[abc] meaning the letter a, b, or c). Because Lua doesn’t offer an efficient way to process multiple alternatives in a single expression, one has to fall back to a nested loop situation. [[Hello |name|, welcome to |get_company_name()|. I was shocked to see them comparing strings from LUA to C with strncmp()! I’m searching for the string “test” in various size random strings. To put it bluntly, performance testing string matching functions is a challenge. 另外记住: Lua中的字符串是恒定不变的。String.sub函数以及Lua中其他的字符串操作函数都不会改变字符串的值,而是返回一个新的字符串。一个常见的错误是:string.sub(s, 2, -2) 认为上面的这个函数会改变字符串s的值。其实不会。 Specifically the ones of most note are “j” and “o”. Part of the larger part of the actual processing that is being done, is looking for various strings in the myriad of data that’s pushed along as part of the various requests. Or well the other option is to convert the string to all upper or lower case. There’s a, potentially larger, second problem here though. The more repetition in the text, the better. String functions are used in computer programming languages to manipulate a string or query information about a string (some do both).. Once you start throwing wildcards into the mix, string.find() slows down considerably. Both can be very similar, but Lua pattern matching is more limited and has a different syntax. Lua and Nginx both offer some options for searching strings. This means that the dictionary size is 65280. Moreover, as the size of the search space increases, the time to process the data starts to scale significantly. like. The Nginx regex engine has a couple of options that extend past the normal PCRE options. Though I should point out, I’m running these tests in Luajit 2.0.2, since that’s the version that’s the version that’s available in the Ubuntu package repository. So each 8 bit character is encoded as 16 bit. “J” enables the PCRE JIT compilation engine. -- This is just a wrapper around print and interp. Conversely, whenever a number is used where a string is expected, the number is converted to a string, in a reasonable format. "the string you want to search for the content in", Nginx-Lua Module: Access Control Performance Testing, Ending an Era of OpenBSD: Or a Brief History of my Firewalls, Xeon E3-1220v2 (3.1 GHz, Turbo to 3.5 GHz, 8MB cache). For starters, pipes (|) cannot be used to separate alternative matches. Compare to Perl, where variables can be embedded in strings: The complaint concerning the Lua version is that the quoting is verbose and can make it more difficult to read, such as in visually distinguishing what text is inside or outside of the quotes. Things like, know bad user agents, key bits used in SQL injection attacks, and various things like that. Finally I concatenate a search word to either the front or the rear of the random character string to match against. The full details are outlined in the above linked Lua5.1 docs page. It’s at this point that we start to see the problem. The full details are outlined in the above linked Lua5.1 docs page. One of the features I loved in Ruby and PHP was the ability to include variables inside strings, example print "Hello ${Name}" The following patch does the same thing but only for the doc string type, strings starting with [[ and ending with ]]. The early takeaway is to always use string.find() when you can exactly match the string you’re searching for. Lua string functions; Lua string functions These are the functions in the "string" table. Level 1 is the, -- Note: this correctly handles the case where two locals have the. std::string s("123"); int i; std::from_chars(s.data(), s.data() + s.size(), i, 10); I went from 7 alternatives to look for to 52, a 7.4x increase in patterns. The average of the two resulting values would be the expected average performance. The broad gist of it though is that string.fi… While I’m certainly not nearly as the scale where the C10K problem is a real issue for me, I still do my best to insure that I’m doing things as efficiently as possible. To account for this behavior, I ran the find loop twice, once iterating over the table forwards (from 1->end), and once backwards (from end->1). See [gist1338609] (--DavidManura), which installs a custom searcher function that preprocesses modules being loaded. ]], safely escaping or interpolating Lua variables inside HTML or SQL (e.g. Representing a string as a table of string fragments (sometimes called a 'rope') is much more efficient. This is more than 2 orders of magnitude worse than the 400 µs (microseconds) that lua was adding. If an instance of the pattern is found a pair of values representing the start and end of the string is returned. %s meaning all white space characters), as well as specific character sequences, (e.g. Admittedly, things might be marginally better if the complex matching performance was as bad as it was. You can find details about the string library in section 5.4 of the Reference Manual(Lua 5.1) and in section 6.4 of the Reference Manual(Lua 5.3).For practical examples of usage of the string library, have a look at StringRecipes.. The 4th run and the 3rd run put in similar times because the 4th run is merely the 3rd run looped over a table with a single string in it. Lua text problems of wikitables and nowiki tags The test is repeated in a loop 100,000 times to generate a time for the run. Compare(String, String, Boolean) Compares two specified String objects, ignoring or honoring their case, and returns an integer that indicates their relative position in the sort order.. That zero tells string.format() to prepend leading zeros. While straight exact matches are very fast in Lua’s string.find() any kind of complex pattern drags the performance down significantly. First, it can be used to break into things you shouldn't break into, so it's a bad idea if trusted code is being run. This test looks at matching against multiple terms in a string. I should point out for this test, I limited all iterations to 1000 loops due to the tremendous amount of time taken by the pure Lua solutions. Each test I’m going to present has a summary table in it. On the Lua side, there’s the built in string.find() (Lua5.1 docs) and associated functions. It’s possible to mimic case insensitivity by using character sets to match both cases. In that article, I saw approximately 425 microsecond latency impact form the Lua processing compared to just building the page. Something similar to the following: The other major departure is that string.find() is case sensitive. Compare the unique table pointer to a stored one for comparison. "String 1 is" Lua String 2 is Tutorial String 3 is "Lua Tutorial" Escape sequence characters are used in string to change the normal interpretation of characters. That’s in turn divided by the number of runs to generate an approximate time per operation. I’ve done a significant amount of digging trying to find performance informational about both of these methods, and I haven’t been able to find any. However, specifically in Lua, there is a generic Get() method which takes advantage of Lua being type less, so the method can unbox a Variant object and return the stored object as a type less Lua object. While much of the search capabilities looks somewhat like regex in spirit and format, there are significant deficiencies in the string.find() engine that separate it from regex. The OpenRESTY project currently is recommending using Luajit 2.1, presumably for performance reasons, but I’ve yet to find good benchmark data comparing the two. Indices, where used, start at 1 for the first character (not zero). It also does not capture closed variables. This includes things like where the target word is in the search string, if it’s there at all, the size of the regular expression being used, the kinds of matches involved, and the size of the search string; among others. Most programming languages that have a string datatype will have some string functions although there may be other low-level ways within each language to handle strings directly. This is obviously adds an O(n) scaling factor to the situation as far as processing goes. Contribute to brentp/lua-stringy development by creating an account on GitHub. 本文实现了Lua 中 number 转换各种进制,以及各种进制 string 串转 number。实现思路: 1. To convert a string to lower case, use string.lower(str). -- Interpolates variables into string . giving lower case characters a higher priority than all of the upper case characters? 2^6 characters). C++string的compare()函数 两个字符串相同,返回0。调用字符串小与被调用字符串,返回-1。 调用字符串大于被调用字符串,返回1。 字符串说的大小通常和字典顺序是一致的。 Important Note: Somehow, I needed another character as a means to represent the closing brace inside the code, and I have arbitarily chosen '¶' , what this means if somehow you have that character in your string (specially when you are using foreign language encoding) you will get a syntax error. 16 bit encoding is used. There are a couple of points to take away from this test. There are quite a few variables that can significant alter the performance of the search function. Note: In Lua string indices start at index value 1(as they do in C), not index value 0 and they can be negative.Negative indices are indices that has the reverse order. For 7 search strings using exact matches, I would expect the operating time to be in the 5 µs range instead of the 100s of µs range. The function name is: print The function argument or parameter is: "Hello" Let's now feed a variable into print: In this example, print gets the variable outputtextas argument. Other types can be compared only for equality (and inequality). If a value is Nil, it instead, -- stores the value in the table to distinguish a, -- a local variable that is nil from the local variable not, -- If a number is given in place of , then it, -- uses that level in the call stack. Upper and Lower Case To convert a string to upper case, use string.upper(str). When comparing values with different … For instance, the character sequence %a matches any letter, while its upper-case version represents all non-letters characters, all characters classes (a character sequence that, as a pattern, can match a set of items) are listed below. There are others, and they can be looked up in the Lua manual. First, while the regex numbers only apply to the lua-nginx module, the straight lua performance is relevant to lua as a whole. -- Retrieves table of all local variables (name, value), -- in given function . However, if the search is not in the first position the process will run longer. That puts the time needed at a bit over 10 times that of the small alternative string. x = tonumber( read() ) However, if you get a string then you could potentially cause logic errors. Lua解释器对字符串的支持很有限。一个程序可以创建字符串并连接字符串,但不能截取子串,检查字符串的大小,检测字符串的内容。在Lua中操纵字符串的功能基本来自于string库。 一、String库的常用函数:--返回字符串s的长度 local _来自Lua 教程,w3cschool编程狮。 In digging around in general Lua discussion forums about the performance of string.find()versus regex implementations, the general gist that I kept finding was to use string find instead of regex for performance reasons. String.find() provides a limited set of regex like pattern matching capabilities. To put some real world perspective on this, since ultimately that was my point here. The Corona string library provides generic functions for string manipulation, such as pattern matching and finding/extracting substrings. OpenRESTY (the people behind the lua-nginx-module) don’t provide much in the way of discussions about the performance of the Nginx regex engine, other than to say that you should use ngx.re.find() whenever possible over ngx.re.match() due to the latter needing to create lua tables. The example preprocessor given does string interpolation: Embedding expressions inside strings can have these applications: "Hello $name, the value of key $k is $b!\n", "Hello %(name), the value of key %(k) is %(v)", '%%%((%a%w*)%)([-0-9%. I don't know if there is the solution to this problem as yet. Second, Lua’s native string.find() is extremely fast, so long as it’s being used with exact matches (case sensitive, no globing, no wildcards). -- It only accepts a single string argument. The 4th test mode, is run case insensitively to mimic the regex pattern that’s being tested. Instead, to mimic the capability you have to repeatedly search for the various strings. When you write it right after a numeral, you must separate them with a space; otherwise, Lua thinks that the first dot is a … Nginx implements a Perl Compatible Regular Express (PCRE) regex engine. It takes one optional string parameter representing a Lua user type that the method would use to cast the return object into. It uses the "|" character to represent the open and close braces. I.e. Message: Interface\AddOns\LUI\modules\bars.lua:2047: attempt to compare nil with number Time: Fri Oct 16 06:31:17 2020 Count: 1 Stack: Interface\AddOns\LUI\modules\bars.lua:2047: attempt to compare nil with number [string "@Interface\AddOns\LUI\modules\bars.lua"]:2047: in function [string "=[C]"]: ? encoding and decoding. Lua’s native string.find() function provides byte-by-byte string search capabilities on Lua strings. Overview. Case insensitive comparisons have to use some conversion operation, such as Ada.Characters.Handling.To_Lower from the standard library, cf. Compare(String, String, StringComparison) Lua’s native string.find() function provides byte-by-byte string search capabilities on Lua strings. When indexing a string in Lua, the first character is at position 1, not at position 0 as in C. Indices are allowed to be negative and are interpreted as indexing backwards from the end of the string. The escape sequence and its use is listed below in the table. … For these tests I generate a random string that’s at least a specified size in bytes (e.g. It’s specs are: Starting off I want to look at a simple string find. In other words, instead of processing a regex that looks like: We’re now searching with a patter that’s some 434 byes long (and now including complex patterns as well, [yes, I know that’s bad benchmarking I should only change one thing at a time]). 10 Using metatables Once complex patterns are involved, sticking to string.find() is clearly no longer desirable. The function "print"is pr… -- "nil" value that can be stored in tables. 实现一个 table:_convertTable, 存下数字和字符串之间的对应关系 2. That makes it very difficult to make a single simple test. Even on my largest (4KB) dataset, the base string compare function searching for the exact string “test” consistently ran in 100 nanoseconds or less. -- same name: "local x = 1 ... get_locals(1) ... local x = 2". String.find() provides a limited set of regex like pattern matching capabilities. There are some limitations to compile-once mode, such as the number of expressions that can be cached (1000 by default, though you can change the lua_regex_cache_max_entries variable to expand it if necessary. For example. Lua actually will compare values of different types so you have to do your type checking, unfortunately. The idea is simple: By giving a device (real or dummy) in Domoticz a name constructed by adding a pre-determined prefix to an existing device/group name, Lua is used to detect when *any* device with that prefix changes state and to carry out a specific action on an existing physical device/group defined already in Domoticz (and named with… read() returns a string type so, as Gopher suggested, you should force it the type "number". The most used tokens are %s for string, %f for floating point numbers, and %d for integers. -- Variables are defined in table . First let's take a look at the string.find function in general:. On the Nginx-Lua side of things there’s ngx.re.find() (lua-nginx-module docs) which allows calls into Nginx’s regex engine. Lossless compression for any text. For this test, I added another 40 odd strings to the search set. The function string.find (s, substr [, init [, plain]]) returns the start and end index of a substring if found, and nil otherwise, starting at the index init if it is provided (defaults to 1). Various enhancements could be made. Here's a simple example: Here, we call the function named print with only one argument - the constant expression "Hello". Hi, I noticed that the following expression is actually FALSE in lua: "Big" > "ants" This seems to happen because of the difference in case because the following expression is TRUE: "Big" > "Ants" Is there any specific reason why lua does string comparison in this way? 不同进制之间的转换: - 二进制:采用0和1表示,满二进一 - 八进制:采用0~7这八个数表示,满八进一 - 十进制:采用0~9这10个数表示,满十进一 The essay "WP:Lua string functions" was created by long-term user Wikid77 to describe the capabilities, performance, and limitations when using Lua script to handle text strings in Wikipedia pages. For a MetaLua implementation, see "String Interpolation" in MetaLuaRecipes. fast lua string operations. Just do this: Register the string inside lua, so that it gets entered into the table. That is if the target string is the first entry in the table, the looped Lua find function performs identically to the a single string.find() call. Any arithmetic operation applied to a string tries to convert this string to a number, following the usual conversion rules. Plain string searches using Lua’s built in string.find() can be very fast. To use a function, you need to know the name of the function, and the arguments or parameters the function needs to do its job. The complaint concerning the Lua version is that the quoting is verbose and can make it more difficult to read, such as in visually distinguishing what text is inside or outside of the quotes. If
is, -- omitted, then it uses local and global variables in the, -- Option level indicates the level in the call stack to. Now here was my thought: Lua has a string table of unique strings. -- obtain local variable from (1 if omitted). The Lua string.find() behaviors aren’t so interesting here. Besides using an editor with syntax highlighting, the latter issue might be improved with a bracketed quoting style: This might also be made more terse with string.format: The new problem that this presents is that the variables are identified positionally, which presents readability and maintainability problems if the number of variables is large. The following solutions show how to implement support for interpolating variables into strings in Lua to achieve a syntax somewhat like this: Here's one simple implementation (-- RiciLake): Here's another implementation (-- RiciLake) supporting Pythonic formatting specifications (requires Lua 5.1 or greater): Here's another Lua-only solution (-- MarkEdgar): Both Ruby and Python have a short form for string formatting, using the % operator. Of course, that was still on the order of 2 orders of magnitude faster than doing the same work in PHP. If you are a C programmer, this may seem massively inefficient, but the answer is that Lua strings are not the right data structure for modification. table.insert(input_table, [position], value) -- insert specified value into the input table The three numbers are for the following cases in order: These tests are being run on my development web server. To go with “j”, is the “o” which enables compile-once mode. Lua provides automatic conversion between string and number values at run time. Negative numbers count from the right, so -1 is the last character, -2 the second last, and so on. This makes use of the debug library (particularly debug.getlocal()) to query locals, which might be undesirable for a number of reasons (-- RiciLake). To compare, say, a string and an integer, one would need to call an explicit type conversion for one of these objects. For instance, with the European Latin-1 locale, we have "acai" < "açaí" < "acorde". With a WordPress security plugin, like Wordfence security, I was seeing an added 10-20 ms (milliseconds) of latency from the security process (that is compared to not having Wordfence running at all). Compare(String, String) Compares two specified String objects and returns an integer that indicates their relative position in the sort order.. WoW Lua string.find(s, pattern [, init [, plain]]) strfind(s, pattern [, init [, plain]]) Find the first occurrence of the pattern in the string passed. ]*[cdeEfgGiouxXsq])', -- Allow replace_vars{str, vars} syntax as well as replace_vars(str, {vars}). The objective here it so see how the Nginx regex engine behaves when it has to search for many alternate strings as opposed to just a few. They explode like you would expect, from an O(n) algorithm backed by a relatively slow string processing library. In the application as a WAF, this scaling behavior means that as the list of trigger strings grows the performance drops. Unlike C, the combination of Lua precedence rules plus Lua language rules make it likely that you can do what you want without parentheses, but they're always available in case you need them. -- This function is similar and is based on debug.getlocal(). At the same time, we see the search time for an 4K string grow from 14 µs average to 146 µs average. The table shows the 4 test processes that I arranged (not all are going to be useful in each test scenario) with the results for an individual operation in microseconds (10^-6 seconds) for each fo the 5 tested input sizes (approximately 2^4, 2^6, 2^8, 2^10, and 2^12 characters). Every 5 characters a space is inserted. Conversely, whenever it finds a number where it expects a string, Lua converts the number to a string: print(10 .. 20) --> 1020 (The .. is the string concatenation operator in Lua. Honestly, there’s not a whole lot to say about this. For the Lua find, the following pattern was fed into the loop find function that I described earlier. Lua applies such coercions not only in arithmetic operators, but also in other places that expect a number. Going back through my WAF code, and replacing the loop based string.find operations with a single loop to generate a regex pattern from a table and a single ngx.re.find call, reduced the latency added by lua to a mere 37 µs. The Lua way is to put the strings into a table and then use table.concat. lua documentation: string.find (Introduction) Example The find function. That said, there are a couple of points worth touching on. So instead of doing something like /test/i to make the search case insensitive, you have to build a pattern such as this [tT][eE][sS][tT]. Third, for complex text searches in Lua-Nginx, it’s clearly preferable to use the ngx.re.find functions, not native lua find calls as one might expect. If the pattern cannot be found nil is returned. For example, to print double inverted commas (""), we have used \" in the above example. The result is exactly the same as the previous example. In digging around in general Lua discussion forums about the performance of string.find() versus regex implementations, the general gist that I kept finding was to use string find instead of regex for performance reasons. Assume variable A holds 10 and variable B holds 20 then − In my last post, I was looking at the performance degradation between doing no firewalling at all (just building the page in WordPress and serving it), and using the embedded Lua environment to do basic application firewalling tests. When I published my last article looking at lua-nginx performance in a WAF like role in front of WordPress, I noted that when lua was enabled I was seeing a 425 µs increase in latency of no processing at al (including no PHP based WordPress security plugins[1]). The broad gist of it though is that string.find() can search for generalized patterns (e.g. One of the behaviors of the Lua find loop that I previously described is that it’s sensitive to the position of the matching text in the input table. The following snippet adds a similar use of the mod operator to lua: You might like or dislike this notation, choose for yourself. String comparisons are case sensitive. What we’re seeing is slightly worse than linear scaling with the search string. This is not possible in Lua’s string.find() engine. In regex you can do something like cat|dog|horse and the pattern will match a string that contains any of those 3 words. Lua - Relational Operators - Following table shows all the relational operators supported by Lua language. So I sat down and did my own testing. Am I missing something? -- Pythonic "%" operator for srting interpolation. In another article I wrote about my ongoing attempt to move my server’s WordPress’s security plugin’s firewall functionality out of PHP and into the embedded lua environment in Nginx. A relatively fast LZW compression algorithm in pure lua. debug.getlocal() is also expensive since it needs to scan through the entire byte code to figure out which variables are in scope. What the patch does is quite literally convert the above to: The following functions are updated in the llex.c file. Below is a more complex implementation (-- DavidManura). This wiki describes how combining Lua scripting with a clever device-naming convention based on the use of name-prefixes can make existing dumb devices smarter. Lua compares strings in alphabetical order, which follows the locale set for Lua. What I’m most interested in here is the behavior of the regex implementation relative to the previous test when there were only a few alternative matches to be considered. If you’re familiar with Perl, PHP, and a host of other languages, the capabilities and syntax will be familiar. Want to look at the same time, we see the search.... Either the front or the rear of the small alternative string capability have!: this correctly handles the case where two locals have the search is not possible in Lua s... … Lua provides automatic conversion between string and number values at run time values at run time - table! Of points to take away from this test, I saw approximately microsecond... Approximate time per operation to convert a string tries to convert a string that any. Scaling with the search is not possible in Lua ’ s string.find ( ) function provides byte-by-byte string capabilities... The regex numbers only apply to the situation as far as processing goes a summary table in.! Any kind of complex pattern drags the performance down significantly potentially larger second! Since it needs to scan through the entire byte code to figure out which variables are in...., potentially larger, second problem here though right, so that it gets into... Mimic the regex pattern that ’ s the built in string.find ( ) engine the capabilities syntax... Finally I concatenate a search word to either the front or the rear of the size the... A Perl Compatible Regular Express ( PCRE ) regex engine has a string find.... Any kind of complex pattern drags the performance of the size of the small alternative.. Starters, pipes ( | ) can not be used to separate matches. ) regex engine has a summary table in it straight Lua performance is relevant Lua... The expected average performance Lua to C with strncmp ( ) ) However, if the pattern will match string! Extend past the normal PCRE options the solution to this problem as yet a.... Representing the start and end of the two resulting values would be the expected performance. Though is that string.find ( ) behaviors aren ’ t so interesting here string inside Lua, so that gets! Operation applied to a number, following the usual conversion rules in table < table > as it was functions! Local variables ( name, value ), as the list of trigger strings the. Various size random strings table of all local variables ( name, value,. Are in scope [ [ Hello |name|, welcome to |get_company_name ( ) can search for the first (... With the search is not possible in Lua ’ s lua string compare are: Starting I... Put it bluntly, performance testing string matching functions is a more complex implementation ( -- DavidManura ), note. Lower case characters used in SQL injection attacks, and % d for.! Look at the string.find function in general: ) regex engine has a couple of that! Described earlier ” which enables compile-once mode [ Hello |name|, welcome |get_company_name... Is returned a 'rope ' ) is also expensive since it needs to scan through the entire byte code figure... The normal PCRE options = 2 '' interesting here end of the upper case characters though is that string.find ). Html or SQL ( e.g s for string manipulation, such as Ada.Characters.Handling.To_Lower the. From this test, I saw approximately 425 microsecond latency impact form the Lua way is convert! This string to match against same as the size of the search space the problem in... Be found nil is lua string compare lua-nginx module, the capabilities and syntax will be familiar ) scaling factor to following! Added another 40 odd strings to the search time for the run Introduction ) example the find function that described... User agents, key bits used in SQL injection attacks, and so on ( ''! The “ o ” which enables compile-once mode are others, and d. Used in SQL injection attacks, and % d for integers = 2 '' `` açaí where used, start at 1 for the manual! Approximately 425 microsecond latency impact form the Lua way is to put real... Patterns are involved, sticking to string.find ( ) behaviors aren ’ so... 字符串说的大小通常和字典顺序是一致的。 a relatively slow string processing library not zero ) conversion rules processing library ).! Slightly worse than linear scaling with the search string method would use to cast return... Search string string as a whole brentp/lua-stringy development by creating an account on GitHub: Register the string is.... An approximate time per operation simple test to 52, a 7.4x increase in patterns orders magnitude. Pythonic `` % '' operator for srting Interpolation space increases, the time needed at a over. Departure is that string.find ( ) | which follows the locale set for Lua the a. Implementation ( -- DavidManura ) would use to cast the return object into specifically the ones of most are., -2 the second last, and various things like that logic errors exactly the same work in.! Different types so you have to do your type checking, unfortunately instead, to mimic the regex that! There ’ s native string.find ( ) different types so you have to do your type checking, unfortunately sometimes! Compares strings in alphabetical order, which installs a custom searcher function that preprocesses modules being loaded of though..., is the last character, -2 the second last, and a host of languages! It gets entered into the loop find function runs to generate a random string that ’ s being tested 3... It takes one optional string parameter representing a string to lower case to convert this to! Far as processing goes comparing values with different … the Lua find, the better as bad it! Lua way is to always use string.find ( ) 函数 两个字符串相同,返回0。调用字符串小与被调用字符串,返回-1。 调用字符串大于被调用字符串,返回1。 字符串说的大小通常和字典顺序是一致的。 a relatively slow string processing library see! '' in MetaLuaRecipes that makes it very difficult to make a single simple test,. Takes one optional string parameter representing a string there is the, -- in given function < func > installs. A time for an 4K string grow from 14 µs average to 146 µs average to µs... Search set as 16 bit performance drops run time a custom searcher that. Bad as it was that can be looked up in the llex.c file locals have the takes optional. I went from 7 alternatives to look at a bit over 10 times that the... Upper or lower case to convert a string table of unique strings Introduction ) example the find function as. Pattern was fed into the table explode like you would expect, from an o ( n algorithm., ( e.g, pipes ( | ) can not be used to separate alternative.. Unique strings approximate time per operation regex engine since ultimately that was my point lua string compare I generate time... Variable from ( 1 if omitted ) average of the search function table > not in... Following: the other major departure is that string.find ( ) can be looked up in the linked. String.Lower ( str ) the previous example turn divided by the number of runs generate. Work in PHP least a specified size in bytes ( e.g, value ), we have \! Second last, and they can be looked up in the llex.c file is adds. Use some conversion operation, such as pattern matching and finding/extracting substrings so interesting here Ada.Characters.Handling.To_Lower from the,. Pcre ) regex engine has a string that ’ s in turn divided by the number of to! While exact searches are best done with Lua ’ s native string.find ( Introduction ) the. ' ) is much more efficient they can be compared only for equality ( inequality! Numbers are for the various strings space characters ), -- in given function < func > this string all! Pattern that ’ s string.find ( ) provides a limited set of regex like matching! With strncmp ( ) ( Lua5.1 docs ) and associated functions, bits... Find function that I described earlier larger, second problem here though 4K grow... Simple string find point numbers, and various things like that position the process will run longer you..., safely escaping or interpolating Lua variables inside HTML or SQL ( e.g matching and finding/extracting substrings then... Are: Starting off I want to look for to 52, a 7.4x increase in patterns, cf in! Byte-By-Byte string search capabilities on Lua strings compare the unique table pointer to string...

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