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  • How does the ? make a quantifier lazy in regex

    - by Uriel Katz
    I've been looking into regex lately and figured that the ? operator makes the *,+, or ? lazy. My question is how does it do that? Is it that *? for example is a special operator, or does the ? have an effect on the *? In other words, does regex recognize *? as one operator in itself, or does regex recognize *? as the two separate operators * and ?? If it is the case that *? is being recognized as two separate operators, how does the ? affect the * to make it lazy. If ? means that the * is optional, shouldn't this mean that the * doesn't have to exists at all. If so, then in a statement .*? wouldn't regex just match separate letters and the whole string instead of the shorter string? Please explain, I'm desperate to understand.

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  • string matching algorithms used by lucene

    - by iamrohitbanga
    i want to know the string matching algorithms used by Apache Lucene. i have been going through the index file format used by lucene given here. it seems that lucene stores all words occurring in the text as is with their frequency of occurrence in each document. but as far as i know that for efficient string matching it would need to preprocess the words occurring in the Documents. example: search for "iamrohitbanga is a user of stackoverflow" (use fuzzy matching) in some documents. it is possible that there is a document containing the string "rohit banga" to find that the substrings rohit and banga are present in the search string, it would use some efficient substring matching. i want to know which algorithm it is. also if it does some preprocessing which function call in the java api triggers it.

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  • How to understand the output of the PHP regex matching below?

    - by smarty
    $file = '{include file="{$COMMON_TPL_PATH}common/header_admin.tpl"} {include file="{$mainPage}"} {include file="{$COMMON_TPL_PATH}common/footer_admin.tpl"}'; preg_match('/^(\{\})|^(\{\*([\S\s]*?)\*\})|^(<\?(?:php\w+|=|[a-zA-Z]+)?)|^([ ]*[ ]+[ ]*)|^(\{strip\})|^(\{\/strip\})|^(\{literal\})|^(\{\s{1,}\/)|^(\{\s{1,})|^(\{\/)|^(\{)|^(([\S\s]*?)(?=([ ]*[ ]+[ ]*|\{|<\?)))|^([\S\s]+)/', $file, $matches); var_dump($matches); Why the output is: array(13) { [0]=> string(1) "{" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(0) "" [4]=> string(0) "" [5]=> string(0) "" [6]=> string(0) "" [7]=> string(0) "" [8]=> string(0) "" [9]=> string(0) "" [10]=> string(0) "" [11]=> string(0) "" [12]=> string(1) "{" } It seems to me that ^([\S\s]+) can match the whole string..

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  • codingbat wordEnds using regex

    - by polygenelubricants
    I'm trying to solve wordEnds from codingbat.com using regex. This is the simplest as I can make it with my current knowledge of regex: public String wordEnds(String str, String word) { return str.replaceAll( String.format( ".*?(?=%s)(?<=(.|^))%1$s(?=(.|$))|.+", java.util.regex.Pattern.quote(word) ), "$1$2" ); } String.format is used to inject word into the pattern for both readability and convenience (it's injected twice). Pattern.quote isn't necessary to pass their tests, but I think it's required for a proper regex-based solution. The regex has two major parts: If after matching as few characters as possible ".*?", word can still be found "(?=%s)", then lookbehind to capture any character immediately preceding it "(?<=(.|^))", match word "%1$s" and lookforward to capture any character following it "(?=(.|$))". The initial "if" test ensures that the atomic lookbehind captures only if there's a word Using lookahead to capture the following character doesn't consume it, so it can be used as part of further matching Otherwise match what's left "|.+" Groups 1 and 2 would capture empty strings I think this works in all cases, but it's obviously quite complex. I'm just wondering if others can suggest a simpler regex to do this. Note: I'm not looking for a solution using indexOf and a loop. I want a regex-based replaceAll solution. I also need a working solution that I can just copy-paste into codingbat and passes.

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  • Regex pattern failing

    - by Scott Chamberlain
    I am trying a substring to find from the beginning of the string to the point that has the escape sequence "\r\n\r\n" my regex is Regex completeCall = new Regex(@"^.+?\r\n\r\n", RegexOptions.Compiled); it works great as long as you only have strings like 123\r\n\r\n however once you have the pattern 123\r\n 456\r\n\r\n the pattern no longer matches. Any advice on what I am doing wrong? Regex completeCall = new Regex(@"^.+?\r\n\r\n", RegexOptions.Compiled); Regex junkLine = new Regex(@"^\D", RegexOptions.Compiled); private void ClientThread() { StringBuilder stringBuffer = new StringBuilder(); (...) while(true) { (...) Match match = completeCall.Match(stringBuffer.ToString()); while (Match.Success) //once stringBuffer has somthing like "123\r\n 456\r\n\r\n" Match.Success always returns false. { if (junkLine.IsMatch(match.Value)) { (...) } else { (...) } stringBuffer.Remove(0, match.Length); // remove the processed string match = completeCall.Match(stringBuffer.ToString()); // check to see if more than 1 call happened while the thread was sleeping. } Thread.Sleep(1000); }

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  • Nested Groups in Regex

    - by cryptic-star
    I'm constructing a regex that is looking for dates. I would like to return the date found and the sentence it was found in. In the code below, the strings on either side of date_string should check for the conditions of a sentence. For your sake, I've omitted the regex for date_string - sufficed to say, it works for picking out dates. While the inside of date_string isn't important, it is grouped as one entire regex. "((?:[^.|?|!]*)"+date_string+"(?:[^.|?|!]*[.|?|!]\s*))" The problem is that date_string is only matching the last number of any given date, presumably because the regex in front of date_string is matching too far and overrunning the date regex. For example, if I say "Independence Day is July 4.", I will get the sentence and 4, even though it should match 'July 4'. In case you're wondering, my regex inside date_string are ordered in such a way that 'July 4' should match first. Is there any way to do this all in one regex? Or do I need to split it up somehow (i.e. split up all text into sentences, and then check each sentence)?

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  • Regex | validation error

    - by MMRUser
    I'm trying to validate a USA mobile number, since I'm using pre-built javascript validation library I just replaced this regex validation with the previous one which comes with the validation library. previous validation regex: "telephone":{ "regex":"/^[0-9\-\(\)\ ]{10,10}$/", "alertText":"* Invalid phone number"}, This works like 2126661234 but not in USA standard. After I changed: "telephone":{ "regex":"/^[2-9]\d{2}-\d{3}-\d{4}$/", "alertText":"* Invalid phone number"}, Now every entry I get an error even if I enter 212-666-1234 I really don't know what is the wrong, so I'm expecting some help.

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  • How does the following regex pattern work?

    - by zSysop
    Hi all, I'm horrible with regex but i'm trying to figure out how an import function works and i came across this regex pattern. Maybe one of you can help me understand how it works. string pattern = @"^""(?<code>.*)"",""(?<last_name>.*)"",""(?<first_name>.*)"",""(?<address>.*)"",""(?<city>.*)"",""(?<state>.*)"",""(?<zip>.*)""$"; Regex re = new Regex(pattern); Match ma = re.Match(_sReader.ReadLine().Trim()); Thanks

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  • regex to check string is certain length

    - by Aly
    Hi, I am trying to write a regex to match pairs of cards (AA, KK, QQ ... 22) and I have the regex ([AKQJT2-9])\1. The problem I have is that this regex will match AA as well as AAbc etc. Is there a way to write the regex such that I can specify I want to match ([AKQJT2-9])\1 and only that (i.e. no more characters after). Thanks

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  • Regex pattern help for phrase OR a character set

    - by andybaird
    I have a PHP regex that I want to fail if the matched word after /blog is just "feed". This MUST be done within the regex itself, not using any other PHP syntax. The regex currently looks like this: blog/([a-zA-Z0-9-]+) What would I add to this to properly negate the regex if "feed" is found after blog/ ?

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  • .NET RegEx for letters and spaces

    - by user70192
    I am trying to create a regular expression in C# that allows only alphanumeric characters and spaces. Currently, I am trying the following: string pattern = @"^\w+$"; Regex regex = new Regex(pattern); if (regex.IsMatch(value) == false) { // Display error } What am I doing wrong?

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  • vbscript multiple replace regex

    - by George
    How do you match more than one pattern in vbscript? Set regEx = New RegExp regEx.Pattern = "[?&]cat=[\w-]+" & "[?&]subcat=[\w-]+" // tried this regEx.Pattern = "([?&]cat=[\w-]+)([?&]subcat=[\w-]+)" // and this param = regEx.Replace(param, "") I want to replace any parameter called cat or subcat in a string called param with nothing. For instance string?cat=meow&subcat=purr or string?cat=meow&dog=bark&subcat=purr I would want to remove cat=meow and subcat=purr from each string.

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  • C# + RegEx for letters and spaces

    - by user70192
    Hello, I am trying to create a regular expression in C# that allows only alphanumeric characters and spaces. Currently, I am trying the following: string pattern = @"^\w+$"; Regex regex = new Regex(pattern); if (regex.IsMatch(value) == false) { // Display error } What am I doing wrong? Thank you!

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  • Is there YAPE::Regex::Explain alternative to python?

    - by S.Mark
    Is there perl's YAPE::Regex::Explain alternative to python? Which could do \w+=\d+|\w+='[^']+' to explanations like this NODE EXPLANATION -------------------------------------------------------------------------------- \w+ word characters (a-z, A-Z, 0-9, _) (1 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- = '=' -------------------------------------------------------------------------------- \d+ digits (0-9) (1 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- | OR -------------------------------------------------------------------------------- \w+ word characters (a-z, A-Z, 0-9, _) (1 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- =' '=\'' -------------------------------------------------------------------------------- [^']+ any character except: ''' (1 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- ' '\''

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  • How can I extract the nth occurrence of a match in a Perl regex?

    - by Zaid
    Is it possible to extract the n'th match in a string of single-quoted words? use strict; use warnings; my $string1 = '\'I want to\' \'extract the word\' \'Perl\',\'from this string\''; my $string2 = '\'What about\',\'getting\',\'Perl\',\'from\',\'here\',\'?\''; sub extract_quoted { my ($string, $index) = @_; my ($wanted) = $string =~ /some_regex_using _$index/; return $wanted; } extract_wanted ($string1, 3); # Should return 'Perl', with quotes extract_wanted ($string2, 3); # Should return 'Perl', with quotes

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  • PHP-REGEX: accented letters matches non-accented ones, and visceversa. How to achive it?

    - by Lightworker
    I want to do the typical higlight code. So I have something like: $valor = preg_replace("/(".$_REQUEST['txt_search'].")/iu", "<span style='background-color:yellow; font-weight:bold;'>\\1</span>", $valor); Now, the request word could be something like "josé". And with it, I want "jose" or "JOSÉ" or "José" or ... highlighted too. With this expression, if I write "josé", it matches "josé" and "JOSÉ" (and all the case variants). It always matches the accented variants only. If I search "jose", it matches "JOSE", "jose", "Jose"... but not the accented ones. So I've partially what I want, cause I have case insensitive on accented and non-accented separately. I need it fully combined, wich means accent (unicode) insensitive, so I can search "jose", and highlight "josé", "josÉ", "José", "JOSE", "JOSÉ", "JoSé", ... I don't want to do a replace of accents on the word, cause when I print it on screen I need to see the real word as it comes. Any ideas? Thanks!

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  • pattern matching in .Net consistent with IsolatedStorageFile.GetFileNames() pattern matching

    - by Mick N
    Is the pattern matching logic used by this API exposed for reuse somewhere in the .Net Framework? Something of the form FilePatternMatch( string searchPattern, stringfileNameToTest ) is what I'm looking for. I'm implementing a temporary workaround for WP7 not filtering the results for this overload and I'd like the solution to both provide a consistent experience and avoid reinventing this functionality if it is exposed. If the behaviour is not exposed for reuse, a regular expression solution (like glob pattern matching in .NET) will suffice and would save me spending the time to test the fine details of what the behaviour should be. Perhaps one of the answers posted in the thread linked above is correct. Since I haven't confirmed the exact behaviour as yet, I wasn't able to determine this at a glance. Feel free to point me to one of those answers if you know it is behaviouraly an exact match to the API referenced in the question title. I could assume the pattern matching is consistent with how DOS handled * and ? in 8.3 file names (I'm familiar with behavioural nuances of that implementation), but it's reasonable to assume Microsoft has evolved pattern matching behaviour for file names in the decade+ since so I thought I would check before proceeding on that assumption.

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  • Regex for circular replacement

    - by polygenelubricants
    How would you use regex to write functions to do the following: Replace lowercase 'a' with uppercase and vice versa Where words are separated by whitespaces and > and < are special markers, replace >word with word< and vice versa Replace postincrement (i++;) with preincrement (++i;) and vice versa. Variable names are [a-z]+. Input is just a bunch of these statements. Bonus: also do decrement. Also interested in solutions in other flavors. Note: this is NOT a homework question. See also my previous explorations of regex: Regex split into overlapping strings (Alan Moore's answer is especially instructive) Can you use zero-width matching regex in String split? (my solution exploits a known Java regex bug with regards to non-obvious length lookbehind!)

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  • NSPredicate and Regex

    - by Dave
    Can someone please help me with using Regex with NSPredicate? NSString *regex = @"(?:[A-Za-z0-9])"; NSPredicate *pred = [NSPRedicate predicateWithFormat:@"SELF MATCHES %@", regex]; if ([pred evaluateWithObject:mystring]) { //do something } testing the above wth mystring - qstring123 doesn't seem to work. I am expecting it to enter the if condition because it supposedly should match the regex. Besides, I need a regex for alpha numberic allowing commas and spaces. will this work? @"(?:[A-Za-z0-9])*(?:,[A-sa-z0-9)*(?:\s[A-sa-s0-9])" Please help.

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  • regular expression with "|"

    - by WtFudgE
    I need to be able to check for a pattern with | in them. For example an expression like d*|*t should return true for a string like "dtest|test". I'm no regular expression hero so I just tried a couple of things, like: Regex Pattern = new Regex("s*\|*d"); //unable to build because of single backslash Regex Pattern = new Regex("s*|*d"); //argument exception error Regex Pattern = new Regex(@"s*\|*d"); //returns true when I use "dtest" as input, so incorrect Regex Pattern = new Regex(@"s*|*d"); //argument exception error Regex Pattern = new Regex("s*\\|*d"); //returns true when I use "dtest" as input, so incorrect Regex Pattern = new Regex("s*" + "\\|" + "*d"); //returns true when I use "dtest" as input, so incorrect Regex Pattern = new Regex(@"s*\\|*d"); //argument exception error I'm a bit out of options, what should I then use? I mean this is a pretty basic regular expression I know, but I'm not getting it for some reason.

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  • Regex question: Why isn't this matching?

    - by AllenG
    I have the following regex: (?<=\.\d+?)0+(?=\D|$) I'm running it against a string which contains the following: SVC~NU^0270~313.3~329.18~~10~~6.00: When it runs, it matches the 6.00 (correctly) which my logic then trims by one zero to turn into 6.0. The regex then runs again (or should) but fails to pick up the 6.0. I'm by no means an expert on Regex, but my understanding of my expression is that it's looking for a decimal with 1 or more optional (so, really zero or more) digits prior to one or more zeros which are then followed by any non-digit character or the line break. Assuming that interpretation is correct, I can't see why it wouldn't match on the second pass. For that matter, I'm not sure why my Regex.Replace isn't matching the full 6.00 on the first pass and removing both of the trailing zeros... Any suggestions?

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  • Rub, regex, sentences

    - by Perello
    I'm currently building a code generator, which aim to generate boiler plate for me once i wrote the templates and/or translations, whatever the language i have to work with, and it has an educationnal part :p. So i have a problem with a regex in ruby. The regex aim to select whatever is between {{{ and }}}, so i can generae functions according to my needs. My regex is currently : /\{\{\{(([a-zA-Z]|\s)+)\}\}\}/m My test data set {{{Demande aaa}}} = {{{tagadatsouintsouin tutu}}} The results are : [["Demande aaa", "a"], ["tagadatsouintsouin tutu", "u"]] So the regex pick each time the last character twice. But, that's not exactly what i want, my need is more about this : /\{\{\{((\w|\W)+)\}\}\}/m But this as a flaw too, the results : [["Demande aaa}}} = {{{tagadatsouintsouin tutu", "u"]] Whereas, i wish to get [["Demande aaa"],["tagadatsouintsouin tutu"]] Any ideas to correct theses regex ? I could use 2 sets of delimiters, but it won't learn me anything.

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  • Replace named group in regex

    - by Tomas Voracek
    I want to use regular expression same way as string.Format. I will explain I have: string pattern = "^(?<PREFIX>abc_)(?<ID>[0-9])+(?<POSTFIX>_def)$"; string input = "abc_123_def"; Regex regex = new Regex(pattern, RegexOptions.IgnoreCase); string replacement = "456"; Console.WriteLine(regex.Replace(input, string.Format("${{PREFIX}}{0}${{POSTFIX}}", replacement))); This works, but i must provide "input" to regex.Replace. I do not want that. I want to use pattern for matching but also for creating strings same way as with string format, replacing named group "ID" with value. Is that possible? I'm looking for something like: string pattern = "^(?<PREFIX>abc_)(?<ID>[0-9])+(?<POSTFIX>_def)$"; string result = ReplaceWithFormat(pattern, "ID", 999); Result will contain "abc_999_def". How to accomplish this?

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