Lua String Introduction

1. All character indexes in the string library are,... from the past; From behind is -1,-2,...
2. All function in the string library does not manipulate the string directly, but instead returns a result

string.byte (String [, POS]): returns the integer representation of the first POS character. If A is 97.

String.char (I1,i2 ...):I1,i2 is an integral type, will i1,i2. Converted to the corresponding character and then concatenated into a string, and returned. If I1=97 returns a.

String.dump (functoin): Returns a 2-based code for a parametric function. Questions

String.find (S,pattern [, Init [, Plain]]): finds the position of pattern in S, returns the start and end position of pattern in S. Init is the location where you started the lookup. Plain unknown.

String.len (s): Returns the length of the string.

String.Lower (s): lowercase.

String.upper (s): capitalize.

String.rep (s,n): copy S n copies, and connect and return.

string.sub (S,i [, J]): takes the self string from start I to J in S. The default j is length.-I is the reciprocal.

For example:

s = "[ABC]"
String.len (s) <== return 5

String.rep ("abc", 2) <== return "ABCABC"
String.Lower ("abc") <== return "ABC"
String.upper ("abc") <== return "ABC"
String.sub (S, 2) <== return "ABC"
String.sub (S,-2) <== return "C]"
String.sub (S, 2,-2) <== return "ABC"
String.Format (FMT, ...) Returns a formatted string similar to printf

String.find (S, pattern, POS)
1th parameter: source string
2nd parameter: The pattern string to be searched
3rd parameter: A hint, start search from POS location
Find match return: match the start and end of the string, otherwise return nil

For example:
s = "[ABC]"
String.len (s) <==

String.gsub (s, pattern, reps)
1th parameter: source string
2nd parameter: The pattern string to be replaced
3rd parameter: Replace with reps
Replaces all pattern strings in s with reps, returns the result string + match number

Print (String.gsub ("Hello, World", "O", "a")) <== Hella, Warld 2

gsubYou can also use copy capture techniques
Print (String.gsub ("Hello, World", "(O)", "%1-%1")) <== Hello-o, Wo-orld 2
Print (String.gsub ("Hello Lua", "(.) (.) ","%2%1 ") <== Ehll Oula 4

function trim (s) return (String.gsub (S, "^%s* (.-)%s*$", "%1")) End <== Note the number of matches is discarded with parentheses

String.gsub (S, Pattern, func)
3rd parameter: Custom function, matching action found, and outgoing replacement value
S, n = string.gsub ("Hello World", "L +", function (s) return "XXX" end)
Print (s, n) <== Hexxxo worxxxd 2

String.gfind (s, pattern)
Returns an iterator that executes each time and returns the next matching string;
iter = String.gfind ("A=b c=d", "[^%s+]=[^%s+]")
Print (ITER ()) <== a=b
Print (ITER ()) <== C=d

Typically used for a generic for loop, the following example results in the same
For S in String.gfind ("A=b c=d", "[^%s+]=[^%s+]") do
Print (s)
Enda simple pattern string
s = "Hello World"
I, j = string.find (S, "Hello")
Print (I, j)-1 5
Print (String.sub (S, I, J))--Hello
Print (String.find (S, "World"))--7 11
I, j = string.find (S, "L")
Print (I, j)-3 3
Print (String.find (S, "lll"))--Nil

formatted pattern string
s = "Deadline is 30/05/1999, firm"
Date = "%d%d/%d%d/%d%d%d%d"
Print (String.sub (S, string.find (s, date)))--30/05/1999

The following table lists all the character classes that LUA supports:
. Any character
%s White space character

%p Punctuation Characters
%c control character

%d numbers
%x hex Digit

%z stands for 0 characters
%a Letter
%l Small Letter
%u Capital letters
%w Letters and Numbers

The uppercase form of the above character class represents the complement of the collection represented by lowercase. For example, '%A ' characters that are not alphabetic:

special characters in a pattern string
( ) . % + - * ? [ ^ $

'% 'an escape character used as a special character
'%. ' Matching point;
' percent ' matches the character '% '.
The escape character '% ' can be used not only to escape special characters, but also for all non-alphabetic characters. When you have questions about a character, escape him with an escape character for security reasons.

Create a character set with ' [] '
' [%w_] ' matches alphanumeric and underscore
' [01] ' matches binary digits
' [%[%]] ' matches a square bracket

use hyphens '-' in ' [] '
'%d ' means ' [0-9] ';
'%x ' means ' [0-9a-fa-f] '
' [0-7] ' means ' [01234567] '

Use ' ^ ' at the beginning of ' [] ' to indicate its complement:
' [^0-7] ' matches any character that is not an octal number;
' [^/n] ' matches any characters of a non-newline character.
' [^%s] ' = = '%s '

Pattern Modifiers

+ Match previous character 1 or more times
* Match previous character 0 or more times; longest match
-Match previous character 0 or more times; shortest match
? Match previous character 0 or 1 times
^ Match string start
$ match End of string

to surround with () the part to be captured
Pair = "name = Anna"
Firstidx, Lastidx, key, value = String.find (pair, "(%a+)%s*=%s* (%a+)")
Print (key, value) <== name Anna

copy Capture (%1-%9)
s = "ABC/" it/' s a cat/""
_,_,_,q = String.find (S, "([/" ']) (.-)%1 "))
Print (q) <== It's a cat if%d represents the first few captured copies.

Lua String Introduction