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• Convert array to CSV/TSV-formated string in Python.

  - by dreeves

  Python provides csv.DictWriter for outputting CSV to a file. What is the simplest way to output CSV to a string or to stdout? For example, given a 2D array like this: [["a b c", "1,2,3"], ["i \"comma-heart\" you", "i \",heart\" u, too"]] return the following string: "a b c, \"1, 2, 3\"\n\"i \"\"comma-heart\"\" you\", \"i \"\",heart\"\" u, too\"" which when printed would look like this: a b c, "1,2,3" "i ""heart"" you", "i "",heart"" u, too" (I'm taking csv.DictWriter's word for it that that is in fact the canonical way to output that array as CSV. Excel does parse it correctly that way, though Mathematica does not. From a quick look at the wikipedia page on CSV it seems Mathematica is wrong.) One way would be to write to a temp file with csv.DictWriter and read it back with csv.DictReader. What's a better way? TSV instead of CSV It also occurs to me that I'm not wedded to CSV. TSV would make a lot of the headaches with delimiters and quotes go away: just replace tabs with spaces in the entries of the 2D array and then just intersperse tabs and newlines and you're done. Let's include solutions for both TSV and CSV in the answers to make this as useful as possible for future searchers.

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• OutOfMemoryException when I read FileStream 500 MB

  - by Alhambra Eidos

  Hi all, I'm using Filestream for read big file ( 500 MB) and I get the OutOfMemoryException. Any solutions about it. My Code is: using (var fs3 = new FileStream(filePath2, FileMode.Open, FileAccess.Read)) { byte[] b2 = ReadFully(fs3, 1024); } public static byte[] ReadFully(Stream stream, int initialLength) { // If we've been passed an unhelpful initial length, just // use 32K. if (initialLength < 1) { initialLength = 32768; } byte[] buffer = new byte[initialLength]; int read = 0; int chunk; while ((chunk = stream.Read(buffer, read, buffer.Length - read)) > 0) { read += chunk; // If we've reached the end of our buffer, check to see if there's // any more information if (read == buffer.Length) { int nextByte = stream.ReadByte(); // End of stream? If so, we're done if (nextByte == -1) { return buffer; } // Nope. Resize the buffer, put in the byte we've just // read, and continue byte[] newBuffer = new byte[buffer.Length * 2]; Array.Copy(buffer, newBuffer, buffer.Length); newBuffer[read] = (byte)nextByte; buffer = newBuffer; read++; } } // Buffer is now too big. Shrink it. byte[] ret = new byte[read]; Array.Copy(buffer, ret, read); return ret; } thanks in advanced,

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• Version Control and Coding Formatting

  - by Martin Giffy D'Souza

  Hi, I'm currently part of the team implementing a new version control system (Subversion) within my organization. There's been a bit of a debate on how to handle code formatting and I'd like to get other peoples opinions and experiences on this topic. We currently have ~10 developers each using different tools (due to licensing and preference). Some of these tools have automatic code formatters and others don't. If we allow "blind" checkins the code will look drastically different each time someone does a check in. This will make things such as diffs and merges complicated. I've talked to several people and they've mentioned the following solutions: Use the same developer program with the same code formatter (not really an option due to licensing) Have a hook (either client or server side) which will automatically format the code before going into the repository Manually format the code. Regarding the 3rd point, the concept is to never auto-format the code and have some standards. Right now that seems to be what we're leaning towards. I'm a bit hesitant on that approach as it could lead to developers spending a lot of time manually formatting code. If anyone can please provide some their thoughts and experience on this that would be great. Thank you, Martin

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• Interface and partial classes

  - by Tomek Tarczynski

  According to rule SA1201 in StyleCop elements in class must appear in correct order. The order is following: Fields Constructors Finalizers (Destructors) Delegates Events Enums Interfaces Properties Indexers Methods Structs Classes Everything is ok, except of Interfaces part, because Interface can contain mehtods, events, properties etc... If we want to be strict about this rule then we won't have all members of Interface in one place which is often very useful. According to StyleCop help this problem can be solved by spliting class into partial classes. Example: /// <summary> /// Represents a customer of the system. /// </summary> public partial class Customer { // Contains the main functionality of the class. } /// <content> /// Implements the ICollection class. /// </content> public partial class Customer : ICollection { public int Count { get { return this.count; } } public bool IsSynchronized { get { return false; } } public object SyncRoot { get { return null; } } public void CopyTo(Array array, int index) { throw new NotImplementedException(); } } Are there any other good solutions to this problem?

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• How to make Doxygen ignore specific PHP functions, when generating documentation from a purely proce

  - by Senthil

  I am writing a PHP Library and I am trying out Doxygen to generate the API documentation. My library does not use OOP. All code is procedural. I use lot of helper functions which have an _ (underscore) prefix in their names. They are not part of the publicly exposed API. They are just used internally. Even though they are commented just like the API functions, I don't want them included when giving out the documentation for the API. I want Doxygen to ignore these functions. I can think of two solutions for this, but I am not able to implement either one of them. First is, I can set some configuration in Doxygen to make it ignore specific function name patterns. I went through Doxygen help documentation and searched the web. There seems to be options to ignore file and folder name patterns. But I am not able to find an option to specify a function name pattern and make it ignore those functions. Second is, along with all the other content in the comments above functions, I could add some other keyword or something and make Doxygen ignore those functions. I haven't been able to find out how to do that either. How can I make Doxygen ignore specific PHP functions when generating documentation? Update I searched within Stack Overflow and came across this question. It looked similar to my question. I found out about EXCLUDE_SYMBOLS config option in one of the answers. You can use that to exclude function names too. More importantly, wildcards were supported. So I am able to ignore all my functions with _ as the prefix :) This ridiculous! I should've done more research :| Someone please delete this question or add this answer as an answer.

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• struts2 trim all string obtained from forms

  - by aelkin

  Hi All, I develop web application using struts2. I want to improve getting string from forms. For this need trim all string and if obtained string is empty then set null to field. For this, I created StringConverter. public class StringConverter extends StrutsTypeConverter { @Override public Object convertFromString(Map context, String[] strings, Class toClass) { if (strings == null || strings.length == 0) { return null; } String result = strings[0]; if (result == null) { return null; } result = result.trim(); if (result.isEmpty()) { return null; } return result; } @Override public String convertToString(Map context, Object object) { if (object != null && object instanceof String) { return object.toString(); } return null; } } Next, I added row to xwork-conversion.properties java.lang.String=com.mypackage.StringConverter Thats all. But I did not get the desired result. convertToString() method is called when jsp build form, but convertFromString() doesn't invoke. What I do wrong? How can I get the same behaviour using another way? Please, not offer solutions such as: remove the value of such form elements using javascript. create util method which will make it using reflection. Then call it for each form bean. Thanks in advance, Alexey.

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• WIKI replacement solution for SharePoint?

  - by Jakub

  I'm trying to research a replacement for the pathetic WIKI that comes with WSS (only wiki code it has is to create url links). I have looked at a few but most 'replacements' I see are MOSS only? (or so it just states MOSS for requirements). Has anyone faced this situation? What did you end up using? I would like something that I can have all in one location (not different apps, hence WSS). With LDAP / AD Integration like WSS. Thanks appreciate any input. I would like to see ~ $3k solutions tho (nothing super expensive, hence why we don't run MOSS). EDIT: Anyone else have any suggestions? EDIT2: Actually since I haven't had much feedback (thanks to those that have). I installed mediawiki under IIS with PHP enabled, and enabled the IIS AD hack for authentication. IIS ends up prompting for authentication (user/pass) if you use a non IE browser, then it sets the $_SERVER["REMOTE_USER"] variable, and grabs some AD info (groups etc). Works rather well, only issues is the UGLY urls so far. But its fully working. Seems like a good setup. Other than having to rely on MYSQL (my company strives to be mainly SQL Server)

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• How to stay DRY when using both Javascript and ERB templates (Rails)

  - by user94154

  I'm building a Rails app that uses Pusher to use web sockets to push updates to directly to the client. In javascript: channel.bind('tweet-create', function(tweet){ //when a tweet is created, execute the following code: $('#timeline').append("<div class='tweet'><div class='tweeter'>"+tweet.username+"</div>"+tweet.status+"</div>"); }); This is nasty mixing of code and presentation. So the natural solution would be to use a javascript template. Perhaps eco or mustache: //store this somewhere convenient, perhaps in the view folder: tweet_view = "<div class='tweet'><div class='tweeter'>{{tweet.username}}</div>{{tweet.status}}</div>" channel.bind('tweet-create', function(tweet){ //when a tweet is created, execute the following code: $('#timeline').append(Mustache.to_html(tweet_view, tweet)); //much cleaner }); This is good and all, except, I'm repeating myself. The mustache template is 99% identical to the ERB templates I already have written to render HTML from the server. The intended output/purpose of the mustache and ERB templates are 100% the same: to turn a tweet object into tweet html. What is the best way to eliminate this repetition? UPDATE: Even though I answered my own question, I really want to see other ideas/solutions from other people--hence the bounty!

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• Problem with EDM in ASP.NET MVC

  - by Mannsi

  Hello, I have a question that is pretty similar to this question: http://stackoverflow.com/questions/899734/strongly-typed-asp-net-mvc-with-entity-framework but the solutions for that question don't work for me. Let me start by saying that I don't know a great deal about the subject I am asking about. I have the following code [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(PaymentInformation paymentInformationToEdit, int pensionFundID) { var originalPaymentInformation = (from PIs in _db.PaymentInformation where PIs.employeeNumber == paymentInformation.employeeNumber select PIs).First(); var laborUnion = (from LUs in _db.LaborUnion where LUs.laborUnionID = laborUnionID select LUs)First(); paymentInformationToEdit.laborUnion = laborUnion; _db.ApplyProperyChanges(originalPaymentInformation.EntityKey.EntitySetName, paymentInformationToEdit); _db.SaveChanges(); } I get an error when I try for the ApplyProperyChanges saying 'The existing object in the ObjectContext is in the Added state. Changes can only be applied when the existing object is in an unchanged or modified state'. I don't know how to change the state to either, or even if I am doing something fundamentally wrong. Please advice. EDIT: I hope this is the way to go here on stackoverflow. I haven't gotten an answer that solved my problem but Gregoire below posted a possible solution that I didn't understand. I hope this edit bumps my question so somebody will see it and help me. Sorry if this is not the way to go.

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• Design pattern to use instead of multiple inheritance

  - by mizipzor

  Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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• How to minimize total cost of shortest path tree

  - by Michael

  I have a directed acyclic graph with positive edge-weights. It has a single source and a set of targets (vertices furthest from the source). I find the shortest paths from the source to each target. Some of these paths overlap. What I want is a shortest path tree which minimizes the total sum of weights over all edges. For example, consider two of the targets. Given all edge weights equal, if they share a single shortest path for most of their length, then that is preferable to two mostly non-overlapping shortest paths (fewer edges in the tree equals lower overall cost). Another example: two paths are non-overlapping for a small part of their length, with high cost for the non-overlapping paths, but low cost for the long shared path (low combined cost). On the other hand, two paths are non-overlapping for most of their length, with low costs for the non-overlapping paths, but high cost for the short shared path (also, low combined cost). There are many combinations. I want to find solutions with the lowest overall cost, given all the shortest paths from source to target. Does this ring any bells with anyone? Can anyone point me to relevant algorithms or analogous applications? Cheers!

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• Get directory path by fd

  - by tylerl

  I've run into the need to be able refer to a directory by path given its file descriptor in Linux. The path doesn't have to be canonical, it just has to be functional so that I can pass it to other functions. So, taking the same parameters as passed to a function like fstatat(), I need to be able to call a function like getxattr() which doesn't have a f-XYZ-at() variant. So far I've come up with these solutions; though none are particularly elegant. The simplest solution is to avoid the problem by calling openat() and then using a function like fgetxattr(). This works, but not in every situation. So another method is needed to fill the gaps. The next solution involves looking up the information in proc: if (!access("/proc/self/fd",X_OK)) { sprintf(path,"/proc/self/fd/%i/",fd); } This, of course, totally breaks on systems without proc, including some chroot environments. The last option, a more portable but potentially-race-condition-prone solution, looks like this: DIR* save = opendir("."); fchdir(fd); getcwd(path,PATH_MAX); fchdir(dirfd(save)); closedir(save); The obvious problem here is that in a multithreaded app, changing the working directory around could have side effects. However, the fact that it works is compelling: if I can get the path of a directory by calling fchdir() followed by getcwd(), why shouldn't I be able to just get the information directly: fgetcwd() or something. Clearly the kernel is tracking the necessary information. So how do I get to it?

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• Open source gravatar-like implementations?

  - by Tauren

  I'm already using gravatar icons for the users of my web service. However, I'm finding several problems with this approach: Only a small percentage of the users take the time to set up a gravatar profile. My users are not tech-savvy, but would be likely to add a dedicated photo to my site. Users of my service are encouraged to use images that depict them in proper uniform for the industry my service relates to. They wouldn't want that same picture to be used for personal purposes throughout the internet. They would not take the time or effort to manage a separate email address and gravatar account just to have an "in-uniform" profile photo for my service. Before I implement my own profile image feature, I was wondering if there are any open-source solutions that I could leverage with similar features to gravatar. Specifically: The ability to display any size thumbnail (up to 512px would be fine) Takes care of caching different sized thumbnails Has support for something like identicons, preferably pluggable with different style algorithms (monsters, etc.), even better if I can customize these Ability to fall-back to gravatar if no photo found Does anything like this exist? I haven't found it yet if it does.

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• Vertically center a fluid image in a fluid container

  - by Ferdy

  I certainly do not want to add to the pile of vertical alignments CSS questions, but I've spent hours trying to find a solution to no avail yet. Here's the situation: I am building a slideshow gallery of images. I want the images to be displayed as large as the user's window allows. So I have this outer placeholder: <section class="photo full"> (Yes, I'm using HTML5 elements). Which has the following CSS: section.photo.full { display:inline-block; width:100%; height:100%; position:absolute; overflow:hidden; text-align:center; } Next, the image is placed inside it. Depending on the orientation of the image, I set either the width or height to 75%, and the other axis to auto: $wide = $bigimage['width'] >= $bigimage['height'] ? true: false; ?> <img src="<?= $bigimage['url'] ?>" width="<?= $wide? "75%" : "auto"?>" height="<?= $wide? "auto" : "75%"?>"/> So, we have a fluid outer container, with inside a fluid image. The horizontal centering of the image works, yet I cannot seem to find a way to vertically center the image within it's container. I have researched centering methods but most assume either the container or image has a known width or height. Then there is the display:table-cell method, which does not seem to work for me either. I'm stuck. I'm looking for a CSS solution, but am open to js solutions too.

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• What are the reasons to store documents into DBMS when using Alfresco DMS

  - by Julia

  Hello guys! I have interview for an internship with company that wants to implement document management system and they are considering on the first place open source solutions, their top choice being Alfresco, but decision is still not final, part of my work there would be to investigate is Alfresco the best solution. What I have seen from project description, is that they would implement Alfresco with MySQL database, and not to use DBMS just for document metadata and indexing, but they actually want to store documents inside. By company profile, type of documents would be mostly PDF and .doc, not images. I have researched a bit, and I have read all the topics here related to storing files into the database, not to duplicate a question. So from what I understand, storing BLOBS is generally not recomendable, and by the profile of the company and their legal obligations with archiving, I see they will have to store larger amount of docs. I would like to be ready as much as I can for the interview and that is why I would like your opinion on these questions: 1) What will be your reasons for deciding to store documents into the DBMS, (especially having in mind that you are installing Alfresco, which stores files in the FS)??? 2) Do you have any experiences with storing documents into the MySQL database specifically??? All the help is very much appreciated, I am really excited about interview and really want this internship, so this is one of things i really want to understand before!! Thank you!!!!

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• How to make a product catalog in C#?

  - by Ervin

  I need to develop a product catalog (about 4000 products) application, which would be given to clients on CD or DVD. The catalog exists in webpage format using PHP and MySQL. IMPORTANT: the application is given to clients who maight have old PC, old System. For minimal requirements I would put Windows XP and Internet Explorer 6 (if needed). I need the following features: 1 search option (after productID AND after keyword) 2 print option (by selecting multiple products) 3 shopping cart (making a list which will be sent to an email address if there is any Internet Connection on the computer) When I was asked to do it I had 2 days to realise a very basic version, so I took the whole website and exported it in HTML pages, and developed an application in C# which contains an embeded browser. So the whole website is now static and put on a CD. Everything fine so far. Now here are the problems: 1. the search option was realized by parsing the html files and reading the productID or looking for keywords inside of them. Put on a CD it was extremely slow (searching in 600MB of html files). FOR THIS I WOULD NEED A SOLUTION WITH A STATIC DATABASE (USING ACCESS OR SOMETHING) TO HAVE INDEXED ROWS, SO THE SEARCH COULD BE A VERY FAST ONE. 2. the printing option was a simply call of the embeded Internet Explorer print functions. Here are two problems: a) user needs IE7 for printing the website scaled (FIT TO PAGE), otherwise the edges of the page are cut down. b) users of this app does not have even the basic PC usage skills, so they can't set the printing settings, so there will appear in header and footer the page numbers and titles. QUESTION: can I set these settings from CSS for printing? 3. couldn't make a a shopping cart as I don't use a database, so I have static websites and content is inside the HTML. QUESTION: WHICH ARE THE BEST SOLUTIONS FOR THE PROBLEMS DESCRIBED ABOVE? PLEASE ANSWER EVEN IF YOUR ANSWER IS FOR ONE QUESTION ONLY. THANKS

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• what webserver / mod / technique should I use to serve everything from memory?

  - by reinier

  I've lots of lookuptables from which I'll generate my webresponse. I think IIS with Asp.net enables me to keep static lookuptables in memory which I can use to serve up my responses very fast. Are there however also non .net solutions which can do the same? I've looked at fastcgi, but I think this starts X processes, of which anyone can handle Y requests. But the processes are by definition shielded from eachother. I could configure fastcgi to use just 1 process, but does this have scalability implications? anything using PHP or any other interpreted language won't fly because it is also cgi or fastcgi bound right? I understand memcache could be an option, though this would require another (local) socket connection which I'd rather avoid since everything in memory would be much faster. The solution can work under WIndows or Unix... it doesn't matter too much. The only thing which matters is that there will be a lot of requests (100/sec now and growing to 500/sec in a year), and I want to reduce the amount of webservers needed to process it. The current solution is done using PHP and memcache (and the occasional hit to the SQL server backend). Although it is fast (for php anyway), Apache has real problems when the 50/sec is passed. I've put a bounty on this question since I've not seen enough responses to make a wise choice. At the moment I'm considering either Asp.net or fastcgi with C(++).

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• Autocomplete and IE7 - slowness, sluggishness as overall pagesize grows?

  - by wchrisjohnson

  Hi, I have the autocomplete plugin (http://bassistance.de/jquery-plugins/jquery-plugin-autocomplete/, version 1.1 and 1.0.2) on a project to add pieces of "equipment" to a "project". On a fresh project the plugin works great; the data returned from the database comes back FAST, you can scroll the list fast, and can select an item and move on to the next one. Once I have a project established with equipment on it, and I go to add equipment, the performance is pretty bad. It takes 4-5 seconds to get the list of data back from the server, scrolling the list is painful, and the cursor takes several seconds to settle on an item. Repainting the page after the list goes away is slow. This is occurring in IE7, latest version. FF3 and Chrome are fine, very snappy. The pagesize is about 40K overall. I'm thinking this is an issue with the IE7 Javascript engine, or an edge case with this plugin and IE7; it works quickly enough in FF3+. I would appreciate any ideas, solutions, known issues, or thoughts on how to more specifically pin this down. I'd love to post sample code, but this is a corporate app, and I'm not how useful it would be given that the server side piece cannot be shown; ie: you can't pull it down and test it like a self contained piece of code.. Thanks in advance! Chris

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• Date difference in Javascript (ignoring time of day)

  - by Alan

  I'm writing an equipment rental application where clients are charged a fee for renting equipment based on the duration (in days) of the rental. So, basically, (daily fee * number of days) = total charge. For instant feedback on the client side, I'm trying to use Javascript to figure out the difference in two calendar dates. I've searched around, but nothing I've found is quite what I'm looking for. Most solutions I've seen are of the form: function dateDiff1(startDate, endDate) { return ((endDate.getTime() - startDate.getTime()) / 1000*60*60*24); } My problem is that equipment can be checked out and returned at any time of day during those two dates with no additional charge. The above code is calculating the number of 24 hour periods between the two dates, when I'm really interested in the number of calendar days. For example, if someone checked out equipment at 6am on July 6th and returned it at 10pm on July 7th, the above code would calculate that more than one 24 hour period had passed, and would return 2. The desired result is 1, since only one calendar date has elapsed (i.e. the 6th to the 7th). The closest solution I've found is this function: function dateDiff2(startDate, endDate) { return endDate.getDate() - startDate.getDate(); } which does exactly what I want, as long as the two dates are within the same month. However, since getDate() only returns the day of month (i.e. 1-31), it doesn't work when the dates span multiple months (e.g. July 31 to August 1 is 1 day, but the above calcuates 1 - 31, or -29). On the backend, in PHP, I'm using gregoriantojd(), which seems to work just fine (see this post for an example). I just can't find an equivalent solution in Javascript. Anyone have any ideas?

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• InvalidArgument=Value of '3' is not valid for 'rowIndex'

  - by Devendra Dwivedi

  Hi all This is my code It is working for if 1 terminal that is having 3 services but it is not working for more than 3 services when I do then I have got following error message: InvalidArgument=Value of '3' is not valid for 'rowIndex' I have so tired to find this problem but couldn't get any solutions. Anybody please help me. MySqlCommand command = new MySqlCommand("VTerminalsLoad");//Procedure MySqlDataAdapter terminalAdapter = this.Database.ExecuteCommand(command); terminalAdapter.Fill(dataSet, "Terminals"); command = new MySqlCommand("VTServicesLoad");//Procedure command.Parameters.Add(new MySqlParameter("pVesselID", 1)); MySqlDataAdapter serviceAdapter = this.Database.ExecuteCommand(command);//Return Adaptor serviceAdapter.Fill(dataSet, "Services"); DataColumn[] parentColumns = { dataSet.Tables[0].Columns["SerialNo"], dataSet.Tables[0].Columns["VesselID"], dataSet.Tables[0].Columns["TerminalID"] }; DataColumn[] childColumns = { dataSet.Tables[1].Columns["SerialNo"], dataSet.Tables[1].Columns["VesselID"], dataSet.Tables[1].Columns["TerminalID"] }; DataRelation relationTS = new DataRelation("TerminalsServices", parentColumns, childColumns); dataSet.Relations.Add(relationTS); //Parent Table ListTerminal.DataSource = dataSet; //ListTerminal Parent datagridview ListTerminal.DataMember = "Terminals"; //Child Table ListServices.DataSource = dataSet;// ListServices Child datagridview ListServices.DataMember = "Terminals.TerminalsServices";

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• Merging k sorted linked lists - analysis

  - by Kotti

  Hi! I am thinking about different solutions for one problem. Assume we have K sorted linked lists and we are merging them into one. All these lists together have N elements. The well known solution is to use priority queue and pop / push first elements from every lists and I can understand why it takes O(N log K) time. But let's take a look at another approach. Suppose we have some MERGE_LISTS(LIST1, LIST2) procedure, that merges two sorted lists and it would take O(T1 + T2) time, where T1 and T2 stand for LIST1 and LIST2 sizes. What we do now generally means pairing these lists and merging them pair-by-pair (if the number is odd, last list, for example, could be ignored at first steps). This generally means we have to make the following "tree" of merge operations: N1, N2, N3... stand for LIST1, LIST2, LIST3 sizes O(N1 + N2) + O(N3 + N4) + O(N5 + N6) + ... O(N1 + N2 + N3 + N4) + O(N5 + N6 + N7 + N8) + ... O(N1 + N2 + N3 + N4 + .... + NK) It looks obvious that there will be log(K) of these rows, each of them implementing O(N) operations, so time for MERGE(LIST1, LIST2, ... , LISTK) operation would actually equal O(N log K). My friend told me (two days ago) it would take O(K N) time. So, the question is - did I f%ck up somewhere or is he actually wrong about this? And if I am right, why doesn't this 'divide&conquer' approach can't be used instead of priority queue approach?

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• remove specific values from multi value dictionary

  - by Anthony

  I've seen posts here on how to make a dictionary that has multiple values per key, like one of the solutions presented in this link: Multi Value Dictionary it seems that I have to use a List< as the value for the keys, so that a key can store multiple values. the solution in the link is fine if you want to add values. But my problem now is how to remove specific values from a single key. I have this code for adding values to a dictionary: private Dictionary<TKey, List<TValue>> mEventDict; // this is for initializing the dictionary public void Subscribe(eVtEvtId inEvent, VtEvtDelegate inCallbackMethod) { if (mEventDict.ContainsKey(inEvent)) { mEventDict[inEvent].Add(inCallbackMethod); } else { mEventDict.Add(inEvent, new List<TValue>() { v }); } } // this is for adding values to the dictionary. // if the "key" (inEvent) is not yet present in the dictionary, // the key will be added first before the value my problem now is removing a specific value from a key. I have this code: public void Unsubscribe(eVtEvtId inEvent, VtEvtDelegate inCallbackMethod) { try { mEventDict[inEvent].Remove(inCallbackMethod); } catch (ArgumentNullException) { MessageBox.Show("The event is not yet present in the dictionary"); } } basically, what I did is just replace the Add() with Remove() . Will this work? Also, if you have any problems or questions with the code (initialization, etc.), feel free to ask. Thanks for the advice.

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• Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

  - by aklin81

  I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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• How to trace the connection pool in a Java Web application - DBMS_APPLICATION_INFO

  - by Cleiton Garcia

  Hello, I need improve the traceability in a Web Application that usually run on fixed db user. The DBA should have a fast access for the information about the heavy users that are degrading the database. 5 years ago, I implemented a .NET ORM engine which makes a log of user and the server using the DBMS_APPLICATION_INFO package. Using a wrapper above the connection manager with the following code: DBMS_APPLICATION_INFO.SET_MODULE('" + User + " - " + appServerMachine + "',''); Each time that a connection get a connection from the pool, the package is executed to log the information in the V$SESSION. Has anyone discover or implemented a solution for this problem using the Toplink or Hibernate? Is there a default implementation for this problem? I found here a solutions as I implemented 5 years ago, but I'd like to know with anyone have a better solution and integrated with the ORM. http://stackoverflow.com/questions/53379/using-dbmsapplicationinfo-with-jboss My application is above Spring, the DAO are implemented with JPA (using hibernate) and actually running directly in Tomcat, with plans to (next year) migrate to SAP Netwevare Application Server. Thanks.

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