If you continue to use this site we will assume that you are happy with it. What would you like to do? It’s hard to break strings down on each character point. Most of these functions are fine to use with UTF8, but there are some things missing. Confused yet? It’s specifically this feature which is why this lesson is placed after so many other things. In this tutorial, I will explain how you can use these very useful expressions to your advantage. RIP Tutorial. Let’s see some of the basic options so that we can know what goes in our format string. Instead of using regex, the Lua string library has a special set of characters used in syntax matches. Standard regular expressions and patterns solve a lot, but not everything. We have another “123” midway in the string as well. Let’s use a pattern first, then pass our string.find to a new function we made print_range to make our formatting easy. We match a digit or more, then anything, then a digit or more. Let’s also look at some of the less commonly used string functions which we won’t spend much time on. We have a bit of a chicken and the egg problem with which is worth teaching first, so we’re going to start with the function first. Don’t worry, we’re going to go over all of these. Let’s go over special characters first since they’re the easiest. The “-” tells us to match any number of times, but to not be greedy. It’s a bit beyond the scope of this article to list out every possibility for string.format. Since it does not store nil values in Lua, it is possible to save lots of memory without any special technique in Lua as compared to special techniques used in other programming languages. Remember in the class lesson where we discussed syntactic sugar? Magic characters can be escaped with %. When we run the above program, we will get the following output. A sample code for character and byte representation, which is used for converting the string from string to internal representation and vice versa. A string that is equivalent to the current string except that all instances of oldValue are replaced with newValue. String is a sequence of characters as well as control characters like form feed. print( string.match( test, “%d+.-%d+”) ) gets us “123 ABC 123”. Parameters: 1. string. Thus, the last character is at position -1, and so on. utf8.reverse The special characters are easy enough, but let’s dive into the magic characters and patterns. Lua provides automatic conversion between string and number values at run time. 1. assert(value[, errormsg]) - asserts a value evaluates to true. Lua data types are automatically converted to Vimscript types (and vice versa). " Returns a string by repeating the same string n number times. If repl is a string, then its value is used for replacement. Use this function sparingly. gsub also returns, as its second value, the total number of matches that occurred. This string may be constructed manually, or generated by another function such as string.dump. We do the same thing as before, but we’re greedy so we match until the last instance of this. Things like match and gmatch will be detailed since each of them has different use cases. String can be initialized with three forms which includes −. Lua's string.match(), string.gmatch() and string.find() built in functions help you find substrings by matching: Syntax: Returns: Does: string.find(s, pattern [, init [, plain]]) index of start of match: By returning the index of the found match this gives you a great way to carve up string. We use cookies to ensure that we give you the best experience on our website. gsub also returns, as its second value, the total number of substitutions made. Most languages require you to pass an array or similar, but Lua has a built in way to handle this. Now we’re just getting weird with this. The name gsub comes from Global SUBstitution. Luckily, there is a good UTF8 library which can be installed via Luarocks. Plain-text string.replace for Lua (string.gsub without patterns) - string-replace.lua. Returns a copy of s in which all (or the first n, if given) occurrences of the pattern (see Pattern) have been replaced by a replacement string specified by repl, which can be a string, a table, or a function. string.gmatch( s, pattern ) is similar to string.match, except it provides all of the matches. string.format is one of the most useful for outputting things, but can be one of the most complicated string functions to master unless you’ve worked with C. Speaking of which, this almost entirely follows printf. We’ll have some new exercises coming up to work with different real life examples soon enough. It’s also hard to deal with lengths and similar. This is useful for certain scenarios where you know roughly where the replacements will need to take place. All gists Back to GitHub Sign in Sign up Sign in Sign up {{ message }} Instantly share code, notes, and snippets. print( string.match( test, “%d*” ) ) gets us “”. Used simply it can replace all instances of the pattern provided with the replacement. Its basic use is to substitute the replacement string for all occurrences of the pattern inside the subject string: s = string.gsub ("Lua is cute", "cute", "great") print (s) --> Lua is great s = string.gsub ("all lii", "l", "x") print (s) --> axx xii s = string.gsub ("Lua is great", "perl", "tcl") print (s) --> Lua is great Lua offers a wide range of functions for working with text. You can use the index to find specific pieces between certain ranges as you slowly take apart the string when writing a parser. If it is, returns value, otherwise causes a Lua error to be thrown. %% becomes %. First let's take a look at the string.find function in general: 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). print( string.match( test, “%d+. The index affects where the search begins, and the boolean for a plain search affects whether it uses regular expressions or patterns. Any arithmetic operation applied to a string tries to convert this string to a number, following the usual conversion rules. Just keep reading. Perl in 2020: Is It Still Worth Learning Now. For example, to print double inverted commas (""), we have used \" in the above example. If replis a string, its value is used for the replacement. Let’s start with a table and introduce each function as we go. A lot of these are directly ported from C, but there are some notable differences. string string.Replace( string str, string find, string replace ) View Source Search Github DescriptionReplaces all occurrences of the supplied second string. 5 12 The new string is lairotuT auL Returns a copy of s in which all occurrences of the pattern have been replaced by a replacement string specified by repl, which may be a string, a table, or a function. Prototype. We’ll get into these in a minute, but first we have to introduce magic characters in the context of patterns. I use it in my translation work to split up characters and map Pinyin from dictionaries. There’s a lot to go over before we can fully use string.format. However, you could use string.gmatch to begin a regular expression matching and the following is a short and neat alternative. This table is just to get you used to what all is on the table. Patterns, which are similar in function to Regex (though far more lightweight), are a way to search for various substrings based on specified information. We look for at least one digit, then anything, then another digit. 'replacement' can be a string in which case it simply replaces the matching pattern. “New Line” is common on all OSes, but “Carriage Returns” are used on Windows in conjunction with “New Lines”. Per the documentation, it includes the following functions: The escape sequence and its use is listed below in the table. print( string.match( test, “%d+” ) ) gets us “123”. Let’s see an example of something easy: Don’t worry about understanding all of this yet. This built-in Vimscript function evaluates a Lua expression string and returns its value. (Added in 1.10.1) 3. date(format, time) - Returns the current date according to the user's machine. s, n = string.gsub (str, pattern, replacement, n) Description. Returns the start index and end index of the findString in the main string and nil if not found. The Corona string library provides generic functions for string manipulation, such as pattern matching and finding/extracting substrings. Returns internal numeric and character representations of input argument. Like Perl and some other languages, you can also use negative indexes. Here’s an example of them in action: This gets us the following from running it: We’re not going to go into these too deep as each of them is self-explanatory. Lua string.find (Introduction) Example The find function. Returns a lower case representation of the argument. N8Gamez. 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. Lua code to replace false with true. utf8.byte Greedy matching means that we match anything which matches the pattern while non-greedy matching means we match until the condition is first matched. A sample code for replacing occurrences of one string with another is given below. string.gsub(str, pattern, repl [, n]) -- Replaces substrings (up to a max of n times). What I am building is essentially a de-macro system for a package of mine, so it should preferably not remove other comments or spaces outside the string it replaces. There are other options, but I have excluded them due to their rarity, and due to the fact some are not implemented/applicable in Lua. Unfortunately, in LUA, there is no inbuilt string splitting function, which is very inconvenient. WoW Lua string.gsub(s, pattern, replace [, n]) gsub(s, pattern, replace [, n]) strreplace(s, pattern, replace [, n]) This is a very powerful function and can be used in multiple ways. utf8.upper. A pair of values is returned, the modified string and the number of substitutions made. We have gone over the basics of %[code] in our table. Substitute strings inside another string. string = "Lua Tutorial" -- replacing strings print(string.find(string,"Tutorial")) reversedString = string.reverse(string) print("The new string is",reversedString) When we run the above program, we will get the following output. A negative index means start from the back, so -1 would be the last character. In this case, however, you just want to search for a specific string, "'s_House", and remove it. String Indexing: wiki: In some languages, e.g. When the returned function is executed the lua script contained within the specified string is run. Python, C and Pascal, you can write a[5] for the fifth (or maybe the sixth) character of the string a.Not in Lua. These functions are part of the Lua programming language (v5.1), described in the Lua 5.1 Reference Manual. These are all extremely common and work in virtually all string operations and should be memorized. utf8.gsub Here’s an easy example: You can limit the number of replacements by adding in an integer n to limit how many occurrences you affect. Returns a copy of str with matches to 'pattern' replaced by 'replacement', for a maximum of n times. Both can be very similar, but Lua pattern matching is more limited and has a different syntax. Note that this function returns an initial index and an ending index which can be passed to string.sub. Read the previous lesson on classes to make sure you understand what this is and why this works. An example for the above three forms are shown below. In addition to this list, see also Debugging Functions. Returns a string by replacing occurrences of findString with replaceString. This is another trivial string function. I hope someone knows how to edit a line in a file with Lua. It is possible to place the elements in a sparse way and it is the way Lua implementation of a matrix works. Greedy matching is useful when you want everything between something even if it would match and end case. Lua String replace, Summary. Non-greedy matching is useful when you want something in between a known set of things and don’t ever want it to spill over. In our string before, we have “123” then a bunch of extra stuff and end with “123” for the test string. You get a breakdown pretty quickly. Share Followers 2. Bemused ramblings some dude says on the internet. @Mico If I just use a Lua replacement function on that example, Lua will not find the string because it contains whitespace and comments. Returns a string by reversing the characters of the passed string. Let’s go over each line. The sequence %0stands for the whole match and the sequence %%stands for a single %. Use string.gsub () to find and replace text within a string. printf can do some awesome formatting and justification, and so can string.format. Here’s an example which touches on all of the basics: Notice that string.format can take a variable number of arguments. If the replacement is a function, not a string, the arguments passed to the function are any captures that are made. Unicode agnostic is good enough for most things, but there are situations where this just doesn’t work, so we’ll introduce a library for working with utf8 in Lua as well. – Gaussler Aug 2 at 19:29 We’re going to go over string.match first, but then we’ll add in our patterns. You get back a string and the number of replacements made. We’ll go over some of it, but it’s best to consult a reference for a lot of it. https://stevedonovan.github.io/Penlight/api/libraries/pl.stringx.html This is useful when you have sequences of similar formatting (think tags in a string or similar). Let’s dive into the easiest to learn string functions first. For this specific library, unlike our, The Quick Guide to Understanding Edge Computing, A Review of Zhou Xiaogeng’s “Essentials of Chinese Lexicology”. Str8 Ballin' Members; Joined: 10/28/2009; 131 Share; Posted May 25, 2020. Lua supports string to manipulate strings −. It allows you to take a string and replace something in it from a pattern. utf8.find The character %works as an escape character: any sequence in replof the form %n, with nbetween 1and 9, stands for the value of the nthcaptured substring. Let’s get into the string operations in Lua. Let’s see an example and then we’ll break down what all string.format can do: Each format is built up of the following: %[flag][length][.[precision]][code]. N8Gamez 131 Posted May 25, 2020. Recommended Posts. Greedy and non-greedy matching get more important with some of the other string formats. utf8.char *%d+”) ) gets us “123 ABC 123 !!! By N8Gamez, May 25, 2020 in Coding. Make sure you have GCC or similar on your system before trying to use this library. The next example collects all pairs key=value from the given string into a table: t = {} s = "from=world, to=Lua" for k, v in string.gmatch (s, " (%w+)= (%w+)") do t [k] = v end If the function returns a string, the … Conversely, whenever a number is used where a string is expected, the number is converted to a string, in a reasonable format. Each of these are easy since they just take a single parameter. The code demonstrates replacing a string “hello”, and also using a capture to duplicate each word in a string. string.match(str, pattern [, index]) -- Matches a pattern once (starting at index) string.gmatch(str, pattern) -- Returns a function that iterates through all matches in str. utf8.match cat d0g -+[] 123”. Embed. VADemon / string-replace.lua. Arguments1 string strThe string we are seeking to replace an occurrence(s).2 string.. 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