In my lua script I need to call a function which takes an arbritary number of arguments with, well, an arbitrary number of arguments…
I am building up my arguments as a table as I cant know how many arguments there will be.
Sample code:
local result = call.someFunc();
local arguments = {}
for k,v in pairs(result) do
table.insert(arguments, v.name)
end
-- here I would like to somehow pass the whole table and each item in the table
-- is then passed as a single argument to "someOtherFunc"
call.someOtherFunc(arguments[1], arguments[2], arguments[3] ....)
I am pretty new to lua, in PHP e. g. I would use call_user_func_array – is there something similiar in lua?
foo(unpack(arguments)) is equivalent to foo(arguments[1], arguments[2], ...).
The long answer can be found on the Lua Users' Wiki.
This covers everything including trailing nil arguments.
Just pass the table as the argument. No need to split it up into single arguments, just have the function loop through the table.
Related
I can't figure out how to get Lua to return ALL matches for a particular pattern match.
I have the following regex which works and is so basic:
.*\n
This just splits a long string per line.
The equivelent of this in Lua is:
.-\n
If you run the above in a regex website against the following text it will find three matches (if using the global flag).
Hello
my name is
Someone
If you do not use the global flag it will return only the first match. This is the behaviour of LUA; it's as if it does not have a global switch and will only ever return the first match.
The exact code I have is:
local test = {string.match(string_variable_here, ".-\n")}
If I run it on the above test for example, test will be a table with only one item (the first row). I even tried using capture groups but the result is the same.
I cannot find a way to make it return all occurrences of a match, does anyone know if this is possible in LUA?
Thanks,
You can use string.gmatch(s, pattern) / s:gmatch(pattern):
This returns a pattern finding iterator. The iterator will search through the string passed looking for instances of the pattern you passed.
See the online Lua demo:
local a = "Hello\nmy name is\nSomeone\n"
for i in string.gmatch(a, ".*\n") do
print(i)
end
Note that .*\n regex is equivalent to .*\n Lua pattern. - in Lua patterns is the equivalent of *? non-greedy ("lazy") quantifier.
Without giving too much details, this sample snippet demonstrates the problem:
-- Add an extra predefined argument
function one_more_arg(...)
local args = {...}
return function()
print(table.unpack(args), "c")
end
end
local my_new_print = one_more_arg("a", "b")
my_new_print() -- "a c"
Apparently unpacking a table does not work in this scenario. Any ideas on how to make this work, ie print will receive "a", "b", "c"? I'm trying to avoid modifying args, unless it's the only way to achieve it.
When you place table.unpack() as an argument to function there should be no other arguments or it should be the last one. Otherwise only first value from table will be passed.
Lua always adjusts the number of results from a function to the
circumstances of the call. When we call a function as a statement, Lua
discards all of its results. When we use a call as an expression, Lua
keeps only the first result. We get all results only when the call is
the last (or the only) expression in a list of expressions. These
lists appear in four constructions in Lua: multiple assignment,
arguments to function calls, table constructors, and return
statements.
From http://www.lua.org/pil/5.1.html
So you can try to put unpack at the end if it is ok for you:
print("c", table.unpack(args))
Or modify args.
table.concat (list [, sep [, i [, j]]])
Given a list where all elements are strings or numbers, returns the string list[i]..sep..list[i+1] ··· sep..list[j]. The default value for sep is the empty string, the default for i is 1, and the default for j is #list. If i is greater than j, returns the empty string.
I am a newcomer to coding in general and I want to learn basic Lua scripting for my own hobby.
After working on a Lua script, the syntax all seems to be without error but I have come across one issue that I don't understand, I broke it down to this basic function:
{$lua}
ID1 = "10"
ID2 = "0"
if (ID1 ~= nil and ID1 == "10") then
writeInteger(ID2,"25")
end
print(ID2)
The issue is that the writeInteger does not seem to work at all, ID2 remains at value "0" while it should become "25".
Any help would be greatly appreciated.
This is not valid Lua, or at least it isn't valid vanilla (out-of-the-box) Lua, and since you have not specified anything else, there is not much we can do to help. I will assume writeInteger is a valid function (since your interpreter isn't complaining about a call to a nil value), but I don't think it works as you expect.
If you want to set the ID2 variable to 25, simply write:
ID2 = 25
Lua will convert the string type to an integer type automatically. You can run print(type(ID2)) to confirm this
If you are using cheat engine (as a quick google search suggests) the writeInteger function requires an address and a value.
function writeInteger(Address, Value): Boolean - Returns true on success.
I am not sure if ID2, a Lua variable, is a valid address, but I am sure that "25" is not an integer. You should remove the quotation marks to start, and since the function returns a boolean you can see if the function was successful by doing:
print(writeInteger(ID2, 25))
Lua uses pass by value for primitive types like numbers, booleans and strings. So if you pass a number to a function like writeInteger, it creates a local copy within the function. The function can alter this copy but it will have no effect on caller (of writeInteger in this case). I don't know how writeInteger is supposed to work but if you want to call a function which alters its argument you can create a table and pass that. Tables are still passed by value but the "value" of a table is its memory address (so in effect tables are passed by reference and you can alter the contents of a table by passing it to a function).
See more here
Function/variable scope (pass by value or reference?)
Luas string.format is pretty straight forward, if you know what to format.
However, I stuck at writing a function which takes a wildcard-string to format, and a variable number of arguments to put into that blank string.
Example:
str = " %5s %3s %6s %6s",
val = {"ttyS1", "232", "9600", "230400"}
Formatting that by hand is pretty easy:
string.format( str, val[1], val[2], val[3], val[4] )
Which is the same as:
string.format(" %5s %3s %6s %6s", "ttyS1, "232", "9600","230400")
But what if I wan't to have a fifth or sixth argument?
For example:
string.format(" %1s %2s %3s %4s %5s %6s %7s %", ... )
How can I implement a string.format with an variable number of arguments?
I want to avoid appending the values one by one because of performance issues.
The application runs on embedded MCUs.
Generate arbitrary number of repeats of whatever format you want with string.rep if format is the same for all arguments. Or fill table with all formats and use table.concat. Remember that you don't need to specify index of argument in format if you don't want to reorder them.
If you just need to concatenate strings together separated by space, use more suitable tool: table.concat(table_of_strings, ' ').
You can create a table using varargs:
function foo(fmt, ...)
local t = {...}
return t[6] -- might be nil
end
Ps, don't use # on the table if you expect the argument list might contain nil. Instead use select("#", ...).
I have a situation where I perform some operations on tables, call them T and V. I have set the metatable up correctly and everything works as expected. The issue is that I usually don't need the result of the calculation. So instead of writing
for i=1,5 do
_=T+V
end
is there a way to just have
for i=1,5 do
T+V
end
?
I am not using the Lua commandline so I cannot just write =T+V.
Make a function that does nothing and pass it to it:
function NOP() end
for i=1,5 do
NOP(T+V)
end
This additionally serves to document your intentions, and that the side-effect is what you're after.
Looking at syntax of Lua in extended BNF I don't see an way to construct an expression (exp) without a equal sign or something else.
There are only 4 cases where an expression (exp) can be used:
Assigning a value e.g. p = exp
As condition e.g. while exp then
In a function call i.e. f(exp)
for indexing i.e. t[exp]