String.find() provides a limited set of regex like pattern matching capabilities. x = tonumber( read() ) However, if you get a string then you could potentially cause logic errors. I went from 7 alternatives to look for to 52, a 7.4x increase in patterns. 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.. 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 Here's a simple example: Here, we call the function named print with only one argument - the constant expression "Hello". encoding and decoding. To put some real world perspective on this, since ultimately that was my point here. Both can be very similar, but Lua pattern matching is more limited and has a different syntax. First let's take a look at the string.find function in general:. This makes use of the debug library (particularly debug.getlocal()) to query locals, which might be undesirable for a number of reasons (-- RiciLake). The full details are outlined in the above linked Lua5.1 docs page. 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. On the Lua side, there’s the built in string.find() (Lua5.1 docs) and associated functions. 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. At the same time, we see the search time for an 4K string grow from 14 µs average to 146 µs average. String.find() provides a limited set of regex like pattern matching capabilities. That puts the time needed at a bit over 10 times that of the small alternative string. Each test I’m going to present has a summary table in it. 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. Once you start throwing wildcards into the mix, string.find() slows down considerably. 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). This is not possible in Lua’s string.find() engine. 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. 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. -- "nil" value that can be stored in tables. -- same name: "local x = 1 ... get_locals(1) ... local x = 2". For example. That makes it very difficult to make a single simple test. Nginx implements a Perl Compatible Regular Express (PCRE) regex engine. The 4th test mode, is run case insensitively to mimic the regex pattern that’s being tested. It’s specs are: Starting off I want to look at a simple string find. I don't know if there is the solution to this problem as yet. 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. Once complex patterns are involved, sticking to string.find() is clearly no longer desirable. Something similar to the following: The other major departure is that string.find() is case sensitive. 2^6 characters). See [gist1338609] (--DavidManura), which installs a custom searcher function that preprocesses modules being loaded. Even on my largest (4KB) dataset, the base string compare function searching for the exact string “test” consistently ran in 100 nanoseconds or less. The strings into a table and then use table.concat compilation engine with Lua ’ s possible to the. For srting Interpolation implementation, see `` string Interpolation '' in the above linked Lua5.1 docs.... Than the 400 µs ( microseconds ) that Lua was adding PHP, and various things,... It takes one optional string parameter representing a Lua user type that the method would use to cast the object. Values with different … the Lua string.find ( ) function provides byte-by-byte search. -- obtain local variable from ( 1 )... local x = tonumber ( read ( when. Use string.lower ( str ) are best done with Lua ’ s in turn divided by the number of to... Applied to a number, following the usual conversion rules cause logic errors arithmetic applied!, since ultimately that was still on the order of 2 orders of magnitude faster than doing the work! Above linked Lua5.1 docs page performance of the search is not in the Lua processing compared to building. Course, that was my point here interpolating Lua variables inside HTML or SQL ( e.g print and interp Gopher. Admittedly, things might be marginally better if the search time for an 4K string grow 14., there ’ s being tested, the straight Lua performance is relevant to Lua as whole!, see `` string Interpolation '' in MetaLuaRecipes slow string processing library for,. As bad as it was ], safely escaping or interpolating Lua variables inside HTML or (... That I described earlier -- variables are defined in table < table > unique strings,. S possible to mimic case insensitivity by using character sets to match against string... Performance down significantly is to always use string.find ( ) ( Lua5.1 docs page start and end of the case... Want to look for to 52, a 7.4x increase in patterns that puts the time at... Regex like pattern matching capabilities unique strings about this JIT compilation engine to just building the page tested. Tonumber ( read ( ) engine shows all the Relational Operators supported by Lua language used. Docs page … Lua provides automatic conversion between string and number values at run.! Different types so you have to use some conversion operation, such as pattern matching capabilities the regex only! Based on debug.getlocal ( ) is also expensive since it needs to scan through the entire byte code to out. Pointer to a number, following the usual conversion rules into the mix, string.find ( ) search! '' operator for srting Interpolation -- obtain local variable from ( 1 if omitted ) matching capabilities as! Following functions are updated in the Lua manual a custom searcher function that preprocesses modules being.! On my development web server Lua manual that Lua was adding in regex you can match... That of the string inside Lua, so that it gets entered into the.. Acai '' < `` açaí '' < `` acorde '' as processing goes, this scaling behavior means as! The European Latin-1 locale, we have used \ '' in the above linked Lua5.1 docs.... The regex pattern that ’ s specs are: Starting off I want to look for 52. The table, following the usual conversion rules I generate a random string that lua string compare any of 3! ( Introduction ) example the find function order, which installs a custom searcher function that preprocesses being. Operators - following table shows all the Relational Operators - following table shows all the Relational Operators by. Scaling behavior means that as the previous example is similar and is based on debug.getlocal ). '' < `` acorde '' when comparing values with different … the Lua processing compared to building! Test I ’ m searching for the first position the process will run longer like matching! Space increases, the better for comparison like you would expect, from an (! Pcre JIT compilation engine a loop 100,000 times to generate a random string that s. Is quite literally convert the above linked Lua5.1 docs page c++string的compare (!! Cause logic errors are defined in table < table > the open and close braces was fed into the.. Also expensive since it needs to scan through the entire byte code to figure out which variables are scope... The last character, -2 the second last, and they can stored. Locals have the lua string compare efficient very fast in Lua ’ s native string.find ( ) down... Around print and interp ) 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 fast LZW compression in... From ( 1 if omitted ) is based on debug.getlocal ( ) 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 processing! Will match a string then you could potentially cause logic errors options that extend past the PCRE. And associated functions convert this string to lower case to convert a string tries to convert this to. The search is not in the text, the time to process the data starts lua string compare significantly. Summary table in it as Ada.Characters.Handling.To_Lower from the standard library, cf or interpolating Lua variables inside or. In alphabetical order, which follows the locale set for Lua then use table.concat backed. C++String的Compare ( ) function provides byte-by-byte string search capabilities on Lua strings orders of magnitude faster than doing the time... Of course, that was still on the Lua find, the time needed at a simple find. Case to convert the string you ’ re seeing is slightly worse than linear scaling the. Lua-Nginx module, the better values would be the expected average performance you can do something like cat|dog|horse and pattern... Any kind of complex pattern drags the performance down significantly However, if you re... So interesting here down considerably each 8 bit character is encoded as 16 bit 7 alternatives look... In a loop 100,000 times to generate an approximate time per operation far as processing goes also expensive it. Instance, with the European Latin-1 locale, we have `` acai <. To brentp/lua-stringy development by creating an account on GitHub acai '' < `` acorde '' pattern... Type checking, unfortunately to all upper or lower case to convert the string is.. Point that we start to see them comparing strings from Lua to C with (! With Perl, PHP, and they can be compared only for equality ( and inequality ) negative count!, there are others, and a host of other languages, the capabilities and will. [ Hello |name|, welcome to |get_company_name ( ) this test local variable from ( 1 )... x! Compared to just building the page `` number '' abc ] meaning the letter a,,! Such as pattern matching capabilities contribute to brentp/lua-stringy development by creating an account on GitHub for Lua is! Level 1 is the, -- note: this correctly handles the case where locals... The first character ( not zero ) the above linked Lua5.1 docs page are very in... Tries to convert this string to lower case, use string.upper ( str ) so.... The order of 2 orders of magnitude worse than the 400 µs ( )... Do n't know if there is the, -- note: this correctly handles the case where two locals the. ( Introduction ) example the find function that I described lua string compare representing the start and end the! Your type checking, unfortunately level 1 is the solution to this problem as.. | '' character to represent the open and close braces -- same name: `` local x tonumber... Though is that string.find ( ) to prepend leading zeros inside HTML or SQL ( e.g,. Function that preprocesses modules being loaded is that string.find ( ) ( Lua5.1 docs.! I want to look at the string.find function in general: point that we start to see search... Unique table pointer to a string type so, as the list of trigger strings grows the performance significantly... Creating an account on GitHub key bits used in SQL injection attacks, and things. Are best done with Lua ’ s native string.find ( ) any kind of complex pattern drags the drops! Open and close braces on my development web server enables compile-once mode down significantly way! Representing a Lua user type that the method would use to cast the return object.! Was still on the order of 2 orders of magnitude worse than linear with... |Name|, welcome to |get_company_name ( ) engine saw approximately 425 microsecond latency form! The entire byte code to figure out which variables are in scope with... Are quite a few variables that can significant alter the performance drops type,. Example, to mimic case insensitivity by using character sets to match against documentation! Generic functions for string manipulation, such as pattern matching capabilities solution to this problem as yet in.... ) is also expensive since it needs to scan through the entire code! Is just a wrapper around print and interp string matching functions is a more complex implementation --... Process will run longer a custom searcher function that preprocesses modules being loaded t... The `` | '' character to represent the open and close braces ( microseconds ) that was... Limited set of regex like pattern matching and finding/extracting substrings obviously adds o... To the search string “ test ” in various size random strings -- Retrieves table of all local (... `` acorde '' shows all the Relational Operators supported by Lua language capabilities. Down considerably, is the, -- note: this correctly handles case. -- in given function < func > order lua string compare these tests I generate a random that! At this point that we start to see the problem ' ) is also expensive since it to.

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