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• Code Golf: Evaluating Mathematical Expressions

  - by Noldorin

  Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, +, -, *, /, (, ). Expressions use (normal) infix notation. Operators should be evaluated in the order they appear, i.e. not as in BODMAS, though brackets should be correctly observed, of course. The function should return the correct result for any possible expression of this form. However, the function does not have to handle malformed expressions (i.e. ones with bad syntax). Examples of expressions: 1 + 3 / -8 = -0.5 (No BODMAS) 2*3*4*5+99 = 219 4 * (9 - 4) / (2 * 6 - 2) + 8 = 10 1 + ((123 * 3 - 69) / 100) = 4 2.45/8.5*9.27+(5*0.0023) = 2.68... Rules I anticipate some form of "cheating"/craftiness here, so please let me forewarn against it! By cheating, I refer to the use of the eval or equivalent function in dynamic languages such as JavaScript or PHP, or equally compiling and executing code on the fly. (I think my specification of "no BODMAS" has pretty much guaranteed this however.) Apart from that, there are no restrictions. I anticipate a few Regex solutions here, but it would be nice to see more than just that. Now, I'm mainly interested in a C#/.NET solution here, but any other language would be perfectly acceptable too (in particular, F# and Python for the functional/mixed approaches). I haven't yet decided whether I'm going to accept the shortest or most ingenious solution (at least for the language) as the answer, but I would welcome any form of solution in any language, except what I've just prohibited above! My Solution I've now posted my C# solution here (403 chars). Update: My new solution has beaten the old one significantly at 294 chars, with the help of a bit of lovely regex! I suspected that this will get easily beaten by some of the languages out there with lighter syntax (particularly the funcional/dynamic ones), and have been proved right, but I'd be curious if someone could beat this in C# still. Update I've seen some very crafty solutions already. Thanks to everyone who has posted one. Although I haven't tested any of them yet, I'm going to trust people and assume they at least work with all of the given examples. Just for the note, re-entrancy (i.e. thread-safety) is not a requirement for the function, though it is a bonus. Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear/semi-obfuscated function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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• Personal Project - Next practical language/tech to learn

  - by Paul Nathan

  I'm working on a personal project doing some finance analysis. It's a totally new field for me, and I'm really having fun with it so far, plus working in the high-level language arena is a great break from my embedded systems daytime work. I have a MySQL backend on a non-local server with a pile of stock data. My task now is to do some analysis of the stocks and produce something approximating a useful result. There are a couple technical difficulties. (1) I have a lot of records. To be precise, I believe I'm near 100K records right now, and this number grows by 6.1K each weekday. I need to create a way to rummage through these fields and do data analysis - based on a given computation, go look at this other set. Fine and dandy, nothing too outre. But this means I could really use a straightforward API for talking to MySQL. (2) Ideally, it runs on OS X 10.4.11. No Windows/Linux machine at home. (3) I can use PHP, C++, Perl, etc. I even have an R installation. I'm pretty flexible with stuff, so long as it runs on OS X. (Lots of options here, pick water, H20, or dihydrogen monoxide ;-) ) (4)Lack of hassle. While I like clever and fun ways of doing things, I'm trying to get some analysis done, not spend ten hours doing installation work and scratching my head figuring out a theoretical syntax question needed to spout out "hello world". What's the question? I'd like to dig into something different than my usual PHP/C++/C toolset. I'm looking for recommendations for languages/technologies that will assist me and meet the above requirements. In particular, I've heard a lot of buzz about F# and Python on SO. I've used CLISP for small problems before, and kinda liked it. I'm seeking opinions about those in particular. edit:since I rent the DB server and have a limited amount of CPU time online, I'm trying to do the analysis on a local machine.

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• "Wrapping" a BindingList<T> propertry with a List<T> property for serialization.

  - by Eric

  I'm writing an app that allows users search and browse catalogs of widgets. My WidgetCatalog class is serialized and deserialized to and from XML files using DataContractSerializer. My app is working now but I think I can make the code a lot more efficient if I started taking advantage of data binding rather then doing everything manually. Here's a stripped down version of my current WidgetCatalog class. [DataContract(Name = "WidgetCatalog")] class WidgetCatalog { [DataContract(Name = "Name")] public string Name { get; set; } [DataContract(Name = "Widgets")] public List<Widget> Widgets { get; set; } } I had to write a lot of extra code to keep my UI in sync when widgets are added or removed from a catalog, or their internal properties change. I'm pretty inexperienced with data-binding, but I think I want a BindingList<Widget> rather than a plain old List<Widget>. Is this right? In the past when I had similar needs I found that BindingList<T> does not serialize very well. Or at least the Event Handers between the items and the list are not serialized. I was using XmlSerializer though, and DataContractSerializer may work better. So I'm thinking of doing something like the code below. [DataContract(Name = "WidgetCatalog")] class WidgetCatalog { [DataMember(Name = "Name")] public string Name { get; set; } [DataMember(Name = "Widgets")] private List<Widget> WidgetSerializationList { get { return this._widgetBindingList.ToList<Widget>(); } set { this._widgetBindingList = new BindingList<Widget>(value); } } //these do not get serialized private BindingList<Widget> _widgetBindingList; public BindingList<Widget> WidgetBindingList { get { return this._widgetBindingList; } } public WidgetCatalog() { this.WidgetSerializationList = new List<Widget>(); } } So I'm serializing a private List<Widget> property, but the GET and SET accessors of the property are reading from, and writing to theBindingList<Widget> property. Will this even work? It seems like there should be a better way to do this.

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• Would Ruby on Rails be appropriate for this Foreign Language project?

  - by Lynne Overesch-Maister

  I'm a Spanish professor & computer groupie. About 15 years ago, I authored in HyperCard a series of verb conjugation programs that are now completely out of date with respect to System OS X. I would like to redo these programs myself because I had a lot of fun doing them last time (mostly I coded while my son played in Leaps and Bounds, you know, one of those places where parents take their kids & let them run wild through the tubes...). Colleagues have mentioned using Flash, Director, and various other solutions, but I saw a presentation on RoR at our SIDLIT conference today, and was inspired. I will be parsing and comparing strings (and there are other features on top of that, but that is the main one), "adding" strings relationally indexed in some kind of database(s). It will also have to handle various foreign characters (accents, upside down question marks, etc.). On top of the main process of the program, it will have to provide a practice vs. test mode, keep track of specific answers as well as totals right/wrong, and print a report. Would this be either easier and/or more efficiently done in RoR than in other languages. I am pretty sure that it will work on a Microsoft server, right? Because I think that is where most of our stuff is. I would be programming either on a Mac or a PC, whichever you think is easier. So, in summary, is RoR the way for me to go with this project? If I have some (little) experience programming in Hypercard and C, should I be able to pick RoR up fairly quickly? What things will I need to start (I already saw something called Redhills foreign key migration plugin, which I assume would be beneficial)? I still have my old scripts from hypercard, however what I would really like to do is to combine all six of my former tense-specific programs into one larger program. I figure that it wouldn't be too hard to reference the individual tenses in some way--could that be a class? Many thanks for any help you can give me on this forum.

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• UITableViewCell with selectable/copyable text that also detects URLs on the iPhone

  - by Jasarien

  Hi guys, I have a problem. Part of my app requires text to be shown in a table. The text needs to be selectable/copyable (but not editable) and any URLs within the text need to be highlighted and and when tapped allow me to take that URL and open my embedded browser. I have seen a couple of solutions that solve one of either of these problems, but not both. Solution 1: Icon Factory's IFTweetLabel The first solution I tried was to use the IFTweetLabel class made possible by Icon Factory and used in Twitterrific. While this solution allows for links (or anything you can find with a regex) to be detected to be handled on a case by case basis, it doesn't allow for selecting and copying. There is also an issue where if a URL is long enough to be wrapped, the button that the class overlays above the URL to make it interactive cannot wrap and draws off screen, looking very odd. Solution 2: Use IFTweetLabel and handle copy manually The second thing I tried was to keep IFTweetLabel in place to handle the links, but to implement the copying using a long-tap gesture, like how the SMS app handles it. This was just about working, but it doesn't allow for arbitrary selection of text, the whole text is copied, or none is copied at all... Pretty black and white. Solution 3: UITextView My third attempt was to add a UITextView as a subview of the table cell. The only thing that this doesn't solve is the fact that detected URLs cannot be handled by me. The text view uses UIApplication's openURL: method which quits my app and launched Safari. Also, as the table view can get quite large, the number of UITextViews added as subviews cause a noticeable performance drag on scrolling throughout the table, especially on iPhone 3G era devices (because of the creation, layout, compositing whenever a cell is scrolled on screen, etc). So my question to all you knowledgeable folk out there is: What can I do? Would a UIWebView be the best option? Aside from a performance drag, I think a webview would solve all the above issues, and if I remember correctly, back in the 2.0 days, the Apple documentation actually recommended web views where text formatting / hyperlinks were required. Can anyone think of a way to achieve this without a performance drag? Many thanks in advance to everyone who can help.

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• Is the design notion of layers contrived?

  - by Bruce

  Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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• LINQ InsertOnSubmit Required Fields needed for debugging

  - by Derek Hunziker

  Hi All, I've been using the ADO.NET Strogly-Typed DataSet model for about 2 years now for handling CRUD and stored procedure executions. This past year I built my first MVC app and I really enjoyed the ease and flexibility of LINQ. Perhaps the biggest selling point for me was that with LINQ I didn't have to create "Insert" stored procedures that would return the SCOPE_IDENTITY anymore (The auto-generated insert statements in the DataSet model were not capable of this without modification). Currently, I'm using LINQ with ASP.NET 3.5 WebForms. My inserts are looking like this: ProductsDataContext dc = new ProductsDataContext(); product p = new product { Title = "New Product", Price = 59.99, Archived = false }; dc.products.InsertOnSubmit(p); dc.SubmitChanges(); int productId = p.Id; So, this product example is pretty basic, right, and in the future, I'll probably be adding more fields to the database such as "InStock", "Quantity", etc... The way I understand it, I will need to add those fields to the database table and then delete and re-add the tables to the LINQ to SQL Class design view in order to refresh the DataContext. Does that sound right? The problem is that any new fields that are non-null are NOT caught by the ASP.NET build processes. For example, if I added a non-null field of "Quantity" to the database, the code above would still build. In the DataSet model, the stored procedure method would accept a certain amount of parameters and would warn me that my Insert would fail if I didn't include a quantity value. The same goes for LINQ stored procedure methods, however, to my knowledge, LINQ doesn't offer a way to auto generate the insert statements and that means I'm back to where I started. The bottom line is if I used insert statements like the one above and I add a non-null field to my database, it would break my app in about 10-20 places and there would be no way for me to detect it. Is my only option to do a solution-side search for the keyword "products.InsertOnSubmit" and make sure the new field is getting assigned? Is there a better way? Thanks!

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• How to pass the 'argument-line' of one PowerShell function to another?

  - by jwfearn

  I'm trying to write some PowerShell functions that do some stuff and then transparently call through to existing built-in function. I want to pass along all the arguments untouched. I don't want to have to know any details of the arguments. I tired using 'splat' to do this with @args but that didn't work as I expected. In the example below, I've written a toy function called myls which supposed to print hello! and then call the same built-in function, Get-ChildItem, that the built-in alias ls calls with the rest of the argument line intact. What I have so far works pretty well: function myls { Write-Output "hello!" Invoke-Expression("Get-ChildItem "+$MyInvocation.UnboundArguments -join " ") } A correct version of myls should be able to handle being called with no arguments, with one argument, with named arguments, from a line containing multiple semi-colon delimited commands, and with variables in the arguments including string variables containing spaces. The tests below compare myls and the builtin ls: [NOTE: output elided and/or compacted to save space] PS> md C:\p\d\x, C:\p\d\y, C:\p\d\"jay z" PS> cd C:\p\d PS> ls # no args PS> myls # pass PS> cd .. PS> ls d # one arg PS> myls d # pass PS> $a="A"; $z="Z"; $y="y"; $jz="jay z" PS> $a; ls d; $z # multiple statements PS> $a; myls d; $z # pass PS> $a; ls d -Exclude x; $z # named args PS> $a; myls d -Exclude x; $z # pass PS> $a; ls d -Exclude $y; $z # variables in arg-line PS> $a; myls d -Exclude $y; $z # pass PS> $a; ls d -Exclude $jz; $z # variables containing spaces in arg-line PS> $a; myls d -Exclude $jz; $z # FAIL! Is there a way I can re-write myls to get the behavior I want?

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• Multiple constructors in C

  - by meepz

  Hello, I am making a string class in C as a homework and I was wondering how I can make multiple constructors with the same name given the parameter. The commented out area is what I tried to do with results from a few searches but that gives me errors. Pretty much I have some cases where I want to create my new string without any parameter then in other cases create a string with a pointer to character. Here is mystring.h #include <stdio.h> #include <stdlib.h> typedef struct mystring { char * c; int length; int (*sLength)(void * s); char (*charAt)(void * s, int i); int (*compareTo)(void * s1, void * s2); struct mystring * (*concat)(void * s1, void * s2); struct mystring * (*subString)(void * s, int begin, int end); void (*printS)(void * s); } string_t; typedef string_t * String; String newString(char * c); String newString2(); int slength(void * s); char charat(void * S, int i); int compareto(void * s1, void * s2); String concat(void * s1, void * s2); String substring(void * S, int begin, int end); void printstring(void * s); And here is mystring.c #include "mystring.h" String newString(){ } String newString(char * input){ //String newString::newString(char * input) { String s; s = (string_t *) malloc(sizeof(string_t)); s->c = (char *) malloc(sizeof(char) * 20); int i = 0; if (input == NULL){ s->c[0] = '\0'; return s; } while (input[i] != '\0') { s->c[i] = input[i]; i++; } //functions s->sLength = slength; s->charAt = charat; s->compareTo = compareto; s->concat = concat; s->subString = substring; s->printS = printstring; return s; }

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• help fixing pagination class

  - by michael

  here is my pagination class. the data in the construct is just an another class that does db queries and other stuff. the problem that i am having is that i cant seem to get the data output to match the pagination printing and i cant seem to get the mysql_fetch_assoc() to query the data and print it out. i get this error: Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in /phpdev/pagination/index.php on line 215 i know that can mean that the query isnt correct for it to fetch the data but i have entered it correctly. sorry for the script being a little long. i thank all in advance for any help. <?php include_once("class.db.php"); mysql_connect("host","login","password"); mysql_select_db("iadcart"); class Pagination { var $adjacents; var $limit; var $param; var $mPage; var $query; var $qData; var $printData; protected $db; function __construct() { $this->db = new MysqlDB; } function show() { $result = $this->db->query($this->query); $totalPages = $this->db->num_rows($result); $limit = $this->limit; /* ------------------------------------- Set Page ------------------------------------- */ if(isset($_GET['page'])) { $page = intval($_GET['page']); $start = ($page - 1) * $limit; } else { $start = 0; } /* ------------------------------------- Set Page Vars ------------------------------------- */ if($page == 0) { $page = 1; } $prev = $page - 1; $next = $page + 1; $lastPage = ceil($totalPages/$limit); $lpm1 = $lastPage - 1; $adjacents = $this->adjacents; $mPage = $this->mPage; //the magic $this->qData = $this->query . " LIMIT $start, $limit"; $this->printData = $this->db->query($this->qData); /* ------------------------------------- Draw Pagination Object ------------------------------------- */ $pagination = ""; if($lastPage > 1) { $pagination .= "<div class='pagination'>"; } /* ------------------------------------- Previous Link ------------------------------------- */ if($page > 1) { $pagination .= "<li><a href='$mPage?page=$prev'> previous </a></li>"; } else { $pagination .= "<li class='previous-off'> previous </li>"; } /* ------------------------------------- Page Numbers (not enough pages - just display active page) ------------------------------------- */ if($lastPage < 7 + ($adjacents * 2)) { for($counter = 1; $counter <= $lastPage; $counter++) { if($counter == $page) { $pagination .= "<li class='active'>$counter</li>"; } else { $pagination .= "<li><a href='$mPage?page=$counter'>$counter</a></li>"; } } } /* ------------------------------------- Page Numbers (enough pages to paginate) ------------------------------------- */ elseif($lastPage > 5 + ($adjacents * 2)) { //close to beginning; only hide later pages if($page < 1 + ($adjacents * 2)) { for ($counter = 1; $counter < 4 + ($adjacents * 2); $counter++) { if ($counter == $page) { $pagination.= "<li class='active'>$counter</li>"; } else { $pagination.= "<li><a href='$mPage?page=$counter'>$counter</a></li>"; } } $pagination.= "..."; $pagination.= "<li><a href='$mPage?page=$lpm1'>$lpm1</a></li>"; $pagination.= "<li><a href='$mPage?page=$lastPage'>$lastPage</a></li>"; } elseif($lastPage - ($adjacents * 2) > $page && $page > ($adjacents * 2)) { $pagination.= "<li><a href='$mPage?page=1'>1</a></li>"; $pagination.= "<li><a href='$mPage?page=2'>2</a></li>"; $pagination.= "..."; for ($counter = $page - $adjacents; $counter <= $page + $adjacents; $counter++) { if ($counter == $page) { $pagination.= "<li class='active'>$counter</li>"; } else { $pagination.= "<li><a href='$mPage?page=$counter'>$counter</a></li>"; } } $pagination.= "..."; $pagination.= "<li><a href='$mPage?page=$lpm1'>$lpm1</a></li>"; $pagination.= "<li><a href='$mPage?page=$lastPage'>$lastPage</a></li>"; } else { $pagination.= "<li><a href='$mPage?page=1'>1</a></li>"; $pagination.= "</li><a href='$mPage?page=2'>2</a></li>"; $pagination.= "..."; for ($counter = $lastPage - (2 + ($adjacents * 2)); $counter <= $lastPage; $counter++) { if ($counter == $page) { $pagination.= "<li class='active'>$counter</li>"; } else { $pagination.= "<li><a href='$mPage?page=$counter'>$counter</a></li>"; } } } } /* ------------------------------------- Next Link ------------------------------------- */ if ($page < $counter - 1) { $pagination.= "<li><a href='$mPage?page=$next'> Next </a></li>"; } else { $pagination.= "<li class='next-off'> Next </li>"; $pagination.= "</div>"; } print $pagination; } } ?> <html> <head> </head> <body> <table style="width:800px;"> <?php mysql_connect("localhost","root","games818"); mysql_select_db("iadcart"); $pagination = new pagination; $pagination->adjacents = 3; $pagination->limit = 10; $pagination->param = $_GET['page']; $pagination->mPage = "index.php"; $pagination->query = "select * from tbl_products where pVisible = 'yes'"; while($row = mysql_fetch_assoc($pagination->printData)) { print $row['pName']; } ?> </table> <br/><br/> <?php $pagination->show(); ?> </body> </html>

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• Trying to send email in Java using gmail always results in username and password not accepted.

  - by Thaeos

  When I call the send method (after setting studentAddress), I get this: javax.mail.AuthenticationFailedException: 535-5.7.1 Username and Password not accepted. Learn more at 535 5.7.1 http://mail.google.com/support/bin/answer.py?answer=14257 y15sm906936wfd.10 I'm pretty sure the code is correct, and 100% positive that the username and password details I'm entering are correct. So is this something wrong with gmail or what? This is my code: import java.util.*; import javax.mail.*; import javax.mail.internet.*; public class SendEmail { private String host = "smtp.gmail.com"; private String emailLogin = "[email protected]"; private String pass = "xxx"; private String studentAddress; private String to; private Properties props = System.getProperties(); public SendEmail() { props.put("mail.smtps.auth", "true"); props.put("mail.smtps.starttls.enable", "true"); props.put("mail.smtp.host", host); props.put("mail.smtp.user", emailLogin); props.put("mail.smtp.password", pass); props.put("mail.smtp.port", "587"); to = "[email protected]"; } public void setStudentAddress(String newAddress) { studentAddress = newAddress; } public void send() { Session session = Session.getDefaultInstance(props, null); MimeMessage message = new MimeMessage(session); try { message.setFrom(new InternetAddress(emailLogin)); InternetAddress[] studentAddressList = {new InternetAddress(studentAddress)}; message.setReplyTo(studentAddressList); message.setRecipient(Message.RecipientType.TO, new InternetAddress(to)); message.setSubject("Test Email"); message.setText("This is a test email!"); Transport transport = session.getTransport("smtps"); transport.connect(host, emailLogin, pass); transport.sendMessage(message, message.getAllRecipients()); transport.close(); } catch (MessagingException me) { System.out.println("There has been an email error!"); me.printStackTrace(); } } } Any ideas...

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• Using OpenID as the only authentication method

  - by iconiK

  I have read the other questions and they mostly talk about the security of doing so. That's not entirely my concern, mostly because the website is question is a browser-based game. However, the larger issue is the user - not every user is literate enough to understand OpenID. Sure RPX makes this pretty easy, which is what I'll use, but what if the user does not have an account at Google or Facebook or whatever, or does not trust the system to log in with an existing account? They'd have to get an account at another provide - I'm sure most will know how to do it, let alone be bothered to do it. There is also the problem of how to manage it in the application. A user might want to use multiple identities with a single account, so it's not as simple as username + password to deal with. How do I store the OpenID identities of a user in the database? Using OpenID gives me a benefit too: RPX can provide extensive profile information, so I can just prefill the profile form and ask the user to edit as required. I currently have this: UserID Email ------ --------------- 86000 [email protected] 86001 [email protected] UserOpenID OpenID ---------- ------ 86000 16733 86001 16839 86002 19361 OpenID Provider Identifier ------ -------- ---------------- 16733 Yahoo https:\\me.yahoo.com\bob#d36bd 16839 Yahoo https:\\me.yahoo.com\bigbobby#x75af 19361 Yahoo https:\\me.yahoo.com\alice#c19fd Is that the right way to store OpenID identifiers in the database? How would I match the identifier RPX gave me with one in the database to log in the user (if the identifier is known). So here are concrete questions: How would I make it accessible to users not having an OpenID or not wanting to use one? (security concerns over say, logging in with their Google account for example) How do I store the identifier in the database? (I'm not sure if the tables above are right) What measures do I need to take in order to prevent someone from logging in as another user and happily doing anything with their account? (as I understand RPX sends the identifier via HTTP, so what anyone would have to do is to just somehow grab it then enter it in the "OpenID" field) What else do I need to be aware of when using OpenID?

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• How to maximize http.sys file upload performance

  - by anelson

  I'm building a tool that transfers very large streaming data sets (possibly on the order of terabytes in a single stream; routinely in the tens of gigabytes) from one server to another. The client portion of the tool will read blocks from the source disk, and send them over the network. The server side will read these blocks off the network and write them to a file on the server disk. Right now I'm trying to decide which transport to use. Options are raw TCP, and HTTP. I really, REALLY want to be able to use HTTP. The HttpListener (or WCF if I want to go that route) make it easy to plug in to the HTTP Server API (http.sys), and I can get things like authentication and SSL for free. The problem right now is performance. I wrote a simple test harness that sends 128K blocks of NULL bytes using the BeginWrite/EndWrite async I/O idiom, with async BeginRead/EndRead on the server side. I've modified this test harness so I can do this with either HTTP PUT operations via HttpWebRequest/HttpListener, or plain old socket writes using TcpClient/TcpListener. To rule out issues with network cards or network pathways, both the client and server are on one machine and communicate over localhost. On my 12-core Windows 2008 R2 test server, the TCP version of this test harness can push bytes at 450MB/s, with minimal CPU usage. On the same box, the HTTP version of the test harness runs between 130MB/s and 200MB/s depending upon how I tweak it. In both cases CPU usage is low, and the vast majority of what CPU usage there is is kernel time, so I'm pretty sure my usage of C# and the .NET runtime is not the bottleneck. The box has two 6-core Xeon X5650 processors, 24GB of single-ranked DDR3 RAM, and is used exclusively by me for my own performance testing. I already know about HTTP client tweaks like ServicePointManager.MaxServicePointIdleTime, ServicePointManager.DefaultConnectionLimit, ServicePointManager.Expect100Continue, and HttpWebRequest.AllowWriteStreamBuffering. Does anyone have any ideas for how I can get HTTP.sys performance beyond 200MB/s? Has anyone seen it perform this well on any environment?

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• Which StackOverflow-style MarkDown (WMD) javascript editor should I use?

  - by Edan Maor

  Background I'm working on an application which requires user-entered content, and I've decided to use a StackOverflow-style MarkDown editor. After researching this topic for the last few days, I realize there are numerous forks of the base WMD editor, some with a few basic enhancements and some with serious differences from the StackOverflow one. Since this will be the heart of the application, I'd like to start with the best code base I can. I'd be happy if anyone can recommend which one of the many solutions out there best fits my needs. Below is requirements, plus what I've managed to find already. I'm hoping this question will help me decide which version to go with, and maybe help me discover a port out there that's an even better fit for my needs. The requirements for my project Live Preview Multiple editors on the same page (not know how many in advance, since the user can dynamically add another editing box). Ability to extend with extra buttons (I'd like a button to upload a picture, instead of just adding an img url). Ability to dynamically show/hide the edit box (and only see the preview box). Not an absolute must, but I'd prefer to stick as close to StackOverflow's look and feel, since it's well known. Don't know if this matters, but the backend is written in Django. Editors I've looked at Here are a few of the code bases I've looked at, with thoughts. Obviously, I might be missing another solution out there. The derobins version. From what I can tell, this is the official StackOverflow version. Seems like it doesn't support multiple editors on one page. JQuery.MarkEdit. Looks very good, but is pretty different from the StackOverflow version. MooWMD. Looks like the winner right now, but I'm a little concerned since it looks less active/hackable than MarkEdit. The wmd-new version. Not sure, looks like an old codebase without much use. The SocialSite branch. Seems like it's not for public use.

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• LSP packet modify

  - by kellogs

  Hello, anybody care to share some insights on how to use LSP for packet modifying ? I am using the non IFS subtype and I can see how (pseudo?) packets first enter WSPRecv. But how do I modify them ? My inquiry is about one single HTTP response that causes WSPRecv to be called 3 times :((. I need to modify several parts of this response, but since it comes in 3 slices, it is pretty hard to modify it accordingly. And, maybe on other machines or under different conditions (such as high traffic) there would only be one sole WSPRecv call, or maybe 10 calls. What is the best way to work arround this (please no NDIS :D), and how to properly change the buffer (lpBuffers-buf) by increasing it ? int WSPAPI WSPRecv( SOCKET s, LPWSABUF lpBuffers, DWORD dwBufferCount, LPDWORD lpNumberOfBytesRecvd, LPDWORD lpFlags, LPWSAOVERLAPPED lpOverlapped, LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine, LPWSATHREADID lpThreadId, LPINT lpErrno ) { LPWSAOVERLAPPEDPLUS ProviderOverlapped = NULL; SOCK_INFO *SocketContext = NULL; int ret = SOCKET_ERROR; *lpErrno = NO_ERROR; // // Find our provider socket corresponding to this one // SocketContext = FindAndRefSocketContext(s, lpErrno); if ( NULL == SocketContext ) { dbgprint( "WSPRecv: FindAndRefSocketContext failed!" ); goto cleanup; } // // Check for overlapped I/O // if ( NULL != lpOverlapped ) { /*bla bla .. not interesting in my case*/ } else { ASSERT( SocketContext->Provider->NextProcTable.lpWSPRecv ); SetBlockingProvider(SocketContext->Provider); ret = SocketContext->Provider->NextProcTable.lpWSPRecv( SocketContext->ProviderSocket, lpBuffers, dwBufferCount, lpNumberOfBytesRecvd, lpFlags, lpOverlapped, lpCompletionRoutine, lpThreadId, lpErrno); SetBlockingProvider(NULL); //is this the place to modify packet length and contents ? if (strstr(lpBuffers->buf, "var mapObj = null;")) { int nLen = strlen(lpBuffers->buf) + 200; /*CHAR *szNewBuf = new CHAR[]; CHAR *pIndex; pIndex = strstr(lpBuffers->buf, "var mapObj = null;"); nLen = strlen(strncpy(szNewBuf, lpBuffers->buf, (pIndex - lpBuffers->buf) * sizeof (CHAR))); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "var com = null;\r\n", 17 * sizeof(CHAR))); pIndex += 18 * sizeof(CHAR); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), pIndex, 1330 * sizeof (CHAR))); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "if (com == null)\r\n" \ "com = new ActiveXObject(\"InterCommJS.Gateway\");\r\n" \ "com.lat = latitude;\r\n" \ "com.lon = longitude;\r\n}", 111 * sizeof (CHAR))); pIndex = strstr(szNewBuf, "Content-Length:"); pIndex += 16 * sizeof(CHAR); strncpy(pIndex, "1465", 4 * sizeof(CHAR)); lpBuffers->buf = szNewBuf; lpBuffers->len += 128;*/ } if ( SOCKET_ERROR != ret ) { SocketContext->BytesRecv += *lpNumberOfBytesRecvd; } } cleanup: if ( NULL != SocketContext ) DerefSocketContext( SocketContext, lpErrno ); return ret; } Thank you

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• Soon to be PhD in Computer Science - Which Path to Follow?

  - by mttr

  I am going to submit my PhD thesis within the next six months. My PhD is on managing the availabiity of large-scale distributed systems, so I have some experience actually building non-trivial systems (+ I have four years experience working as a programmer). I am now trying to figure out what I should do following the PhD. I enjoy research (a quick definition: identify problem, come up with solution, ask interesting questions, find ways to answer them, build system, experiment, contribute some new knowledge and publish). I also like teaching and supervising students. It would seem that a career in academia is the ideal thing to do (can work on non-trivial problems and contribute something of use to some or more people). However, a career in academia has two significant drawbacks. First, it can be difficult to gain access to real systems with real users which then display real problems. This creates the danger that you do work that seems important (to you and maybe to some of your colleagues), but is not really relevant to anything or anyone. Second, the pay is pretty sad. Apparently, you have to sacrifice this for the privilege of doing research. I enjoy programming, but don't just want to hack some web-based system for the rest of my life. That is, working in IT for a bank is not a future I see myself enjoying. I want to work on interesting problms (that's difficult to define clearly): things where you don't know how to start, that take some time to figure out and attack, that require a rigorous approach to demonstrate that the problem has been solved, and problems that need a solution in the real world. Give the experience of people on stackoverflow, what do you think suitable options are and why (or alternatively, what gaps in my thinking does the above reveal)? Is industrial research (aka IBM Research, Microsoft Research) the only alternative avenue to a career in academia? What other areas, companies, occupations, etc. could provide me with stimulating, inspiring work? Which regions, countries am I most likely to find such work? Please share your experience.

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• Why is this class re-initialized every time?

  - by pinnacler

  I have 4 files and the code 'works' as expected. I try to clean everything up, place code into functions, etc... and everything looks fine... and it doesn't work. Can somebody please explain why MatLab is so quirky... or am I just stupid? Normally, I type terminator = simulation(100,20,0,0,0,1); terminator.animate(); and it should produce a map of trees with the terminator walking around in a forest. Everything rotates to his perspective. When I break it into functions... everything ceases to work. I really only changed a few lines of code, shown in comments. Code that works: classdef simulation properties landmarks robot end methods function obj = simulation(mapSize, trees, x,y,heading,velocity) obj.landmarks = landmarks(mapSize, trees); obj.robot = robot(x,y,heading,velocity); end function animate(obj) %Setup Plots fig=figure; xlabel('meters'), ylabel('meters') set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator') xymax = obj.landmarks.mapSize*3; xymin = -(obj.landmarks.mapSize*3); l=scatter([0],[0],'bo'); axis([xymin xymax xymin xymax]); obj.landmarks.apparentPositions %Simulation Loop THIS WAS ORGANIZED for n = 1:720, %Calculate and Set Heading/Location obj.robot.headingChange = navigate(n); %Update Position obj.robot.heading = obj.robot.heading + obj.robot.headingChange; obj.landmarks.heading = obj.robot.heading; y = cosd(obj.robot.heading); x = sind(obj.robot.heading); obj.robot.x = obj.robot.x + (x*obj.robot.velocity); obj.robot.y = obj.robot.y + (y*obj.robot.velocity); obj.landmarks.x = obj.robot.x; obj.landmarks.y = obj.robot.y; %Animate set(l,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); rectangle('Position',[-2,-2,4,4]); drawnow end end end end ----------- classdef landmarks properties fixedPositions %# positions in a fixed coordinate system. [ x, y ] mapSize = 10; %Map Size. Value is side of square x=0; y=0; heading=0; headingChange=0; end properties (Dependent) apparentPositions end methods function obj = landmarks(mapSize, numberOfTrees) obj.mapSize = mapSize; obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5); end function apparent = get.apparentPositions(obj) %-STILL ROTATES AROUND ORIGINAL ORIGIN currentPosition = [obj.x ; obj.y]; apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)'; apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')'; end end end ---------- classdef robot properties x y heading velocity headingChange end methods function obj = robot(x,y,heading,velocity) obj.x = x; obj.y = y; obj.heading = heading; obj.velocity = velocity; end end end ---------- function headingChange = navigate(n) %steeringChange = 5 * rand(1) * sign(rand(1) - 0.5); Most chaotic shit %Draw an S if n <270 headingChange=1; elseif n<540 headingChange=-1; elseif n<720 headingChange=1; else headingChange=1; end end Code that does not work... classdef simulation properties landmarks robot end methods function obj = simulation(mapSize, trees, x,y,heading,velocity) obj.landmarks = landmarks(mapSize, trees); obj.robot = robot(x,y,heading,velocity); end function animate(obj) %Setup Plots fig=figure; xlabel('meters'), ylabel('meters') set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator') xymax = obj.landmarks.mapSize*3; xymin = -(obj.landmarks.mapSize*3); l=scatter([0],[0],'bo'); axis([xymin xymax xymin xymax]); obj.landmarks.apparentPositions %Simulation Loop for n = 1:720, %Calculate and Set Heading/Location %Update Position headingChange = navigate(n); obj.robot.updatePosition(headingChange); obj.landmarks.updatePerspective(obj.robot.heading, obj.robot.x, obj.robot.y); %Animate set(l,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); rectangle('Position',[-2,-2,4,4]); drawnow end end end end ----------------- classdef landmarks properties fixedPositions; %# positions in a fixed coordinate system. [ x, y ] mapSize; %Map Size. Value is side of square x; y; heading; headingChange; end properties (Dependent) apparentPositions end methods function obj = createLandmarks(mapSize, numberOfTrees) obj.mapSize = mapSize; obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5); end function apparent = get.apparentPositions(obj) %-STILL ROTATES AROUND ORIGINAL ORIGIN currentPosition = [obj.x ; obj.y]; apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)'; apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')'; end function updatePerspective(obj,tempHeading,tempX,tempY) obj.heading = tempHeading; obj.x = tempX; obj.y = tempY; end end end ----------------- classdef robot properties x y heading velocity end methods function obj = robot(x,y,heading,velocity) obj.x = x; obj.y = y; obj.heading = heading; obj.velocity = velocity; end function updatePosition(obj,headingChange) obj.heading = obj.heading + headingChange; tempy = cosd(obj.heading); tempx = sind(obj.heading); obj.x = obj.x + (tempx*obj.velocity); obj.y = obj.y + (tempy*obj.velocity); end end end The navigate function is the same... I would appreciate any help as to why things aren't working. All I did was take the code from the first section from under comment: %Simulation Loop THIS WAS ORGANIZED and break it into 2 functions. One in robot and one in landmarks. Is a new instance created every time because it's constantly printing the same heading for this line int he robot class obj.heading = obj.heading + headingChange;

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• Wildcard searching and highlighting with Solr 1.4

  - by andy

  Hey guys, I've got a pretty much vanilla install of SOLR 1.4 apart from a few small config and schema changes. <requestHandler name="standard" class="solr.SearchHandler" default="true"> <!-- default values for query parameters --> <lst name="defaults"> <str name="defType">dismax</str> <str name="echoParams">explicit</str> <str name="qf"> text </str> <str name="spellcheck.dictionary">default</str> <str name="spellcheck.onlyMorePopular">false</str> <str name="spellcheck.extendedResults">false</str> <str name="spellcheck.count">1</str> </lst> </requestHandler> The main field type I'm using for Indexing is this: <fieldType name="textNoHTML" class="solr.TextField" positionIncrementGap="100"> <analyzer type="index"> <charFilter class="solr.HTMLStripCharFilterFactory" /> <tokenizer class="solr.WhitespaceTokenizerFactory"/> <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" enablePositionIncrements="true" /> <filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" generateNumberParts="1" catenateWords="1" catenateNumbers="1" catenateAll="0" splitOnCaseChange="1"/> <filter class="solr.LowerCaseFilterFactory"/> <filter class="solr.SnowballPorterFilterFactory" language="English" protected="protwords.txt"/> </analyzer> <analyzer type="query"> <tokenizer class="solr.WhitespaceTokenizerFactory"/> <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" ignoreCase="true" expand="true"/> <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" enablePositionIncrements="true" /> <filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" generateNumberParts="1" catenateWords="0" catenateNumbers="0" catenateAll="0" splitOnCaseChange="1"/> <filter class="solr.LowerCaseFilterFactory"/> <filter class="solr.SnowballPorterFilterFactory" language="English" protected="protwords.txt"/> </analyzer> </fieldType> now, when I perform a search using "q=search+term&hl=on" I get highlighting, and nice accurate scores. BUT, for wildcard, I'm assuming you need to use "q.alt"? Is that true? If so my query looks like this: "q.alt=search*&hl=on" When I use the above query, highlighting doesn't work, and all the scores are "1.0". What am I doing wrong? is what I want possible without bypassing some of the really cool SOLR optimizations. cheers!

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• How to represent different entities that have identical behavior?

  - by Dominik

  I have several different entities in my domain model (animal species, let's say), which have a few properties each. The entities are readonly (they do not change state during the application lifetime) and they have identical behavior (the differ only by the values of properties). How to implement such entities in code? Unsuccessful attempts: Enums I tried an enum like this: enum Animals { Frog, Duck, Otter, Fish } And other pieces of code would switch on the enum. However, this leads to ugly switching code, scattering the logic around and problems with comboboxes. There's no pretty way to list all possible Animals. Serialization works great though. Subclasses I also thought about where each animal type is a subclass of a common base abstract class. The implementation of Swim() is the same for all Animals, though, so it makes little sense and serializability is a big issue now. Since we represent an animal type (species, if you will), there should be one instance of the subclass per application, which is hard and weird to maintain when we use serialization. public abstract class AnimalBase { string Name { get; set; } // user-readable double Weight { get; set; } Habitat Habitat { get; set; } public void Swim(); { /* swim implementation; the same for all animals but depends uses the value of Weight */ } } public class Otter: AnimalBase{ public Otter() { Name = "Otter"; Weight = 10; Habitat = "North America"; } } // ... and so on Just plain awful. Static fields This blog post gave me and idea for a solution where each option is a statically defined field inside the type, like this: public class Animal { public static readonly Animal Otter = new Animal { Name="Otter", Weight = 10, Habitat = "North America"} // the rest of the animals... public string Name { get; set; } // user-readable public double Weight { get; set; } public Habitat Habitat { get; set; } public void Swim(); } That would be great: you can use it like enums (AnimalType = Animal.Otter), you can easily add a static list of all defined animals, you have a sensible place where to implement Swim(). Immutability can be achieved by making property setters protected. There is a major problem, though: it breaks serializability. A serialized Animal would have to save all its properties and upon deserialization it would create a new instance of Animal, which is something I'd like to avoid. Is there an easy way to make the third attempt work? Any more suggestions for implementing such a model?

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• Calculating multiple column average in SQLite3

  - by Benjamin Oakes

  I need to average some values in a row-wise fashion, rather than a column-wise fashion. (If I were doing a column-wise average, I could just use avg()). My specific application of this requires me ignore NULLs in averaging. It's pretty straightforward logic, but seems awfully difficult to do in SQL. Is there an elegant way of doing my calculation? I'm using SQLite3, for what it's worth. Details If you need more details, here's an illustration: I have a a table with a survey: | q1 | q2 | q3 | ... | q144 | |----|-------|-------|-----|------| | 1 | 3 | 7 | ... | 2 | | 4 | 2 | NULL | ... | 1 | | 5 | NULL | 2 | ... | 3 | (Those are just some example values and simple column names. The valid values are 1 through 7 and NULL.) I need to calculate some averages like so: q7 + q33 + q38 + q40 + ... + q119 / 11 as domain_score_1 q10 + q11 + q34 + q35 + ... + q140 / 13 as domain_score_2 ... q2 + q5 + q13 + q25 + ... + q122 / 12 as domain_score_14 ...but i need to pull out the nulls and average based on the non-nulls. So, for domain_score_1 (which has 11 items), I would need to do: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 (3 + 5 + 7 + 2 + 3 + 1 + 5 + 1) / (11 - 3) 27 / 8 3.375 A simple algorithm I'm considering is: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 Coalesce each value to 0 if NULL: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 Sum: 27 Get the number of non-zeros by converting values 0 to 1 and sum: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 8 Divide those two numbers 27 / 8 3.375 But that seems like a lot more programming than this should take. Is there an elegant way of doing this that I'm not aware of? Update: Unless I'm misunderstanding something, avg() won't work for this. Example of what I would want to do: select avg(q7, q33, q38, ..., q119) from survey; Output: SQL error near line 3: wrong number of arguments to function avg()

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• Rush Hour - Solving the game

  - by Rubys

  Rush Hour if you're not familiar with it, the game consists of a collection of cars of varying sizes, set either horizontally or vertically, on a NxM grid that has a single exit. Each car can move forward/backward in the directions it's set in, as long as another car is not blocking it. You can never change the direction of a car. There is one special car, usually it's the red one. It's set in the same row that the exit is in, and the objective of the game is to find a series of moves (a move - moving a car N steps back or forward) that will allow the red car to drive out of the maze. I've been trying to think how to solve this problem computationally, and I can really not think of any good solution. I came up with a few: Backtracking. This is pretty simple - Recursion and some more recursion until you find the answer. However, each car can be moved a few different ways, and in each game state a few cars can be moved, and the resulting game tree will be HUGE. Some sort of constraint algorithm that will take into account what needs to be moved, and work recursively somehow. This is a very rough idea, but it is an idea. Graphs? Model the game states as a graph and apply some sort of variation on a coloring algorithm, to resolve dependencies? Again, this is a very rough idea. A friend suggested genetic algorithms. This is sort of possible but not easily. I can't think of a good way to make an evaluation function, and without that we've got nothing. So the question is - How to create a program that takes a grid and the vehicle layout, and outputs a series of steps needed to get the red car out? Sub-issues: Finding some solution. Finding an optimal solution (minimal number of moves) Evaluating how good a current state is Example: How can you move the cars in this setting, so that the red car can "exit" the maze through the exit on the right?

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• Beautifulsoup recursive attribute

  - by Marcos Placona

  Hi, trying to parse an XML with Beautifulsoup, but hit a brick wall when trying to use the "recursive" attribute with findall() I have a pretty odd xml format shown below: <?xml version="1.0"?> <catalog> <book id="bk101"> <author>Gambardella, Matthew</author> <title>XML Developer's Guide</title> <genre>Computer</genre> <price>44.95</price> <publish_date>2000-10-01</publish_date> <description>An in-depth look at creating applications with XML.</description> <catalog>true</catalog> </book> <book id="bk102"> <author>Ralls, Kim</author> <title>Midnight Rain</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2000-12-16</publish_date> <description>A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.</description> <catalog>false</catalog> </book> </catalog> As you can see, the catalog tag repeats inside the book tag, which causes an error when I try to to something like: from BeautifulSoup import BeautifulStoneSoup as BSS catalog = "catalog.xml" def open_rss(): f = open(catalog, 'r') return f.read() def rss_parser(): rss_contents = open_rss() soup = BSS(rss_contents) items = soup.findAll('catalog', recursive=False) for item in items: print item.title.string rss_parser() As you will see, on my soup.findAll I've added recursive=false, which in theory would make it no recurse through the item found, but skip to the next one. This doesn't seem to work, as I always get the following error: File "catalog.py", line 17, in rss_parser print item.title.string AttributeError: 'NoneType' object has no attribute 'string' I'm sure I'm doing something stupid here, and would appreciate if someone could give me some help on how to solve this problem. Changing the HTML structure is not an option, this this code needs to perform well as it will potentially parse a large XML file. Thanks in advance, Marcos

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• NoSQL DB for .Net document-based database (ECM)

  - by Dane

  I'm halfway through coding a basic multi-tenant SaaS ECM solution. Each client has it's own instance of the database / datastore, but the .Net app is single instance. The documents are pretty much read only (i.e. an image archive of tiffs or PDFs) I've used MSSQL so far, but then started thinking this might be viable in a NoSQL DB (e.g. MongoDB, CouchDB). The basic premise is that it stores documents, each with their own particular indexes. Each tenant can have multiple document types. e.g. One tenant might have an invoice type, which has Customer ID, Invoice Number and Invoice Date. Another tenant might have an application form, which has Member Number, Application Number, Member Name, and Application Date. So far I've used the old method which Sharepoint (used?) to use, and created a document table which has int_field_1, int_field_2, date_field_1, date_field_2, etc. Then, I've got a "mapping" table which stores the customer specific index name, and the database field that will map to. I've avoided the key-value pair model in the DB due to volume of documents. This way, we can support multiple document types in the one table, and get reasonably high performance out of it, and allow for custom document type searches (i.e. user selects a document type, then they're presented with a list of search fields). However, a NoSQL DB might make this a lot simpler, as I don't need to worry about denormalizing the document. However, I've just got concerns about the rest of the data around a document. We store an "action history" against the document. This tracks views, whether someone emails the document from within the system, and other "future" functionality (e.g. faxing). We have control over the document load process, so we can manipulate the data however it needs to be to get it in the document store (e.g. assign unique IDs). Users will not be adding in their own documents, so we shouldn't need to worry about ACID compliance, as the documents are relatively static. So, my questions I guess : Is a NoSQL DB a good fit Is MongoDB the best for Asp.Net (I saw Raven and Velocity, but they're still kinda beta) Can I store a key for each document, and then store the action history in a MSSQL DB with this key? I don't need to do joins, it would be if a person clicks "View History" against a document. How would performance compare between the two (NoSQL DB vs denormalized "document" table) Volumes would be up to 200,000 new documents per month for a single tenant. My current scaling plan with the SQL DB involves moving the SQL DB into a cluster when certain thresholds are reached, and then reviewing partitioning and indexing structures.

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• DataRelation Insert and ForeignKey

  - by Steve

  Guys, I have a winforms application with two DataGridViews displaying a master-detail relationship from my Person and Address tables. Person table has a PersonID field that is auto-incrementing primary key. Address has a PersonID field that is the FK. I fill my DataTables with DataAdapter and set Person.PersonID column's AutoIncrement=true and AutoIncrementStep=-1. I can insert records in the Person DataTable from the DataGridView. The PersonID column displays unique negative values for PersonID. I update the database by calling DataAdapter.Update(PersonTable) and the negative PersonIDs are converted to positive unique values automatically by SQL Server. Here's the rub. The Address DataGridView show the address table which has a DataRelation to Person by PersonID. Inserted Person records have the temporary negative PersonID. I can now insert records into Address via DataGridView and Address.PersonID is set to the negative value from the DataRelation mapping. I call Adapter.Update(AddressTable) and the negative PersonIDs go into the Address table breaking the relationship. How do you guys handle primary/foreign keys using DataTables and master-detail DataGridViews? Thanks! Steve EDIT: After more googling, I found that SqlDataAdapter.RowUpdated event gives me what I need. I create a new command to query the last id inserted by using @@IDENTITY. It works pretty well. The DataRelation updates the Address.PersonID field for me so it's required to Update the Person table first then update the Address table. All the new records insert properly with correct ids in place! Adapter = new SqlDataAdapter(cmd); Adapter.RowUpdated += (s, e) => { if (e.StatementType != StatementType.Insert) return; //set the id for the inserted record SqlCommand c = e.Command.Connection.CreateCommand(); c.CommandText = "select @@IDENTITY id"; e.Row[0] = Convert.ToInt32( c.ExecuteScalar() ); }; Adapter.Fill(this); SqlCommandBuilder sb = new SqlCommandBuilder(Adapter); sb.GetDeleteCommand(); sb.GetUpdateCommand(); sb.GetInsertCommand(); this.Columns[0].AutoIncrement = true; this.Columns[0].AutoIncrementSeed = -1; this.Columns[0].AutoIncrementStep = -1;

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• Adding unique objects to Core Data

  - by absolut

  I'm working on an iPhone app that gets a number of objects from a database. I'd like to store these using Core Data, but I'm having problems with my relationships. A Detail contains any number of POIs (points of interest). When I fetch a set of POI's from the server, they contain a detail ID. In order to associate the POI with the Detail (by ID), my process is as follows: Query the ManagedObjectContext for the detailID. If that detail exists, add the poi to it. If it doesn't, create the detail (it has other properties that will be populated lazily). The problem with this is performance. Performing constant queries to Core Data is slow, to the point where adding a list of 150 POI's takes a minute thanks to the multiple relationships involved. In my old model, before Core Data (various NSDictionary cache objects) this process was super fast (look up a key in a dictionary, then create it if it doesn't exist) I have more relationships than just this one, but pretty much every one has to do this check (some are many to many, and they have a real problem). Does anyone have any suggestions for how I can help this? I could perform fewer queries (by searching for a number of different ID's), but I'm not sure how much this will help. Some code: POI *poi = [NSEntityDescription insertNewObjectForEntityForName:@"POI" inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]]; poi.POIid = [attributeDict objectForKey:kAttributeID]; poi.detailId = [attributeDict objectForKey:kAttributeDetailID]; Detail *detail = [self findDetailForID:poi.POIid]; if(detail == nil) { detail = [NSEntityDescription insertNewObjectForEntityForName:@"Detail" inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]]; detail.title = poi.POIid; detail.subtitle = @""; detail.detailType = [attributeDict objectForKey:kAttributeType]; } -(Detail*)findDetailForID:(NSString*)detailID { NSManagedObjectContext *moc = [[UIApplication sharedApplication].delegate managedObjectContext]; NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Detail" inManagedObjectContext:moc]; NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; [request setEntity:entityDescription]; NSPredicate *predicate = [NSPredicate predicateWithFormat: @"detailid == %@", detailID]; [request setPredicate:predicate]; NSLog(@"%@", [predicate description]); NSError *error; NSArray *array = [moc executeFetchRequest:request error:&error]; if (array == nil || [array count] != 1) { // Deal with error... return nil; } return [array objectAtIndex:0]; }

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