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• Regular expression: who's greedier?

  - by polygenelubricants

  My primary concern is with the Java flavor, but I'd also appreciate information regarding others. Let's say you have a subpattern like this: (.*)(.*) Not very useful as is, but let's say these two capture groups (say, \1 and \2) are part of a bigger pattern that matches with backreferences to these groups, etc. So both are greedy, in that they try to capture as much as possible, only taking less when they have to. My question is: who's greedier? Does \1 get first priority, giving \2 its share only if it has to? What about: (.*)(.*)(.*) Let's assume that \1 does get first priority. Let's say it got too greedy, and then spit out a character. Who gets it first? Is it always \2 or can it be \3? Let's assume it's \2 that gets \1's rejection. If this still doesn't work, who spits out now? Does \2 spit to \3, or does \1 spit out another to \2 first?

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• jQuery Nested Droppables

  - by John

  I have a nested set of jQuery droppables...one outer droppable that encompasses most of the page and an a set of nested inner droppables on the page. The functionality I want is: If a draggable is dropped outside of any of the inner droppables it should be accepted by the outer droppable. If a draggable is dropped onto any of the inner droppables it should NOT be accepted by the outer droppable, regardless of whether the inner droppable accepts the draggable. So that would be easy if I could guarantee 1+ inner droppables would accept the draggable, because the greedy attribute would make sure it would only get triggered once. Unfortunately the majority of the time the inner droppable will also reject the draggable, meaning the greedy option doesn't really help. Summary: The basic functionality is a set of valid/invalid inner droppables to accept the draggable, but when you toss the draggable outside any of the draggables it gets destroyed by the outer droppable. What's the best way of doing this?

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• Parsing srt subtitles

  - by Vojtech R.

  Hi, I want to parse srt subtitles: 1 00:00:12,815 --> 00:00:14,509 Chlapi, jak to jde s tema pracovníma svetlama?. 2 00:00:14,815 --> 00:00:16,498 Trochu je zesilujeme. 3 00:00:16,934 --> 00:00:17,814 Jo, sleduj. Every item into structure. With this regexs: A: RE_ITEM = re.compile(r'''(?P<index>\d+).(?P<start>\d{2}:\d{2}:\d{2},\d{3}) --> (?P<end>\d{2}:\d{2}:\d{2},\d{3}).(?P<text>.*?)''', re.DOTALL) B: RE_ITEM = re.compile(r'''(?P<index>\d+).(?P<start>\d{2}:\d{2}:\d{2},\d{3}) --> (?P<end>\d{2}:\d{2}:\d{2},\d{3}).(?P<text>.*)''', re.DOTALL) And this code: for i in Subtitles.RE_ITEM.finditer(text): result.append((i.group('index'), i.group('start'), i.group('end'), i.group('text'))) With code B I have only one item in array (because of greedy .*) and with code A I have empty 'text' because of no-greedy .*? How to cure this? Thanks

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• Parsing: How to make error recovery in grammars like " a* b*"?

  - by Lavir the Whiolet

  Let we have a grammar like this: Program ::= a* b* where "*" is considered to be greedy. I usually implement "*" operator naively: Try to apply the expression under "*" to input one more time. If it has been applied successfully then we are still under current "*"-expression; try to apply the expression under "*" one more time. Otherwise we have reached next grammar expression; put characters parsed by expression under "*" back into input and proceed with next expression. But if there are errors in input in any of "a*" or "b*" part such a parser will "think" that in position of error both "a*" and "b*" have finished ("let's try "a"... Fail! OK, it looks like we have to proceed to "b*". Let's try "b"... Fail! OK, it looks like the string should have been finished...). For example, for string "daaaabbbbbbc" it will "say": "The string must end at position 1, delete superflous characters: daaaabbbbbbc". In short, greedy "*" operator becomes lazy if there are errors in input. How to make "*" operator to recover from errors nicely?

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• regexp target last main li in list

  - by veilig

  I need to target the starting tag of the last top level LI in a list that may or may-not contain sublists in various positions - without using CSS or Javascript. Is there a simple/elegant regexp that can help with this? I'm no guru w/ them, but it appears the need for greedy/non-greedy selectors when I'm selecting all the middle text (.*) / (.+) changes as nested lists are added and moved around in the list - and this is throwing me off. $pattern = '/^(<ul>.*)<li>(.+<\/li><\/ul>)$/'; $replacement = '$1<li id="lastLi">$3'; Perhaps there is an easier approach?? converting to XML to target the LI and then convert back? ie: Single Element <ul> <li>TARGET</li> </ul> Multiple Elements <ul> <li>foo</li> <li>TARGET</li> </ul> Nested Lists before end <ul> <li> foo <ul> <li>bar</li> </ul> <li> <li>TARGET</li> </ul> Nested List at end <ul> <li>foo</li> <li> TARGET <ul> <li>bar</li> </ul> </li> </ul>

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• Match Anything Except a Sub-pattern

  - by Tim Lytle

  I'd like to accomplish what this (invalid I believe) regular expression tries to do: <p><a>([^(<\/a>)]+?)<\/a></p>uniquestring Essentially match anything except a closing anchor tag. Simple non-greedy doesn't help here because `uniquestring' may very well be after another distant closing anchor tag: <p><a>text I don't <tag>want</tag> to match</a></p>random data<p><a>text I do <tag>want to</tag> match</a></p>uniquestring more matches <p><a>of <tag>text I do</tag> want to match</a></p>uniquestring So I have more tag in between the anchor tags. And I'm using the presence of uniquestring to determine if I want to match the data. So a simple non-greedy ends up matching everything from the start of the data I don't want to the end of the data I do want. I know I'm edging close to the problems regular expressions (or at least my knowledge of them) aren't good at solving. I could just through the data at an HTML/XML parser, but it is just one simple(ish) search. Is there some easy way to do this that I'm just missing?

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• Which is the correct design pattern for my PHP application?

  - by user1487141

  I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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• Do running times match with O(nlogn)?

  - by user472221

  Hi I have written a class(greedy strategy) that at first i used sort method which has O(nlogn) Collections.sort(array, new SortingObjectsWithProbabilityField()); and then i used the insert method of binary search tree which takes O(h) and h here is the tree height. for different n ,the running time will be : n,running time 17,515428 33,783340 65,540572 129,1285080 257,2052216 513,4299709 which I think is not correct because for increasing n , the running time should almost increase. This method will take the running time: Exponent = -1; for(int n = 2;n<1000;n+=Math.pow(2,exponent){ for (int j = 1; j <= 3; j++) { Random rand = new Random(); for (int i = 0; i < n; i++) { Element e = new Element(rand.nextInt(100) + 1, rand.nextInt(100) + 1, 0); for (int k = 0; k < i; k++) { if (e.getDigit() == randList.get(k).getDigit()) { e.setDigit(e.getDigit() + 1); } } randList.add(e); } double sum = 0.0; for (int i = 0; i < randList.size(); i++) { sum += randList.get(i).getProbability(); } for (Element i : randList) { i.setProbability(i.getProbability() / sum); } //Get time. long t2 = System.nanoTime(); GreedyVersion greedy = new GreedyVersion((ArrayList<Element>) randList); long t3 = System.nanoTime(); timeForGreedy = timeForGreedy + t3 - t2; } System.out.println(n + "," + "," + timeForGreedy/3 ); exponent++; } thanks

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• What exactly does an installer do and why might I need one?

  - by Jan

  this is probably the noob-question of the day: So I've written this game. Now there's the .exe file that does the work, a folder with my beautiful, beautiful assets and a bunch of .dll files and other stuff that I probably shouldn't touch. To run the game, I copy the whole lot to the desired computer, double-click the .exe file and start shooting some dudes. Yay! But what exactly is the difference between that and using an installer? What else does an installer do besides copying files and looking more professional than a .zip-file? Is there generally a lot of patching/configuring involved when trying to make a game run on a different computer? I tested my game on all windows computers I could get my greedy fingers on and it works great. Thanks for your time.

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• Lexer antlr3 token problem

  - by nioo

  Can I construct a token ENDPLUS: '+' (options (greedy = false;):.) * '+' ; being considered by the lexer only if it is preceded by a token PREwithout including in ENDPLUS? PRE: '<<' ; Thanks.

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• Convert latitude and longitude into northern and eastings

  - by Rippo

  Hi I have the following UK postcode dy8 3xt and know that the latitude and longitude is:- 52.190108 -2.517266 I also know that the Eastings, Northings for the postcode is:- 389490 283880 However I am struggling to find the equation that converts lat/long to northings and Eastings, I would prefer to have the equation in both in jScript and c# (I am being greedy)! Can anyone help?

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• lexer/parser ambiguity

  - by John Leidegren

  How does a lexer solve this ambiguity? /*/*/ How is it that it doesn't just say, oh yeah, that's the begining of a multi-line comment, followed by another multi-line comment. Wouldn't a greedy lexer just return the following tokens? /* /* / I'm in the midst of writing a shift-reduce parser for CSS and yet this simple comment thing is in my way. You can read this question if you wan't some more background information.

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• Simple java regular expression replace question.

  - by Yang

  I have a simple xml file and I want to remove everything before the first tag. ..... item1 .... The following java code is not working: String cleanxml = rawxml.replace("^[\\s\\S]+<item>", ""); What is the correct way to do this? And how do I address the non-greedy issue? Sorry I'm a C# programmer.

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• PHP - preg_replace with multiple matches

  - by Neil

  Let's say I have a string like: $text = "<object>item_id1a2b3</object>xxx<object>item_id4c5d6</object>" I want to convert it to: %ITEM:1a2b3xxx%ITEM:4c5d6 Here's what I've got: $text = preg_replace("/<object.*item_id([a-zA-Z0-9]+).*<\/object/","%ITEM:$1",$text); This isn't quite right, as the search is greedy. Thoughts? Thanks!

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• Is there a more modern regexp handler for Open Object Rexx

  - by Brent.Longborough

  The regular expression class (rxregexp.dll) that comes with ooRexx (I'm on 4.0.0) is relatively low on function compared, say, with Python's re module (even at 2.5.2). It appears to have no assertions, no facilities for group extraction, or for substitution. Greedy or lazy matching is a global pattern option, rather than flagged by an additional "?". Basically, a pre-PCRE regular expression engine. Does anyone know if anything with more up-to-date function is available?

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• Regular expression - stop at first match

  - by publicRavi

  My pattern looks something like <xxxx location="file path/level1/level2" xxxx some="xxx"> I am only interested in the part in quotes assigned to location. Shouldn't it be as easy as below without the greedy switch? Does not seem to work :( /.*location="(.*)".*/

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• Is there a way to determine the original size or file count of a 7-zip archive?

  - by Zac B

  I know that when I compress an archive with the 7za utility, it gives me stats like the number of files processed and the amount of bytes processed (the original size of the data). Is it possible, using the commandline (on linux) or some programming language, to determine: the original size of an archive, before it was compressed? the number of files/directories contained within an archive? The answer might be "no, just decompress the whole archive and do counting/sizing then", but it would be useful to know if there was a faster/less space-greedy way.

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• How are suspected DoS attacks handled by webservers?

  - by Jan Kuboschek

  I rent a server somewhere out in Canada or so that I'm using to host a website of mine. That website has close to 400,000 pages that I wanted to index today. For that, I wrote a crawler a while back (see JCrawler on Stackoverflow.com). Now, I'm greedy and didn't want it to take too long so I ran multiple threads resulting in some 60+ requests per second from my IP. A couple minutes later, my server locked me out. I can still FTP into it, but I can't HTTP it. As server administrator or user, do you have any idea how servers usually handle these situations? Is it common to place a permanent or temporary ban on the IP or what is typically done? Naturally, I'll re-run my software with fewer requests once I'm back on.

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• Red Gate and the Community

  - by RedAndTheCommunity

  I was lucky enough to join the Communities team in April 2011, having worked in the equally awesome (but more number-crunchy), Finance team at Red Gate for about four years before that. Being totally passionate about Red Gate, and easily excitable, it seems like the perfect place to be. Not only do I get to talk to people who love Red Gate every day, I get to think up new ways to make them love us even more. Red Gate sponsored 178 SQL Server and .NET events and user group meetings in 2011. They ranged from SQL Saturdays and Code Camps to 10 person user group meetings, from California to Krakow. We've given away cash, software, Kindles, and of course swag. The Marketing Cupboard is like a wonderland of Red Gate goodies; it is guarded day and night to make sure the greedy Red Gaters don't pilfer the treasure inside. There are Red Gate yo-yos, books, pens, ice scrapers and, over the Holidays, there were some special bears. We had to double the patrols guarding the cupboard to protect them. You can see why: Over the Holidays, we gave funding and special Holiday swag (including the adorable bears), to 10 lucky user groups, who held Christmas parties - doing everything from theatre trips to going to shooting ranges. What next? So, what about this year? In 2012 our main aim is to be out there meeting more of you. So get ready to see an army of geeks in red t-shirts at your next event! We also want to do more fun things like our Christmas party giveaway. What cool ideas do you have for sponsorship in 2012? An Easter Egg hunt with SQL server clues? A coding competition? A duelling contest with a license of SQL Toolbelt for the winner? Let me know.

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• A new mission statement for my school's algorithms class

  - by Eric Fode

  The teacher at Eastern Washington University that is now teaching the algorithms course is new to eastern and as a result the course has changed drastically mostly in the right direction. That being said I feel that the class could use a more specific, and industry oriented (since that is where most students will go, though suggestions for an academia oriented class are also welcome) direction, having only worked in industry for 2 years I would like the community's (a wider and much more collectively experienced and in the end plausibly more credible) opinion on the quality of this as a statement for the purpose an algorithms class, and if I am completely off target your suggestion for the purpose of a required Jr. level Algorithms class that is standalone (so no other classes focusing specifically on algorithms are required). The statement is as follows: The purpose of the algorithms class is to do three things: Primarily, to teach how to learn, do basic analysis, and implement a given algorithm found outside of the class. Secondly, to teach the student how to model a problem in their mind so that they can find a an existing algorithm or have a direction to start the development of a new algorithm. Third, to overview a variety of algorithms that exist and to deeply understand and analyze one algorithm in each of the basic algorithmic design strategies: Divide and Conquer, Reduce and Conquer, Transform and Conquer, Greedy, Brute Force, Iterative Improvement and Dynamic Programming. The Question in short is: do you agree with this statement of the purpose of an algorithms course, so that it would be useful in the real world, if not what would you suggest?

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• What types of programming contest problems are there?

  - by Alex

  Basically, I want to make a great reference for use with programming contests that would have all of the algorithms that I can put together that I would need during a contest as well as sample useage for the code. I'm planning on making this into a sort of book that I could print off and take with me to competitions. I would like to do this rather than simply bringing other books (such as Algorithms books) because I think that I will learn a lot more by going over all of the algorithms myself as well as I would know exactly what I have in the book, making it more efficient to have and use. So, I've been doing research to determine what types of programming problems and algorithms are common on contests, and the only thing I can really find is this (which I have seen referenced a few times): Hal Burch conducted an analysis over spring break of 1999 and made an amazing discovery: there are only 16 types of programming contest problems! Furthermore, the top several comprise almost 80% of the problems seen at the IOI. Here they are: Dynamic Programming Greedy Complete Search Flood Fill Shortest Path Recursive Search Techniques Minimum Spanning Tree Knapsack Computational Geometry Network Flow Eulerian Path Two-Dimensional Convex Hull BigNums Heuristic Search Approximate Search Ad Hoc Problems The most challenging problems are Combination Problems which involve a loop (combinations, subsets, etc.) around one of the above algorithms - or even a loop of one algorithm with another inside it. These seem extraordinarily tricky to get right, even though conceptually they are ``obvious''. Now that's good and all, but that study was conducted in 1999, which was 13 years ago! One thing I know is that there are no BigNums problems any more (as Java has a BigInteger class, they have stopped making those problems). So, I'm wondering if anyone knows of any more recent studies of the types of problems that may be seen in a programming contest? Or what the most helpful algorithms on contests would be?

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• Speaking in Sweden in April

  - by Fabrice Marguerie

  As this is my first post in 2011, I wish you all the best for this new year. I don't know for you, but it will be a year of changes for me. I'll tell you more about that when the time comes. For the time being, I just wanted to announce my next speaking engagement: I'll be presenting at SDC2011, the Scandinavian Developer Conference. This event will take place on April 4 and 5 in Göteborg, Sweden. My session will be based on my article about memory leaks: How to detect and avoid memory and resources leaks in .NET applicationsDuring this session we will analyze the most common leak sources in .NET applications and we will see how to detect them in practice. We will demonstrate with live examples several tools that can help you to troubleshoot your applications. The goal of this session is to help you fix and avoid leaks in your .NET applications, whether they are built with Windows Forms, WPF, Silverlight, ASP.NET, or as console or Windows services. You will also get advices on how to improve your applications so they become less greedy. I hope to see you there if you're around in April :-)

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• algorithm for Virtual Machine(VM) Consolidation in Cloud

  - by devansh dalal

  PROBLEM: We have N physical machines(PMs) each with ram Ri, cpu Ci and a set of currently scheduled VMs each with ram requirement ri and ci respectively Moving(Migrating) any VM from one PM to other has a cost associated which depends on its ram ri. A PM with no VMs is shut down to save power. Our target is to minimize the weighted sum of (N,migration cost) by migrating some VMs i.e. minimize the number of working PMs as well as not to degrade the service level due to excessive migrations. My Approach: Brute Force approach is choosing the minimum loaded PM and try to fit its VMs to other PMs by First Fit Decreasing algorithm or we can select the victim PMs and target PMs based on their loading level and shut down victims if possible by moving their VMs to targets. I tried this Greedy approach on the Data of Baadal(IIT-D cloud) but It isn't giving promising results. I have also tried to study the Ant colony optimization for dynamic VM consolidating but was unable to understand very much. I used the links. http://dumas.ccsd.cnrs.fr/docs/00/72/52/15/PDF/Esnault.pdf http://hal.archives-ouvertes.fr/docs/00/72/38/56/PDF/RR-8032.pdf Would anyone please explain the solution or suggest any new approach for better performance soon. Thanks in advance.

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• accessing live usb files from new hd ubuntu install

  - by Robin Bailey

  After my live USB (ubuntu 12.04 lts) refused to boot, I proceeded to install the same Ubuntu version on the laptop hard drive (a dual boot next to Win xp). This all went well without a hitch. Previous to this, I spent several weeks enjoying and exploring ubuntu from the usb pendrive. During this time I changed lots of settings and customized Firefox and more. Now, I'd like to import the home folder from the usb drive into the new install home folder on the hard disk, which is the purported folder that holds all those special settings to my knowledge. Unfortunately and only being familiar with Windows file systems, the view of the usb file system from the new hdd install is totally perplexing. I can't find anything that looks anywhere close to the original file system. More, I can't find any of the files I had created and stored there, like the LibreOfficeCalc file that has all my passwords (this one is really discouraging) that was stored on the ubuntu desktop. Help me find this file alone and I'll bow down with full apologies to any and all computer gods. Being able to import all those customizing settings into the new install would be a major bonus also, but hey, I'm not greedy. I'll take the passwords file and be happy! And humble! I would be very grateful for some clear, understandable help on this. Thanks

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• Efficient algorithm for Virtual Machine(VM) Consolidation in Cloud

  - by devansh dalal

  PROBLEM: We have N physical machines(PMs) each with ram Ri, cpu Ci and a set of currently scheduled VMs each with ram requirement ri and ci respectively Moving(Migrating) any VM from one PM to other has a cost associated which depends on its ram ri. A PM with no VMs is shut down to save power. Our target is to minimize the weighted sum of (N,migration cost) by migrating some VMs i.e. minimize the number of working PMs as well as not to degrade the service level due to excessive migrations. My Approach: Brute Force approach is choosing the minimum loaded PM and try to fit its VMs to other PMs by First Fit Decreasing algorithm or we can select the victim PMs and target PMs based on their loading level and shut down victims if possible by moving their VMs to targets. I tried this Greedy approach on the Data of Baadal(IIT-D cloud) but It isn't giving promising results. I have also tried to study the Ant colony optimization for dynamic VM consolidating but was unable to understand very much. I used the links. http://dumas.ccsd.cnrs.fr/docs/00/72/52/15/PDF/Esnault.pdf http://hal.archives-ouvertes.fr/docs/00/72/38/56/PDF/RR-8032.pdf Would anyone please clarify the solution or suggest any new approach/resources for better performance. I am basically searching for the algorithms not the physical optimizations and I also know that many commercial organizations have provided these solution but I just wanted to know more the underlying algorithms. Thanks in advance.

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