LÖVE

Posted: **Fri Aug 10, 2012 12:24 am**

Here are some things that at some time probably made me go "Wow, I didn't know you could do that! I mean, until just now, that is." Feel free to add your own!

Did you know...

There are languages that have been used with LÖVE other than Lua: Killa (which I think is being used for the new Concerned Joe which is in-development) and Moonscript (used for the Ludum Dare entries Volcanox and Wulcan, by Leafo)

To insert that Ö character you can use Alt+153 in Windows, Ctrl+Shift+u then 00d6<Enter> in Ubuntu (maybe there is an easier way?), or Shift+Alt+V in gVim.

Methods can be used on literal strings and entries can be accessed from literal tables by putting parentheses around the strings/tables:

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({'aquamarine', 'azure', 'auburn'})[math.random(1, 3)]
('This really should be in all caps'):upper()

love.load can take command line arguments. You could use them to specify an input file, or a level to jump to, or to enable debugging mode...

To launch LÖVE games with their compatible version, you could install each version of LÖVE to a separate location (old versions can be found here), change the file extension of your .love files to represent their version number, (e.g. .love072), and change the default application with which they open with to the appropriate LÖVE executable.

Parentheses can be omitted from function calls if it has a single argument which is either a literal string...

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require 'RequireIsAFunction'
love.graphics.setCaption 'Test'

or a table constructor.

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for i, v in ipairs{'a', 'b', 'c'}
end

You can share code with other people using pastebin services such as hastebin.

You can change the icon of Windows executable files using Resource Hacker.

Varargs (...) and the return values from functions can be put into tables using table constructors:

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function f(...)
    args = {...}
    print('The second argument is '..args[2])
end

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positions = {love.mouse.getPosition()}
print('x position is '..positions[1])
print('y position is '..positions[2])

You can make your very own errors using assert, and you can also print error messages to the terminal.

You can reduce the filesize of PNG files using PNG optimization software such as PNGGauntlet.

LÖVE apparently works best with Ogg Vorbis audio, which other formats can be converted to using Audacity or SoX from the command line.

I hope someone knows something now that they didn't know before!

If you have some fun facts which I didn't think of, you could totally post them here (they don't even need to be fun or factual!)

EDIT: Oh yeah, I forgot something!

To easily comment and uncomment a section like this:

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---[[
    The first "-" of ---[[ can be removed or added
    to comment and uncomment these lines.
--]]

Posted: **Fri Aug 10, 2012 1:47 am**

Well, I already most of the things you cited, about Lua's syntax. Well, probably because I went through the whole book PiL.
However, I learnt some knew stuff. Thanks.
Nice topic.

Well, I'll add my own, a single link : Lua Hacks
I also made two libraries, which provides syntactic sugars for tables and strings handling: Moses and Allen.
Also, If one have ever felt the need to make Lua behave like C, using preprocessing macros, see LuaMacro
And oh, I'll mention Bartbes and Robin's Meta, which provides some extras to Lua scripting.

Posted: **Fri Aug 10, 2012 2:25 am**

Wow, that Lua Hacks page will require some careful reading!

I was actually inspired to create this more "general" thread after your recent thread which turned out really well I thought. (Although this thread might be too general.

) I think I'll follow Inny's advice, and actually read PiL cover-to-cover, and more of the lua-users wiki.

Your libraries look really cool, as does Meta, I should read over them sometime to see if I can work out what's going on, and read LuaMacro's readme.

I have so much to learn.

Thanks for the response!

Posted: **Fri Aug 10, 2012 4:02 am**

Santos wrote:I was actually inspired to create this more "general" thread after your recent thread which turned out really well I thought. (Although this thread might be too general. ) I think I'll follow Inny's advice, and actually read PiL cover-to-cover, and more of the lua-users wiki.

If you want to get super advanced with Lua, there's a book called Lua Programming Gems. My favorite chapter is the one where an update in the GUI library screwed their startup time so they came up with a way to dynamically require libraries during runtime. It inspired this code snippet of mine:

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-- Class loader
local Origin = {}
function Origin.__index( t, k )
  local f = k:lower():gsub("(_)", "/")
  if love.filesystem.isFile(f..".lua") then
    print( "Require", f )
    require( f )
    return rawget(_G, k)
  elseif love.filesystem.isFile("lib/"..f..".lua") then
    print( "Require lib", f )
    require( "lib/"..f )
    return rawget(_G, k)
  end
end

setmetatable( _G, Origin )

Though I haven't tested this in 0.8.0, and it could use a rewriting.

Posted: **Fri Aug 10, 2012 6:06 am**

I've been told that require works best with dots, in other to be compatible on all systems.

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-- Class loader
local Origin = {}
function Origin.__index( t, k )
  local f = k:lower():gsub("(_)", "/")
  if love.filesystem.isFile(f..".lua") then
    print( "Require", f:gsub('/','.') )
    require( f )
    return rawget(_G, k)
  elseif love.filesystem.isFile("lib/"..f..".lua") then
    print( "Require lib", f )
    require( "lib/"..f:gsub('/','.') )
    return rawget(_G, k)
  end
end

setmetatable( _G, Origin )

Well, if the library returns a local var, instead of setting something in the global space, some adjustments need to be made. Maybe set _G[libName] = require (libPath), before returning it with rawget.

Posted: **Fri Aug 10, 2012 9:43 am**

I like this thread. These things are so easy to miss even if you use lua for years.

Posted: **Fri Aug 10, 2012 12:02 pm**

Ö on Ubuntu: hold down AltGR (or Ctrl+Alt, I think) and shift, press :, then release every key and type O normally, either by using caps lock or holding shift
ö on Ubuntu: it's the same, just type a lowercase "o" after Alt+Ctrl+Shift+:

Posted: **Tue Aug 14, 2012 7:51 pm**

Wow.
I came back on variables scoping in Lua, but I didn't find was I was looking for.
It is not even mentionned in he book, it seems. Anayway, I didn't know that was doable.

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function a(b)
b = b or 1
print(b)
end

a() --> 1
a() --> 1
a() --> 1
print(b) --> nil!

I found it strange, because I was pretty sure that this function, when given no arg, creates a global var named b, with value 1, before printing it.
So there's no difference between the snippet above and this one, huh ?

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function a(b)
local b = b or 1
print(b)
end

a() --> 1
a() --> 1
a() --> 1
print(b) --> nil!

Posted: **Tue Aug 14, 2012 8:25 pm**

Here's a mostly-correct explanation why: Lua works with lexical scoping, in particular a version where the scope is known at compile-time.

In more details:
There are three kinds of variables:

Globals
Locals
Up-values (that is, locals for a function that encloses the current function)

Arguments are locals.

This:

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x = "global"
local y = "local"
function foo()
   local z = "local"
   y = "y is an up-value here"
end

will get compiled to something like the following:

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get the string "global"
set the global variable "x" to it
get the string "local"
set the local no. 0 to it
create a function with the following code:
    get the string "local"
    set the local no. 0 to it
    get the string "y is an up-value here"
    set the local no. 1 to it
this function should have local no. 1 that is a reference to our local no. 0
set the global variable "foo" to it

I hope that makes it clear how things work.

Posted: **Tue Aug 14, 2012 8:47 pm**

Robin wrote:Up-values (that is, locals for a function that encloses the current function)

Yes. Since you mentionned that very word. Thanks. Karma ya.

LÖVE

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