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• Signable, streamable, "readable" archive format?

  - by alexvoda

  Is there any archive format that offers the following: be digitally sign-able with a digital certificate from a trusted source like Verisign - for preventing changes to the file (I am not referring to read only, but in case the file was changed it should no longer be signed telling the user this is not the original file) be stream-able - be able to be opened even if not all of the content has been transfered (also not strictly linearly) be "readable" - be able to read the data without extracting to a temporary folder (AFAIK if you open a file in a zip archive it is extracted first, and this stays true even for zip based formats like OOXML. This is not what I want) be portable - support on at least Windows, Linux and Mac OS X is a must, or at least future support be free of patents - Be open source - also preferably a license that allows commercial use(as far as i know GPL a share-alike licence so it doesn't allow comercial use, BSD on the other hand alows it) Note: Though it may come in handy eventually I can not think right now of a scenario that would require both point 1 and point 2 simultaneously. Or lets leave it a be able to check the signature only when the whole file was downloaded. I am not interested in: being able to be compressed being supported on legacy systems Does any existing archive format fit this description (tar evolutions like DAR and pax come to mind) ? If there is, are there programing libraries available for the above mentioned OSs? If not, would it be hard to create such a thing? EDIT: clarrified piont 5 EDIT 2: added a note to clarify point 1 and 2 P.S.: This is my first question on StackOverflow

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• What is a good way to assign order #s to ordered rows in a table in Sybase

  - by DVK

  I have a table T (structure below) which initially contains all-NULL values in an integer order column: col1 varchar(30), col2 varchar(30), order int NULL I also have a way to order the "colN" columns, e.g. SELECT * FROM T ORDER BY some_expression_involving_col1_and_col2 What's the best way to assign - IN SQL - numeric order values 1-N to the order table, so that the order values match the order of rows returned by the above ORDER BY? In other words, I would like a single query (Sybase SQL syntax so no Oracle's rowcount) which assigns order values so that SELECT * FROM T ORDER BY order returns 100% same order of rows as the query above. The query does NOT necessarily need to update the table T in place, I'm OK with creating a copy of the table T2 if that'll make the query simpler. NOTE1: A solution must be real query or a set of queries, not involving a loop or a cursor. NOTE2: Assume that the data is uniquely orderable according to the order by above - no need to worry about situation when 2 rows can be assigned the same order at random. NOTE3: I would prefer a generic solution, but if you wish a specific example of ordering expression, let's say: SELECT * FROM T ORDER BY CASE WHEN col1="" THEN "AAAAAA" ELSE col1 END, ISNULL(col2, "ZZZ")

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• Parsing two-dimensional text

  - by alexbw

  I need to parse text files where relevant information is often spread across multiple lines in a nonlinear way. An example: 1234 1 IN THE SUPERIOR COURT OF THE STATE OF SOME STATE 2 IN AND FOR THE COUNTY OF SOME COUNTY 3 UNLIMITED JURISDICTION 4 --o0o-- 5 6 JOHN SMITH and JILL SMITH, ) ) 7 Plaintiffs, ) ) 8 vs. ) No. 12345 ) 9 ACME CO, et al., ) ) 10 Defendants. ) ___________________________________) I need to pull out Plaintiff and Defendant identities. These transcripts have a very wide variety of formattings, so I can't always count on those nice parentheses being there, or the plaintiff and defendant information being neatly boxed off, e.g.: 1 SUPREME COURT OF THE STATE OF SOME OTHER STATE COUNTY OF COUNTYVILLE 2 First Judicial District Important Litigation 3 --------------------------------------------------X THIS DOCUMENT APPLIES TO: 4 JOHN SMITH, 5 Plaintiff, Index No. 2000-123 6 DEPOSITION 7 - against - UNDER ORAL EXAMINATION 8 OF JOHN SMITH, 9 Volume I 10 ACME CO, et al, 11 Defendants. 12 --------------------------------------------------X The two constants are: "Plaintiff" will occur after the name of the plaintiff(s), but not necessarily on the same line. Plaintiffs and defendants' names will be in upper case. Any ideas?

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• How to do parrallel processing in Unix Shell script?

  - by Bikram Agarwal

  I have a shell script that transfers a build.xml file to a remote unix machine (devrsp02) and executes the ANT task wldeploy on that machine (devrsp02). Now, this wldeploy task takes around 15 minutes to complete and while this is running, the last line at the unix console is - "task {some digit} initialized". Once this task is complete, we get a "task Completed" msg and the next task in the script is executed only after that. But sometimes, there might be a problem with the weblogic domain and the deployment might be failing internally, with no effect on the status of the wldeploy task. The unix console will still be stuck at "task {some digit} initialized". The error of the deployment will be getting logged in a file called output.a So, what I want now is - Start a time counter before running wldeploy. If the wldeploy runs for more than 15 minutes, the following command should be run - tail -f output.a ## without terminating the wldeploy or cat output.a ## after terminating the wldeploy forcefully Point to be noted here is - I can't run the wldeploy task in background, as in that case the user won't get to know when the task is complete, which is crucial for this script. Could you please suggest anything to achieve this?

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• Downloading Spreadsheets From Google Docs

  - by jeremynealbrown

  Hello, I am working on an Android app that uses the gdata-java-client to download documents for display only. So far I have an application that authenticates with the services and displays a list of user documents. When the user selects a document another query is made for the documents itself. A request for txt, html, rtf and doc files works well, however when I request a spreadsheet in either .csv or .xsl format the result is unexpected. I'm using an HTTPResponse object to store the result of a an HTTPRequest. When I request a document in .csv or .xsl format the HTTPResponse.parseAsString() method produces an entire html page which appears to be the Google Docs home page. Sounds strange, but the result is the actual html for the login page. The HTTPResponse.getStatusMessage returns a 200. Seems like I am missing something simple here. Is there another property of the HTTPResponse that contains the .csv data? I am pretty sure that I am using the correct uri for downloading spreadsheets because it works when I download through my browser. In any case here is an example uri: https://spreadsheets.google.com/feeds/download/spreadsheets/Export?key=0AsE_6_YIr797dHBTUWlHMUFXeTV4ZzJlUGxWRnJXanc&exportFormat=csv Thanks in advance for any help :)

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• PHP cURL error: "Empty reply from server"

  - by ABach

  All, I have a class function to interface with the RESTful API for Last.FM - its purpose is to grab the most recent tracks for my user. Here it is: private static $base_url = 'http://ws.audioscrobbler.com/2.0/'; public static function getTopTracks($options = array()) { $options = array_merge(array( 'user' => 'bachya', 'period' => NULL, 'api_key' => 'xxxxx...', // obfuscated, obviously ), $options); $options['method'] = 'user.getTopTracks'; // Initialize cURL request and set parameters $ch = curl_init(); curl_setopt_array($ch, array( CURLOPT_URL => self::$base_url, CURLOPT_POST => TRUE, CURLOPT_POSTFIELDS => $options, CURLOPT_RETURNTRANSFER => TRUE, CURLOPT_TIMEOUT => 30, CURLOPT_USERAGENT => 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)' )); $results = curl_exec($ch); return $results; } This returns "Empty reply from server". I know that some have suggested that this error comes from some fault in network infrastructure; I do not believe this to be true in my case. If I run a cURL request through the command line, I get my data; the Last.FM service is up and accessible. Before I go to those folks and see if anything has changed, I wanted to check with you fine folks and see if there's some issue in my code that would be causing this. Thanks!

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• Rails running multiple delayed_job - lock tables

  - by pepernik

  Hey. I use delayed_job for background processing. I have 8 CPU server, MySQL and I start 7 delayed_job processes RAILS_ENV=production script/delayed_job -n 7 start Q1: I'm wondering is it possible that 2 or more delayed_job processes start processing the same process (the same record-row in the database delayed_jobs). I checked the code of the delayed_job plugin but can not find the lock directive in a way it should be. I think each process should lock the database table before executing an UPDATE on lock_by column. They lock the record simply by updating the locked_by field (UPDATE delayed_jobs SET locked_by...). Is that really enough? No locking needed? Why? I know that UPDATE has higher priority than SELECT but I think this does not have the effect in this case. My understanding of the multy-threaded situation is: Process1: Get waiting job X. [OK] Process2: Get waiting jobs X. [OK] Process1: Update locked_by field. [OK] Process2: Update locked_by field. [OK] Process1: Get waiting job X. [Already processed] Process2: Get waiting jobs X. [Already processed] I think in some cases more jobs can get the same information and can start processing the same process. Q2: Is 7 delayed_jobs a good number for 8CPU server? Why yes/not. Thx 10x!

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• Very weird C file-handling anomaly

  - by KáGé

  Hello, I got a very weird issue that I cant figure out in my school project, which is the simulation of a simple filesystem in a human-readable textfile. Unfortunately I don't yet have enough time to translate the comments in my code or make it less gibberish, so if you are bothered by that, you don't have to help, I understand. See the code HERE. Now in drive.h, at line 574 is this part: i = getline(); #ifdef DEBUG printf("Free space in all found at %d.\n\n", i); if(drive.disk != NULL){ printf("Disk OK\n\n"); } #endif //write in data state = seekline(i); Before this it finds place for the allocation database entry in the ALL sector (see the "image files" in the mounts folder, this issue was tested on mount_30.efs-dbf), then gets the line with i = getline() fine (getline is in lglobal.h, line 39), but after that any file manipulation (in this case seekline's fseek, but if I comment that out, then the first fprintf after that) crashes the program straight away. I think the file gets somehow corrupted (though the Disk OK message appears) but can't figure out how. I've tried putting i = getline(); into comment, but it didn't make any difference. I've also tried asking at local programming forums but they didn't really help either. The last few lines of the output before it crashes: Dir written. (drive.h line 562) Seekline entered: 268 (called at drive.h line 564) Getline entered. (called at drive.h line 574) Line got: 268. Free space in all found at 268. (drive.h line 576) Seekline entered: 268 (called at drive.h line 582, note that this exact call was run successfully less than 20 lines back. This one should set the pointer to the beginning of the line it is currently in) After this it crashes. Does anyone has any idea of what causes this and how could I fix it? Thank you.

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• How to extract block of XML from a log file on Linux

  - by dragonmantank

  I have a log file that looks like the following: 2010-05-12 12:23:45 Some sort of log entry 2010-05-12 01:45:12 Request XML: <RootTag> <Element>Value</Element> <Element>Another Value</Element> </RootTag> 2010-05-12 01:45:32 Response XML: <ResponseRoot> <Element>Value</Element> </ResponseRoot> 2010-05-12 01:45:49 Another log entry What I want to do is extract the Request and Response XML (and ultimately dump them into their own single files). I had a similar parser that used egrep but the XML was all on one line, not multiple ones like above. The log files are also somewhat large, hitting 500-600 megs a log. Smaller logs I would read in via a PHP script and use regex matching, but the amount of memory required for such a large file would more than likely kill the script. Is there an easy way using the built-in tools on a Linux box (CentOS in this case) to extract multiple lines or am I going to have to bite the bullet and use Perl or PHP to read in the entire file to extract it?

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• Lucene wildcard queries

  - by Javi

  Hello, I have this question relating to Lucene. I have a form and I get a text from it and I want to perform a full text search in several fields. Suppose I get from the input the text "textToLook". I have a Lucene Analyzer with several filters. One of them is lowerCaseFilter, so when I create the index, words will be lowercased. Imagine I want to search into two fields field1 and field2 so the lucene query would be something like this (note that 'textToLook' now is 'texttolook'): field1: texttolook* field2:texttolook* In my class I have something like this to create the query. I works when there is no wildcard. String text = "textToLook"; String[] fields = {"field1", "field2"}; //analyser is the same as the one used for indexing Analyzer analyzer = fullTextEntityManager.getSearchFactory().getAnalyzer("customAnalyzer"); MultiFieldQueryParser parser = new MultiFieldQueryParser(fields, analyzer); org.apache.lucene.search.Query queryTextoLibre = parser.parse(text); With this code the query would be: field1: texttolook field2:texttolook but If I set text to "textToLook*" I get field1: textToLook* field2:textToLook* which won't find correctly as the indexes are in lowercase. I have read in lucene website this: " Wildcard, Prefix, and Fuzzy queries are not passed through the Analyzer, which is the component that performs operations such as stemming and lowercasing" My problem cannot be solved by setting the behaviour case insensitive cause my analyzer has other fields which for examples remove some suffixes of words. I think I can solve the problem by getting how the text would be after going through the filters of my analyzer, then I could add the "*" and then I could build the Query with MultiFieldQueryParser. So in this example I woud get "textToLower" and after being passed to to these filters I could get "texttolower". After this I could make "textotolower*". But, is there any way to get the value of my text variable after going through all my analyzer's filters? How can I get all the filters of my analyzer? Is this possible? Thanks

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• What's the best NAME for "quick" Category you add to a file?

  - by Joe Blow

  So the other day I was sick of typing out repetetive addTarget:action:forControlEvents:s, and macros are only entertaining for so long, so I did this: @implementation UIControl (xx) -(void)addTarget:(id)target action:(SEL)action { [self addTarget:target action:action forControlEvents:UIControlEventTouchUpInside]; } @end *and simply added it at the top of the .m file in question. Works great of course, but notice the "xx".* What's the best thing to NAME a "quick" Category like this? Annoyingly, it appears you can not leave the xx blank - it would then become an "Extension" (which, incidentally, I don't understand at all). I was thinking maybe: a single underscore the name of the class again identically "quick" perhaps the name of the class in this file (as in "quick extra routines for UIControl in CherryBomb") - so it would be UIControl(CherryBomb), ie, remind you that these extra routines are handy for CherryBomb "x" your or your company's initials (use the same "quick" Category name everywhere) "ThisTextNeverUsedAnywhere" By the way, I've been assuming that Categories only happen in the files that see them (CherryBomb.m in the example) - they do not from then on apply app-wide. ie they only apply where you include the header file (UIControl+NattyStuff) or in the "quick" case only in the file to which one adds the text. (By the way ... it appears you do not actually need to include an interface for such a Category, i.e. you can omit... //you can actually get away without these lines... //#import <UIKit/UIControl.h> //@interface UIControl (x) //-(void)addTarget:(id)target action:(SEL)action; //@end ... that part and it works fine.) For people who love Categories, and who doesn't, what's the answer to this troubling question? What should you name a "quick" Category where the name is never going to be referenced again and is irrelevant? Is "_" a solution?

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• On-Demand thumbnail creation with django and nginx

  - by sharjeel

  I want to generate thumbnails of images on the fly. My site is built with django and deployed using nginx which serves all the static content and communicates with django/apache using reverse proxy. Right now, for every image in my site, I generate all required sizes of thumbnails on-hand and deliver them when required. The problem is that whenever I change the size of a thumbnail, I have to regenerate all of them (and they are tons). However now I'd like to generate the thumbnail the first time it is accessed and later on nginx would deliver the same file over n over. If I delete that thumbnail file because of lesser accesses, it should get generated automatically the next time. Thumbnails in my case also have watermarks which require some computation logic of my application so a webserver thumbnail module might not work very well. The size of the thumbnail can be embedded in the URL. So http://www.example.com/thumbnail/abc_320x240.jpg gets the 320x240 size of the thumbnail. The approach I'm looking right now is to let nginx lookup the file and if it doesn't exist, forward the query to my django application which would create the thumbnail and send either the response or a redirect string. However I'm not sure about the concurrency issues and any other issues which might pop up later. What is the appropriate way to achieve this?

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• How do I get started designing and implementing a script interface for my .NET application?

  - by Peter Mortensen

  How do I get started designing and implementing a script interface for my .NET application? There is VSTA (the .NET equivalent of VBA for COM), but as far as I understand I would have to pay a license fee for every installation of my application. It is an open source application so this will not work. There is also e.g. the embedding of interpreters (IronPython?), but I don't understand how this would allow exposing an "object model" (see below) to external (or internal) scripts. What is the scripting interface story in .NET? Is it somehow trivial in .NET to do this? Background: I have once designed and implemented a fairly involved script interface for a Macintosh application for acquisition and analysis of data from a mass spectrometer (Mac OS, System 7) and later a COM interface for a Windows application. Both were designed with an "object model" and classes (that can have properties). These are overloaded words, but in a scripting interface context object model is essentially a containment hiarchy of objects of specific classes. Classes have properties and lists of contained objects. E.g. like in the COM interfaces exposed in Microsoft Office applications, where the application object can be used to add to its list of documents (with the side effect of creating the GUI representation of a document). External scripts can create new objects in a container and navigate through the content of the hiarchy at any given time. In the Macintosh case scripts could be written in e.g. AppleScript or Frontier. On the Macintosh the implementation of a scripting interface was very complicated. Support for it in Metroworks' C++ class library (the name escapes me right now) made it much simpler.

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• Tablet interface for the physically disabled?

  - by Glenn

  My sister has Cerebral Palsy, which in her case means she has only gross motor control and her speech is slurred. Implications should be obvious: traditional computer/phone/tablet interfaces won't work for her and she can't speak clearly enough for speech recognition software to help her at all. She enjoys reading but has difficulty holding the book and/or turning a page. There are a few options for helping her use a computer, but nothing for tablets or eReaders. That's where you come in. I would like to make (or buy, if such a thing exists) a better interface to an Android tablet that would work for someone with little to no physical dexterity or speech ability. I'd also be interested in work on the Kindle or iPad, but I'm most familiar with Android so I'm starting there. I know Android has Bluetooth capability. Is it possible to interface a joystick to control the Android device? By "control", I mean the entire operating system - selecting an app, launching it, controlling the menus, etc. I want to give her control over the whole thing, not just a specific app. On a PC this can be accomplished by creating a generic USB HID interface and an arcade joystick to move the mouse over the screen and click on thigns. Is it possible to do something like that in Android? Any help you can offer would be greatly appreciated. Thanks!

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• Is there a language with native pass-by-reference/pass-by-name semantics, which could be used in mod

  - by Bubba88

  Hi! This is a reopened question. I look for a language and supporting platform for it, where the language could have pass-by-reference or pass-by-name semantics by default. I know the history a little, that there were Algol, Fortran and there still is C++ which could make it possible; but, basically, what I look for is something more modern and where the mentioned value pass methodology is preferred and by default (implicitly assumed). I ask this question, because, to my mind, some of the advantages of pass-by-ref/name seem kind of obvious. For example when it is used in a standalone agent, where copyiong of values is not necessary (to some extent) and performance wouldn't be downgraded much in that case. So, I could employ it in e.g. rich client app or some game-style or standalone service-kind application. The main advantage to me is the clear separation between identity of a symbol, and its current value. I mean when there is no reduntant copying, you know that you're working with the exact symbol/path you have queried/received. And intristing boxing of values will not interfere with the actual logic of program. I know that there is C# ref keyword, but it's something not so intristic, though acceptable. Equally, I realize that pass-by-reference semantics could be simulated in virtually any language (Java as an instant example) and so on.. not sure about pass by name :) What would you recommend - create a something like DSL for such needs wherever it be appropriate; or use some languages that I already know? Maybe, there is something that I'm missing? Thank you!

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• Message queue proxy in Python + Twisted

  - by gasper_k

  Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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• general learning methodology

  - by momo

  just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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• PHP Regex to match lines with all-caps with occaisional hyphens.

  - by Yaaqov

  I'm trying to to convert an existing PHP Regular Expression match case to apply to a slightly different style of document. Here's the original style of the document: **FOODS - TYPE A** ___________________________________ **PRODUCT** 1) Mi Pueblito Queso Fresco Authentic Mexican Style Fresh Cheese; 2) La Fe String Cheese **CODE** Sell by date going back to February 1, 2009 And the successfully-running PHP Regex match code that only returns "true" if the line is surrounded by asterisks, and stores each side of the "-" as $m[1] and $m[2], respectively. if ( preg_match('#^\*\*([^-]+)(?:-(.*))?\*\*$#', $line, $m) ) { // only for **header - subheader** $m[2] is set. if ( isset($m[2]) ) { return array(TYPE_HEADER, array(trim($m[1]), trim($m[2]))); } else { return array(TYPE_KEY, array($m[1])); } } So, for line 1: $m[1] = "FOODS" AND $m[2] = "TYPE A"; Line 2 would be skipped; Line 3: $m[1] = "PRODUCT", etc. The question: How would I re-write the above regex match if the headers did not have the asterisks, but still was all-caps, and was at least 4 characters long? For example: FOODS - TYPE A ___________________________________ PRODUCT 1) Mi Pueblito Queso Fresco Authentic Mexican Style Fresh Cheese; 2) La Fe String Cheese CODE Sell by date going back to February 1, 2009 Thank you.

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• Cannot write the output to a text file in cpp program

  - by swapedoc

  I have this input file "https://code.google.com/codejam/contest/351101/dashboard/do/A-large-practice.in?cmd=GetInputFile&problem=374101&input_id=1&filename=A-large-practice.in&redownload_last=1&agent=website&csrfmiddlewaretoken=OWMxNTVmMTUyODBiYjhhN2Q2OTM3ZGJiMTNhNDkwMDF8fDEzNzIxNzI1NTE3ODAzMjA%3D" I tried to read this file :-using freopen("filename.txt",r,stdin); and then I wanted the output written to be written to another text file which I can upload in this codejam practice question for the judge. #include<iostream> #include<cstdio> using namespace std; int main() { int t,k=0,a[2000]; freopen("ab.txt","r",stdin); scanf("%d",&t); while(t--) { freopen("cb.txt","w",stdout); int c; scanf("%d",&c); int n; scanf("%d",&n); for(int i=0;i<n;i++) scanf("%d",&a[i]); printf("Case #%d: ",++k); for(int i=0;i<n-1;i++) {for(int j=i+1;j<n;j++) if((a[i]+a[j])==c) {printf("%d %d\n",i+1,j+1); i=n;} } } return 0; } This is my code. Now the problem is the output file cb.txt contains only the last line of the input. I want the the whole of the output to be written to cb.txt,so what should I do.

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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• Testing for interface implementation in WCF/SOA

  - by rabidpebble

  I have a reporting service that implements a number of reports. Each report requires certain parameters. Groups of logically related parameters are placed in an interface, which the report then implements: [ServiceContract] [ServiceKnownType(typeof(ExampleReport))] public interface IService1 { [OperationContract] void Process(IReport report); } public interface IReport { string PrintedBy { get; set; } } public interface IApplicableDateRangeParameter { DateTime StartDate { get; set; } DateTime EndDate { get; set; } } [DataContract] public abstract class Report : IReport { [DataMember] public string PrintedBy { get; set; } } [DataContract] public class ExampleReport : Report, IApplicableDateRangeParameter { [DataMember] public DateTime StartDate { get; set; } [DataMember] public DateTime EndDate { get; set; } } The problem is that the WCF DataContractSerializer does not expose these interfaces in my client library, thus I can't write the generic report generating front-end that I plan to. Can WCF expose these interfaces, or is this a limitation of the serializer? If the latter case, then what is the canonical approach to this OO pattern? I've looked into NetDataContractSerializer but it doesn't seem to be an officially supported implementation (which means it's not an option in my project). Currently I've resigned myself to including the interfaces in a library that is common between the service and the client application, but this seems like an unnecessary extra dependency to me. Surely there is a more straightforward way to do this? I was under the impression that WCF was supposed to replace .NET remoting; checking if an object implements an interface seems to be one of the most basic features required of a remoting interface?

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• Passing IDisposable objects through constructor chains

  - by Matt Enright

  I've got a small hierarchy of objects that in general gets constructed from data in a Stream, but for some particular subclasses, can be synthesized from a simpler argument list. In chaining the constructors from the subclasses, I'm running into an issue with ensuring the disposal of the synthesized stream that the base class constructor needs. Its not escaped me that the use of IDisposable objects this way is possibly just dirty pool (plz advise?) for reasons I've not considered, but, this issue aside, it seems fairly straightforward (and good encapsulation). Codes: abstract class Node { protected Node (Stream raw) { // calculate/generate some base class properties } } class FilesystemNode : Node { public FilesystemNode (FileStream fs) : base (fs) { // all good here; disposing of fs not our responsibility } } class CompositeNode : Node { public CompositeNode (IEnumerable some_stuff) : base (GenerateRaw (some_stuff)) { // rogue stream from GenerateRaw now loose in the wild! } static Stream GenerateRaw (IEnumerable some_stuff) { var content = new MemoryStream (); // molest elements of some_stuff into proper format, write to stream content.Seek (0, SeekOrigin.Begin); return content; } } I realize that not disposing of a MemoryStream is not exactly a world-stopping case of bad CLR citizenship, but it still gives me the heebie-jeebies (not to mention that I may not always be using a MemoryStream for other subtypes). It's not in scope, so I can't explicitly Dispose () it later in the constructor, and adding a using statement in GenerateRaw () is self-defeating since I need the stream returned. Is there a better way to do this? Preemptive strikes: yes, the properties calculated in the Node constructor should be part of the base class, and should not be calculated by (or accessible in) the subclasses I won't require that a stream be passed into CompositeNode (its format should be irrelevant to the caller) The previous iteration had the value calculation in the base class as a separate protected method, which I then just called at the end of each subtype constructor, moved the body of GenerateRaw () into a using statement in the body of the CompositeNode constructor. But the repetition of requiring that call for each constructor and not being able to guarantee that it be run for every subtype ever (a Node is not a Node, semantically, without these properties initialized) gave me heebie-jeebies far worse than the (potential) resource leak here does.

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• How do I abort a socket.recv() from another thread in python?

  - by Samuel Skånberg

  I have a main thread that waits for connection. It spawns client threads that will echo the response from the client (telnet in this case). But say that I want to close down all sockets and all threads after some time, like after 1 connection. How would I do? If I do clientSocket.close() from the main thread, it won't stop doing the recv. It will only stop if I first send something through telnet, then it will fail doing further sends and recvs. My code look like this: # Echo server program import socket from threading import Thread import time class ClientThread(Thread): def __init__(self, clientSocket): Thread.__init__(self) self.clientSocket = clientSocket def run(self): while 1: try: # It will hang here, even if I do close on the socket data = self.clientSocket.recv(1024) print "Got data: ", data self.clientSocket.send(data) except: break self.clientSocket.close() HOST = '' PORT = 6000 serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) serverSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) serverSocket.bind((HOST, PORT)) serverSocket.listen(1) clientSocket, addr = serverSocket.accept() print 'Got a new connection from: ', addr clientThread = ClientThread(clientSocket) clientThread.start() time.sleep(1) # This won't make the recv in the clientThread to stop immediately, # nor will it generate an exception clientSocket.close()

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• using an alternative string quotation syntax in python

  - by Cawas

  Just wondering... I find using escape characters too distracting. I'd rather do something like this: print ^'Let's begin and end with sets of unlikely 2 chars and bingo!'^ Let's begin and end with sets of unlikely 2 chars and bingo! Note the ' inside the string, and how this syntax would have no issue with it, or whatever else inside for basically all cases. Too bad markdown can't properly colorize it (yet), so I decided to <pre> it. Sure, the ^ could be any other char, I'm not sure what would look/work better. That sounds good enough to me, tho. Probably some other language already have a similar solution. And, just maybe, Python already have such a feature and I overlooked it. I hope this is the case. But if it isn't, would it be too hard to, somehow, change Python's interpreter and be able to select an arbitrary (or even standardized) syntax for notating the strings? I realize there are many ways to change statements and the whole syntax in general by using pre-compilators, but this is far more specific. And going any of those routes is what I call "too hard". I'm not really needing to do this so, again, I'm just wondering.

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• How to assign class property as display data memeber in datagridview

  - by KoolKabin

  hi guys, I am trying to display my data in datagridview. I created a class with different property and used its list as the datasource. it worked fine. but i got confused how to do that in case we have nested class. My Classes are as follows: class Category property UIN as integer property Name as string end class class item property uin as integer property name as string property mycategory as category end class my data list as follows: dim myDataList as list(of Item) = new List(of Item) myDataList.Add(new Item(1,"item1",new category(1,"cat1"))) myDataList.Add(new Item(2,"item2",new category(1,"cat1"))) myDataList.Add(new Item(3,"item3",new category(1,"cat1"))) myDataList.Add(new Item(4,"item4",new category(2,"cat2"))) myDataList.Add(new Item(5,"item5",new category(2,"cat2"))) myDataList.Add(new Item(6,"item6",new category(2,"cat2"))) Now I binded the datagridview control like: DGVMain.AutoGenerateColumns = False DGVMain.ColumnCount = 3 DGVMain.Columns(0).DataPropertyName = "UIN" DGVMain.Columns(0).HeaderText = "ID" DGVMain.Columns(1).DataPropertyName = "Name" DGVMain.Columns(1).HeaderText = "Name" DGVMain.Columns(2).DataPropertyName = "" **'here i want my category name** DGVMain.Columns(2).HeaderText = "category" DGVMain.datasource = myDataList DGVMain.refresh() I have tried using mycategory.name but it didn't worked. What can be done to get expected result? Is there any better idea other than this to accomplish the same task?

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