lua_basics.txt

References:
	http://www.lua.org/manual/5.3/manual.html#2
	Programming in Lua
Basics:
	extension language, written in clean C
	no notion of "main" program
	works in a host client
	can register C functions tobe called by Lua code 
	dynamically typed language, like python, variables do ont have types but values do

Values and types
	eight basic types in Lua: nil, boolean, number, string, function, userdata, thread, and table.
	boolean: Both nil and false make a condition false
	Lua is 8-bit clean: strings can contain any 8-bit value, including embedded zeros ('\0')
	number: integer, float
	userdata allows arbitrary C data to be stored in Lua variables. Userdata values cannot be created or modified in Lua, only through the C API.
		full userdata 
		light userdata (a C pointer value)
	thread is used to implement coroutines
	table: can have as indices any lua value except nil and NaN, and can be heterogeneous (contain values of all types except nil)
	Tables, functions, threads, and (full) userdata values are objects: variables do not actually contain these values, only references to them.

Coroutines, a.k.a.  collaborative multithreading. 
	 coroutine.create
	 coroutine.resume
	 coroutine.yield 
	 coroutine.wrap
	 C API: lua_newthread, lua_resume, and lua_yield

The Language, Lexical Conventions
	reserved words: then, until, goto, elseif, repeat, in ...
	case-sensitive, e.g. And is different from AND
	avoid creating names that start with an underscore followed by one or more uppercase letters (such as _VERSION)
	other tokens: ~=, |, {}, .., ..., //, #, ::
	short literal string (ASCii code):
		\xXX, where XX is a sequence of exactly two hexadecimal digits
		\ddd, where ddd is a sequence of up to three decimal digits