Lua基本类型及Basic Functions
Lua基本类型及Basic Functions
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概述
Lua的基本类型
基本类型
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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<li><a href="/posts.html#Lua">Lua <span>2</span></a></li>
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