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• Avoiding mass propagation of properties and events for exposure to ViewModels.

  - by firoso

  I have an MVVM application I am developing that is to the point where I'm ready to start putting together a user interface (my client code is largely functional) I'm now running into the issue that I'm trying to get my application data to where I need it so that it can be consumed by the view model and then bound to the view. Unfortunately, it seems that I've either got a few structural oversights, or I'm just going to have to face the reality that I need to be propogating events and raising excessive amounts of errors to notify view models that thier properties have changed. Let me go into some examples of my issue: I have a class "Unit" contained in a class "Test", contained in a class "Session" contained in a class "TestManager" which is contained in "TestDataModel" which is utilized by "TestViewModel" which is databound to by my "TestView" .... WHOA. Now, consider that Unit (the bottom of the heiarchy) has a property called "Results" that is updated periodically, I want to expose that to my viewmodel and then databind it to my view, trouble is, the only way I can really think to do this is to perpetuate events WAY up a chain that say "I've been updated!" and then request the new value... This seems like an aweful way to do this. Alternatively, I could register a static event and raise it, and have the appropriate "Unit view model" grab the event and request the update. This SEEMS better... but... static events? Is that a taboo idea? Also, having an expression like: TestDataModel.TestManager.Session.Test.Unit.Results[i] Seems REALLY gross to have on a View Model. I know this all reeks of a bad design issue, but I can't figure out what I did wrong? Should I be using more singleton/container controlled lifetimes type objects? Register object instances with static helper containers? Obviously these are hard questions to answer without being intimate with the existing structure, but if you've run into situations like this, what did you do to refactor? Should I just live with this, add mass events, and propogate them?

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• Shrinking the transaction log of a mirrored SQL Server 2005 database

  - by Peter Di Cecco

  I've been looking all over the internet and I can't find an acceptable solution to my problem, I'm wondering if there even is a solution without a compromise... I'm not a DBA, but I'm a one man team working on a huge web site with no extra funding for extra bodies, so I'm doing the best I can. Our backup plan sucks, and I'm having a really hard time improving it. Currently, there are two servers running SQL Server 2005. I have a mirrored database (no witness) that seems to be working well. I do a full backup at noon and at midnight. These get backed up to tape by our service provider nightly, and I burn the backup files to dvd weekly to keep old records on hand. Eventually I'd like to switch to log shipping, since mirroring seems kinda pointless without a witness server. The issue is that the transaction log is growing non-stop. From the research I've done, it seems that I can't truncate a log file of a mirrored database. So how do I stop the file from growing!? Based on this web page, I tried this: USE dbname GO CHECKPOINT GO BACKUP LOG dbname TO DISK='NULL' WITH NOFORMAT, INIT, NAME = N'dbnameLog Backup', SKIP, NOREWIND, NOUNLOAD GO DBCC SHRINKFILE('dbname_Log', 2048) GO But that didn't work. Everything else I've found says I need to disable the mirror before running the backup log command in order for it to work. My Question (TL;DR) How can I shrink my transaction log file without disabling the mirror?

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• How to partition bits in a bit array with less than linear time

  - by SiLent SoNG

  This is an interview question I faced recently. Given an array of 1 and 0, find a way to partition the bits in place so that 0's are grouped together, and 1's are grouped together. It does not matter whether 1's are ahead of 0's or 0's are ahead of 1's. An example input is 101010101, and output is either 111110000 or 000011111. Solve the problem in less than linear time. Make the problem simpler. The input is an integer array, with each element either 1 or 0. Output is the same integer array with integers partitioned well. To me, this is an easy question if it can be solved in O(N). My approach is to use two pointers, starting from both ends of the array. Increases and decreases each pointer; if it does not point to the correct integer, swap the two. int * start = array; int * end = array + length - 1; while (start < end) { // Assume 0 always at the end if (*end == 0) { --end; continue; } // Assume 1 always at the beginning if (*start == 1) { ++start; continue; } swap(*start, *end); } However, the interview insists there is a sub-linear solution. This makes me thinking hard but still not get an answer. Can anyone help on this interview question?

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• To OpenID or not to OpenID? Is it worth it?

  - by Eloff

  Does OpenID improve the user experience? Edit Not to detract from the other comments, but I got one really good reply below that outlined 3 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information. Things that definitely need to be gathered in a checkout process: Full name Email (I'm pretty sure I'll have to ask for these myself) Billing address Shipping address Credit card info There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard? /Edit (You may have noticed stackoverflow uses OpenID) It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site. With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever. I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :) OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?

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• How to display a busy message over a wpf screen

  - by dave

  Hey, I have a WPF application based on Prism4. When performing slow operations, I want to show a busy screen. I will have a large number of screens, so I'm trying to build a single solution into the framework rather than adding the busy indicator to each screen. These long running operations run in a background thread. This allows the UI to be updated (good) but does not stop the user from using the UI (bad). What I'd like to do is overlay a control with a spinning dial sort of thing and have that control cover the entire screen (the old HTML trick with DIVs). When the app is busy, the control would display thus block any further interaction as well as showing the spinny thing. To set this up, I thought I could just have my app screen in a canvas along with the spinny thing (with a greater ZIndex) then just make the spinny thing visible as required. This, however, is getting hard. Canvases do not seem well set up for this and I think I might be barking up the wrong tree. I would appreciate any help. Thanks.

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• How would I instruct extconf.rb to use additional g++ optimization flags, and which are advisable?

  - by mohawkjohn

  I'm using Rice to write a C++ extension for a Ruby gem. The extension is in the form of a shared object (.so) file. This requires 'mkmf-rice' instead of 'mkmf', but the two (AFAIK) are pretty similar. By default, the compiler uses the flags -g -O2. Personally, I find this kind of silly, since it's hard to debug with any optimization enabled. I've resorted to editing the Makefile to take out the flags I don't like (e.g., removing -fPIC -shared when I need to debug using main() instead of Ruby's hooks). But I figure there's got to be a better way. I know I can just do $CPPFLAGS += " -DRICE" to add additional flags. But how do I remove things without editing the Makefile directly? A secondary question: what optimizations are safe for shared objects loaded by Ruby? Can I do things like -funroll-loops? What do you all recommend? It's a scientific computing project, so the faster the better. Memory is not much of an issue. Many thanks!

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• Atomic operations on several transactionless external systems

  - by simendsjo

  Say you have an application connecting 3 different external systems. You need to update something in all 3. In case of a failure, you need to roll back the operations. This is not a hard thing to implement, but say operation 3 fails, and when rolling back, the rollback for operation 1 fails! Now the first external system is in an invalid state... I'm thinking a possible solution is to shut down the application and forcing a manual fix of the external system, but then again... It might already have used this information (and perhaps that's why it failed), or we might not have sufficient access. Or it might not even be a good way to rollback the action! Are there some good ways of handling such cases? EDIT: Some application details.. It's a multi user web application. Most of the work is done with scheduled jobs (through Quartz.Net), so most operations is run in it's own thread. Some user actions should trigger jobs that update several systems though. The external systems are somewhat unstable. I Was thinking of changing the application to use the Command and Unit Of Work pattern

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• Java queue and multi-dimention array question? [Beginner level]

  - by javaLearner.java

  First of all, this is my code (just started learning java): Queue<String> qe = new LinkedList<String>(); qe.add("b"); qe.add("a"); qe.add("c"); qe.add("d"); qe.add("e"); My question: Is it possible to add element to the queue with two values, like: qe.add("a","1"); // where 1 is integer So, that I know element "a" have value 1. If I want to add a number let say "2" to element a, I will have like a = 3. If this cant be done, what else in java classes that can handle this? I tried to use multi-dimention array, but its kinda hard to do the queue, like pop, push etc. (Maybe I am wrong) How to call specific element in the queue? Like, call element a, to check its value. [Note] Please don't give me links that ask me to read java docs. I was reading, and I still dont get it. The reason why I ask here is because, I know I can find the answer faster and easier.

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• Any suggestions to improve my PDO connection class?

  - by Scarface

  Hey guys I am pretty new to pdo so I basically just put together a simple connection class using information out of the introductory book I was reading but is this connection efficient? If anyone has any informative suggestions, I would really appreciate it. class PDOConnectionFactory{ public $con = null; // swich database? public $dbType = "mysql"; // connection parameters public $host = "localhost"; public $user = "user"; public $senha = "password"; public $db = "database"; public $persistent = false; // new PDOConnectionFactory( true ) <--- persistent connection // new PDOConnectionFactory() <--- no persistent connection public function PDOConnectionFactory( $persistent=false ){ // it verifies the persistence of the connection if( $persistent != false){ $this->persistent = true; } } public function getConnection(){ try{ $this->con = new PDO($this->dbType.":host=".$this->host.";dbname=".$this->db, $this->user, $this->senha, array( PDO::ATTR_PERSISTENT => $this->persistent ) ); // carried through successfully, it returns connected return $this->con; // in case that an error occurs, it returns the error; }catch ( PDOException $ex ){ echo "We are currently experiencing technical difficulties. We have a bunch of monkies working really hard to fix the problem. Check back soon: ".$ex->getMessage(); } } // close connection public function Close(){ if( $this->con != null ) $this->con = null; } }

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• Handling close-to-impossible collisions on should-be-unique values

  - by balpha

  There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

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• How to link different Servlet together?

  - by Harry Pham

  First of all, I did not use Spring MVC. :) :) Just want to get it out first. Now what I have is different JSP pages that making calls to different Servlets. All the pieces work great individually but I kind of need to link them together. If all of jsp pages make GET request then it would be easy, since I would just pass a type via the web address, and on my servlet side, I would just enumerated through all the parameter, determine which type is it, and delegate to the right servlet. But not all jsp pages make GET request, some make POST request via form. Let see example A.jsp $.getJSON('GenericServlet?type=A', ... GenericServlet.java String type = request.getParameter("type"); if(type.equals("A")){ //Somehow delegate to Servlet A (Not sure how to do that yet :)) } but in B.jsp I would have something like this B.jsp <form action="GenericServlet" method="post"> <table border=0 cellspacing=10 cellpadding=0> <tr> <td>User Name:</td> <td><input type="text" name="username" size=22/></td> </tr> <tr> <td>Password:</td> <td><input type="password" name="password" size=22/></td> </tr> </table> <input type="submit" value="Create User" /> </form> It kind of hard for me to determine in GenericServlet.java that this need to go to servletB

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• Need a better way to execute console commands from python and log the results

  - by Wim Coenen

  I have a python script which needs to execute several command line utilities. The stdout output is sometimes used for further processing. In all cases, I want to log the results and raise an exception if an error is detected. I use the following function to achieve this: def execute(cmd, logsink): logsink.log("executing: %s\n" % cmd) popen_obj = subprocess.Popen(\ cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) (stdout, stderr) = popen_obj.communicate() returncode = popen_obj.returncode if (returncode <> 0): logsink.log(" RETURN CODE: %s\n" % str(returncode)) if (len(stdout.strip()) > 0): logsink.log(" STDOUT:\n%s\n" % stdout) if (len(stderr.strip()) > 0): logsink.log(" STDERR:\n%s\n" % stderr) if (returncode <> 0): raise Exception, "execute failed with error output:\n%s" % stderr return stdout "logsink" can be any python object with a log method. I typically use this to forward the logging data to a specific file, or echo it to the console, or both, or something else... This works pretty good, except for three problems where I need more fine-grained control than the communicate() method provides: stdout and stderr output can be interleaved on the console, but the above function logs them separately. This can complicate the interpretation of the log. How do I log stdout and stderr lines interleaved, in the same order as they were output? The above function will only log the command output once the command has completed. This complicates diagnosis of issues when commands get stuck in an infinite loop or take a very long time for some other reason. How do I get the log in real-time, while the command is still executing? If the logs are large, it can get hard to interpret which command generated which output. Is there a way to prefix each line with something (e.g. the first word of the cmd string followed by :).

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• How to make a calculator in PHP?

  - by Giulio Muscarello

  I want to use PHP to calculate simple algebraic expressions like, 8*(5+1), entered via an <input> tag by a normal user (which means, normal notation: no syntax changes like Multiply(8, Add(5, 1))). Also, it has to show all steps, but that's not hard. The problem, right now, is calculating the value of the expressions. Note: this is what I thought so far, which is quite inefficient but it's a provisory solution. Just replace strings where possible: in our example, recognize the string 5+1 and replace it with 6. Then, loop again, replace (6) with 6, loop again, and replace 8*6 with 48. The code for multiplying, for example, should look like this: for ($a=1; $a < 1000; $a++) { for ($b=1; $b < 1000; $b++) { string_replace($a . '*' . $b, $a*$b, $string); } }

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• Combining two-part SQL query into one query

  - by user332523

  Hello, I have a SQL query that I'm currently solving by doing two queries. I am wondering if there is a way to do it in a single query that makes it more efficient. Consider two tables: Transaction_Entries table and Transactions, each one defined below: Transactions - id - reference_number (varchar) Transaction_Entries - id - account_id - transaction_id (references Transactions table) Notes: There are multiple transaction entries per transaction. Some transactions are related, and will have the same reference_number string. To get all transaction entries for Account X, then I would do SELECT E.*, T.reference_number FROM Transaction_Entries E JOIN Transactions T ON (E.transaction_id=T.id) where E.account_id = X The next part is the hard part. I want to find all related transactions, regardless of the account id. First I make a list of all the unique reference numbers I found in the previous result set. Then for each one, I can query all the transactions that have that reference number. Assume that I hold all the rows from the previous query in PreviousResultSet UniqueReferenceNumbers = GetUniqueReferenceNumbers(PreviousResultSet) // in Java foreach R in UniqueReferenceNumbers // in Java SELECT * FROM Transaction_Entries where transaction_id IN (SELECT * FROM Transactions WHERE reference_number=R Any suggestions how I can put this into a single efficient query?

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• parsing the output of the 'w' command?

  - by Blackbinary

  I'm writing a program which requires knowledge of the current load on the system, and the activity of any users (it's a load balancer). This is a university assignment, and I am required to use the w command. I'm having a hard time parsing this command because it is very verbose. Any suggestions on what I can do would be appreciated. This is a small part of the program, and I am free to use whatever method i like. The most condensed version of w which still has the information I require is `w -u -s -f' which produces this: 10:13:43 up 9:57, 2 users, load average: 0.00, 0.00, 0.00 USER TTY IDLE WHAT fsm tty7 22:44m x-session-manager fsm pts/0 0.00s w -u -s -f So out of that, I am interested in the first number after load average and the smallest idle time (so i will need to parse them all). My background process will call w, so the fact that w is the lowest idle time will not matter (all i will see is the tty time). Do you have any ideas? Thanks (I am allowed to use alternative unix commands, like grep, if that helps).

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• Wrapping text and div as a unit

  - by mathee

  I have the following that I would like wrapped as units. <div class='tag-box'> <a href=#>Axe Committee</a> <div class='circle'><a href=#>x</a></div> </div> The CSS for these classes are: .tag-box { display:inline; } .circle { display:inline; padding-left:4px; padding-right:4px; background:rgb(196,15,24); /*dark red*/ -moz-border-radius:10px; -webkit-border-radius:10px; } .circle a { font-size:10px; text-decoration:none; color:#fff; position:relative; top:-2px; } I can have upwards of 20 or 30 of these tag-boxes displayed inline. The problem is that the wrapping will break the words from each other or even break the red circle from the link. This makes it hard to differentiate which circle belongs to which link. (In the future, each circle corresponds to a different action with respect to the link.) See below. How do I prevent this kind of wrapping from occurring?

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• Am I going the right way to make login system secure with this simple password salting?

  - by LoVeSmItH

  I have two fields in login table password salt And I have this little function to generate salt function random_salt($h_algo="sha512"){ $salt1=uniqid(rand(),TRUE); $salt2=date("YmdHis").microtime(true); if(function_exists('dechex')){ $salt2=dechex($salt2); } $salt3=$_SERVER['REMOTE_ADDR']; $salt=$salt1.$salt2.$salt3; if(function_exists('hash')){ $hash=(in_array($h_algo,hash_algos()))?$h_algo:"sha512"; $randomsalt=hash($hash,md5($salt)); //returns 128 character long hash if sha512 algorithm is used. }else{ $randomsalt=sha1(md5($salt)); //returns 40 characters long hash } return $randomsalt; } Now to create user password I have following $userinput=$_POST["password"] //don't bother about escaping, i have done it in my real project. $static_salt="THIS-3434-95456-IS-RANDOM-27883478274-SALT"; //some static hard to predict secret salt. $salt=random_salt(); //generates 128 character long hash. $password =sha1($salt.$userinput.$static_salt); $salt is saved in salt field of database and $password is saved in password field. My problem, In function random_salt(), I m having this FEELING that I'm just making things complicated while this may not generate secure salt as it should. Can someone throw me a light whether I m going in a right direction? P.S. I do have an idea about crypt functions and like such. Just want to know is my code okay? Thanks.

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• Is there a IDE/compiler PC benchmark I can use to compare my PCs performance?

  - by RickL

  I'm looking for a benchmark (and results on other PCs) which would give me an idea of the development performance gain I could get by upgrading my PC, also the benchmark could be used to justify the upgrade to my boss. I use Visual Studio 2008 for my development, so I'd like to get an idea of by what factor the build times would be improved, and also it would be good if the benchmark could incorporate IDE performance (i.e. when editing, using intellisense, opening code files etc) into its result. I currently have an AMD 3800x2, with 2GB RAM on Vista 32. For example, I'd like to know what kind of performance gain I'd see in Visual Studio 2008 with a Q6600, 4GB RAM on Vista 64. And also with other processors, and other RAM sizes... also see whether hard disk performance is a big factor. EDIT: I mentioned Vista 64 because I'm aware that Vista 32 can only use 3GB RAM maximum. So I'd presume that wanting to use more RAM would require Vista 64, but perhaps it could still be slower overall there is a large overhead in using the 32 bit VS 2008 on 64 bit OS.

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• Rewarding iOS app beta testers with in app purchase?

  - by Partridge

  My iOS app is going to be free, but with additional functionality enabled via in app purchase. Currently beta testers are doing a great job finding bugs and I want to reward them for their hard work. I think the least I can do is give them a full version of the app so that they don't have to buy the functionality themselves. However, I'm not sure what the best way to do this is. There do not appear to be promo codes for in app purchase so I can't just email out promo codes. I have all the tester device UDIDs so when the app launches I could grab the device UDID and compare it to an internal list of 'approved' UDIDs. Is this what other developers do? My concerns: The in app purchase content would not be tied to their iTunes account, so if beta testers move to a new device they would not be able to enable the content unless I released a new build in the app store with their new UDID. So they may have to buy it eventually anyway. Having an internal list leaves a hole for hackers to modify the list and add themselves to it. What would you do?

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• How to manage a single-selection (exclusive) list?

  - by Andy

  I've got a detail view that consists of a table view with a few rows of data. I can fill the rows just fine, and moving back and forth from the parent view to the subview works too. This detail view should allow the user to select a single value, placing a checkmark accessory in the cell and then returning to the parent view (where the selected value becomes the cell.textLabel.text property of the cell from which the detail view was called). This all works as of right now. However, when the user taps the cell in the parent view to go back to the detail view (to change their selection), my checkmark has disappeared and I cannot for the life of me figure out how to make it stay. Here's my cellForRowAtIndexPath: method: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; } NSString *labelText = [[phones objectAtIndex:indexPath.row] valueForKey:@"phoneNumberLabel"]; cell.textLabel.text = labelText; NSString *currentLabel = [ruleBuilder.tableView cellForRowAtIndexPath:selectedIndexPath].textLabel.text; if (labelText == currentLabel) { cell.accessoryType = UITableViewCellAccessoryCheckmark; } NSString *detailText = [[phones objectAtIndex:indexPath.row] valueForKey:@"phoneNumber"]; cell.detailTextLabel.text = detailText; return cell; } I've checked out Apple's sample code for exclusive-list management in Table View Programming Guide, but the snippet seems incomplete, and I can't find the related code in Apple's sample code. This doesn't seem like it ought to be that hard to do.

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• Will a Ph. D. in Computer Science help?

  - by Francisco Garcia

  I am close to my 30s and still learning about programming and software engineering. Like most people who like their profession I truly believe that I should aim to improve and keep updated. One of the things I do is reading technical papers from professional publications (IEEE and ACM) but I admit there are very good bloggers out there too. Lately I started to think (should I say realize?) that Ph. D people actually are expected to expand constantly their knowledge, but little is expected from lower classes once they know enough This made me think that maybe having a Ph. D will help to have more... respect? but I also believe that I am already getting old for that. Futhermore I see many master and doctor programs that does not seem to add any value over hard experience and self learning. I belive that a degree in computer science, althought not necessary, can lay out a good base for programming work. However: What can a Ph. D. degree give you that you cannot learn on your own? (if you are not into something VERY specific and want to work in a non academic environment)

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• C# Retrieving Data From XML File

  - by Christopher MacKinnon

  I seem to be having a problem with retrieving XML values with C#, which I know it is due to my very limited knowledge of C# and .XML. I was given the following XML file <PowerBuilderRunTimes> <PowerBuilderRunTime> <Version>12</Version> <Files> <File>EasySoap110.dll</File> <File>exPat110.dll</File> <File>pbacc110.dll</File> </File> </PowerBuilderRunTime> </PowerBuilderRunTimes> I am to process the XML file and make sure that each of the files in the exist in the folder (that's the easy part). It's the processing of the XML file that I have having a hard time with. Here is what I have done thus far: var runtimeXml = File.ReadAllText(string.Format("{0}\\{1}", configPath, Resource.PBRuntimes)); var doc = XDocument.Parse(runtimeXml); var topElement = doc.Element("PowerBuilderRunTimes"); var elements = topElement.Elements("PowerBuilderRunTime"); foreach (XElement section in elements) { //pbVersion is grabbed earlier. It is the version of PowerBuilder if( section.Element("Version").Value.Equals(string.Format("{0}", pbVersion ) ) ) { var files = section.Elements("Files"); var fileList = new List<string>(); foreach (XElement area in files) { fileList.Add(area.Element("File").Value); } } } My issue is that the String List is only ever populated with one value, "EasySoap110.dll", and everything else is ignored. Can someone please help me, as I am at a loss.

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• Big-O for calculating all routes from GPS data

  - by HH

  A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is the amount of neighbour vertices. Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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• How do you use stl's functions like for_each?

  - by thomas-gies

  I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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