Lua基本类型及Basic Functions 

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概述

Lua的基本类型

基本类型

lua data type

e.g.
function testType()
	print (string.format("the type of _G = %s ", type(_G)))
	print (string.format("the type of _VERSION = %s ", type(_VERSION)))
	print (string.format("the type of X = %s ", X))
	print (string.format("the type of nil = %s ", type(nil)))
	print (string.format("the type of 1 + 1 = %s ", type(1 + 1)))
	print (string.format("the type of {a='a'} = %s ", type({a='a'})))
	print (string.format("the type of true = %s ", type(true)))
	print (string.format("the type of Hello world = %s ", type("Hello world")))
	print (string.format("the type of testType = %s ", type(testType)))
end

output:

the type of _G = table

the type of _VERSION = string

the type of X = nil

the type of nil = nil

the type of 1 + 1 = number

the type of {a='a'} = table

the type of true = boolean

the type of Hello world = string

the type of testType = function

注意事项
  • 在Lua中，false和nil会被逻辑运算符当成false，其他都为true(0也是true)

Basic Functions

Lua语言built-in方法其实并不多，最基本的也就二十几个，比起其他语言可谓是小巫见大巫。现在罗列一下以便以后查阅。

sequence function or variable des
1 assert (v [, message]) assert函数检查其第一个参数是否为true。若为true，则简单地返回该参数；否则(为false或nil)就会引发一个错误
2 collectgarbage ([limit]) Sets the garbage-collection threshold to the given limit (in Kbytes) and checks it against the byte counter
3 dofile (filename) 读入文件编译并执行, 本质上位辅助函数，真正实现其功能的是loadfile()
4 error (message [, level]) Terminates the last protected function called and returns message as the error message. Function error never returns
5 _G holds the global environment (that is, _G._G = _G)
6 getfenv (f) 返回当前函数的运行环境，如果f为0，则返回全局环境变量；只有setfenv了环境，getfenv才能生效。
7 getmetatable (object) 返回对象的元表(metatable) [如果元表(metatable)中存在__metatable键值，当返回__metatable的值]
8 gcinfo () Returns two results: the number of Kbytes of dynamic memory that Lua is using and the current garbage collector threshold (also in Kbytes)
9 ipairs (t) Returns an iterator function
10 loadfile (filename) Loads a file as a Lua chunk (without running it)
11 loadlib (libname, funcname) Links the program with the dynamic C library libname
12 loadstring (string [, chunkname]) Loads a string as a Lua chunk (without running it)
13 next (table [, index]) Allows a program to traverse all fields of a table
14 pairs (t) Returns the next function and the table t (plus a nil), so that the construction for k,v in pairs(t) do … end will iterate over all key–value pairs of table t.
15 pcall (f, arg1, arg2, …) Calls function f with the given arguments in protected mode
16 print (e1, e2, …) Receives any number of arguments, and prints their values in stdout, using the tostring function to convert them to strings
17 rawequal (v1, v2) Checks whether v1 is equal to v2, without invoking any metamethod. Returns a boolean.
18 rawget (table, index) Gets the real value of table[index], without invoking any metamethod
19 rawset (table, index, value) Sets the real value of table[index] to value, without invoking any metamethod
20 require (packagename) Loads the given package
21 setfenv (f, table) Sets the current environment to be used by the given function
22 setmetatable (table, metatable) Sets the metatable for the given table
23 tonumber (e [, base]) Tries to convert its argument to a number
24 tostring (e) Receives an argument of any type and converts it to a string in a reasonable format
25 type (v) Returns the type of its only argument, coded as a string. The possible results of this function are “nil” (a string, not the value nil), “number”, “string”, “boolean, “table”, “function”, “thread”, and “userdata”.
27 unpack (list) Returns all elements from the given list
28 _VERSION A global variable (not a function) that holds a string containing the current interpreter version.
29 xpcall (f, err) A global variable (not a function) that holds a string containing the current interpreter version. 
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