[n][m] in multiline triggers. Above script would look like this if above regex would be the first regex in the multiline trigger:

myGold = myGold + tonumber( multimatches[1][2] )
mySilver = mySilver + tonumber( multimatches[1][3] )

What makes multiline triggers really shine is the ability to react to MUD output that is spread over multiple lines and only fire the action (=run the script) if all conditions have been fulfilled in the specified amount of lines.

Regex in Lua

Lua has its own, fast and lightweight pattern matching built in - see 20.2 – Patterns. Should you need proper regex however, Mudlet has lrexlib available - which works as a drop-in replacement; replace string. with rex. - for example string.gsub to rex.gsub. See manual for documentation.

-- example: strip out trailing .0's from text using a regex
local stripped = rex.gsub("1.0.0", [[(\.0+)+$]], '')
print(stripped)

Coroutines

Mudlet supports Lua's coroutines starting with 3.2.0, which opens up a whole lot of possibilities for the way you program your scripts. A pretty technical description and a tutorial is available, but for a quick explanation, think of coroutines allowing you to pause and resume running a function. If you're familiar with other clients, it is something like a #wait statement where a script will stop running, except unlike a #wait which auto-resumes the script later, you resume it when it yourself whenever you'd like.

Here's an example - add this code as a new script:

-- mudlet.supports didn't always exist, so if it's not already defined - define it
mudlet = mudlet or {}
mudlet.supports = mudlet.supports or {}

function ritual()
  send("get wood")
  -- think of coroutine.yield as yielding (giving away) control,
  -- so the function will stop here and resume on making fire 
  -- when called the next time
  coroutine.yield()
  send("make fire")
  coroutine.yield()
  send("jump around")
  coroutine.yield()
  send("sacrifice goat")
end

Make a ^ritual$ alias - which seems big, but that's just because there's a lot of explanation inside it:

-- coroutines weren't supported before 3.2, so don't do anything if this alias
-- is used in an older Mudlet
if not mudlet.supports.coroutines then return end

-- create a coroutine that'll be running our ritual function
-- or re-use the one we're already using if there is one
ritualcoroutine = ritualcoroutine or coroutine.create(ritual)

-- run the coroutine until a coroutine.yield() and see
-- if there's any more code to run
local moretocome = coroutine.resume(ritualcoroutine)

-- if there's no more code to run - remove the coroutine,
-- so next time you call the alias - a new one gets made
if not moretocome then
  ritualcoroutine = nil
end

Now try doing the ritual command. You'll see that the send()'s are being sent one at a time, instead of all at once as they would have been without the yields. Cool, huh?

You can also install the demo as a package - paste this into Mudlet:

lua function downloaded_package(a,b)if not b:find("oci",1,true)then return end installPackage(b)os.remove(b)cecho("package installed!\n")end registerAnonymousEventHandler("sysDownloadDone","downloaded_package")downloadFile(getMudletHomeDir().."/oci.mpackage","http://wiki.mudlet.org/images/3/36/Ritual-coroutine-demo.zip")

Note that if you'll be using coroutines as part of a package you'll give to others, remember about the if mudlet.supportscoroutines then return end bit. Older Mudlets that don't support coroutines might crash, which sucks. Newer ones that do support them are completely fine, however!

Coroutines have many uses: finite state machines, running intensive tasks (yielding every once in a while so Mudlet isn't frozen), and so on.

Introspective Facilities

Lua brings a helpful debug.getinfo(function) function, which gets you some information about functions defined, either by yourself in Mudlet object, or actual built-in Mudlet functions, which may come from Lua or C++ source themselves. If Lua, you will also see the filename, to review the function definition. Maybe you can learn from it, or help Mudlet improve otherwise. If the function stems from C++ the available information is limited however. Follow the link above to see more details and hints for using debug.getinfo() to your advantage.

Manual:Advanced Lua

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