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  • How do I indicate that a class doesn't support certain operators?

    - by romeovs
    I'm writing a class that represents an ordinal scale, but has no logical zero-point (eg time). This scale should permit addition and substraction (operator+, operator+=, ...) but not multiplication. Yet, I always felt it to be a good practice that when one overloads one operator of a certain group (in this case the math operators), one should also overload all the others that belong to that group. In this case that would mean I should need to overload the multiplication and division operators also, because if a user can use A+B he would probable expect to be able the other operators. Is there a method that I can use to throw an error for this at compiler time? The easiest method would be just no to overload the operators operator*, ... yet it would seem appropriate to add a bit more explaination than operator* is not know for class "time". Or is this something that I really should not care about (RTFM user)?

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  • Doctrine2 - relationship

    - by Filip Golonka
    I'm developing an application, which is looking for optimal route and timetable in public transport. I have some experience about Doctrine1, but it's my first time with Doctrine2. There is soem new fields to describe relations (mappedBy and inversedBy) and also some new ways of mapping. I have following code: $query = $this->em->createQuery("SELECT partial cls.{stop}, partial t.{arriveTime, departureTime} FROM \Entities\Timetable t JOIN t.ride r JOIN t.carrierLineStop cls WHERE t.departureTime>=:time AND r.idCarrierLine=:carrierLine AND (cls.idStop=:firstStop OR cls.idStop=:lastStop)"); $query->setParameters(array( 'time' => $time, 'carrierLine' => $path->getLine(), 'firstStop' => $path->getFirstStop(), 'lastStop' => $path->getLastStop() )); When I try to execute that script I've got an error: [Semantical Error] line 0, col 24 near '}, partial t.{arriveTime,': Error: There is no mapped field named 'stop' on class Entities\CarrierLineStop. Mapping files: Entities\CarrierLineStop: type: entity table: carrier_line_stop fields: idCarrierLineStop: id: true type: integer unsigned: false nullable: false column: id_carrier_line_stop generator: strategy: IDENTITY nextStop: type: integer unsigned: false nullable: true column: next_stop manyToOne: idCarrierLine: targetEntity: Entities\CarrierLine cascade: { } mappedBy: null inversedBy: null joinColumns: id_carrier_line: referencedColumnName: id_carrier_line orphanRemoval: false stop: column: id_stop targetEntity: Entities\Stop cascade: { } mappedBy: null inversedBy: carrierLineStop joinColumns: id_stop: referencedColumnName: id_stop orphanRemoval: false lifecycleCallbacks: { } - Entities\Stop: type: entity table: stop fields: idStop: id: true type: integer unsigned: false nullable: false column: id_stop generator: strategy: IDENTITY name: type: string length: 45 fixed: false nullable: true miejscowosc: type: string length: 45 fixed: false nullable: true latitude: type: decimal nullable: true longitude: type: decimal nullable: true oneToMany: carrierLineStop: targetEntity: Entities\CarrierLineStop cascade: { } mappedBy: stop inversedBy: null joinColumns: id_stop: referencedColumnName: id_stop orphanRemoval: false lifecycleCallbacks: { } I have no idea about where the problem is...

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  • C# SendMessage to C++ WinProc

    - by jws
    I need to send a string from C# to a C++ WindowProc. There are a number of related questions on SO related to this, but none of the answers have worked for me. Here's the situation: PInvoke: [DllImport("user32", CharSet = CharSet.Auto)] public extern static int SendMessage(IntPtr hWnd, uint wMsg, IntPtr wParam, string lParam); C#: string lparam = "abc"; NativeMethods.User32.SendMessage(handle, ConnectMsg, IntPtr.Zero, lparam); C++: API LRESULT CALLBACK HookProc (int code, WPARAM wParam, LPARAM lParam) { if (code >= 0) { CWPSTRUCT* cwp = (CWPSTRUCT*)lParam; ... (LPWSTR)cwp->lParam <-- BadPtr ... } return ::CallNextHookEx(0, code, wParam, lParam); } I've tried a number of different things, Marshalling the string as LPStr, LPWStr, also tried creating an IntPtr from unmanaged memory, and writing to it with Marshal.WriteByte. The pointer is the correct memory location on the C++ side, but the data isn't there. What am I missing?

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  • PHP and MS Access: Number of Records returned by SELECT query

    - by VarunGupta
    I am running following PHP code to interact with a MS Access database. $odbc_con = new COM("ADODB.Connection"); $constr = "DRIVER={Microsoft Access Driver (*.mdb)}; DBQ=" . $db_path . ";"; $odbc_con -> open($constr); $rs_select = $odbc_con -> execute ("SELECT * FROM Main"); Using ($rs_select - RecordCount) gives -1 though the query is returning non-zero records. (a) What can be the reason? (b) Is there any way out? I have also tried using count($rs_select -> GetRows()). This satisfies the need but looks inefficient as it will involve copying of all the records into an array first.

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  • Where can an absolute beginner of Kohana PHP go to learn how to use it from the ground up?

    - by Sergio Tapia
    Hi guys! I have a month of free time and I've decided to launch my own website. It's going to be big and have dymanic content where different users with different roles can perform modifications to the site. Place comments, rate stores, list items, etc. This sound like a perfect opportunity for me to expand my horizons and learn a PHP Framework. I've used PHP bare bones before but nothing too complex. As of now, do you think Kohana is a mature framework to use? I've used Zend in the past for a course in Uni but it sucked horribly, I was new to the MVC model, but Zend had pretty much zero workable tutorials and guides for newbies. That's why I hated it. Where can I go to learn how to use Kohana from a retarded starting point? Thank you very much for your time.

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  • Why doesn't ConcurrentQueue<T>.Count return 0 when IsEmpty == true?

    - by DanTup - Danny Tuppeny
    I was reading about the new concurrent collection classes in .NET 4 on James Michael Hare's blog, and the page talking about ConcurrentQueue<T> says: It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. I'm curious - if there is a reason to use IsEmpty instead of comparing Count to 0, why does the class not internally check IsEmpty and return 0 before doing any of the expensive work to count? E.g.: public int Count { get { // Check IsEmpty so we can bail out quicker if (this.IsEmpty) return 0; // Rest of "expensive" counting code } } It seems strange to suggest this if it could be "fixed" so easily with no side-effects?

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  • Warning as Error - How to rid these

    - by coffeeaddict
    I cannot figure out how to get rid of errors that basically should not be halting my compile in VS 2010 and should not be show stoppers, or at least I will fix them later but I don't want the compile to just error and halt on these kinds of problems. For example I'm getting the following error: Error 1 Warning as Error: XML comment on 'ScrewTurn.Wiki.SearchEngine.Relevance.Finalize(float)' has a paramref tag for 'IsFinalized', but there is no parameter by that name C:\www\Wiki\Screwturn3_0_2_509\SearchEngine\Relevance.cs 60 70 SearchEngine for this code: /// /// Normalizes the relevance after finalization. /// /// The normalization factor. /// If is false ( was not called). public void NormalizeAfterFinalization(float factor) { if(factor < 0) throw new ArgumentOutOfRangeException("factor", "Factor must be greater than or equal to zero"); if(!isFinalized) throw new InvalidOperationException("Normalization can be performed only after finalization"); value = value * factor; } I looked in Tools | Options and I don't see where I can tweak the compiler and tell it not to worry about comment or XHTML based errors.

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  • Problem about socket communication

    - by Ahmet Altun
    I have two separate socket projects in VS.NET. One of them is sender, other one is receiver. After starting receiver, i send data from sender. Although send method returns 13 bytes as successfully transferred, the receiver receives 0 (zero). The receiver accepts sender socket and listens to it. But cannot receive data. Why? P.S. : If sender code is put in receiver project, receiver can get data, as well.

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  • fortran error I/O

    - by jpcgandre
    I get this error when compiling: forrtl: severe (256): unformatted I/O to unit open for formatted transfers, unit 27, file C:\Abaqus_JOBS\w.txt The error occurs in the beginning of the analysis. At the start, the file w.txt is created but is empty. The error may be related to the fact that I want to read from an empty file. My code is: OPEN(27, FILE = "C:/Abaqus_JOBS/w.txt", status = "UNKNOWN") READ(27, *, iostat=stat) w IF (stat .NE. 0) CALL del_file(27, stat) SUBROUTINE del_file(uFile, stat) IMPLICIT NONE INTEGER uFile, stat C If the unit is not open, stat will be non-zero CLOSE(unit=uFile, status='delete', iostat=stat) END SUBROUTINE Ref: Close multiple files If you agree with my opion about the cause of the error, is there a way to solve it? Thanks

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  • Problem with averaging corrupted images to eliminate the noise in MATLAB

    - by Mertie Pertie
    I want to average some .jpg images which are corrupted by zero-mean Gaussian additive noise. After searching around, I figured out to add the image matrices and divide the sum by the number of matrices. However, the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But when I use more images it gets darker. I am using 800x600 black and white .jpg images. Here is the script I used: image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av);

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  • create board for game with events support in WPF

    - by netmajor
    How can I create board for simple game, looks like for chess,but user could dynamically change number of column and rows? In cells I could insert symbol of pawn, like small image or just ellipse or rectangle with fill. This board should have possibility add and remove pawn from cells and move pown from one cell to another. My first idea was Grid. I do it in code behind, but it's hurt to implement events or everything in runtime create board :/ int size = 12; Grid board = new Grid(); board.ShowGridLines = true; for (int i = 0; i < size;i++ ) { board.ColumnDefinitions.Add(new ColumnDefinition()); board.RowDefinitions.Add(new RowDefinition()); } //komputer Rectangle ai = new Rectangle(); ai.Height = 20; ai.Width = 20; ai.AllowDrop = true; ai.Fill = Brushes.Orange; Grid.SetRow(ai, 0); Grid.SetColumn(ai,0); //czlowiek Rectangle hum = new Rectangle(); hum.Height = 20; hum.Width = 20; hum.AllowDrop = true; hum.Fill = Brushes.Green; Grid.SetRow(hum,size); Grid.SetColumn(hum,size); board.Children.Add(ai); board.Children.Add(hum); this.Content = board; It's a way to do this dynamically col and row change in XAML ? It's better way to implement that board create and implement events on move pawn from one cell to another ?

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  • Range annotation between nothing and 100?

    - by aticatac
    Hi I have a [Range] annotation that looks like this: [Range(0, 100)] public int AvailabilityGoal { get; set; } It works as it should, I can only enter values between 0 and 100 but I also want the input box to be optional, the user shouldn't get an validation error if the input box is empty. If the user leaves it empty it should make AvailabilityGoal = 0 but I don't want to force the user to enter a zero. I tried this but it (obviously) didn't work: [Range(typeof(int?), null, "100")] Is it possible to solve this with Data Annotations or in some other way? Thanks in advance. Bobby

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  • JS 2 minute countdown then execute a function?

    - by Cyprus106
    I'm not that great at Javascript, for the record! I DO know how to use ajax. I just need a bit of help. I'm having a hard time figuring out how to display a 5 minute countdown, and once the countdown hits zero, to run a function. I need to pass a variable to the function that needs to run. I tried SetInterval but this isn't exactly my strong suit. Does anyone have any suggestions? I can post the code I've got, but I would equate it to a gorilla fumbling in the dark at a typewriter!

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  • getting web page data as json object?

    - by encryptor
    I have a url, the data of which page i need as a json object. I ve tried xmlhttprequest and ajaxobject both but doesnt work. It doesnt even give a responseText when I give it as an alert Ill post both the code snippets here. url = http://mydomain.com:port/a/b/c AJAX : var ajaxRequest = new ajaxObject(URL); ajaxRequest.callback = function (responseText,responseStatus) { alert(responseStatus); JSONData = responseText.parseJSON(); processData(JSONData); } USING xmlhttprequest: var client = new XMLHttpRequest(); client.open('GET',URL,true ); data = JSON.parse(client.responseText); alert(data.links.length); can someone please help me out with this. I understand cross scripting may be an issue, but how to come over it? and shouldn't then too it should give the alerts as zero or null

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  • Hashtable is that fast

    - by Costa
    Hi s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]. Is the hash function of the java string, I assume the rest of languages is similar or close to this implementation. If we have hash-Table and a list of 50 elements. each element is 7 chars ABCDEF1, ABCDEF2, ABCDEF3..... ABCDEFn If each bucket of hashtable contains 5 strings (I think this function will make it one string per bucket, but let us assume it is 5). If we call col.Contains("ABCDEFn"); // will do 6 comparisons and discover the difference on the 7th. The hash-table will take around 70 operations (multiplication and additions) to get the hashcode and to compare with 5 strings in bucket. and BANG it found. For list it will take around 300 comparisons to find it. for the case that there is only 10 elements, the list will take around 70 operations but the Hashtable will take around 50 operations. and note that hashtable operations are more time consuming (it is multiplications). I conclude that HybirdDictionary in .Net probably is the best choice for that most cases that require Hashtable with unknown size, because it will let me use a list till the list becomes more than 10 elements. still need something like HashSet rather than a Dictionary of keys and values, I wonder why there is no HybirdSet!! So what do u think? Thanks

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  • Can I do transactions and locks in CouchDB?

    - by damian
    I need to do transactions (begin, commit or rollback), locks (select for update). How can I do it in a document model db? Edit: The case is this: I want to run an auctions site. And I think how to direct purchase as well. In a direct purchase I have to decrement the quantity field in the item record, but only if the quantity is greater than zero. That is why I need locks and transactions. I don't know how to address that without locks and/or transactions. Can I solve this with CouchDB?

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  • Is there alternative way to write this query?

    - by Kugel
    I have tables A, B, C, where A represents items which can have zero or more sub-items stored in C. B table only has 2 foreign keys to connect A and C. I have this sql query: select * from A where not exists (select * from B natural join C where B.id = A.id and C.value > 10); Which says: "Give me every item from table A where all sub-items have value less than 10. Is there a way to optimize this? And is there a way to write this not using exists operator?

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  • Eliminating cyclic flows from a graph

    - by Jon Harrop
    I have a directed graph with flow volumes along edges and I would like to simplify it by removing all cyclic flows. This can be done by finding the minimum of the flow volumes along each edge in any given cycle and reducing the flows of every edge in the cycle by that minimum volume, deleting edges with zero flow. When all cyclic flows have been removed the graph will be acyclic. For example, if I have a graph with vertices A, B and C with flows of 1 from A?B, 2 from B?C and 3 from C?A then I can rewrite this with no flow from A?B, 1 from B?C and 2 from C?A. The number of edges in the graph has reduced from 3 to 2 and the resulting graph is acyclic. Which algorithm(s), if any, solve this problem?

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  • Averaging corrupted images to eliminate the noise in Matlab

    - by Mertie Pertie
    Hi all As you can get it from the title, I want to average some .jpg images which are corrupted by zero-mean Gaussian additive. After searching over internet, I figured out to add image matrices and divide the sum by the # of matrices. However the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But When I use more images it gets darker. I am using 800x600 black and white images with .jpg ext Here is the script I used; image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av); Thanks in advance

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  • Why does a C# System.Decimal remember trailing zeros?

    - by Rob Davey
    Is there a reason that a C# System.Decimal remembers the number of trailing zeros it was entered with? See the following example: public void DoSomething() { decimal dec1 = 0.5M; decimal dec2 = 0.50M; Console.WriteLine(dec1); //Output: 0.5 Console.WriteLine(dec2); //Output: 0.50 Console.WriteLine(dec1 == dec2); //Output: True } The decimals are classed as equal, yet dec2 remembers that it was entered with an additional zero. What is the reason/purpose for this?

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  • Tool to diagonalize large matrices

    - by Xodarap
    I want to compute a diffusion kernel, which involves taking exp(b*A) where A is a large matrix. In order to play with values of b, I'd like to diagonalize A (so that exp(A) runs quickly). My matrix is about 25k x 25k, but is very sparse - only about 60k values are non-zero. Matlab's "eigs" function runs of out memory, as does octave's "eig" and R's "eigen." Is there a tool to find the decomposition of large, sparse matrices? Dunno if this is relevant, but A is an adjacency matrix, so it's symmetric, and it is full rank.

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  • Latex multicols. Can I group content so it won't split over cols and/or suggest colbreaks?

    - by valadil
    Hi. I'm trying to learn LaTeX. I've been googling this one for a couple days, but I don't speak enough LaTeX to be able to search for it effectively and what documentation I have found is either too simple or goes way over my head (http://www.uoregon.edu/~dspivak/files/multicol.pdf) I have a document using the multicol package. (I'm actually using multicols* so that the first col fills before the second begins instead of trying to balance them, but I don't think that's relevant here.) The columns output nicely, but I want to be able to indicate that some content won't be broken up into different columns. For instance, aaaaaaaa bbbbbbb aaaaaaaa bbbbbbb aaaaaaaa ccccccc bbbbbbbb ccccccc That poor attempt at ascii art columns is what's happening. I'd like to indicate that the b block is a whole unit that shouldn't be broken up into different columns. Since it doesn't fit under the a block, the entirety of the b block should be moved to the second column. Should b be wrapped in something? Is there a block/float/section/box/minipage/paragraph structure I can use? Something specific to multicol? Alternatively is there a way that I can suggest a columnbreak? I'm thinking of something like \- that suggests a hyphenated line break if its convenient, but this would go between blocks. Thanks!

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  • Hebbian learning

    - by Bane
    I have asked another question on Hebbian learning before, and I guess I got a good answer which I accepted, but, the problem is that I now realize that I've mistaken about Hebbian learning completely, and that I'm a bit confused. So, could you please explain how it can be useful, and what for? Because the way Wikipedia and some other pages describe it - it doesn't make sense! Why would we want to keep increasing the weight between the input and the output neuron if the fire together? What kind of problems can it be used to solve, because when I simulate it in my head, it certainly can't do the basic AND, OR, and other operations (say you initialize the weights at zero, the output neurons never fire, and the weights are never increased!)

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  • Sonata Media Bundle sortBy created_at

    - by tony908
    I use SonataMediaBundle and i would like sort Gallery by created_at field. In repository class i have (without orderBy working good!): $qb = $this->createQueryBuilder('m') ->orderBy('j.expires_at', 'DESC'); $query = $qb->getQuery(); return $query->getResult(); and this throw error: An exception has been thrown during the rendering of a template ("[Semantical Error] line 0, col 80 near 'created_at D': Error: Class Application\Sonata\MediaBundle\Entity\Gallery has no field or association named created_at") so i add this field to Gallery class: /** * @var \DateTime */ private $created_at; /** * Set created_at * * @param \DateTime $createdAt * @return Slider */ public function setCreatedAt($createdAt) { $this->created_at = $createdAt; return $this; } /** * Get created_at * * @return \DateTime */ public function getCreatedAt() { return $this->created_at; } but now i have error: FatalErrorException: Compile Error: Declaration of Application\Sonata\MediaBundle\Entity\Gallery::setCreatedAt() must be compatible with Sonata\MediaBundle\Model\GalleryInterface::setCreatedAt(DateTime $createdAt = NULL) in /home/tony/www/test/Application/Sonata/MediaBundle/Entity/Gallery.php line 32 GalleryInterface: https://github.com/sonata-project/SonataMediaBundle/blob/master/Model/GalleryInterface.php So... how can i use sortBy in my example?

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  • Can't use where clause on correlated columns.

    - by Keyo
    I want to add a where clause to make sure video_count is greater than zero. Only categories which are referenced once or more in video_category.video_id should be returned. Because video_count is not a field in any table I cannot do this. Here is the query. SELECT category . * , ( SELECT COUNT( * ) FROM video_category WHERE video_category.category_id = category.category_id ) AS 'video_count' FROM category WHERE category.status = 1 AND video_count > '0' AND publish_date < NOW() ORDER BY updated DESC; Thanks for the help.

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