Actually I am writting a programming language in Lua. It was quite fun. I've wrote a bit of standard library (stack op and simple io). Then I've thought about labels. It would look like in assembly. While and for loop aren't funny in any bit so programming in that language can be quite challenging. Here are some requirements for this system:
Label stack (or array, dictionary) must be accessible from global context.
Jump instruction handler will be in separate file.
This is how my label-handling function look like:
function handleLabel(name,currentLine)
end
I have no idea how to implement this kind of magic. First I've thought about that:
LabelLineIDS = {}
Labels = {}
Labelamount = 1;
function handleLabel(name,currentLine)
LabelLineIDS[Labelamount]=currentline
Labels[Labelamount]=name
Labelamount=Labelamount+1
end
-- In file "jump.lua":
local function has_value (tab, val)
for index, value in ipairs(tab) do
if value == val then
return index
end
end
print ("Error: Label not defined.") -- Bail out.
os.exit(1)
end
local function _onlabel()
local labelName = globalparams --Globalparams variable contain parameters to each function, at the moment
--this will contain label name. It _can_ be nil.
return LabelLineIDS[has_value(Labels, labelName)]
end
CurrLine = _onlabel() --Currline - current line that get's parsed.
--1 command per one line.
But I'm unsure is this well written or even work. Can you give me idea how to parse labels in my programming language (and write jump functions)? Or if my code is pretty ok at the moment, can you help me to improve it?
Using line counter in my parser I've decided to implement gotos like we can see in BASIC. Thanks everyone for help.
Related
I have a Lua function where I build a table of value and attempt to add it to a global table with a named key.
The key name is pulled from the function arguments. Basically, it's a filename, and I'm pairing it up with data about the file.
Unfortunately, the global table always comes back nil. Here's my code: (let me know if you need to see more)
(Commented parts are other attempts, although many attempts have been deleted already)
Animator = Class{}
function Animator:init(atlasfile, stringatlasfriendlyname, totalanimationstates, numberofframesperstate, booleanstatictilesize)
-- Define the Animator's operation mode. Either static tile size or variable.
if booleanstatictilesize ~= false then
self.isTileSizeStatic = true
else
self.isTileSizeStatic = false
end
-- Define the total animation states (walking left, walking right, up down, etc.)
-- And then the total frames per state.
self.numAnimationStates = totalanimationstates or 1
self.numAnimationFrames = numberofframesperstate or 2
-- Assign the actual atlas file and give it a programmer-friendly name.
self.atlasname = stringatlasfriendlyname or removeFileExtension(atlasfile, 'animation')
generateAnimationQuads(atlasfile, self.atlasname, self.numAnimationStates, self.numAnimationFrames)
end
function generateAnimationQuads(atlasfile, atlasfriendlyname, states, frames)
spriteWidthDivider = atlasfile:getWidth() / frames
spriteHeightDivider = atlasfile:getHeight() / states
animationQuadArray = generateQuads(atlasfile, spriteWidthDivider, spriteHeightDivider)
animationSetValues = {atlasarray = animationQuadArray, width = spriteWidthDivider, height = spriteHeightDivider}
--gAnimationSets[#gAnimationSets+1] = atlasfriendlyname
gAnimationSets[atlasfriendlyname] = animationSetValues
--table.insert(gAnimationSets, atlasfriendlyname)
end
Note: when using print(atlasfriendlyname) and print(animationSetValues), neither are empty or nil. They both contain values.
For some reason, the line(s) that assign the key pair to gAnimationSets does not work.
gAnimationSets is defined a single time at the top of the program in main.lua, using
gAnimationSets = {}
Animator class is called during the init() function of a character class called Bug. And the Bug class is initialized in the init() function of StartState, which extends from BaseState, which simply defines dummy init(), enter(), update() etc. functions.
StartState is invoked in main.lua using the StateMachine class, where it is passed into StateMachine as a value of a global table declared in main.lua.
gAnimationSets is declared after the table of states and before invoking the state.
This is using the Love2D engine.
Sorry that I came here for help, I've been picking away at this for hours.
Edit: more testing.
Trying to print the animationQuadArray at the index gTextures['buganimation'] always returns nil. Huh?
Here's gTextures in Main.lua
gTextures = {
['background'] = love.graphics.newImage('graphics/background.png'),
['main'] = love.graphics.newImage('graphics/breakout.png'),
['arrows'] = love.graphics.newImage('graphics/arrows.png'),
['hearts'] = love.graphics.newImage('graphics/hearts.png'),
['particle'] = love.graphics.newImage('graphics/particle.png'),
['buganimation'] = love.graphics.newImage('graphics/buganimation.png')
}
Attempting to return gTextures['buganimation'] returns a file value as normal. It's not empty.
My brain is so fried right now I can't even remember why I came to edit this. I can't remember.
Global table in Main.lua, all other functions can't access it.
print(gTextures['buganimation']) works inside the function in question. So gTextures is absolutely accessible.
Table isn't empty. AnimationSetValues is not empty.
I'm adding second answer because both are correct in context.
I ended up switching IDE's to VS Code and now the original one works.
I was originally using Eclipse LDT with a Love2D interpreter and in that environment, my original answer is correct, but in VS Code, the original is also correct.
So Dimitry was right, they are equivalent, but something about my actual Eclipse setup was not allowing that syntax to work.
I switched to VS Code after I had another strange syntax problem with the interpreter where goto syntax was not recognized and gave a persistent error. The interpreter thought goto was the name of a variable.
So I switched, and now both things are fixed. I guess I just won't use LDT for now.
Solution: Lua syntax. Brain Fry Syndrome
I wrote:
animationSetValues = {atlasarray = animationQuadArray, width = spriteWidthDivider, height = spriteHeightDivider}
Should be:
animationSetValues = {['atlasfile']=atlasfile, ['atlasarray']=animationQuadArray, ['width']=spriteWidthDivider, ['height']=spriteHeightDivider}
Edit: I'm fully aware of how to use answers. This was posted here to reserve my spot for an answer so I could edit it later when I returned back home, which is exactly what I'm doing right now. I'll keep the old post for archival purposes.
Original:
I solved it. I apologize for not posting the solution right now. My brain is melted into gravy.
I will post it tomorrow. Just wanted to "answer" saying no need to help. Solved it.
Solution is basically, "oh it's just one of those Lua things". Wonderful. I'm having so much fun with this language - you can tell by my blank expression.
From the language without line endings or brackets, but forced print parentheses... ugh. I'm going back to C# when this class is done.
This code is for a modding engine, Unitale base on Unity Written in Lua
So I am trying to use a Boolean Variable in my script poseur.lua, so when certain conditions are met so I can pass it to the other script encounter.lua, where a engine Predefined functions is being uses to make actions happens base on the occurring moment.
I tried to read the engine documentation multiple times, follow the exact syntax of Lua's fonction like GetVar(), SetVar(), SetGobal(),GetGlobal().
Searching and google thing about the Language, post on the subreddit and Game Exchange and tried to solve it by myself for hours... I just can't do it and I can't understand why ?
I will show parts of my codes for each.
poseur:
-- A basic monster script skeleton you can copy and modify for your own creations.
comments = {"Smells like the work\rof an enemy stand.",
"Nidhogg_Warrior is posing like his\rlife depends on it.",
"Nidhogg_Warrior's limbs shouldn't\rbe moving in this way."}
commands = {"GREET", "JUMP", "FLIRT", "CRINGE"}
EndDialougue = {" ! ! !","ouiii"}
sprite = "poseur" --Always PNG. Extension is added automatically.
name = "Nidhogg_Warrior"
hp = 99
atk = 1
def = 1
check = "The Nidhogg_Warrior is\rsearching for the Nidhogg"
dialogbubble = "rightlarge" -- See documentation for what bubbles you have available.
canspare = false
cancheck = true
GreetCounter = 5
Berserk = false
encounter:
-- A basic encounter script skeleton you can copy and modify for your own creations.
encountertext = "Nidhogg_Warrior is\rrunning frantically"
nextwaves = {"bullettest_chaserorb"}
wavetimer = 5.0
arenasize = {155, 130}
music = "musAncientGuardian"
enemies = {"poseur"}
require("Monsters.poseur")
enemypositions = {{0, 0}}
-- A custom list with attacks to choose from.
-- Actual selection happens in EnemyDialogueEnding().
-- Put here in case you want to use it.
possible_attacks = {"bullettest_bouncy", "bullettest_chaserorb", "bullettest_touhou"}
function EncounterStarting()
-- If you want to change the game state immediately, this is the place.
Player.lv = 20
Player.hp = 99
Player.name = "Teemies"
poseur.GetVar("Berserk")
end
Thank you for reading.
The answer to my problem was to use SetGobal(), GetGobal().
For some reasons my previous attempt to simply use SetGobal()Resulted in nil value despite writing it like that SetGobal("Berserk",true) gave me a nill value error, as soon as I launch the game.
But I still used them wrong. First I needed to put it SetGobal() at the end of the condition instead of at the start of the the poseur.lua script because the change of value... for some reasons was being overwritten by it first installment.
And to test the variable in the function in my encounter.lua, I needed to write it like that
function EnemyDialogueStarting()
-- Good location for setting monster dialogue depending on how the battle is going.
if GetGlobal("Jimmies") == true then
TEEEST()
end
end
Also any tips an suggestions are still welcome !
Well firstly, in lua simple values like bool and number are copied on assignment:
global={}
a=2
global.a=a--this is a copy
a=4--this change won't affect value in table
print(global.a)--2
print(a)--4
Secondly,
SetGobal and the other mentioned functions are not part of lua language, they must be related to your engine. Probably, they use word 'Global' not as lua 'global' but in a sense defined by engine.
Depending on the engine specifics these functions might as well do a deep copy of any variable they're given (or might as well not work with complicated objects).
I have a problem which i suppose must be very common and most of you would have faced it.
I have written a program in lua, say main.lua which on receiving key event should modify the coordinates and display the geometry figure.
This lua code calls reg.c, where it kind of registers.
Now in reg.c i have a function engine which receives the key pressed and passes it to the lua function responsible for key handling.
But by the time key event comes, lua code is done with the registration and exits, thus the call from engine() becomes illegal memory access leading to segmentation fault.
Also i suppose we can't have lua call hanging in reg function, and call engine function from somewhere else.
Then what should be the solution, please guide me through this.
#jacob: here is the prototype of what i am trying to achieve:
function key_handler() //this function will get the latest key pressed from some other function
{
draw.image();
draw.geometry();
...
...
while(1)
{
//draw Points until some condition goes wrong
}
}
Now, once entered into key_handler, while he is busy drawing the points unless and until the failing condition occurs, i am unable to receive key pressed till that time.
I hope this explanation is much simpler and have made my point, and will help others to understand the problem.
I am really sorry, but i am not good at expressing or making others understand.
One more thing, i ahve followed the C syntax to explain, however this is completely implemented in lua
Your code snippet is still largely non-informative (ideally one should be able to just run your code in a stock Lua interpreter and see your problem). If you're describing a Lua problem, use Lua code to describe it.
However I'm beginning to see where you want to go.
The thing you need to could do is have a coroutine that's called in your key handler, which passes an argument back to your handler:
function isContinue() --just to simulate whatever function you use getting keypresses.
-- in whatever framework you're using there will probably be a function key_pressed or the like.
print('Initialize checking function')
while true do
print('Continue looping?')
local ans = io.read():match('[yY]')
local action
if not ans then
print('Do what instead?')
action = io.read()
if action:match('kill') then -- abort keychecker.
break
end
end
coroutine.yield(ans,action)
end
print('finalizing isContinue')
return nil,'STOP' -- important to tell key_handler to quit too, else it'll be calling a dead coroutine.
end
function key_handler()
local coro = coroutine.create(isContinue)
local stat,cont,action
while true do
print'Draw point'
stat,cont,action = coroutine.resume(coro)
if not stat then
print('Coroutine errored:',cont)
elseif not cont then
print('isContinue interrupted keyhandler')
print("We'll "..action.." instead.")
break
end
end
print('finalizing key_handler')
end
key_handler()
-- type something containing y or Y to continue, all else aborts.
-- when aborting, you get asked what to do instead of continuing,
--- with "kill" being a special case.
This should be self explanatory. You should probably take a good look at Programming in Lua, chapter 9: Coroutines.
The big difficulty (well, if you're not accustomed to collaborative threading) is that a coroutine should yield itself: it's not the calling function that's in charge of returning control.
Hope this helps you.
For example, I have a table
table.insert( t, 1, function()
print ("rock");
end );
Is there any way to get function name from this table. I know that I can store name like a key, but what if I want to keep numeric index and also I want to know function name?
Is there any way to do it?
Thanks, on advance.
Say you have this code:
t = {}
x = 5
table.insert(t, 1, x)
t would then be {[1] = 5}. "5" is just a number - it has no name, and isn't associated with the variable "x"; it's a value.
In Lua, functions are treated exactly the same way, as values:
t = {}
x = function() print("test! :D") end
table.insert(t, 1, x)
The value of x is not associated with x in any way, shape, or form. If you want to manually name a function, you can do it by wrapping the function in a table, for example:
t = {}
x = function() print("test! :D") end
table.insert(t, 1, {
name = "MyFunctionName",
func = x
})
That is how you would do it!
...unless..
..you break the rules!
When Lua was developed, the developers realised that the anonymous nature of functions would make productive error messages difficult to produce, if not impossible.
The best thing you'd see would be:
stdin: some error!
stdin: in function 'unknown'
stdin: in function 'unknown'
So, they made it so that when Lua code was parsed, it would record some debug information, to make life easier. To access this information from Lua itself, the debug library is provided.
Be very careful with functions in this library.
You should exert care when using this library. The functions provided here should be used exclusively for debugging and similar tasks, such as profiling. Please resist the temptation to use them as a usual programming tool: they can be very slow. Moreover, several of these functions violate some assumptions about Lua code (e.g., that variables local to a function cannot be accessed from outside or that userdata metatables cannot be changed by Lua code) and therefore can compromise otherwise secure code.
To achieve your desired effect, you must use the debug.getinfo function; an example:
x = function()
print("test!")
print(debug.getinfo(1, "n").name)
end
x() -- prints "test!" followed by "x"
Unfortunately, the form of debug.getinfo that operates directly on a function doesn't fill the name argument (debug.getinfo(x, "n").name == nil) and the version above requires you to run the function.
It seems hopeless!
...unless..
..you really break the rules.
The debug.sethook function allows you to interrupt running Lua code at certain events, and even change things while it's all happening. This, combined with coroutines, allows you to do some interestingly hacky stuff.
Here is an implementation of debug.getfuncname:
function debug.getfuncname(f)
--[[If name found, returns
name source line
If name not found, returns
nil source line
If error, returns
nil nil error
]]
if type(f) == "function" then
local info = debug.getinfo(f, "S")
if not info or not info.what then
return nil, nil, "Invalid function"
elseif info.what == "C" then
-- cannot be called on C functions, as they would execute!
return nil, nil, "C function"
end
--[[Deep magic, look away!]]
local co = coroutine.create(f)
local name, source, linedefined
debug.sethook(co, function(event, line)
local info = debug.getinfo(2, "Sn")
name = info.namewhat ~= "" and info.name or nil
source, linedefined = info.short_src, info.linedefined
coroutine.yield() -- prevent function from executing code
end, "c")
coroutine.resume(co)
return name, source, linedefined
end
return nil, nil, "Not a function"
end
Example usage:
function test()
print("If this prints, stuff went really wrong!")
end
print("Name = ", debug.getfuncname(test))
This function isn't very reliable - it works sometimes, and doesn't others. The debug library is very touchy, so it's to be expected.
Note that you should never use this for actual release code! Only for debugging!
The most extreme case that is still acceptable is logging errors on piece of released software, to help the developer fix issues. No vital code should depend on functions from the debug library.
Good luck!
The function hasn't got any name. If you want you can assign it to a named variable:
theFunction = t[1]
-- Call it:
theFunction()
If what you want is storing a named function to the table, define it beforehand and use its name to store it:
theFunction = function()
print ("rock");
end
table.insert(t, 1, theFunction)
If this is not what you meant, give more details; for example how you would like to access the function. You're question is a bit misty.
The thing is table.insert considers the table as a sequence, only with numeric keys.
If you want to be able to call the function as t.fun() you'll have to use the table as an associative array and hence use a string as key. (BTW any type except nil or NaN are allowed as key)
t={}
t['MyFun']=function print'foo' end
t.myFun() -- uses syntactic sugar for string keys that are valid identifiers.
You might also notice that functions are passed by reference. So all functions are actually anonymous, and are just stored as a value to a certain key or variable.
You can store the names in a separate table.
functions = {}
functionNames = {}
function addFunction(f, name)
table.insert(functions, f)
functionNames[name] = f
end
To get the function, you can use the index. Once you have the function, you can get its name from function_names:
f = functions[3]
name = functionNames[f]
Good luck!
I've implemented my own class system and I'm having trouble with __tostring; I suspect a similar issue can happen with other metamethods, but I haven't tried.
(Brief detour: each class has a __classDict attribute, holding all methods. It is used as the class instances' __index. At the same time, the __classDict's __index is the superclass' __classDict, so methods in superclasses are authomatically looked up.)
I wanted to have a "default tostring" behavior in all instances. But it didn't work: the "tostring" behavior doesn't "propagate" through subclasses correctly.
I've done this test exemplifying my issue:
mt1 = {__tostring=function(x) return x.name or "no name" end }
mt2 = {}
setmetatable(mt2, {__index=mt1})
x = {name='x'}
y = {name='y'}
setmetatable(x, mt1)
setmetatable(y, mt2)
print(x) -- prints "x"
print(mt2.__tostring(y)) -- prints "y"
print(y) -- prints "table: 0x9e84c18" !!
I'd rather have that last line print "y".
Lua's "to_String" behaviour must be using the equivalent of
rawget(instance.class.__classDict, '__tostring')
instead of doing the equivalent of
instance.class.__classDict.__tostring
I suspect the same happens with all metamethods; rawget-equivalent operations are used.
I guess one thing I could do is copying all the metamethods when I do my subclassing (the equivalent on the above example would be doing mt2.__tostring = mt1.__tostring) but that is kind of inelegant.
Has anyone fought with this kind of issue? What where your solutions?
I suspect the same happens with all metamethods; rawget-equivalent operations are used.
That is correct.
from the lua manual:
... should be read as rawget(getmetatable(obj) or {}, event). That is, the access to a metamethod does not invoke other metamethods, and the access to objects with no metatables does not fail (it simply results in nil).
Generally each class has its own metatable, and you copy all references to functions into it.
That is, do mt2.__tostring = mt1.__tosting
Thanks to daurnimator's comments, I think I found a way to make metamethods "follow" __index as I want them to. It's condensed on this function:
local metamethods = {
'__add', '__sub', '__mul', '__div', '__mod', '__pow', '__unm', '__concat',
'__len', '__eq', '__lt', '__le', '__call', '__gc', '__tostring', '__newindex'
}
function setindirectmetatable(t, mt)
for _,m in ipairs(metamethods) do
rawset(mt, m, rawget(mt,m) or function(...)
local supermt = getmetatable(mt) or {}
local index = supermt.__index
if(type(index)=='function') then return index(t,m)(...) end
if(type(index)=='table') then return index[m](...) end
return nil
end)
end
return setmetatable(t, mt)
end
I hope it is straightforward enough. When a new metatable is set, it initializes it with all metamethods (without replacing existing ones). These metamethods are prepared to "pass on" requests to "parent metatables".
This is the simplest solution I could find. Well, I actually found a solution that used less characters and was a bit faster, but it involved black magic (it involved metatable functions de-referencing themselves inside their own bodies) and it was much less readable than this one.
If anyone finds a shorter, simpler function that does the same, I'll gladly give him the answer.
Usage is simple: replace setmetatable by setindirectmetatable when you want it to "go up":
mt1 = {__tostring=function(x) return x.name or "no name" end }
mt2 = {}
setmetatable(mt2, {__index=mt1})
x = {name='x'}
y = {name='y'}
setmetatable(x, mt1)
setindirectmetatable(y, mt2) -- only change in code
print(x) -- prints "x"
print(mt2.__tostring(y)) -- prints "y"
print(y) -- prints "y"
A little word of warning: setindirectmetatable creates metamethods on mt2. Changing that behavior so a copy is made, and mt2 remains unaltered, should be trivial. But letting them set up by default is actually better for my purposes.
From my experience with Lua 5.1, metamethods are looked up in metatables using rawget(), and that's why you must copy the reference to the function into every class table you create.
See the Inheritance Tutorial on the Lua Users Wiki.