An easy lua tutorial would be nice.
Look at Programming in Lua:
http://www.lua.org/pil/
The online free version targets Lua 5.0, which is somewhat outdated, but it's worth reading (not the 4th Part, but mostly all the others).
There's also partially free online avaible Lua Programming Gems
http://www.lua.org/gems/
It's a bit harder to read, and not so useful for us, but please! read the Lua Performance Tips by Roberto Ierusalimschy (
http://www.lua.org/gems/sample.pdf ) -- and this should do all modders.
You
really don't need to do much for optimize your Lua-code, just few things i see in likely every mod:
1.You need to compare with
nil only, and really
only if You need to distinguish between
nil and
false:
Code:
local x = 42
if x ~= nil then print'x~=nil' end
if x then print'x~=nil w/o comparsion that costs CPU time' end
x = nil
if x == nil then print'now it is nil' end
if x then print'this print is skipped' end
if not x then print'but this is not!' end
2. Use locals. They are fast.
2.a. If You are using a function/table/tablekey(read-only) a lot, make a local of it. In a mod i'm working on it looks like that:
Code:
somef = function(self)
local self_m_Instance = self.m_Instance
-- here some bad loop
--...
self_m_Instance.things:DoSomething()
self_m_Instance.otherthings:DoSomethingElse()
--...
self_m_Instance[somekey]:SetHide(true)
--...
-- and so on many times
-- end of the loop
end -- of function
3. Avoid using
table.insert. It's
slow, and seldom needed. A good way to append a value to array is:
Code:
local t = {}
for i = 42,666 do t[#t+1]=i end
4. Make use of Lua's lazy evaluation:
Code:
local f = function() -- some costly function
local j
for i = 1, 10e10 do
j = j + i*i
end
return j > 10e20
end
local cond = true -- some condition
if f() or cond then -- wrong order, f evaluated always
print'f() or cond'
end
if cond or f() then -- right order, f evaluated only if cond is false
print'cond or f()'
end
Surely, optimization hurts readability. But above "tricks" in most cases are harmless to it but can improve performance a lot. And CiV already needs a lot of PC resources.
