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  • Nullability (Regular Expressions)

    - by danportin
    In Brzozowski's "Derivatives of Regular Expressions" and elsewhere, the function d(R) returning ? if a R is nullable, and Ø otherwise, includes clauses such as the following: d(R1 + R2) = d(R1) + d(R2) d(R1 · R2) = d(R1) ? d(R2) Clearly, if both R1 and R2 are nullable then (R1 · R2) is nullable, and if either R1 or R2 is nullable then (R1 + R2) is nullable. It is unclear to me what the above clauses are supposed to mean, however. My first thought, mapping (+), (·), or the Boolean operations to regular sets is nonsensical, since in the base case, d(a) = Ø (for all a ? S) d(?) = ? d(Ø) = Ø and ? is not a set (nor is the return type of d, which is a regular expression). Furthermore, this mapping isn't indicated, and there is a separate notation for it. I understand nullability, but I'm lost on the definition of the sum, product, and Boolean operations in the definition of d: how are ? or Ø returned from d(R1) ? d(R2), for instance, in the definition off d(R1 · R2)?

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  • Is there a way to get the PREMATCH ($`) and POSTMATCH ($') from pcrecpp?

    - by Eric Peers
    Is there a way to obtain the C++ equivalent of Perl's PREMATCH ($`) and POSTMATCH ($') from pcrecpp? I would be happy with a string, a char *, or pairs indices/startpos+length that point at this. StringPiece seems like it might accomplish part of this, but I'm not certain how to get it. in perl: $_ = "Hello world"; if (/lo\s/) { $pre = $`; #should be "Hel" $post = $'; #should be "world" } in C++ I would have something like: string mystr = "Hello world"; //do I need to map this in a StringPiece? if (pcrecpp::RE("lo\s").PartialMatch(mystr)) { //should I use Consume or FindAndConsume? //What should I do here to get pre+post matches??? } pcre plainjane c seems to have the ability to return the vector with the matches including the "end" portion of the string, so I could theoretically extract such a pre/post variable, but that seems like a lot of work. I like the simplicty of the pcrecpp interface. Suggestions? Thanks! --Eric

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  • js regexp problem

    - by Alexander
    I have a searching system that splits the keyword into chunks and searches for it in a string like this: var regexp_school = new RegExp("(?=.*" + split_keywords[0] + ")(?=.*" + split_keywords[1] + ")(?=.*" + split_keywords[2] + ").*", "i"); I would like to modify this so that so that I would only search for it in the beginning of the words. For example if the string is: "Bbe be eb ebb beb" And the keyword is: "be eb" Then I want only these to hit "be ebb eb" In other words I want to combine the above regexp with this one: var regexp_school = new RegExp("^" + split_keywords[0], "i"); But I'm not sure how the syntax would look like. I'm also using the split fuction to split the keywords, but I dont want to set a length since I dont know how many words there are in the keyword string. split_keywords = school_keyword.split(" ", 3); If I leave the 3 out, will it have dynamic lenght or just lenght of 1? I tried doing a alert(split_keywords.lenght); But didnt get a desired response

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  • JavaScript regular expression literal persists between function calls

    - by Charles Anderson
    I have this piece of code: function func1(text) { var pattern = /([\s\S]*?)(\<\?(?:attrib |if |else-if |else|end-if|search |for |end-for)[\s\S]*?\?\>)/g; var result; while (result = pattern.exec(text)) { if (some condition) { throw new Error('failed'); } ... } } This works, unless the throw statement is executed. In that case, the next time I call the function, the exec() call starts where it left off, even though I am supplying it with a new value of 'text'. I can fix it by writing var pattern = new RegExp('.....'); instead, but I don't understand why the first version is failing. How is the regular expression persisting between function calls? (This is happening in the latest versions of Firefox and Chrome.) Edit Complete test case: <!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-type" content="text/html;charset=UTF-8"> <title>Test Page</title> <style type='text/css'> body { font-family: sans-serif; } #log p { margin: 0; padding: 0; } </style> <script type='text/javascript'> function func1(text, count) { var pattern = /(one|two|three|four|five|six|seven|eight)/g; log("func1"); var result; while (result = pattern.exec(text)) { log("result[0] = " + result[0] + ", pattern.index = " + pattern.index); if (--count <= 0) { throw "Error"; } } } function go() { try { func1("one two three four five six seven eight", 3); } catch (e) { } try { func1("one two three four five six seven eight", 2); } catch (e) { } try { func1("one two three four five six seven eight", 99); } catch (e) { } try { func1("one two three four five six seven eight", 2); } catch (e) { } } function log(msg) { var log = document.getElementById('log'); var p = document.createElement('p'); p.innerHTML = msg; log.appendChild(p); } </script> </head> <body><div> <input type='button' id='btnGo' value='Go' onclick='go();'> <hr> <div id='log'></div> </div></body> </html> The regular expression continues with 'four' as of the second call on FF and Chrome, not on IE7 or Opera.

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  • Jquery validator plugin- Validates at least one in the group

    - by christian
    [http://jsfiddle.net/mhmBs/][1] I tried using the method that he uses in a jquery validator plugin.. My error container is separated from the form, it is outside the form. When I use that method to validated that the user input at least one from 3 input text boxes. It validates the field, but the other items to be validated is ignored specially the items before 3 input text boxes.

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  • Switch statement for string matching in JavaScript

    - by yaya3
    How do I write a swtich for the following conditional? If the url contains "foo", then settings.base_url is "bar". The following is achieving the effect required but I've a feeling this would be more manageable in a switch: var doc_location = document.location.href; var url_strip = new RegExp("http:\/\/.*\/"); var base_url = url_strip.exec(doc_location) var base_url_string = base_url[0]; //BASE URL CASES // LOCAL if (base_url_string.indexOf('xxx.local') > -1) { settings = { "base_url" : "http://xxx.local/" }; } // DEV if (base_url_string.indexOf('xxx.dev.yyy.com') > -1) { settings = { "base_url" : "http://xxx.dev.yyy.com/xxx/" }; } Thanks

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  • Match string which doesn't start with

    - by Pinky
    I have a string that looks like this: var str = "Hello world, &nbsp;hello &gt;world, hello world!"; ... and I'd like to replace all the hellos with e.g. bye and world with earth, except the words that start with &nbsp or &gt. Those should be ignored. So the result should be: bye earth, &nbsp;hello &gt;world, bye earth! Tried to this with str.replace(/(?!\&nbsp;)hello/gi,'bye')); But it doesn't work.

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  • Alter Regular Expression to Return 2 Values Instead of 3 from userAgent String

    - by Jay
    I've taken a regular expression from jQuery to detect if a browser's engine is WebKit and gets it's version number, it returns 3 values extracted from the userAgent string: webkit/….…, webkit and ….… [“….…” being the version number]. I would like the regular expression to return just 2 values: webkit and ….…. I'm rubbish at regular expressions, so please can you give an explanation of the expression with your answer. The regular expression I'm currently working with and wish to improve is: /(webkit)[\/]([\w.]+)/. I appreciate all your help, thanks in advance!

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  • Use matching value of a RegExp to name the output file.

    - by fx42
    I have this file "file.txt" which I want to split into many smaller ones. Each line of the file has an id field which looks like "id:1" for a line belonging to id 1. For each id in the file, I like to create a file named idid.txt and put all lines that belong to this id in that file. My brute force bash script solution reads as follows. count=1 while [ $count -lt 19945 ] do cat file.txt | grep "id:$count " >> ./sets/id$count.txt count='expr $count + 1' done Now this is very inefficient as I have do read through the file about 20.000 times. Is there a way to do the same operation with only one pass through the file? - What I'm probably asking for is a way to use the value that matches for a regular expression to name the associated output file.

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  • Python RegExp exception

    - by Jasie
    How do I split on all nonalphanumeric characters, EXCEPT the apostrophe? re.split('\W+',text) works, but will also split on apostrophes. How do I add an exception to this rule? Thanks!

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  • python: multiline regular expression

    - by facha
    Hi, everyone I have a piece of text and I've got to parse usernames and hashes out of it. Right now I'm doing it with two regular expressions. Could I do it with just one multiline regular expression? #!/usr/bin/env python import re test_str = """ Hello, UserName. Please read this looooooooooooooooong text. hash Now, write down this hash: fdaf9399jef9qw0j. Then keep reading this loooooooooong text. Hello, UserName2. Please read this looooooooooooooooong text. hash Now, write down this hash: gtwnhton340gjr2g. Then keep reading this loooooooooong text. """ logins = re.findall('Hello, (?P<login>.+).',test_str) hashes = re.findall('hash: (?P<hash>.+).',test_str)

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  • RegExp to validate a formula (string/boolean/numeric expression)?

    - by JSteve
    I have used regExp quit a bit of times but still far from being an expert. This time I want to validate a formula (or math expression) by regExp. The difficult part here is to validate proper starting and ending parentheses with in the formula. I believe, there would be some sample on the web but I could not find it. Can somebody post a link for such example? or help me by some other means?

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  • Change Number Format

    - by gsembilan
    I have a lot lines contains XXXXXXXXX number format. I want change number XXXXXXXXX to XX.XXX.XXX.X XXXXXXXXX = 9 digit random number Anyone can help me? Thanks in advance

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  • Simple PHP form Validation and the validation symbols

    - by Cool Hand Luke UK
    Hi have some forms that I want to use some basic php validation (regular expressions) on, how do you go about doing it? I have just general text input, usernames, passwords and date to validate. I would also like to know how to check for empty input boxes. I have looked on the interenet for this stuff but I haven't found any good tutorials. Thanks

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  • RichFaces Toolbargroup centering a group

    - by Jeremiah
    Hello there I am trying use a toolbar so that it has three parts part A is aligned left part B is aligned Center part C is aligned right both the right and left i can use the location attribute ... but since there is no center attribute i am not able to center part b. I can use a rich:spacer but this makes the toolbar rigid and when the screen size is reduced the toolbar gets overlapped ... is there any i can center this without the toolbar getting over lapped. Any suggestions or workarounds is welcome cheers

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  • regular expression and escaping

    - by pstanton
    Sorry if this has been asked, my search brought up many off topic posts. I'm trying to convert wildcards from a user defined search string (wildcard is "*") to postgresql like wildcard "%". I'd like to handle escaping so that "%" => "\%" and "\*" => "*" I know i could replace \* with something else prior to replacing * and then swap it back, but i'd prefer not to and instead only convert * using a pattern that selects it when not proceeded by \. String convertWildcard(String like) { like = like.replaceAll("%", "\\%"); like = like.replaceAll("\\*", "%"); return like; } Assert.assertEquals("%", convertWildcard("*")); Assert.assertEquals("\%", convertWildcard("%")); Assert.assertEquals("*", convertWildcard("\*")); // FAIL Assert.assertEquals("a%b", convertWildcard("a*b")); Assert.assertEquals("a\%b", convertWildcard("a%b")); Assert.assertEquals("a*b", convertWildcard("a\*b")); // FAIL ideas welcome.

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  • regular expression

    - by xyz
    I need regular expression to match braces correct e.g for every open one close one abc{abc{bc}xyz} I need it get all it from {abc{bc}xyz} not get {abc{bc} I tried this ({.*?})

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  • PHP & Regular expression: keyword just occurs once

    - by lauthiamkok
    Hi, how can I make sure a certain keyword just occurs once in the input with regular expression? I think there is some mistakes in the expression below as I can repeat the same keywords, if (!preg_match('/\b(.php?){1}\b/', $cfg_path)) { $error = true; echo '<error elementid="cfg_path" message="PATH - make sure you have a \'.php?\' in the path."/>'; } I just want this to be true, form.php?category=something or form.php? but not this, form.php?.php?category=something or form.php?.php? please let me know how to fix it. thanks.

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  • Problem with regular expression for some special parttern.

    - by SpawnCxy
    Hi all, I got a problem when I tried to find some characters with following code: preg_match_all('/[\w\uFF10-\uFF19\uFF21-\uFF3A\uFF41-\uFF5A]/',$str,$match); //line 5 print_r($match); And I got error as below: Warning: preg_match_all() [function.preg-match-all]: Compilation failed: PCRE does not support \L, \l, \N, \U, or \u at offset 4 in E:\mycake\app\webroot\re.php on line 5 I'm not so familiar with reg expression and have no idea about this error.How can I fix this?Thanks.

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