Lua Programming Help Thread

[PSPhakkor]

Yeah. But it has some annoying features like if you type "(", you get "( )". I never use that.

And I got some errors determining available memory... I guess that has something to do with the fact that I'm on a pc:)

[AZeyC]

Yeah. But it has some annoying features like if you type "(", you get "( )". I never use that.

And I got some errors determining available memory... I guess that has something to do with the fact that I'm on a pc:)

I agree te "( )" thing is a bit annoying, but it doesn't bother me that much, maybe post a suggection in the LuaDevKit thread/

[yaustar]

Wow. Thanks for doing research for me!

So you're saying that if I use a different text editor, It will work? That's funny.

Unfortunately, I'm limited to LuaDevKit because I don't have my psp at the moment, and I can only test my programs on its tester thing. It's really handy.

However, I did realize that when I used "\n" (or whatever is the correct one, I can't remember!), it wasn't outputted to the file. Unfortunately, neither was the new line. I just got the two strings right next to each other. I hope the different editor will fix this.


Thanks again for your time

No, that is incorrect. The file that you 'write' to in the Lua script

newFile = io.open( "THIS FILE.txt", "w" )

Needs to be opened in a different text editor for you to see the line breaks.

[eldiablov]

ok what's wrong with this statement ?


if (Player.x + playerWidth > Cheese.x) and (Player.x < Cheese.x + Cheese.width) and (Player.y + playerHeight > Cheese.y) and (Player.y < Cheese.y + Cheese.height) then
score = score + 1 and Cheese.x = math.random(5,420) and Cheese.y = math.random(5,100)
end

[yaustar]

ok what's wrong with this statement ?


if (Player.x + playerWidth > Cheese.x) and (Player.x < Cheese.x + Cheese.width) and (Player.y + playerHeight > Cheese.y) and (Player.y < Cheese.y + Cheese.height) then
score = score + 1 and Cheese.x = math.random(5,420) and Cheese.y = math.random(5,100)
end

This

score = score + 1 and Cheese.x = math.random(5,420) and Cheese.y = math.random(5,100)

Why is there lots of ANDs in this line of code?

Shouldn't it be:

score = score + 1 
Cheese.x = math.random(5,420)
Cheese.y = math.random(5,100)

[eldiablov]

omg i feel so dumb but thank you anyway. My game is now ready for it's alpha release.
-= Double Post =-
Wait one more thing os.exit() is valid in luaplayer 0.19 ?

everytime i execute that command it just crashes

[PSPhakkor]

No, that is incorrect. The file that you 'write' to in the Lua script

newFile = io.open( "THIS FILE.txt", "w" )

Needs to be opened in a different text editor for you to see the line breaks.

WOW I feel like an idiot too!!!

eldiablov, you're not alone. Congrats on your game's release! Feels so good, doesn't it?


yaustar, thanks so much for helping me solve the problem. Thanks, thanks, thank you!


Another question now(I feel like I'm overusing this thread): Is it possible to use an array of functions? Like

function table[1]()
body
end

function table[2]()
body
end

[eldiablov]

yeah it feels great. I just hope people think its quite alright as a first release.
link to release thread : http://forums.qj.net/f-psp-developme...v01-91371.html

i appreciate everybodys comments

[yaustar]

WOW I feel like an idiot too!!!

eldiablov, you're not alone. Congrats on your game's release! Feels so good, doesn't it?


yaustar, thanks so much for helping me solve the problem. Thanks, thanks, thank you!


Another question now(I feel like I'm overusing this thread): Is it possible to use an array of functions? Like

function table[1]()
body
end

function table[2]()
body
end

Yes, bear with me here since this is from memory:

function HelloWorld()
    screen:print( 1, 1, "Hello World", green )
end

function GoodbyeWorld()
    screen:print( 1, 1, "Goodbye World", green )
end

functionArray = {}
functionArray.function1 = HelloWorld
functionArray.function2 = GoodbyeWorld

-- To use it
functionArray.function1()

[PSPhakkor]

Ah, I see. I have to use the variable then a period then the "second" variable name. I never really learned that but I think I get it form looking at some code. Thanks, yet again yaustar!

Eldiablov, I'm gonna check out your game as soon as I get my psp. It better be good!

[yaustar]

Ah, I see. I have to use the variable then a period then the "second" variable name. I never really learned that but I think I get it form looking at some code. Thanks, yet again yaustar!

Eldiablov, I'm gonna check out your game as soon as I get my psp. It better be good!

Read up on tables in Lua before doing anything. http://lua-users.org/wiki/TablesTutorial

[SG57]

Tables are quite interseting. Their arrays, structures and classes combined. Quite the change going from C/C++ to Lua...

[EminentJonFrost]

Question: Whats the name of the app that lets you edit/create lua scripts like on the computer, except its all on PSP?
I've seen it before, I've even used it so I know it exists, but deleted it when I upgraded to 2.71 (back when it wasnt cracked) to play Monster Hunter knowingly abandoning homebrew.

[GuitarGod1134]

Im just trying to make a little tag game here and Im getting an error.

error: snake.lua:82: bad argument #2 to 'print' (string expected, got nil)

Spoiler for My code:

--Lua Tag

--load colors
red = Color.new(255,0,0)
black = Color.new(0,0,0)
blue = Color.new(0,0,255)

--create our people
player1 = Image.createEmpty(10,10)
        player1:clear(red)
player2 = Image.createEmpty(10,10)
        player2:clear(red)
--levels
level1 = Image.load("level1.png")

--array for player coordinates
player1c = {x = 30, y = 100}
player2c = {x = 70, y = 20}

--whos it
it = nil
wit = math.random(0,1)
    if wit == 0 then
       it = p1
          elseif wit == 1  then
          it = p2
end
--whoever is it is slightly faster
if it == p1 then
   p1speed = 3
   p2speed = 2
           elseif it == p2 then
                  p2speed = 3
                  p1speed = 2
                  end



--declare movement functions
function moveplayer1()
         if pad:up() then
            player1c.y = player1c.y - p1speed
end
   if pad:down() then
      player1c.y = player1c.y + p1speed
end
   if pad:left() then
      player1c.x = player1c.x - p1speed
end
   if pad:right() then
      player1c.x = player1c.x + p1speed
end
end
function moveplayer2()
         if pad:triangle() then
            player2c.y = player2c.y - p2speed
end
   if pad:cross() then
      player2c.y = player2c.y + p2speed
end
   if pad:circle() then
      player2c.x = player2c.x + p2speed
end
   if pad:square() then
      player2c.x = player2c.x - p2speed
end
end

--start the main loop
while true do
screen:clear()
pad = Controls.read()
--blit map
screen:blit(0,0,level1)
--call the move player functions
moveplayer1()
moveplayer2()
--blit the players
screen:blit(player1c.x,player1c.y,player1)
screen:blit(player2c.x,player2c.y,player2)
--print whos it
screen:print(0,0,it,red)
--flip the screen and what not
screen.waitVblankStart()
screen.flip()
end

It works just fine when I remove the line that prints the variable it to the screen. But if I leave itI get that error.

[PSPhakkor]

Here's what I think you have wrong:

right here when you declared the 'it' variable:

--whos it
it = nil
wit = math.random(0,1)
    if wit == 0 then
       it = p1
          elseif wit == 1  then
          it = p2

You had 'it' set equal to a p1, which the PSP thinks is supposed to be a variable, but there's no value it can find for a variable named 'p1' or 'p2' as the case may be. Therefore, it sets 'it' equal to 'nil', and then when you tried to print 'p1' to the screen, you gave the PSP a nil value to print to the screen.

The way to fix this is actually give 'p1' (or p2) a value before declaring 'it' equal to 'p1' (or p2).

Or you could set 'it' equal to a different value. There are a few ways to fix it, I think you'll figure it out. just use what I wrote above

[Grimfate126]

Im just trying to make a little tag game here and Im getting an error.

error: snake.lua:82: bad argument #2 to 'print' (string expected, got nil)

Spoiler for My code:

--Lua Tag

--load colors
red = Color.new(255,0,0)
black = Color.new(0,0,0)
blue = Color.new(0,0,255)

--create our people
player1 = Image.createEmpty(10,10)
        player1:clear(red)
player2 = Image.createEmpty(10,10)
        player2:clear(red)
--levels
level1 = Image.load("level1.png")

--array for player coordinates
player1c = {x = 30, y = 100}
player2c = {x = 70, y = 20}

--whos it
it = nil
wit = math.random(0,1)
    if wit == 0 then
       it = p1
          elseif wit == 1  then
          it = p2
end
--whoever is it is slightly faster
if it == p1 then
   p1speed = 3
   p2speed = 2
           elseif it == p2 then
                  p2speed = 3
                  p1speed = 2
                  end



--declare movement functions
function moveplayer1()
         if pad:up() then
            player1c.y = player1c.y - p1speed
end
   if pad:down() then
      player1c.y = player1c.y + p1speed
end
   if pad:left() then
      player1c.x = player1c.x - p1speed
end
   if pad:right() then
      player1c.x = player1c.x + p1speed
end
end
function moveplayer2()
         if pad:triangle() then
            player2c.y = player2c.y - p2speed
end
   if pad:cross() then
      player2c.y = player2c.y + p2speed
end
   if pad:circle() then
      player2c.x = player2c.x + p2speed
end
   if pad:square() then
      player2c.x = player2c.x - p2speed
end
end

--start the main loop
while true do
screen:clear()
pad = Controls.read()
--blit map
screen:blit(0,0,level1)
--call the move player functions
moveplayer1()
moveplayer2()
--blit the players
screen:blit(player1c.x,player1c.y,player1)
screen:blit(player2c.x,player2c.y,player2)
--print whos it
screen:print(0,0,it,red)
--flip the screen and what not
screen.waitVblankStart()
screen.flip()
end

It works just fine when I remove the line that prints the variable it to the screen. But if I leave itI get that error.

in this line:

screen:print(0,0,it,red)

'it' is NOT a string. i string has quotes around it. how to solve this? two ways:

1. wherever you assign a value to 'it', put it in quotes. (like: "p2" instead of just p2)

2. use an if statement:

if it == p1 then
     screen:print(0,0,"p1",red)
elseif it == p2 then
     screen:print(0,0,"p2",red)
end

-= Double Post =-

Here's what I think you have wrong:

right here when you declared the 'it' variable:

--whos it
it = nil
wit = math.random(0,1)
    if wit == 0 then
       it = p1
          elseif wit == 1  then
          it = p2

You had 'it' set equal to a p1, which the PSP thinks is supposed to be a variable, but there's no value it can find for a variable named 'p1' or 'p2' as the case may be. Therefore, it sets 'it' equal to 'nil', and then when you tried to print 'p1' to the screen, you gave the PSP a nil value to print to the screen.

The way to fix this is actually give 'p1' (or p2) a value before declaring 'it' equal to 'p1' (or p2).

Or you could set 'it' equal to a different value. There are a few ways to fix it, I think you'll figure it out. just use what I wrote above

im going to have to disagree with that. in lua, when you do that, it still keeps it for reference. in C/C++ however, that may give you problems.

[GuitarGod1134]

Ok thanks guys. one more thing. im on the lua player functions website and I see this

Bool System.powerIsPowerOnline ()

and it says bool first. so does that mean this is a valid statement

if System.powerIsPowerOnline () == true then
bla
end
?

[Grimfate126]

Ok thanks guys. one more thing. im on the lua player functions website and I see this

Bool System.powerIsPowerOnline ()

and it says bool first. so does that mean this is a valid statement

if System.powerIsPowerOnline () == true then
bla
end
?

i think so, but this will probably work:

if System.powerIsPowerOnline() then
bla
end

because a bool returns a true or false value so it would be the same as saying:

if (true) then
...
end

OR

if (false) then
...
end

[GuitarGod1134]

I keep getting an unexpected symbol "=" at line 5. Im just making this to get a feel for some psp exclusive lua player functions but im not sure im doing thsi right because the website did not provide examples.

Spoiler for QuickLook:

--Quick Look
--By GuitarGod1134      
--define colors
red = Color.new(255,0,0)
System.powerGetBatteryLifePercent() = batstat
System.powerGetBatteryLifeTime() = batper
while true do
if System.powerIsPowerOnline() == true then
screen:print(200,100,"Power is online",red)
end
if System.powerIsBatteryExist() == true then
screen:print(200,110,"You have a battery",red)
end
if System.powerIsBatteryCharging() == true then
screen:print(200,120,"Your battery is charging",red)
end
screen:print(0,0,"Battery Power ="..batstat,red)
screen:print(0,10,"Esitmated time till dead battery ="..batper,red)

--wrap it up
screen.waitVblankStart()
screen.flip()
end

-= Double Post =-
Ok Ill try that. thx

[PSPhakkor]

No problem.

You new problem is due to the fact that most programming languages, Lua included, when asked to assign a value to a variable, will assign the variable to the left of the equals sign the value of the variable or constant on the right. You are trying to set System.powerGetBatteryLif ePercent() to the value stored in batper, which is not possible. Simple solution: switch batper and System.powerGetBatteryLif ePercent() around. Be aware that you will have to do the same thing on the next line

[TacticalPenguin]

Also, you do not need to put if something == true then, you can just put if something then

And instead of if something == false then you can do if not something then
-= Double Post =-

Question: Whats the name of the app that lets you edit/create lua scripts like on the computer, except its all on PSP?
I've seen it before, I've even used it so I know it exists, but deleted it when I upgraded to 2.71 (back when it wasnt cracked) to play Monster Hunter knowingly abandoning homebrew.

PSPPDA is the most commonly known one.

[PSPhakkor]

When I try to use the '#' operator, to determine the number of elements on a table, I can get toe game to work in LDK, but on a psp, there are errors whenever it gets to that point in the code. Does anyone know if that operator is usable on a psp? Or do I have something else wrong?

any similar issues with modulus (%) also?

[SG57]

PSPhakkor - Switching from C to LUA, i expected the modulus to be % as well, but its actually just: math.mod(number,modulo)

TP - Theres nothing wrong with using

== true

or

== false

There good programming habits, for JUST starting as when just starting, your cramming alot of info in your head, and one thing is bound to slip and be forgotten, thus making your code foreign to you (atleast that one line with no == true or == false)

Its just more typing (and soon youll find that to be a pain :S)

[TacticalPenguin]

PSPhakkor - Switching from C to LUA, i expected the modulus to be % as well, but its actually just: math.mod(number,modulo)

TP - Theres nothing wrong with using

== true

or

== false

There good programming habits, for JUST starting as when just starting, your cramming alot of info in your head, and one thing is bound to slip and be forgotten, thus making your code foreign to you (atleast that one line with no == true or == false)

Its just more typing (and soon youll find that to be a pain :S)

I NEVER said it's bad or anything I just said it is not required.

And if you dont believe me, ask super on this one. Making it a habit to use the shortest method makes for small scripts.

Also, to get the number of items in a table:

blah = table.getn(nameoftablewit houtquotes)

blah will be a number equal to the number of items in the table.

[TheBressman]

I'm having the same problem as PSPHakkor, the # command seems to work fine in LuaDevKit, but on the PSP it gives me an error at the first point that # lies. I managed to change one so the command no longer involved # but then it just shows an error at the next #. Any ideas ?

[SG57]

TP - I never said you did say you said it was wrong. (lololol wow... migrain)

Its just the way you put it - you made it seem like he was doing somethign wrong... Atleast thats how I interpreted your post... But to be honest, at his skill level (no offense, im just implying by your post on what experience you are at in programming) that 100 bytes (not kilo... just bytes) extra file size in return for a risk free understandability (atleast for hte whole == true or == false thing)

The Bressman - LDK uses WLP. Current version of WLP is = to PSP Lua Player v2.0 (or wahtever it is, its just a 2... like 2.0, 0.2, just something as a 2). Update your luaplayer would be my suggestion.

[TacticalPenguin]

Alright.

ANyways for you people having troubles with the number thingie, to get the number of items in a table use this:

blah = table.getn(nameoftablewit houtquotes)

blah will now be a number equal to the number of items in the table.

[GuitarGod1134]

Getting something really wierd here. Trying to implement the get remaining memory function but it gives me this

error : index.lua:38: 'end' expected (to close 'while' at line 10) near (eof)'

Spoiler for Code:

--Quick Look
--By GuitarGod1134      
--define colors
red = Color.new(255,0,0)
--define variables
batstat = System.powerGetBatteryLifePercent()
batper = System.powerGetBatteryLifeTime()
freemem = System.getFreeMemory()
--start the loop
while true do
if System.powerIsPowerOnline() then
screen:print(200,100,"Power is online",red)
end
if System.powerIsLowBattery() then
screen:print(200,110,"You need to get your charger!",red)
if System.powerIsBatteryExist() then
screen:print(200,120,"A battery is inserted",red)
end
if System.powerIsBatteryCharging() then
screen:print(200,130,"Your battery is charging",red)
end
screen:print(0,20,"Remaining Megabytes on MS = "..freemem,red)
screen:print(0,0,"Battery Power = "..batstat,red)
screen:print(0,10,"Esitmated time till dead battery = "..batper,red)
--wrap it up
screen.waitVblankStart()
screen.flip()
end

Now I looked at this error and did an experiment and added an end after the end and it creates a .stackdump file in the root of my stick and says that system on line 11 is a nil value along with a bunch of hexidecimals.

[emericaska8r]

if System.powerIsLowBattery() then
screen:print(200,110,"You need to get your charger!",red)

the line that you have this doesn't have an end for the if statement.

[GuitarGod1134]

omg i missed that lol thx