Page 1 of 1
Possibly useful code snippets
Posted: Sun Jun 01, 2014 1:14 am
by Form
While writing games I often come across some cool things that you can do with Lua, so I figured why not post them here.
If anyone else wants to join in feel free to, but as a legal warning I would just like to state that all code I post in this thread will be under the Whatever the Fuck you please Permissive License (sorry for the vulgarity). Anyone posting in this thread should also include a, small, permissive license, too.
Code: Select all
local WAIT = coroutine.wrap(function(f, returnvar)
local starttime = {}
local duration = {}
local counter = 0
local timecheck = false
local wordcount = 0
for i in love.filesystem.lines("main.lua") do
if string.find(i, "WAIT%b()") then
wordcount = wordcount + 1
end
end
while #starttime < wordcount do
local time = coroutine.yield()
starttime[#starttime + 1] = love.timer.getTime()
duration[#duration + 1] = time
end
while true do
timecheck = false
if love.timer.getTime() >= starttime[#starttime - counter] + duration[#duration - counter] then
starttime[#starttime - counter] = love.timer.getTime()
timecheck = returnvar or true
end
counter = counter + 1
if counter >= #starttime then
counter = 0
end
coroutine.yield(timecheck)
end
end)
This counts how many times WAIT() appears on your main.lua, so it will break if you use a call to it that doesn't exist in plain text on your main.lua. Besides that it works great.
Re: Possibly useful code snippets
Posted: Sun Jun 01, 2014 1:20 am
by Karai17
Lua's require function acts just like any normal function. You can pass in variables. require uses the "..." list of arguments so you can pass data into a file while loading it.
Code: Select all
local lib = require("some.lib", 123, "qwerty")
You'll notice that the first argument is the path to the lib in question. Assuming you only use the path and no other args, and your lib needs to call several other files (not just the init file), you can do a hilarious thing:
Code: Select all
-- main.lua
local lib = require("some.lib")
-- some/lib/init.lua
local path = ... .. "." -- "some.lib."
local other_thing = require(path .. "file")
... .. "." makes me laugh every time.
Re: Possibly useful code snippets
Posted: Tue Jun 03, 2014 6:09 pm
by CaptainMaelstrom
Recursive "find in table" function. Here, tbl is the table to look in, val is the value to find (can be a table, too), and depth is how deep to check for values, default being 1.
Code: Select all
function table.find(tbl,val,depth)
local function table.equal(a,b)
assert(type(a)=='table' and type(b)=='table', 'Input values must be tables')
for k,v in pairs(a) do
if b[k] ~= v then return false end
end
return true
end
assert(type(tbl)=='table' ,"First argument must be a table")
assert(val ,"Second argument (value to find) must not be nil:" .. tostring(val) .. ' ' .. type(val))
local depth = depth or 1 --how deep to go recursively
local j
if type(val)~='table' then
for i,v in pairs(tbl) do
if type(v)~='table' or depth==1 then
if val==v then return i end
else
j = {table.find(tbl[i],val,depth-1)}
if j then
if next(j) then return i,unpack(j) end
end
end
end
else
for k,v in pairs(tbl) do
if type(v)=='table' then
if table.equal(v,val) then
return k
else
if depth > 1 then
j = {table.find(v,val,depth-1)}
end
if j then
if next(j) then return k,unpack(j) end
end
end
end
end
end
return nil
end
Re: Possibly useful code snippets
Posted: Wed Jun 04, 2014 1:13 pm
by Robin
That doesn't work, for several reasons. Have you ever tested it? Because I have doubts it would actually parse.
Re: Possibly useful code snippets
Posted: Sat Jun 07, 2014 9:48 am
by Roland_Yonaba
Well, this is possibly something lots of people have already find out, or have better ways to do it.
I was writing something today, and I needed to pass a vararg to a function. This function was supposed to catch the first arg of the passed-in vararg, pass it to another function that would also return a function, and forward the rest of the args to the resulting function and return the latter call result.
Still with me ?
Without magic, I would have written this:
Code: Select all
local function foo(...)
local arg = {...} -- collect all args to a table
local first_arg = arg[1] -- get the first arg
table.remove(arg,1) -- remove it from the table
local fcall = bar(first_arg) -- pass it to another func, returns a func named fcall
return fcall(unpack(arg)) -- return the result of fcall with the rest of the args
end
I shortened it to the following:
Code: Select all
local function foo(...)
local arg = {...}
return bar(arg[1])(select(2,unpack(arg)))
end
In case someone has a better proposal, I'd love to see that
Re: Possibly useful code snippets
Posted: Sat Jun 07, 2014 9:51 am
by bartbes
I do!
Code: Select all
local function foo(a, ...)
return bar(a)(...)
end
Re: Possibly useful code snippets
Posted: Sat Jun 07, 2014 11:43 am
by Roland_Yonaba
bartbes wrote:I do!
Meh...! I hate you bartbes
Beautiful. Elegant. Short. And simple. I'll take it. Thanks!