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  • Simple C++ container class that is thread-safe for writing

    - by conradlee
    I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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  • What is the best way to expose a callback API - C++

    - by rursw1
    Hi, I have a C++ library that should expose some system\ resource calls as callbacks from the linked application. For example: the interfacing application (which uses this library) can send socket management callback functions - send, receive, open, close etc., and the library will use this implementation in stead of the library's implementation. (This way enables the application to manage the sockets by itself, can be useful). This library has to expose also more callbacks, like, for example, a password validation, so I wonder if there is a preferred method to expose the callback sending option in one API. Something like: int AddCallbackFunc (int functionCallbackType, <generic function prototype>, <generic way to pass some additional arguments>) Then within my library I will assign the callback to the appropriate function pointer according to the functionCallbackType parameter. Is there any way to implement it in a generic way which will fit ANY function prototype and ANY additional arguments? Your help will be more than appreciated... Thanks!

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  • Reading a file over a network path

    - by Sin5k4
    I have this weird issue,when I use > File FileToRead = new File("\\\\MYSERVER\\MYFOLDER\\MYFOLDER\\MYPICTURE.JPG"); to read a file over a network,all I get is a null pointer exception.Normally a local path works with this,but when on a network path,I just couldn't manage to get it to work.Any ideas? PS:oh and my network connection seems to work,no issues when accessing data in windows explorer... More of the code: File FileToRead = new File("file://DOKSERVICE/Somefolder/ProductImage/01001.JPG"); // File FileToRead = new File("c:\\dog.jpg"); local test BufferedImage image = ImageIO.read(FileToRead); BufferedImage resizedimage = new BufferedImage(260, 260,BufferedImage.TYPE_INT_RGB ); Graphics2D g = resizedimage.createGraphics(); g.drawImage(image, 0, 0, 260, 260, null); g.dispose(); picture.setIcon(new ImageIcon(image));

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  • What exactly does a self-describing type in .Net mean?

    - by tzup
    Given this MSDN article, we learn that the Common Type System in .Net has this classification of reference types: "Reference types can be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values of self-describing types. Self-describing types are further split into arrays and class types." So an array, for instance, is a self-describing type because we can determine it's type from its values? How? Is that it, or is there more to this definition?

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  • Linq GroupBy - how to specify the grouping key at runtime?

    - by toasteroven
    is there a good way to do a Linq GroupBy where the grouping key is determined at runtime? e.g. I want the grouping key to be built from a user-selected list of fields - can you do this? I know I can do it easily if I convert everything to a table of strings, but I was wondering if there was an elegant or clever way to accomplish this otherwise. class Item { public int A, B; public DateTime D; public double X, Y, Z; } I have a List<Item> called data. I want to do things like retrieve the sum of X grouped by A, or the sums of X, Y, and Z, grouped by A and B. but what fields go into the grouping should be able to be specified at runtime in some way.

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  • Remove duplicates in entries, scala way

    - by andersbohn
    I have a list of entries stating a production value in a given interval. Entries stating the exact same value at a later time adds no information and can safely be left out. case class Entry(minute:Int, production:Double) val entries = List(Entry(0, 100.0), Entry(5, 100.0), Entry(10, 100.0), Entry(20, 120.0), Entry(30, 100.0), Entry(180, 0.0)) Experimenting with the scala 2.8 collection functions, so far I have this working implementation: entries.foldRight(List[Entry]()) { (entry, list) => list match { case head :: tail if (entry.production == head.production) => entry :: tail case head :: tail => entry :: list case List() => entry :: List() } } res0: List[Entry] = List(Entry(0,100.0), Entry(20,120.0), Entry(30,100.0), Entry(180,0.0)) Any comments? Am I missing out on some scala magic?

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  • memset on array of structures in C++

    - by garry
    I have another memset question. It appears as if the code I am editing may have some issues (or it's not done the same way in different files) A::LRM las[9]; //A and LRM are both structures with BOOLS and INTS memset(&las, 0, sizeof(las)); typedef Sec SecArray[16]; SecArray rad_array; memset(rad_array, 0, sizeof(SecArray)); The second example appears to be correct because rad_array is the same as the first position in the array. Then the sizeof(SecArray)) would make sense. The first one doesn't seem correct to me. All structs are just BOOLs and INTS nothing dynamic in them. My understanding from my other post about memset was that it followed this format. memset("pointer to object", "what to set it to", "size of object") Can anyone tell me what exactly is going on here if I am incorrect with my theory.

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  • What are possible suffixes after variable name in VBA?

    - by archimed7592
    As I've already figured out, there is at least six of them: !@#$%&. Here is snip: Dim A!, B@, C#, D$, E%, F& Debug.Print "A! - " & TypeName(A) Debug.Print "B@ - " & TypeName(B) Debug.Print "C# - " & TypeName(C) Debug.Print "D$ - " & TypeName(D) Debug.Print "E% - " & TypeName(E) Debug.Print "F& - " & TypeName(F) Outputs A! - Single B@ - Currency C# - Double D$ - String E% - Integer F& - Long Where is documentation on this syntax sugar? What other possible suffixes are there? Is there one for Date?

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  • Floating point innacuracies

    - by Greg
    While writing a function which will perform some operation with each number in a range I ran into some problems with floating point inaccuracies. The problem can be seen in the code below: #include <iostream> using namespace std; int main() { double start = .99999, end = 1.00001, inc = .000001; int steps = (end - start) / inc; for(int i = 0; i <= steps; ++i) { cout << (start + (inc * i)) << endl; } } The problem is that the numbers the above program outputs look like this: 0.99999 0.999991 0.999992 0.999993 0.999994 0.999995 0.999996 0.999997 0.999998 0.999999 1 1 1 1 1 1.00001 1.00001 1.00001 1.00001 1.00001 1.00001 They only appear to be correct up to the first 1. What is the proper way to solve this problem?

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  • How to interpret situations where Math.Acos() reports invalid input?

    - by Sean Ochoa
    Hey all. I'm computing the angle between two vectors, and sometimes Math.Acos() returns NaN when it's input is out of bounds (-1 input && input 1) for a cosine. What does that mean, exactly? Would someone be able to explain what's happening? Any help is appreciated! Here's me method: public double AngleBetween(vector b) { var dotProd = this.Dot(b); var lenProd = this.Len*b.Len; var divOperation = dotProd/lenProd; // http://msdn.microsoft.com/en-us/library/system.math.acos.aspx return Math.Acos(divOperation) * (180.0 / Math.PI); }

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  • Why do virtual memory addresses for linux binaries start at 0x8048000?

    - by muteW
    Disassembling an ELF binary on a Ubuntu x86 system I couldn't help but notice that the code(.text) section starts from the virtual address 0x8048000 and all lower memory addresses seem to be unused. This seems to be rather wasteful and all Google turns up is either folklore involving STACK_TOP or protection against null-pointer dereferences. The latter case looks like it can be fixed by using a single page instead of leaving a 128MB gap. So my question is this - is there a definitive answer to why the layout has been fixed to these values or is it just an arbitrary choice?

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  • read text file line by line and insert/update values in table

    - by I__
    i am exploring the option of whether DoCmd.TransferText will do what i need, and it seems like it wont. i need to insert data if it does not exist and update it if it does exist i am planning to read a text file line by line like this: Dim intFile As Integer Dim strLine As String intFile = FreeFile() Open myFile For Input As #intFile Line Input #intFile, strLine Close #intFile i guess each individual line will be a record. it will probably be comma separated and some fields will have a " text qualifier because within the field itself i will have commas my question is how would i read a comma delimited text file that has double quotes sometimes as text qualifiers into a table in access?

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  • Looking at the C++ new[] cookie. How portable is this code?

    - by carleeto
    I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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  • C++ inheritance question

    - by user233973
    Hi guys, I have a C++ inheritance related question. I have a set of classes like this (I have not given the complete class structure coz I am lazy :) ). I want to access chiComponent class public methods using com pointer. How should I go about it? Note that I am having to change the object which "com" is pointing to in a lot of places. So I do not think I can have another chiComponent *ccom = <some_cast> com; ccom.chiComponentMethod() How should I go about it? class Component{ }; class chiComponent : public Component { public: void chiComponentMethod() { cout << "Hi! Chi component function called!!"; } } class parent { protected: Component *com; }; class child : public parent{ public: child() { com = new chiComponent(); } } Regards Arun

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  • Clickonce application does not update or launch.

    - by jhunter
    I have a winforms application that I have deployed using clickonce, but the users navigate to a network drive and double click on setup.msi instead of using a webpage to install it. I have two users that have it installed and it's worked in the past. I did an udpate last week and now when the users try to launch the application the window that says "Verifying Application Requirements" pops up then when it disappears nothing happens. The dialog asking if it's ok to update never pops up. The network people have verified that they have permissions on the network drive (though, I would expect an error message if this were the issue). Any clues what could cause this to happen?

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  • render json data returned from mvc controller

    - by user1765862
    I'm having js function which calls mvc controller action method which return list of data as json. function FillCountryCities(countryId) { $.ajax({ type: 'GET', url: '/User/FillCityCombo', data: { countryId: countryId }, contentType: 'application/json', success: function (data) { alert(data[0].Name); } error: function () { alert('something bad happened'); } .... format of data which sent back from controller is Name (string) and Id (Guid) Now I just want to alert Name on success first item from collection. Double checked controller sends 20 records, so it should alert first from collection but I'm getting error something bad happened update: public JsonResult FillCityCombo(Guid countryId) { var cities = repository.GetData() .Where(x = x.Country.Id == countryId).ToList(); if (Request.IsAjaxRequest()) { return new JsonResult { Data = cities, JsonRequestBehavior = JsonRequestBehavior.AllowGet }; } else { return new JsonResult { Data = "Not Valid Request", JsonRequestBehavior = JsonRequestBehavior.AllowGet }; } }

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  • What is the logic behind defining macros inside a struct?

    - by systemsfault
    As apparent in the title, I'm questioning the reason behind defining the macros inside a struct. I frequently see this approach in network programming for instance following snippet: struct sniff_tcp { u_short th_sport; /* source port */ u_short th_dport; /* destination port */ tcp_seq th_seq; /* sequence number */ tcp_seq th_ack; /* acknowledgement number */ u_char th_offx2; /* data offset, rsvd */ #define TH_OFF(th) (((th)->th_offx2 & 0xf0) >> 4) u_char th_flags; #define TH_FIN 0x01 #define TH_SYN 0x02 #define TH_RST 0x04 #define TH_PUSH 0x08 #define TH_ACK 0x10 #define TH_URG 0x20 #define TH_ECE 0x40 #define TH_CWR 0x80 #define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR) u_short th_win; /* window */ u_short th_sum; /* checksum */ u_short th_urp; /* urgent pointer */ }; This example is from sniffex.c code in tcpdump's web site. Is this for enhancing readability and making code clearer.

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  • How do I change the class of an object to a subclass of its current class in C++?

    - by Jared P
    I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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  • How to add style to parent <li> item if child <ul> exists?

    - by user1292760
    I'm trying to make a menu in advance to be seen whether there is a double nesting. <ul class="parent"> <li class="child"></li> <li class="child"> <ul slass="nesting"> <li></li> <li></li> </ul> </li> <li class="child"></li> </ul> So ul class="nesting" hidden by default but appears during the hover of li class="child". I want to make another design on the li class="child" which have a nested ul. Another words how can i show nesting before hover by the means of Javascript/JQuery? Thnaks in advance!

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  • Calculating the angle between two points

    - by kingrichard2005
    I'm currently developing a simple 2D game for Android. I have a stationary object that's situated in the center of the screen and I'm trying to get that object to rotate and point to the area on the screen that the user touches. I have the constant coordinates that represent the center of the screen and I can get the coordinates of the point that the user taps on. I'm using the formula outlined in this forum: How to get angle between two points? -It says as follows "If you want the the angle between the line defined by these two points and the horizontal axis: double angle = atan2(y2 - y1, x2 - x1) * 180 / PI;". -I implemented this, but I think the fact the I'm working in screen coordinates is causing a miscalculation, since the Y-coordinate is reversed. I'm not sure if this is the right way to go about it, any other thoughts or suggestions are appreciated.

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  • To Switch To The Design View Of A Windows Form

    - by June
    Hi Friends I create new project in Windows Form Application using Visual Studio in VB.Net. I place some controls on my form. I don't write any code at this time. I close this project. When i open this project again , i found Form1.vb. I double-click that file , but the design view doesn't appear. I also find Form1.Designer.vb. What in this file is code. How can i switch to Design View of Form1 ? I need to write some codes for that form's objects like Button Click Event. June

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  • std::out_of_range error?

    - by vette982
    I'm dealing with a file with a linked list of lines with each node looking like this: struct TextLine{ //The actual text string text; //The line number of the document int line_num; //A pointer to the next line TextLine * next; }; and I'm writing a function that adds spaces at the beginning of the lines found in the variable text, by calling functions like linelist_ptr->text.insert(0,1,'\t'); The program compiles, but when I run it I get this error: terminate called after throwing an instance of 'std::out_of_range' what(): basic_string::at Aborted Any ideas?

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  • Passing arguments to Shared Function - C

    - by SpyrosR
    I have used dlopen to load an object and dlsym to get a function pointer to a shared object function. Everything works fine. I have tested it calling then the shared function which (for now) only prints and it works-prints fine in the main program calling it. Now I want to pass two arguments to this function. An int and a char * .Can anyone help me understand how can I pass arguments to a shared function? I have searched in the web but I cannot understand how it works.

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  • Data-binding taking to long to update

    - by Justin
    In my application I have this code in my view model: hiddenTextContainer.PreHideVerticalOffset = VerticalOffset; hiddenTextContainer.HiddenText = Text.Remove(SelectionStart, SelectionLength); hiddenTextContainer.HasHiddenText = true; hiddenTextContainer.NonHiddenTextStart = SelectionStart; Text = Text.Substring(SelectionStart, SelectionLength); SelectionStart = Text.Length; hiddenTextContainer.ImmediatePostHideVerticalOffset = VerticalOffset; This code is used to hide selected text in a textbox. Text is a string property data bound to the text property of a textbox and VerticalOffset is a double property data bound to the VerticalOffset property of that same textbox. I need to save the VerticalOffset before and after the hiding of selected text takes place, but with my code below both hiddenTextContainer.PreHideVerticalOffset and hiddenTextContainer.ImmediatePostHideVerticalOffset are always set to the same value no matter what. I have figured out that this is because the text of the textbox has not been updated by the time the code reaches: hiddenTextContainer.ImmediatePostHideVerticalOffset = VerticalOffset; Is there any way I can fix this?

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  • How can I make external script output link to code in Visual Studio?

    - by JoelFan
    I sometimes need to search code for patterns in a way that goes beyond the regex capabilities of Visual Studio (e.g. patterns that depend on what was seen previously in the file or on the contents of other files). So I use Perl to analyze the source and output matching lines, along with the file name and line number. Since this is the exact same format as is produced by the search feature of Visual Studio, I wonder if there is a way to duplicate the functionality where I can double-click on a line and it will display that line in context in Visual Studio. Any ideas?

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