Lua Study Share
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Lua is a lightweight scripting language that supports object-oriented, functional and data-driven programming. It is embedded into applications and has a simple syntax and learning curve. Lua compiles to bytecode and integrates well with C/C++. It uses garbage collection and supports features like modules, coroutines, metatables and standard libraries.
![Values and Type
Lua is dynamically typed language.
Types
◦ Nil
◦ Boolean
◦ Number
◦ String
◦ Function
◦ Userdata
◦ Thread
◦ Table
Values
◦ Initial : nil
◦ Boolean => nil/false : false, others : true
◦ Number : double-precision floating-point.
◦ String : ‘’, “”, [[]], [==[ ]==]](https://image.slidesharecdn.com/lua-141014053420-conversion-gate02/85/Lua-Study-Share-7-320.jpg)
![Comment
Single comment
◦ --
Block comment
◦ --[[
◦ ]]--](https://image.slidesharecdn.com/lua-141014053420-conversion-gate02/85/Lua-Study-Share-8-320.jpg)
![The type “Table”
Like
◦ ActionScript Array
◦ Php Array
◦ Perl Hash
◦ Map
Indexed Array
◦ Index is start from 1
Associative Array
◦ Nil and NaN both cannot be as a key
Get length : # operator
Constructor
◦ a = {}
◦ a = { prop1, prop2 } => a[1] = prop1, a[2] = prop2
◦ a = { prop = “test” } => a[“prop”] = “test”
◦ a = { [f(x)] = 2 } => a[f(x)] = 2](https://image.slidesharecdn.com/lua-141014053420-conversion-gate02/85/Lua-Study-Share-10-320.jpg)
![Funciton
Definition
function func_name ([args])
do something
end
method:
function a.b.c:func_name(self, body) body end
anonymous:
function()
do something
end
call function
• func_name(args);
• table.func_name(agrs)](https://image.slidesharecdn.com/lua-141014053420-conversion-gate02/85/Lua-Study-Share-11-320.jpg)
![Statements
if exp then block {elseif exp then
block} [else block] end
while exp do block end
repeat block until exp](https://image.slidesharecdn.com/lua-141014053420-conversion-gate02/85/Lua-Study-Share-14-320.jpg)
Lua Study Share
- 1. Lua A powerful, light-weight scripting language
- 2. Introduction Lua name Support for ◦ Object-oriented programming ◦ Functional programming ◦ Data-driven programming Embedding program Interpreted Language
- 3. Introduction is implemented in pure ANSI C and compiles Strongly integrated with C and C++ Cross-platform Good performance ◦ To claim to be "as fast as Lua" Multi-thread ◦ Coroutines Easy learning curve. Free
- 4. Uses Angry Bird Simcity 4 World of Warcraft Adobe Photoshop Lightroom Other sort of applications.
- 5. IDE LuaEdit ◦ Download Eclipse Plug-in ◦ Lua Development Tools
- 6. Hello World! Download Lua Execute Lua Interpreter Print(‘Hello World’);
- 7. Values and Type Lua is dynamically typed language. Types ◦ Nil ◦ Boolean ◦ Number ◦ String ◦ Function ◦ Userdata ◦ Thread ◦ Table Values ◦ Initial : nil ◦ Boolean => nil/false : false, others : true ◦ Number : double-precision floating-point. ◦ String : ‘’, “”, [[]], [==[ ]==]
- 8. Comment Single comment ◦ -- Block comment ◦ --[[ ◦ ]]--
- 9. Variable 3 kinds of Scope ◦ Global _G ◦ Local local ◦ Table self Multiple assignment ◦ a,b = 1,2 ◦ a,b = b,a
- 10. The type “Table” Like ◦ ActionScript Array ◦ Php Array ◦ Perl Hash ◦ Map Indexed Array ◦ Index is start from 1 Associative Array ◦ Nil and NaN both cannot be as a key Get length : # operator Constructor ◦ a = {} ◦ a = { prop1, prop2 } => a[1] = prop1, a[2] = prop2 ◦ a = { prop = “test” } => a[“prop”] = “test” ◦ a = { [f(x)] = 2 } => a[f(x)] = 2
- 11. Funciton Definition function func_name ([args]) do something end method: function a.b.c:func_name(self, body) body end anonymous: function() do something end call function • func_name(args); • table.func_name(agrs)
- 12. Function Call method • table:func_name(args) Result return ◦ Able to return multiple result • return a; • return a,b; • return a or b
- 13. Logical Operator Not And Or • not(a==1) • return a and b • return func1() and func2() • return a or b • return func1() or func2()
- 14. Statements if exp then block {elseif exp then block} [else block] end while exp do block end repeat block until exp
- 15. For statement numeric ◦ work with number calculation • for I = 1, 10 do block end • for I = 1, 10, 2 do block end • for I = 1, #(table1) do block end generic ◦ work with iterators, stop when value is nil • for namelist in explist do block end • for k, v in pairs(table1) do block end • for k, v in ipairs(table1) do block end
- 16. Metatables and Metamethods Every value has metatable and metamethod The key of metatable => event The value of metatable => metamethod getmetatable -> get the metatable of any value setmetatable -> set the metatable of table
- 17. Metatables and Metamethods Add Sub Mul Mod Pow Unm Concat Len Eq Lt Le Index Newindex Call
- 18. For OOP purpose Person={} function Person:new(p) local obj = p if (obj == nil) then obj = {name="ChenHao", age=37, handsome=true} end self.__index = self return setmetatable(obj, self) end function Person:toString() return self.name .." : ".. self.age .." : ".. (self.handsome and "handsome" or "ugly") end
- 19. Modules require(‘hello’); ◦ package.loaded to record which module is loaded dofile(‘hello.lua’); loadfile(‘hello.lua’);
- 20. Standard Libraries Basic library Coroutine library Package library String manipulation Table manipulation Mathematical functions Bitwise operations Input and Output Etc.
- 21. Error Handling Throw exception ◦ The error function Catch exception ◦ pcall or xpcall
- 22. Garbage Collection Auto memory management. 2 indexes to determine GC ◦ The garbage-collector pause ◦ The garbage-collector step multiplier