String - string (Lua)

character string

string yes Lua One of the eight major data types in ,Lua There is no concept of characters in , All texts are string.Lua Medium string In order to 8 A bit To store .

Lua The strings in are the same as most language strings Not variable . All changes string The operation of , All generate new string.Lua in string The data structure uses the string pool realized by hash algorithm . This approach is to ensure that memory does not leak , And the performance of string comparison is greatly improved .

---

Representation
string There are two ways to express

• ’ Single quotation marks Such as 's'
• " Double quotes Such as "s"

They are all ways of representing string constants , It is recommended to use one , Don't mix .

---

Long string
string have access to [[ ]] In this way Writing of multi president strings
Such as

local s = [[ L u a]]

---

Escape character

Escape character	significance	ASCII Code value （ Decimal system ）
\a	Ring the bell (BEL)	007
\b	Backspace (BS) , Move the current position to the previous column	008
\f	Change the page (FF), Move the current position to the beginning of the next page	012
\n	Line break (LF) , Moves the current position to the beginning of the next line	010
\r	enter (CR) , Move the current position to the beginning of the line	013
\t	Horizontal TAB (HT) （ Skip to the next TAB Location ）	009
\v	Vertical tabulation (VT)	011
\	Represents a backslash character ’‘’	092
’	Represents a single quotation mark （ apostrophe ） character	039
"	Represents a double quote character	034
\0	Null character (NULL)	000
\ddd	1 To 3 Any character represented by an octal number	Three octal
\xhh	1 To 2 Any character represented by hexadecimal digits	Binary hexadecimal

---

Common functions （ String standard library ）

..: Link two strings （ It's equivalent to... In other languages + Symbol , Connect the two strings to generate a new string ）

string.upper: All strings are converted to Capital .
string.lower: All strings are converted to Lowercase letters .

string.gusb: In the string Replace .

string.reverse: character string reverse

string.find: Find substring , Return the start index and end index of this substring ( You can use pattern matching )

string:rep: Return string string Of n A copy

string.char: char take Convert integer numbers to characters And connect
string.byte: byte transformation Characters are integer values

string.len: Calculate string length （ You can also use #）

string.sub: Intercepting string

string.gmatch: Return to one iterator function , Every time this function is called , Returns a string in str The next one found matches pattern Substring of description . If parameters pattern Description string not found , The iteration function returns nil.( Pattern matching )

string.match: Just look for the source string str The first pairing in . Parameters init Optional , Specify the starting point of the search process , The default is 1.
On successful pairing , The function returns all capture results in the pairing expression ; If the capture flag is not set , Returns the entire pairing string . When there is no successful pairing , return nil.( Pattern matching )

Lua String pattern matching in supports regular expressions （ Incomplete support ）. See the official documents for details

See the official documents for specific use

---

UTF - 8 code
Lua It's supporting UTF-8 Of , It also provides some library functions for processing （Lua5.3）.

local s = "Lua Language "

-- We need to intercept the next two Chinese characters , The method is as follows 
local s1 = s:sub(utf8.offset(s, -2) -- Language 

-- get UTF-8 Code length 
local len = utf8.len(s) --5

-- Traverse UTF-8 Encode the characters in the string 
for p, c in utf8.codes(s) do --p Is in the string s The location of , c yes utf8 Coded character encoding （ Can convert ）
	print(utf8.char(c))
end

Lua Also available utf8.char and utf8.codepoint Two processing functions, character encoding conversion to string and string conversion to number
This is related to string Of string.char and string.byte similar

---

Cast

In the use of Arithmetic operator when , If the operation is a string ,Lua Will try to string Type changed to Floating point numbers .

print("2" * 2) --4.0
print("2" * "2") --4.0

Empathy , Using a string Connector .., If the operation is number,Lua Will try to number The type will be converted to character string

print("20" .. 22) --2022
print(20 .. 22) --2022

---

Thank you for watching