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  • Are .NET's regular expressions Turing complete?

    - by Robert
    Regular expressions are often pointed to as the classical example of a language that is not Turning complete. For example "regular expressions" is given in as the answer to this SO question looking for languages that are not Turing complete. In my, perhaps somewhat basic, understanding of the notion of Turning completeness, this means that regular expressions cannot be used check for patterns that are "balanced". Balanced meaning have an equal number of opening characters as closing characters. This is because to do this would require you to have some kind of state, to allow you to match the opening and closing characters. However the .NET implementation of regular expressions introduces the notion of a balanced group. This construct is designed to let you backtrack and see if a previous group was matched. This means that a .NET regular expressions: ^(?<p>a)*(?<-p>b)*(?(p)(?!))$ Could match a pattern that: ab aabb aaabbb aaaabbbb ... etc. ... Does this means .NET's regular expressions are Turing complete? Or are there other things that are missing that would be required for the language to be Turing complete?

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  • Dealing with regular expressions, Python

    - by Gusto
    I want to remove some symbols from a string using a regular expression, for example: == (that occur both at the beginning and at the end of a line), * (at the beginning of a line ONLY). def some_func(): clean = re.sub(r'= {2,}', '', clean) #Removes 2 or more occurrences of = at the beg and at the end of a line. clean = re.sub(r'^\* {1,}', '', clean) #Removes 1 or more occurrences of * at the beginning of a line. What's wrong with my code? It seems like expressions are wrong. How do I remove a character/symbol if it's at the beginning or at the end of the line (with one or more occurrences)?

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  • A more elegant way to parse a string with ruby regular expression using variable grouping?

    - by i0n
    At the moment I have a regular expression that looks like this: ^(cat|dog|bird){1}(cat|dog|bird)?(cat|dog|bird)?$ It matches at least 1, and at most 3 instances of a long list of words and makes the matching words for each group available via the corresponding variable. Is there a way to revise this so that I can return the result for each word in the string without specifying the number of groups beforehand? ^(cat|dog|bird)+$ works but only returns the last match separately , because there is only one group.

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  • How can I execute a bunch of editor commands stored in a file in VIM?

    - by LES2
    I have read the other posts, e.g., http://stackoverflow.com/questions/1830886/vim-executing-a-list-of-editor-commands and others. The answer isn't clear to me for my case. I have some editor commands that I generated from an SQL query. It uses :s/foo/bar to change country codes (from FIPS to a non-standard code set). Here's a sample of the file: :s/CB/CAMBO :s/CQ/NMARI :s/KV/KOSOV :s/PP/PAPUA ... I have saved that in a file called fipsToNonStd.vim (unsure about the correct extension). I want to run those commands one after another. What's the easiest way to do so? Thanks a bunch! SO Rocks!

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  • best REGEXP friendly Text Editors + most powerful REGEXP syntax?

    - by John
    I am fluent with Microsoft Visual 2005 regular expressions and they are a big time saver. I seem to learn them best by having a vaguely organized cheat sheet thrown at me, at which point I read just a little and play with them until I understand what's going on. That learning approach has worked well for me, for now. I would really like to take this to the next level though. Basically -- What is the REGEXP convention that is generally regarded as the most open-ended and powerful? VS2005 Regexps seem kind of gimped, so maybe I'm a kid playing in a sandbox. Are there text editors out there that can perform a highlight all matches, list lines containing string, or some kind of powerful function like that in conjunction with the very strongest REGEXP language? If not I can just use multiple programs and a weird technique but I'd like to avoid that. I wonder if a stronger REGEXP language or a "stronger" regEXP writer might be able to have his search match all results on all lines even by clicking a "find next" by adding some simple criteria to the search. Anyway, please provide advice!

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  • Regular Expressions .NET

    - by Fosa
    I need a regular expression for some arguments that must match on a string. here it is... The string exists out of minimum 8 en maximum 20 characters. These characters of this string may be characters of the alfabet or special chars --With other words..all charachters except from the whitespaces In the complete string there must be atleast 1 number. The string cannot start with a number or an underscore The last 2 characters of the string must be identical, But it doenst matter if those last --identical characters are capital or non-capital (case insensitive) Must match all : +234567899 a_1de*Gg xy1Me*__ !41deF_hij2lMnopq3ss C234567890123$^67800 *5555555 sDF564zer"" !!!!!!!!!4!!!!!!!!!! abcdefghijklmnopq9ss May not match : Cannot be less then 8 or more then 20 chars: a_1+Eff B41def_hIJ2lmnopq3stt Cannot contain a whitespace: A_4 e*gg b41def_Hij2l nopq3ss Cannot start with a number or an underscore: __1+Eff 841DEf_hij2lmnopq3stt cannot end on 2 diffrent characters: a_1+eFg b41DEf_hij2lmnopq3st Cannot be without a number in the string: abCDefghijklmnopqrss abcdef+++dF !!!!!!!!!!!!!!!!!!!! ------------------------------------------------------ This is what I have so far...But I'm really breaking my head on this... If you Don't know the answer completely it's not a problem... I just want to get in the right direction ([^0-9_])(?=.*\d)(\S{8,20})(?i:[\S])\1

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  • Extract string that is delimited with constant and ends with two numbers (numbers have to be included)

    - by Edmon
    I have a text that contains string of a following structure: text I do not care about, persons name followed by two IDs. I know that: a person's name is always preceded by XYZ code and that is always followed by two, space separated numbers. Name is not always just a last name and first name. It can be multiple last or first names (think Latin american names). So, I am looking to extract string that follows the constant XYZ code and that is always terminated by two separate numbers. You can say that my delimiter is XYZ and two numbers, but numbers need to be part of the extracted value as well. From blah, blah XYZ names, names 122322 344322 blah blah I want to extract: names, names 122322 344322 Would someone please advise on the regular expression for this that would work with Python's re package.

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  • [Python] OR in regular expression?

    - by www.yegorov-p.ru
    Hello. I have text file with several thousands lines. I want to parse this file into database and decided to write a regexp. Here's part of file: blablabla checked=12 unchecked=1 blablabla unchecked=13 blablabla checked=14 As a result, I would like to get something like (12,1) (0,13) (14,0) Is it possible?

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  • Regular Expression with Names and Emails

    - by Nina
    I am having a problem with regular expressions at the moment. What I'm trying to do is that for each line through the iteration, it checks for this type of pattern: Lastname, Firstname If it finds the name, then it will take the first letter of the first name, and the first six letters of the lastname and form it as an email. I have the following: $checklast = "[A-z],"; $checkfirst = "[A-z]"; if (ereg($checklast, $parts[1])||ereg($checkfirst, $parts[2])){ $first = preg_replace($checkfirst, $checkfirst{1,1}, $parts[2]); print "<a href='mailto:[email protected];'> $parts[$i] </a>"; } This one obviously broke the code. But I was initially attempting to find only the first letter of the firstname and then after that the first six letters of the lastname followed by the @email.com This didn't work out too well. I'm not sure what to do at this point. Any help is much appreciated.

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  • re.sub emptying list

    - by jmau5
    def process_dialect_translation_rules(): # Read in lines from the text file specified in sys.argv[1], stripping away # excess whitespace and discarding comments (lines that start with '##'). f_lines = [line.strip() for line in open(sys.argv[1], 'r').readlines()] f_lines = filter(lambda line: not re.match(r'##', line), f_lines) # Remove any occurances of the pattern '\s*<=>\s*'. This leaves us with a # list of lists. Each 2nd level list has two elements: the value to be # translated from and the value to be translated to. Use the sub function # from the re module to get rid of those pesky asterisks. f_lines = [re.split(r'\s*<=>\s*', line) for line in f_lines] f_lines = [re.sub(r'"', '', elem) for elem in line for line in f_lines] This function should take the lines from a file and perform some operations on the lines, such as removing any lines that begin with ##. Another operation that I wish to perform is to remove the quotation marks around the words in the line. However, when the final line of this script runs, f_lines becomes an empty lines. What happened? Requested lines of original file: ## English-Geek Reversible Translation File #1 ## (Moderate Geek) ## Created by Todd WAreham, October 2009 "TV show" <=> "STAR TREK" "food" <=> "pizza" "drink" <=> "Red Bull" "computer" <=> "TRS 80" "girlfriend" <=> "significant other"

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  • What is the right method for parsing a blog post?

    - by Zedwal
    Hi guys, Need a guide line .... I am trying to write a personal blog. What is the standard structure for for input for the post. I am trying the format like: This is the simple text And I am [b] bold text[/b]. This is the code part: [code lang=java] public static void main (String args[]) { System.out.println("Hello World!"); } [/code] Is this the right way to store post in the database? And What is the right method to parse this kind of post? Shall I use regular expression to parse this or there is another standard for this. If the above mentioned format is not the right way for storage, then what it could be? Thanks

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  • Why does this regular expression for sed break inside Makefile?

    - by jcrocholl
    I'm using GNU Make 3.81, and I have the following rule in my Makefile: jslint : java org.mozilla.javascript.tools.shell.Main jslint.js mango.js \ | sed 's/Lint at line \([0-9]\+\) character \([0-9]\+\)/mango.js:\1:\2/' This works fine if I enter it directly on the command line, but the regular expression does not match if I run it with "make jslint". However, it works if I replace \+ with \{1,\} in the Makefile: jslint : java org.mozilla.javascript.tools.shell.Main jslint.js mango.js \ | sed 's/Lint at line \([0-9]\{1,\}\) character \([0-9]\{1,\}\)/mango.js:\1:\2/' Is there some special meaning to \+ in Makefiles, or is this a bug?

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  • Regular Expression Sanitize (PHP)

    - by atif089
    Hello, I would like to sanitize a string in to a URL so this is what I basically need. Everything must be removed except alphanumeric characters and spaces and dashed. Spaces should be converter into dashes. Eg. This, is the URL! must return this-is-the-url Thanks

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  • Trying to create a Reg Ex for the following patterns

    - by Travis
    Here are the patterns: Red,Green (and so on...) Red (+5.00),Green (+6.00) (and so on...) Red (+5.00,+10.00),Green (+6.00,+20.00) (and so on...) Red (+5.00),Green (and so on...) Each attribute ("Red,"Green") can have 0, 1, or 2 modifiers (shown as "+5.00,+10.00", etc.). I need to capture each of the attributes and their modifiers as a single string (i.e. "Red (+5.00,+10.00)", "Green (+6.00,+20.00)". Help?

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  • How to replace only part of the match with python re.sub

    - by Arty
    I need to match two cases by one reg expression and do replacement 'long.file.name.jpg' - 'long.file.name_suff.jpg' 'long.file.name_a.jpg' - 'long.file.name_suff.jpg' I'm trying to do the following re.sub('(\_a)?\.[^\.]*$' , '_suff.',"long.file.name.jpg") But this is cut the extension '.jpg' and I'm getting long.file.name_suff. instead of long.file.name_suff.jpg I understand that this is because of [^.]*$ part, but I can't exclude it, because I have to find last occurance of '_a' to replace or last '.' Is there a way to replace only part of the match?

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  • php Dollar amount Regular Expression

    - by Thildemar
    I am have completed javascript validation of a form using Regular Expressions and am now working on redundant verification server-side using PHP. I have copied this regular expression from my jscript code that finds dollar values, and reformed it to a PHP friendly format: /\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/ Specifically: if (preg_match("/\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/", $_POST["cost"])){} While the expression works great in javascript I get : Warning: preg_match() [function.preg-match]: Compilation failed: nothing to repeat at offset 1 when I run it in PHP. Anyone have a clue why this error is coming up?

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  • Regular expressions in a Python find-and-replace script?

    - by Haidon
    I'm new to Python scripting, so please forgive me in advance if the answer to this question seems inherently obvious. I'm trying to put together a large-scale find-and-replace script using Python. I'm using code similar to the following: findreplace = [ ('term1', 'term2'), ] inF = open(infile,'rb') s=unicode(inF.read(),charenc) inF.close() for couple in findreplace: outtext=s.replace(couple[0],couple[1]) s=outtext outF = open(outFile,'wb') outF.write(outtext.encode('utf-8')) outF.close() How would I go about having the script do a find and replace for regular expressions? Specifically, I want it to find some information (metadata) specified at the top of a text file. Eg: Title: This is the title Author: This is the author Date: This is the date and convert it into LaTeX format. Eg: \title{This is the title} \author{This is the author} \date{This is the date} Maybe I'm tackling this the wrong way. If there's a better way than regular expressions please let me know! Thanks!

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  • Regexs in Ruby getting filename

    - by user1290757
    i am extracting file names of html files using line: filename = File.basename(input_filename, ".*") which currently prints full file name excluding .html extension All files are stored in the form of http^x.x.edu^1^2 all file names begin with http^ and contain edu^ what i want is to extract 2 (which changes) but it is always the second element after .edu I have attempted destructive gsub! but i m weak with regular expressions.

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  • Which is more efficient regular expression?

    - by Vagnerr
    I'm parsing some big log files and have some very simple string matches for example if(m/Some String Pattern/o){ #Do something } It seems simple enough but in fact most of the matches I have could be against the start of the line, but the match would be "longer" for example if(m/^Initial static string that matches Some String Pattern/o){ #Do something } Obviously this is a longer regular expression and so more work to match. However I can use the start of line anchor which would allow an expression to be discarded as a failed match sooner. It is my hunch that the latter would be more efficient. Can any one back me up/shoot me down :-)

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  • multiline sed using backreferences...

    - by pagid
    Hi, I'm converting patch scripts using a commandline script - within these scripts there's the combination two lines like: --- /dev/null +++ filename.txt which needs to be converted to: --- filename.txt +++ filename.txt Initially I tried: less file.diff | sed -e "s/---\/dev\null\n+++ \(.*\)/--- \1\n+++ \1/" But I had to find out that multiline-handling is much more complex in sed :( Any help is appreciated...

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