lua 字符串管理（String Manipulation）

1、When indexing a string in Lua, the first character is at position 1 (not at 0, as in C). Indices are allowed to be negative and are interpreted as indexing backwards, from the end of the string. Thus, the last character is at position -1, and so on.

例子：

local str = "abcdefg"

local str_forward = ""

local str_backward = ""

local str_len = str:len()

for i=1,str_len do

str_forward = str_forward..str:sub(i,i)

end

for i=-1,-str_len,-1 do

str_backward = str_backward..str:sub(i,i)

end

print(str_len)

print(str_backward)

print(str_forward)

2、string.dump(function [, strip]) 函数序列化与反序列化

Returns a string containing a binary representation (a binary chunk) of the given function, so that a later load on this string returns a copy of the function (but with new upvalues). If strip is a true value, the binary representation may not include all debug information about the function, to save space.

例子：

function add( a,b )

    return a+b

end

--序列化

str_dump = string.dump(add)

print(str_dump)            --

--反序列化

addfunc = load(str_dump)   

--调用函数

print(addfunc(1,2))

说明：strip是boolean值。如果是ture,在dump函数为序列的时候，会忽略此函数的debug信息而节省空间。

3、对string.char(...)的扩展string.xchar(argtable)

function string.xchar(argtable)

local boarder = #argtable

local argstr=""

if boarder>0 then

argstr = argtable[1]

for i=2,boarder do

argstr = argstr..','..argtable[i]

end

end

f = load("return string.char("..argstr..")")

return f()

end

arg1 = {97,98,99}

print(string.xchar(arg1))

print(string.char(97,98,99))

说明：argtable是ascii码表。

4、For convenience, when the opening long bracket is immediately followed by a newline, the newline is not included in the string

例子：

    a = 'alo\n123"'

    a = "alo\n123\""

    a = '\97lo\10\04923"'

    a = [[alo

    123"]]

    a = [==[

    alo

    123"]==]

它们是相同的字符串