Search Results

Search found 11972 results on 479 pages for 'writing'.

Page 438/479 | < Previous Page | 434 435 436 437 438 439 440 441 442 443 444 445  | Next Page >

  • SimpleXML SOAP response Namespace issues

    - by Stu
    Hi. After spending SEVERAL frustrated hours on this I am asking for your help. I am trying to get the content of particular nodes from a SOAP response. The response is $XmlStr = <?xml version="1.0" encoding="UTF-8"?><env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"<xmlns:ns1="http://soap.xxxxxx.co.uk/"><env:Body><ns1:PlaceOrderResponse><xxxxxOrderNumber></xxxxxOrderNumber><ErrorArray><Error><ErrorCode>24</ErrorCode><ErrorText>The+client+order+number+3002254+is+already+in+use</ErrorText></Error><Error><ErrorCode>1</ErrorCode><ErrorText>Aborting</ErrorText></Error></ErrorArray></ns1:PlaceOrderResponse></env:Body></env:Envelope> I am trying to get at the nodes and children of <ErrorArray. Because of the XML containing namespaces $XmlArray = new SimpleXMLElement($XmlStr); foreach ($XmlArray->env:Envelope->env:Body->ns1:PlaceOrderResponse->ErrorArray->Error as $Error) { echo $Error->ErrorCode."<br />";<br /> } doesn't work. I have read a number of articles such as http://www.sitepoint.com/blogs/2005/10/20/simplexml-and-namespaces/ htp://blog.stuartherbert.com/php/2007/01/07/using-simplexml-to-parse-rss-feeds/ and about 20 questions on this site which unfortunately are not helping. (the second link has htp:// as a newbie here I cannot post more than one link) Even writing, $XmlArray = new SimpleXMLElement($XmlStr); echo "<br /><br /><pre>\n"; print_r($XmlArray); echo "<pre><br /><br />\n"; gives SimpleXMLElement Object ( ) which makes me wonder if the soap response ($XmlStr) is actually a valid input for SimpleXMLElement. It seems that the line $XmlArray = new SimpleXMLElement($XmlStr); is not doing what I expect it to. Any help on how to get the nodes from the XML above would be very welcome. Obviously getting it to work (having a working example) is what I need in the short term, but if someone could help me understand what I am doing wrong would be better in the long term. Cheers. Stu

    Read the article

  • Complex relationship between tables in NHibernate

    - by Ilya Kogan
    Hi all, I'm writing a Fluent NHibernate mapping for a legacy Oracle database. The challenge is that the tables have composite primary keys. If I were at total freedom, I would redesign the relationships and auto-generate primary keys, but other applications must write to the same database and read from it, so I cannot do it. These are the two tables I'll focus on: Example data Trips table: 1, 10:00, 11:00 ... 1, 12:00, 15:00 ... 1, 16:00, 19:00 ... 2, 12:00, 13:00 ... 3, 9:00, 18:00 ... Faults table: 1, 13:00 ... 1, 23:00 ... 2, 12:30 ... In this case, vehicle 1 made three trips and has two faults. The first fault happened during the second trip, and the second fault happened while the vehicle was resting. Vehicle 2 had one trip, during which a fault happened. Constraints Trips of the same vehicle never overlap. So the tables have an optional one-to-many relationship, because every fault either happens during a trip or it doesn't. If I wanted to join them in SQL, I would write: select ... from Faults left outer join Trips on Faults.VehicleId = Trips.VehicleId and Faults.FaultTime between Trips.TripStartTime and Trips.TripEndTime and then I'd get a dataset where every fault appears exactly once (one-to-many as I said). Note that there is no Vehicles table, and I don't need one. But I did create a view that contains all VehicleIds from both tables, so I can use it as a junction table. What am I actually looking for? The tables are huge because they cover years of data, and every time I only need to fetch a range of a few hours. So I need a mapping and a criteria that will run something like the following SQL underneath: select ... from Faults left outer join Trips on Faults.VehicleId = Trips.VehicleId and Faults.FaultTime between Trips.TripStartTime and Trips.TripEndTime where Faults.FaultTime between :p0 and :p1 Do you have any ideas how to achieve it? Note 1: Currently the application shouldn't write to the database, so persistence is not a must, although if the mapping supports persistence, it may help at some point in the future. Note 2: I know it's a tough one, so if you give me a great answer, you will be properly rewarded :) Thank you for reading this long question, and now I only hope for the best :)

    Read the article

  • jQuery: Trying to write my first plugin, how can I pass a selector to my func?

    - by Jannis
    Hi, I am trying to start writing some simple jQuery plugins and for my first try if figured I would write something that does nothing else but apply .first & .last classes to passed elements. so for instance i want to ultimately be able to: $('li').firstnlast(); So that in this html structure: <ul> <li></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li></li> </ul> it would create the following: <ul> <li class="first"></li> <li></li> <li></li> <li class="last"></li> </ul> <ul> <li class="first"></li> <li class="last"></li> </ul> What i have written so far in my plugin is this: (function($) { $.fn.extend({ firstnlast: function() { $(this) .first() .addClass('first') .end() .last() .addClass('last'); } }); })(jQuery); However the above only returns this: <ul> <li class="first"></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li class="last"></li> </ul> It seems that passing only the li into the function it will look at all li elements on the entire page and then apply the classes to it. What I need to figure out is how i can basically make the function 'context aware' so that passing the above li into the function would apply the classes to those lis inside of the parent ul, not to the first and last li on the entire page. Any hints, ideas and help would be much appreciated. Thanks for reading, Jannis

    Read the article

  • What's the best way to do base36 arithmetic in perl?

    - by DVK
    What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

    Read the article

  • WordPress Write Cache Problem with Multiple Sessions

    - by Volomike
    I'm working on a content dripper custom plugin in WordPress that my client asked me to build. He says he wants it to catch a page view event, and if it's the right time of day (24 hours since last post), to pull from a resource file and output another post. He needed it to also raise a flag and prevent other sessions from firing that same snippet of code. So, raise some kind of flag saying, "I'm posting that post, go away other process," and then it makes that post and releases the flag again. However, the strangest thing is occurring when placed under load with multiple sessions hitting the site with page views. It's firing instead of one post -- it's randomly doing like 1, 2, or 3 extra posts, with each one thinking that it was the right time to post because it was 24 hours past the time of the last post. Because it's somewhat random, I'm guessing that the problem is some kind of write caching where the other sessions don't see the raised flag just yet until a couple microseconds pass. The plugin was raising the "flag" by simply writing to the wp_options table with the update_option() API in WordPress. The other user sessions were supposed to read that value with get_option() and see the flag, and then not run that piece of code that creates the post because a given session was already doing it. Then, when done, I lower the flag and the other sessions continue as normal. But what it's doing is letting those other sessions in. To make this work, I was using add_action('loop_start','checkToAddContent'). The odd thing about that function though is that it's called more than once on a page, and in fact some plugins may call it. I don't know if there's a better event to hook. Even still, even if I find an event to hook that only runs once on a page view, I still have multiple sessions to contend with (different users who may view the page at the same time) and I want only one given session to trigger the content post when the post is due on the schedule. I'm wondering if there are any WordPress plugin devs out there who could suggest another event hook to latch on to, and to figure out another way to raise a flag that all sessions would see. I mean, I could use the shared memory API in PHP, but many hosting plans have that disabled. Can't use a cookie or session var because that's only one single session. About the only thing that might work across hosting plans would be to drop a file as a flag, instead. If the file is present, then one session has the flag. If the file is not present, then other sessions can attempt to get the flag. Sure, I could use the file route, but it's kind of immature in my opinion and I was wondering if there's something in WordPress I could do.

    Read the article

  • Would someone mind giving suggestions for this new assembly language?

    - by Noctis Skytower
    Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo save Store load Retrieve L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

    Read the article

  • Understanding CLR 2.0 Memory Model

    - by Eloff
    Joe Duffy, gives 6 rules that describe the CLR 2.0+ memory model (it's actual implementation, not any ECMA standard) I'm writing down my attempt at figuring this out, mostly as a way of rubber ducking, but if I make a mistake in my logic, at least someone here will be able to catch it before it causes me grief. Rule 1: Data dependence among loads and stores is never violated. Rule 2: All stores have release semantics, i.e. no load or store may move after one. Rule 3: All volatile loads are acquire, i.e. no load or store may move before one. Rule 4: No loads and stores may ever cross a full-barrier (e.g. Thread.MemoryBarrier, lock acquire, Interlocked.Exchange, Interlocked.CompareExchange, etc.). Rule 5: Loads and stores to the heap may never be introduced. Rule 6: Loads and stores may only be deleted when coalescing adjacent loads and stores from/to the same location. I'm attempting to understand these rules. x = y y = 0 // Cannot move before the previous line according to Rule 1. x = y z = 0 // equates to this sequence of loads and stores before possible re-ordering load y store x load 0 store z Looking at this, it appears that the load 0 can be moved up to before load y, but the stores may not be re-ordered at all. Therefore, if a thread sees z == 0, then it also will see x == y. If y was volatile, then load 0 could not move before load y, otherwise it may. Volatile stores don't seem to have any special properties, no stores can be re-ordered with respect to each other (which is a very strong guarantee!) Full barriers are like a line in the sand which loads and stores can not be moved over. No idea what rule 5 means. I guess rule 6 means if you do: x = y x = z Then it is possible for the CLR to delete both the load to y and the first store to x. x = y z = y // equates to this sequence of loads and stores before possible re-ordering load y store x load y store z // could be re-ordered like this load y load y store x store z // rule 6 applied means this is possible? load y store x // but don't pop y from stack (or first duplicate item on top of stack) store z What if y was volatile? I don't see anything in the rules that prohibits the above optimization from being carried out. This does not violate double-checked locking, because the lock() between the two identical conditions prevents the loads from being moved into adjacent positions, and according to rule 6, that's the only time they can be eliminated. So I think I understand all but rule 5, here. Anyone want to enlighten me (or correct me or add something to any of the above?)

    Read the article

  • How do I read Unicode characters from an MS Access 2007 database through Java?

    - by Peter
    In Java, I have written a program that reads a UTF8 text file. The text file contains a SQL query of the SELECT kind. The program then executes the query on the Microsoft Access 2007 database and writes all fields of the first row to a UTF8 text file. The problem I have is when a row is returned that contains unicode characters, such as "?". These characters show up as "?" in the text file. I know that the text files are read and written correctly, because a dummy UTF8 character ("?") is read from the text file containing the SQL query and written to the text file containing the resulting row. The UTF8 character looks correct when the written text file is opened in Notepad, so the reading and writing of the text files are not part of the problem. This is how I connect to the database and how I execute the SQL query: ---- START CODE Connection c = DriverManager.getConnection("jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=C:/database.accdb;Pwd=temp"); ResultSet r = c.createStatement().executeQuery(sql); ---- END CODE I have tried making a charSet property to the Connection but it makes no difference: ---- START CODE Properties p = new Properties(); p.put("charSet", "utf-8"); p.put("lc_ctype", "utf-8"); p.put("encoding", "utf-8"); Connection c = DriverManager.getConnection("...", p); ---- END CODE Tried with "utf8"/"UTF8"/"UTF-8", no difference. If I enter "UTF-16" I get the following exception: "java.lang.IllegalArgumentException: Illegal replacement". Been searching around for hours with no results and now turn my hope to you. Please help! I also accept workaround suggestions. =) What I want to be able to do is to make a Unicode query (for example one that searches for posts that contain the "?" character) and to have results with Unicode characters receieved and saved correctly. Thank you!

    Read the article

  • iPhone dev: load a file from resource folder

    - by thomax
    I'm writing an iPhone app with a UIWebView which should display various html files I have in the app resource folder. In xcode my project overview, these html files are displayed like this: dirA |---> index.html |---> a1.html |---> a2.html |---> my.css |---> dirB |---> b1.html |---> b2.html |---> dirC |---> c1.html |---> c2.html These resources where added to the project as such: - Checked "Copy items into destination groups folder (if needed)". - Reference type: Default. - Text encoding: Unicode (utf-8). - Recursively create groups for any added folders. The links in my html are relative, meaning they look like this: <a href="a1.html">a2</a> <a href="a2.html">a2</a> <a href="dirB/b2.html">b2</a> <a href="dirC/c1.html">b2</a> In order to display the index.html when the app starts up, I use the following code: NSString *path = [[NSBundle mainBundle] pathForResource:@"index" ofType:@"html"]; NSURL *url = [NSURL fileURLWithPath:path]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; [webView loadRequest:request]; This works fine. Following links from the index file also works fine, as long as the html files requested are directly under dirA. If the link followed points to a file in a sub-directory, then didFailLoadWithError will catch the situation and report that the requested file does not exist. Note that [webView loadHtmlString:myHtml]; cannot be part of the solution, as I need back and forward buttons to work in my web view. So the question is: How can I follow a relative link to an html file in a sub directory within my resources? I've been all over stackoverflow and the rest of the tubes for the past few days trying to figure this one out, but nowhere have I come across the solution to this exact problem. Any insight at all would be very, very much appreciated!

    Read the article

  • Unique element ID, even if element doesn't have one

    - by Robert J. Walker
    I'm writing a GreaseMonkey script where I'm iterating through a bunch of elements. For each element, I need a string ID that I can use to reference that element later. The element itself doesn't have an id attribute, and I can't modify the original document to give it one (although I can make DOM changes in my script). I can't store the references in my script because when I need them, the GreaseMonkey script itself will have gone out of scope. Is there some way to get at an "internal" ID that the browser uses, for example? A Firefox-only solution is fine; a cross-browser solution that could be applied in other scenarios would be awesome. Edit: If the GreaseMonkey script is out of scope, how are you referencing the elements later? They GreaseMonkey script is adding events to DOM objects. I can't store the references in an array or some other similar mechanism because when the event fires, the array will be gone because the GreaseMonkey script will have gone out of scope. So the event needs some way to know about the element reference that the script had when the event was attached. And the element in question is not the one to which it is attached. Can't you just use a custom property on the element? Yes, but the problem is on the lookup. I'd have to resort to iterating through all the elements looking for the one that has that custom property set to the desired id. That would work, sure, but in large documents it could be very time consuming. I'm looking for something where the browser can do the lookup grunt work. Wait, can you or can you not modify the document? I can't modify the source document, but I can make DOM changes in the script. I'll clarify in the question. Can you not use closures? Closuses did turn out to work, although I initially thought they wouldn't. See my later post. It sounds like the answer to the question: "Is there some internal browser ID I could use?" is "No."

    Read the article

  • Why does my ko computed observable not update bound UI elements when its value changes?

    - by Allen
    I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

    Read the article

  • Scala actors: receive vs react

    - by jqno
    Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

    Read the article

  • How to work with file and streams in php,case: if we open file in Class A and pass open stream to Cl

    - by Rachel
    I have two class, one is Business Logic Class{BLO} and the other one is Data Access Class{DAO} and I have dependency in my BLO class to my Dao class. Basically am opening a csv file to write into it in my BLO class using inside its constructor as I am creating an object of BLO and passing in file from command prompt: Code: $this->fin = fopen($file,'w+') or die('Cannot open file'); Now inside BLO I have one function notifiy, which call has dependency to DAO class and call getCurrentDBSnapshot function from the Dao and passes the open stream so that data gets populated into the stream. Code: Blo Class Constructor: public function __construct($file) { //Open Unica File for parsing. $this->fin = fopen($file,'w+') or die('Cannot open file'); // Initialize the Repository DAO. $this->dao = new Dao('REPO'); } Blo Class method that interacts with Dao Method and call getCurrentDBSnapshot. public function notifiy() { $data = $this->fin; var_dump($data); //resource(9) of type (stream) $outputFile=$this->dao->getCurrentDBSnapshot($data); // So basically am passing in $data which is resource((9) of type (stream) } Dao function: getCurrentDBSnapshot which get current state of Database table. public function getCurrentDBSnapshot($data) { $query = "SELECT * FROM myTable"; //Basically just preparing the query. $stmt = $this->connection->prepare($query); // Execute the statement $stmt->execute(); $header = array(); while ($row=$stmt->fetch(PDO::FETCH_ASSOC)) { if(empty($header)) { // Get the header values from table(columnnames) $header = array_keys($row); // Populate csv file with header information from the mytable fputcsv($data, $header); } // Export every row to a file fputcsv($data, $row); } var_dump($data);//resource(9) of type (stream) return $data; } So basically in am getting back resource(9) of type (stream) from getCurrentDBSnapshot and am storing that stream into $outputFile in Blo class method notify. Now I want to close the file which I opened for writing and so it should be fclose of $outputFile or $data, because in both the cases it gives me: var_dump(fclose($outputFile)) as bool(false) var_dump(fclose($data)) as bool(false) and var_dump($outputFile) as resource(9) of type (Unknown) var_dump($data) as resource(9) of type (Unknown) My question is that if I open file using fopen in class A and if I call class B method from Class A method and pass an open stream, in our case $data, than Class B would perform some work and return back and open stream and so How can I close that open stream in Class A's method or it is ok to keep that stream open and not use fclose ? Would appreciate inputs as am not very sure as how this can be implemented.

    Read the article

  • Double Buffering for Game objects, what's a nice clean generic C++ way?

    - by Gary
    This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

    Read the article

  • xslt test if a variable value is contained in a node set

    - by Aamir
    I have the following two files: <?xml version="1.0" encoding="utf-8" ?> <!-- D E F A U L T H O S P I T A L P O L I C Y --> <xas DefaultPolicy="open" DefaultSubjectsFile="subjects.xss"> <rule id="R1" access="deny" object="record" subject="roles/*[name()!='Staff']"/> <rule id="R2" access="deny" object="diagnosis" subject="roles//Nurse"/> <rule id="R3" access="grant" object="record[@id=$user]" subject="roles/member[@id=$user]"/> </xas> and the other xml file called subjects.xss is: <?xml version="1.0" encoding="utf-8" ?> <subjects> <users> <member id="dupont" password="4A-4E-E9-17-5D-CE-2C-DD-43-43-1D-F1-3F-5D-94-71"> <name>Pierre Dupont</name> </member> <member id="durand" password="3A-B6-1B-E8-C0-1F-CD-34-DF-C4-5E-BA-02-3C-04-61"> <name>Jacqueline Durand</name> </member> </users> <roles> <Staff> <Doctor> <member idref="dupont"/> </Doctor> <Nurse> <member idref="durand"/> </Nurse> </Staff> </roles> </subjects> I am writing an xsl sheet which will read the subject value for each rule in policy.xas and if the currently logged in user (accessible as variable "user" in the stylesheet) is contained in that subject value (say roles//Nurse), then do something. I am not being able to test whether the currently logged in user ($user which is equal to say "durand") is contained in roles//Nurse in the subjects file (which is a different xml file). Hope that clarifies my question. Any ideas? Thanks in advance.

    Read the article

  • How to stream XML data using XOM?

    - by Jonik
    Say I want to output a huge set of search results, as XML, into a PrintWriter or an OutputStream, using XOM. The resulting XML would look like this: <?xml version="1.0" encoding="UTF-8"?> <resultset> <result> [child elements and data] </result> ... ... [1000s of result elements more] </resultset> Because the resulting XML document could be big (tens or hundreds of megabytes, perhaps), I want to output it in a streaming fashion (instead of creating the whole Document in memory and then writing that). The granularity of outputting one <result> at a time is fine, so I want to generate one <result> after another, and write it into the stream. Assume there's already a method that helps with iterating the results and generating Element objects: public nu.xom.Element getNextResult(); So I'd simply like to do something like this pseudocode (automatic flushing enabled, so don't worry about that) : open stream/writer write declaration write start tag for <resultset> while more results: write next <result> element write end tag for <resultset> close stream/writer I've been looking at Serializer, but the necessary methods, writeStartTag(Element), writeEndTag(Element), write(DocType) are protected, not public! Is there no other way than to subclass Serializer to be able to use those methods, or to manually write the start and end tags directly into the stream as Strings, bypassing XOM altogether? (The latter wouldn't be too bad in this simple example, but in the general case it would get quite ugly.) Am I missing something or is XOM just not made for this? With dom4j I could do this easily using XMLWriter - it has constructors that take a Writer or OutputStream, and methods writeOpen(Element), writeClose(Element), writeDocType(DocumentType) etc. Compare to XOM's Serializer where the only public write method is the one that takes a whole Document. Please refrain from answering if you're not familiar with XOM! I specifically want to know if and how you can do this kind of streaming with that library. (This is related to my question about the best dom4j replacement where XOM is a strong contender.)

    Read the article

  • Getting a screenshot of a page using .NET - Need help with code

    - by Ender
    I'm writing a specialized crawler and parser for internal use and I require the ability to take a screenshot of a web page in order to check what colours are being used throughout. The program will take in around ten web addresses and will save them as a bitmap image, from there I plan to use LockBits in order to create a list of the five most used colours within the image. To my knowledge it's the easiest way to get the colours used within a web page but if there is an easier way to do it please chime in with your suggestions. Anyway, I was going to use this program until I saw the price tag. I'm also fairly new to C#, having only used it for a few months. Can anyone provide me with a solution to my problem of taking a screenshot of a web page in order to extract the colour scheme? EDIT: Sorry for not getting back to this sooner, but I've been busy with some other things. Anyway, the code seems to work well, but the problem I am having right now is that I am running it within a form, and naturally with Application.Run() being called I cannot run two instances of the same form at once. It recommended Form.showDialog() but that broke everything. Can anyone give me a hand with this code? public static void buildScreenshotFromURL(string url) { int width = 800; int height = 600; using (WebBrowser browser = new WebBrowser()) { browser.Width = width; browser.Height = height; browser.ScrollBarsEnabled = true; // This will be called when the page finishes loading browser.DocumentCompleted += new System.Windows.Forms.WebBrowserDocumentCompletedEventHandler(OnDocumentCompleted); //browser.DocumentCompleted += OnDocumentCompleted; browser.Navigate(url); // This prevents the application from exiting until // Application.Exit is called // Application.Run() does not work as it cannot be called twice, recommended form.showDialog() // but still issues Application.Run(); } } public static void OnDocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { // Define size of thumbnail neded int thumbSize = 50; // Now that the page is loaded, save it to a bitmap WebBrowser browser = (WebBrowser)sender; // Code edited from example below to make smaller bitmap and save as PNG using (Graphics graphics = browser.CreateGraphics()) { using (Bitmap bitmap = new Bitmap(browser.Width, browser.Height, graphics)) { Rectangle bounds = new Rectangle(0, 0, bitmap.Width, bitmap.Height); browser.DrawToBitmap(bitmap, bounds); Bitmap thumbBitmap = new Bitmap(bitmap.GetThumbnailImage(thumbSize, thumbSize, thumbCall, IntPtr.Zero)); thumbBitmap.Save("screenshot.png", ImageFormat.Png); handleImage(thumbBitmap); } }

    Read the article

  • Share a "deep link" from a Windows 8/WinRT application

    - by Dave Parker
    I have searched using many different terms and phrases, and waded through many pages of results, but I have (remarkably) not seen anyone else addressing, even asking, about, this issue. So here goes... Ultimate Goal: Allow a user viewing a content-based page (may contain both text and images) within a Windows Store app to share that content with someone else. Description I am working on taking a fair amount of content and making it available for browsing/navigating as a Windows 8/WinRT/Windows Store (we need a consistent name here) application. One of the desired features is to take advantage of the Share Charm, such that someone viewing a page could share that page with someone else. The ideal behavior is for the application to implement the Share Source contract which would share an email message that contained some explanatory text, a link to get the app from the Windows Store, and a "deep link" into the shared page in the application. Solutions Considered We had originally looked at just generating a PDF representation of the page, but there are very few external libraries that would work under WinRT, and having to include externally licensed code would be problematic as well. Writing our own PDF generation code would out of scope. We have also considered generating a Word document or PowerPoint slide using OpenXML, but again, we run up against the limitaions of WinRT. In this case, it is highly unlikely the OpenXML SDK is useable in a WinRT application. Another thought was to pre-generate all of the pages as .pdf files, store them as resources, and when the Share Charm is invoked, share the .pdf file associated with the current page. The problem here is the application will have at least 150 content pages, and depending on how we break the content down, up to over 600. This would likely cause serious bloat. Where We Are At Thus we have come to sharing URIs. From what I can tell, though, the "deep linking" feature is only intended for use on Secondary Tiles tied to your application. Another avenue I considered was registering a protocol like, "my-special-app:" with the OS and having it fire up the application but that would require HKCR registry access, which is outside the WinRT sandbox. If it matters, we are leaning towards an HTML/JS application, rather than XAML/C#, because the converted content will all be in HTML and the WebView control in WinRT is fairly limited. This decision is not yet final, though. Conclusion So, is this possible, and if so, how would it be done or where can I find documentation on it? Thanks, Dave Parker

    Read the article

  • Prevent SQL Injection in Dynamic column names

    - by Mr Shoubs
    I can't get away without writing some dynamic sql conditions in a part of my system (using Postgres). My question is how best to avoid SQL Injection with the method I am currently using. EDIT (Reasoning): There are many of columns in a number of tables (a number which grows (only) and is maintained elsewhere). I need a method of allowing the user to decide which (predefined) column they want to query (and if necessary apply string functions to). The query itself is far too complex for the user to write themselves, nor do they have access to the db. There are 1000's of users with varying requirements and I need to remain as flexible as possible - I shouldn't have to revisit the code unless the main query needs to change - Also, there is no way of knowing what conditions the user will need to use. I have objects (received via web service) that generates a condition (the generation method is below - it isn't perfect yet) for some large sql queries. The _FieldName is user editable (parameter name was, but it didn't need to be) and I am worried it could be an attack vector. I put double quotes (see quoted identifier) around the field name in an attempt to sanitize the string, this way it can never be a key word. I could also look up the field name against a list of fields, but it would be difficult to maintain on a timely basis. Unfortunately the user must enter the condition criteria, I am sure there must be more I can add to the sanatize method? and does quoting the column name make it safe? (my limited testing seems to think so). an example built condition would be "AND upper(brandloaded.make) like 'O%' and upper(brandloaded.make) not like 'OTHERBRAND'" ... Any help or suggestions are appreciated. Public Function GetCondition() As String Dim sb As New Text.StringBuilder 'put quote around the table name in an attempt to prevent some sql injection 'http://www.postgresql.org/docs/8.2/static/sql-syntax-lexical.html sb.AppendFormat(" {0} ""{1}"" ", _LogicOperator.ToString, _FieldName) Select Case _ConditionOperator Case ConditionOperatorOptions.Equals sb.Append(" = ") ... End Select sb.AppendFormat(" {0} ", Me.UniqueParameterName) 'for parameter Return Me.Sanitize(sb) End Function Private Function Sanitize(ByVal sb As Text.StringBuilder) As String 'compare against a similar blacklist mentioned here: http://forums.asp.net/t/1254125.aspx sb.Replace(";", "") sb.Replace("'", "") sb.Replace("\", "") sb.Replace(Chr(8), "") Return sb.ToString End Function Public ReadOnly Property UniqueParameterName() As String Get Return String.Concat(":" _UniqueIdentifier) End Get End Property

    Read the article

  • [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

    - by fatai
    I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

    Read the article

  • How do I print out objects in an array in python?

    - by Jonathan
    I'm writing a code which performs a k-means clustering on a set of data. I'm actually using the code from a book called collective intelligence by O'Reilly. Everything works, but in his code he uses the command line and i want to write everything in notepad++. As a reference his line is >>>kclust=clusters.kcluster(data,k=10) >>>[rownames[r] for r in k[0]] Here is my code: from PIL import Image,ImageDraw def readfile(filename): lines=[line for line in file(filename)] # First line is the column titles colnames=lines[0].strip( ).split('\t')[1:] rownames=[] data=[] for line in lines[1:]: p=line.strip( ).split('\t') # First column in each row is the rowname rownames.append(p[0]) # The data for this row is the remainder of the row data.append([float(x) for x in p[1:]]) return rownames,colnames,data from math import sqrt def pearson(v1,v2): # Simple sums sum1=sum(v1) sum2=sum(v2) # Sums of the squares sum1Sq=sum([pow(v,2) for v in v1]) sum2Sq=sum([pow(v,2) for v in v2]) # Sum of the products pSum=sum([v1[i]*v2[i] for i in range(len(v1))]) # Calculate r (Pearson score) num=pSum-(sum1*sum2/len(v1)) den=sqrt((sum1Sq-pow(sum1,2)/len(v1))*(sum2Sq-pow(sum2,2)/len(v1))) if den==0: return 0 return 1.0-num/den class bicluster: def __init__(self,vec,left=None,right=None,distance=0.0,id=None): self.left=left self.right=right self.vec=vec self.id=id self.distance=distance def hcluster(rows,distance=pearson): distances={} currentclustid=-1 # Clusters are initially just the rows clust=[bicluster(rows[i],id=i) for i in range(len(rows))] while len(clust)>1: lowestpair=(0,1) closest=distance(clust[0].vec,clust[1].vec) # loop through every pair looking for the smallest distance for i in range(len(clust)): for j in range(i+1,len(clust)): # distances is the cache of distance calculations if (clust[i].id,clust[j].id) not in distances: distances[(clust[i].id,clust[j].id)]=distance(clust[i].vec,clust[j].vec) #print 'i' #print i #print #print 'j' #print j #print d=distances[(clust[i].id,clust[j].id)] if d<closest: closest=d lowestpair=(i,j) # calculate the average of the two clusters mergevec=[ (clust[lowestpair[0]].vec[i]+clust[lowestpair[1]].vec[i])/2.0 for i in range(len(clust[0].vec))] # create the new cluster newcluster=bicluster(mergevec,left=clust[lowestpair[0]], right=clust[lowestpair[1]], distance=closest,id=currentclustid) # cluster ids that weren't in the original set are negative currentclustid-=1 del clust[lowestpair[1]] del clust[lowestpair[0]] clust.append(newcluster) return clust[0] def kcluster(rows,distance=pearson,k=4): # Determine the minimum and maximum values for each point ranges=[(min([row[i] for row in rows]),max([row[i] for row in rows])) for i in range(len(rows[0]))] # Create k randomly placed centroids clusters=[[random.random( )*(ranges[i][1]-ranges[i][0])+ranges[i][0] for i in range(len(rows[0]))] for j in range(k)] lastmatches=None for t in range(100): print 'Iteration %d' % t bestmatches=[[] for i in range(k)] # Find which centroid is the closest for each row for j in range(len(rows)): row=rows[j] bestmatch=0 for i in range(k): d=distance(clusters[i],row) if d<distance(clusters[bestmatch],row): bestmatch=i bestmatches[bestmatch].append(j) # If the results are the same as last time, this is complete if bestmatches==lastmatches: break lastmatches=bestmatches # Move the centroids to the average of their members for i in range(k): avgs=[0.0]*len(rows[0]) if len(bestmatches[i])>0: for rowid in bestmatches[i]: for m in range(len(rows[rowid])): avgs[m]+=rows[rowid][m] for j in range(len(avgs)): avgs[j]/=len(bestmatches[i]) clusters[i]=avgs return bestmatches

    Read the article

  • Exception opening TAdoDataset: Arguments are of the wrong type, are out of acceptable range, or are

    - by Dave Falkner
    I've been trying to debug the following problem for several weeks now - this method is called from several places within the same datamodule, but this exception (from the subject line of this post) only occurs when integers for a certain purpose (pickup orders vs. orders that we ship through a carrier) are used - and don't ask me how the application can tell the difference between one integer's purpose and another! Furthermore, I cannot duplicate this issue on my machine - the error occurs on a warehouse machine but not my own development machine, even when working with the same production database. I have suspected an MDAC version conflict between the two machines, but have run a version checker and confirmed that both machines are running 2.8, and additionally have confirmed this by logging the TAdoDataset's .Version property at runtime. function TdmESShip.SecondaryID(const PrimaryID : Integer ): String; begin try with qESPackage2 do begin if Active then Close; LogMessage('-----------------------------------'); LogMessage('Version: ' + FConnection.Version); LogMessage('DB Info: ' + FConnection.Properties['Initial Catalog'].Value + ' ' + FConnection.Properties['Data Source'].Value); LogMessage('Setting the parameter.'); Parameters.ParamByName('ParameterName').Value := PrimaryID; LogMessage('Done setting the parameter.'); Open; Ninety-nine times out of 100 this logging code logs a successful operation as follows: Version: 2.8 DB Info: (database name and instance) Setting the parameter. Done setting the parameter. Opened the dataset. But then whenever a "pickup" order is processed, this exception gets thrown whenever the dataset is opened: Version: 2.8 DB Info: (database name and instance) Setting the parameter. Done setting the parameter. GetESPackageID() threw an exception. Type: EOleException, Message: Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another Error: Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another for packageID 10813711 I've tried eliminating the parameter and have built the commandtext for this dataset programmatically, suspecting that some part of the TParameter's configuration might be out of whack, but the same error occurs under the same circumstances. I've tried every combination of TParameter properties that I can think of - this is the millionth TParameter I've created for my millionth dataset, and I've never encountered this error. I've even created a second dataset from scratch and removed all references to the original dataset in case some property of the original dataset in the .dfm might be corrupted, but the same error occurs under the same circumstances. The commandtext for this dataset is a simple select ValueA from TableName where ValueB = @ParameterB I'm about ready to do something extreme, such as writing a web service to look these values up - it feels right now as though I could destroy my machine, rebuild it, rewrite this entire application from scratch, and the application would still know to throw an exception whenever I try to look up a secondary value from a primary value, but only for pickup orders, and only from the one machine in the warehouse, but I'm probably missing something simple. So, any help anyone could provide would be greatly appreciated.

    Read the article

  • OpenGL suppresses exceptions in MFC dialog-based application

    - by Mikhail
    Hello. I have an MFC-driven dialog-based application created with MSVS2005. Here is my problem step by step. I have button on my dialog and corresponding click-handler with code like this: int* i = 0; *i = 3; I'm running debug version of program and when I click on the button, Visual Studio catches focus and alerts "Access violation writing location" exception, program cannot recover from the error and all I can do is to stop debugging. And this is the right behavior. Now I add some OpenGL initialization code in the OnInitDialog() method: HDC DC = GetDC(GetSafeHwnd()); static PIXELFORMATDESCRIPTOR pfd = { sizeof(PIXELFORMATDESCRIPTOR), // size of this pfd 1, // version number PFD_DRAW_TO_WINDOW | // support window PFD_SUPPORT_OPENGL | // support OpenGL PFD_DOUBLEBUFFER, // double buffered PFD_TYPE_RGBA, // RGBA type 24, // 24-bit color depth 0, 0, 0, 0, 0, 0, // color bits ignored 0, // no alpha buffer 0, // shift bit ignored 0, // no accumulation buffer 0, 0, 0, 0, // accum bits ignored 32, // 32-bit z-buffer 0, // no stencil buffer 0, // no auxiliary buffer PFD_MAIN_PLANE, // main layer 0, // reserved 0, 0, 0 // layer masks ignored }; int pixelformat = ChoosePixelFormat(DC, &pfd); SetPixelFormat(DC, pixelformat, &pfd); HGLRC hrc = wglCreateContext(DC); ASSERT(hrc != NULL); wglMakeCurrent(DC, hrc); Of course this is not exactly what I do, it is the simplified version of my code. Well now the strange things begin to happen: all initialization is fine, there are no errors in OnInitDialog(), but when I click the button... no exception is thrown. Nothing happens. At all. If I set a break-point at the *i = 3; and press F11 on it, the handler-function halts immediately and focus is returned to the application, which continue to work well. I can click button again and the same thing will happen. It seems like someone had handled occurred exception of access violation and silently returned execution into main application message-receiving cycle. If I comment the line wglMakeCurrent(DC, hrc);, all works fine as before, exception is thrown and Visual Studio catches it and shows window with error message and program must be terminated afterwards. I experience this problem under Windows 7 64-bit, NVIDIA GeForce 8800 with latest drivers (of 11.01.2010) available at website installed. My colleague has Windows Vista 32-bit and has no such problem - exception is thrown and application crashes in both cases. Well, hope good guys will help me :) PS The problem originally where posted under this topic.

    Read the article

  • Java "compare cannot be resolved to a type" error

    - by King Triumph
    I'm getting a strange error when attempting to use a comparator with a binary search on an array. The error states that "compareArtist cannot be resolved to a type" and is thrown by Eclipse on this code: Comparator<Song> compare = new Song.compareArtist(); I've done some searching and found references to a possible bug with Eclipse, although I have tried the code on a different computer and the error persists. I've also found similar issues regarding the capitalization of the compare method, in this case compareArtist. I've seen examples where the first word in the method name is capitalized, although it was my understanding that method names are traditionally started with a lower case letter. I have experimented with changing the capitalization but nothing has changed. I have also found references to this error if the class doesn't import the correct package. I have imported java.util in both classes in question, which to my knowledge allows the use of the Comparator. I've experimented with writing the compareArtist method within the class that has the binary search call as well as in the "Song" class, which according to my homework assignment is where it should be. I've changed the constructor accordingly and the issue persists. Lastly, I've attempted to override the Comparator compare method by implementing Comparator in the Song class and creating my own method called "compare". This returns the same error. I've only moved to calling the comparator method something different than "compare" after finding several examples that do the same. Here is the relevant code for the class that calls the binary search that uses the comparator. This code also has a local version of the compareArtist method. While it is not being called currently, the code for this method is the same as the in the class Song, where I am trying to call it from. Thanks for any advice and insight. import java.io.*; import java.util.*; public class SearchByArtistPrefix { private Song[] songs; // keep a direct reference to the song array private Song[] searchResults; // holds the results of the search private ArrayList<Song> searchList = new ArrayList<Song>(); // hold results of search while being populated. Converted to searchResults array. public SearchByArtistPrefix(SongCollection sc) { songs = sc.getAllSongs(); } public int compareArtist (Song firstSong, Song secondSong) { return firstSong.getArtist().compareTo(secondSong.getArtist()); } public Song[] search(String artistPrefix) { String artistInput = artistPrefix; int searchLength = artistInput.length(); Song searchSong = new Song(artistInput, "", ""); Comparator<Song> compare = new Song.compareArtist(); int search = Arrays.binarySearch(songs, searchSong, compare);

    Read the article

  • Why does SFINAE not apply to this?

    - by Simon Buchan
    I'm writing some simple point code while trying out Visual Studio 10 (Beta 2), and I've hit this code where I would expect SFINAE to kick in, but it seems not to: template<typename T> struct point { T x, y; point(T x, T y) : x(x), y(y) {} }; template<typename T, typename U> struct op_div { typedef decltype(T() / U()) type; }; template<typename T, typename U> point<typename op_div<T, U>::type> operator/(point<T> const& l, point<U> const& r) { return point<typename op_div<T, U>::type>(l.x / r.x, l.y / r.y); } template<typename T, typename U> point<typename op_div<T, U>::type> operator/(point<T> const& l, U const& r) { return point<typename op_div<T, U>::type>(l.x / r, l.y / r); } int main() { point<int>(0, 1) / point<float>(2, 3); } This gives error C2512: 'point<T>::point' : no appropriate default constructor available Given that it is a beta, I did a quick sanity check with the online comeau compiler, and it agrees with an identical error, so it seems this behavior is correct, but I can't see why. In this case some workarounds are to simply inline the decltype(T() / U()), to give the point class a default constructor, or to use decltype on the full result expression, but I got this error while trying to simplify an error I was getting with a version of op_div that did not require a default constructor*, so I would rather fix my understanding of C++ rather than to just do what works. Thanks! *: the original: template<typename T, typename U> struct op_div { static T t(); static U u(); typedef decltype(t() / u()) type; }; Which gives error C2784: 'point<op_div<T,U>::type> operator /(const point<T> &,const U &)' : could not deduce template argument for 'const point<T> &' from 'int', and also for the point<T> / point<U> overload.

    Read the article

< Previous Page | 434 435 436 437 438 439 440 441 442 443 444 445  | Next Page >