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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • How to implement a mailing system with Rails that sends emails in the background

    - by Tam
    I want to implement a reliable mailing system with Ruby on Rails that sends emails in the background as sending email sometimes takes like 10 seconds or more so I don't want the user to wait. Some ideas I thought of: 1- Write to a table in DB a have a background process that go over and send email (concern: potential many reads/writes to DB slows down my application) 2- Messaging Queue background process / Rake task (concern: if server crashes queued mails will be lost also might eat up a lot of memory if many emails) I was wondering if you a know of a good solution that provides a balance between reliability and performance.

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  • double fork using vfork

    - by Oren S
    HI I am writing a part of a server which should dispatch some other child processes. Because I want to wait on some of the processes, and dispatch others without waiting for completion, I use double fork for the second kind of processes (thus avoiding the zombie processes). Problem is, my server holds a lot of memory, so forking takes a long time (even the copy-on-write fork used in Linux which copies only the paging tables) I want to replace the fork() with vfork(), and it's easy for the second fork (as it only calls execve() in the child), but I couldn't find any way I can replace the first one. Does anyone know how I can do that? Thanks! The server is a linux (RH5U4), written in C++.

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  • Render asp.net repeater as-and-when chunks of html is ready (streaming)

    - by sash
    The problem is to render huge reports. Basically we have lots of data that get rendered in html reports (mostly using repeater or gridview). As it so happens, the data started out small and now we have tons of it. There are lots of such reports already built so total rewrite is not an option. Heck, the business is not even letting us page the data. Now server memory is shooting up each time we try to render some reports. So the question is - is there some way we can bind data to repeater and have it stream html to browser as and when chunks are ready? That way we hope to not bring all that data into app server at once. I'm thinking we'll use a datareader or something to get parts of data and render it to browser. Any pointers, links, ideas?

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  • Why is 'volatile' parasitic in C++?

    - by Steve
    Consider the following code: int main() { int i; volatile int* p = &i; int *v = p; return 0; } This gives an error in g++: $ g++ -o volatile volatile.cpp volatile.cpp: In function ‘int main()’: volatile.cpp:6: error: invalid conversion from ‘volatile int*’ to ‘int*’ My intention was that I want to make p volatile. However, once I've read the value of p, I don't care if accessing v is volatile. Why is it required that v be declared volatile? This is hypothetical code of course. In a real situation you could imagine that p points to a memory location, but is modified externally and I want v to point to the location that p pointed to at the time of v = p, even if later p is externally modified. Therefore p is volatile, but v is not. By the way I am interested in the behaviour both when this is considered C and C++, but in C this only generates a warning, not an error.

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  • efficient way to detect if an image is empty

    - by Jos
    Hi, I need a very fast method to detect if an image is empty. Im my case then all pixels are white and transparant. The images are png's. My current method is to load them in a memory bitmap and check each pixel value, but this is way to slow. Is there a more efficient way? This is my current code: 'Lock the bitmap bits. Dim bmpData As System.Drawing.Imaging.BitmapData = bmp.LockBits(rectBmp, _ Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat) Try Dim x As Integer Dim y As Integer For y = 0 To bmpData.Height - 1 For x = 0 To bmpData.Width - 1 If System.Runtime.InteropServices.Marshal.ReadByte(bmpData.Scan0, (bmpData.Stride * y) + (4 * x) + 3) <> 0 Then Return True Exit For End If Next Next Finally bmp.UnlockBits(bmpData) End Try

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • Why MSSQL keeps throwing me Exceptions?

    - by Augusto Càzares
    I have my project in .NET that uses a db in MSSQL Server,i'm using LINQ , sometimes when the projec throws me an exception (Constraint) in a part of the project this same error keeps showing in other part of the project when i do another thing with the db, like when i do an insertion and i had before an exception on delete the insertion throws me the delete exeption, and it remainds this way until i close and open again the project, my major problem is when this happen in my online project, this error in my project causes me problems in the project i'm testing online (i use the same db). I don't know if this exception is on the memory or something but its have been causing me a lot of headechs.

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  • How do I do a join in ActiveRecord after records have been returned?

    - by Russ Bradberry
    I am using ActiveRecord in Rails 3 to pull data from two different tables in two different databases. These databases can not join on each other, but I have the need to do a simple join after-the-fact. I would like to preserve the relation so that I can chain it down the line. here is a simplified version of what I am doing browsers = Browser.all # <-- this is fairly small and can reside in memory events = Event.where(:row_date=>Date.today).select(:name, :browser_id) So as you can see, I want to join browsers in on the events relation, where browser_id should equal browsers.name. events is a relation and I can still add clauses to it down the line, so I dont want to run the query on the db just yet. How would I accomplish this?

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  • How can I access and modify objects inside frames with AS3 in a permanent way?

    - by curro
    I have a MovieClip symbol created with flash in a fla file library. There is a textfield in frame one of this movieclip's timeline . There is another frame in the movieclip timeline. There is a custon class definition for this symbol. It is a flipping card in a memory game. I access the textfield by going to frame 2 (gotoAndStop(2)) and setting the textfield's text property ( this.field.text = "hello" ). However if I go to frame 1 and then return to frame 2, the text becomes the original one in the library's symbol. I have to modify the text propery again in a showFace method I've written. Besides, I cannot pass parameters in the constructor because it is a symbol in the library and that would give errors. I find this behaviour of flash extremely weird. Is there a way I can set properties inside frames permanently? Thank you

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  • Can't inherit from auto_str without problems

    - by fret
    What I want to do is this: #include <memory> class autostr : public std::auto_ptr<char> { public: autostr(char *a) : std::auto_ptr<char>(a) {} autostr(autostr &a) : std::auto_ptr<char>(a) {} // define a bunch of string utils here... }; autostr test(char a) { return autostr(new char(a)); } void main(int args, char **arg) { autostr asd = test('b'); return 0; } (I actually have a copy of the auto_ptr class that handles arrays as well, but the same error applies to the stl one) The compile error using GCC 4.3.0 is: main.cpp:152: error: no matching function for call to `autostr::autostr(autostr)' main.cpp:147: note: candidates are: autostr::autostr(autostr&) main.cpp:146: note: autostr::autostr(char*) I don't understand why it's not matching the autostr argument as a valid parameter to autostr(autostr&).

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  • just-in-time list

    - by intuited
    I'd like to know if there is a class available, either in the standard library or in pypi, that fits this description. The constructor would take an iterator. It would implement the container protocol (ie _getitem_, _len_, etc), so that slices, length, etc., would work. In doing so, it would iterate and retain just enough values from its constructor argument to provide whatever information was requested. So if jitlist[6] was requested, it would call self.source.next() 7 times, save those elements in its list, and return the last one. This would allow downstream code to use it as a list, but avoid unnecessarily instantiating a list for cases where list functionality was not needed, and avoid allocating memory for the entire list if only a few members ended up being requested. It seems like a pretty easy one to write, but it also seems useful enough that it's likely that someone would have already made it available in a module.

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  • Creating additional Window by a thread - C

    - by Jamie Keeling
    Hello, I have a windows form that has a simple menu and performs a simple operation, I want to be able to create another windows form with all the functionality of a menu bar, message pump etc.. as a separate thread so I can then share the results of the operation to the second window. I.E. 1) Form A opens Form B opens as a separate thread 2)Form A performs operation 3)Form A passes results via memory to Form B 4)Form B display results I'm confused as to how to go about it, the main app runs fine but i'm not sure how to add a second window if the first one already exists. I hope it makes sense. Thanks!

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  • POST data disapearing on large file upload

    - by DfKimera
    I'm having issues with a file uploading utility in my PHP application. When sending large files (9MB+) over the form, I get a very odd behaviour: the POST data I've included in the form dissapears, including the file information. I've already increased all PHP limits I could (time limit, max input time, post max size, memory limit and upload max filesize) and I still can't get the proper behaviour. I've tried replacing the regular HTTP forms with a Flash-based solution (SWFUpload, www.swfupload.org), still the same behaviour. I've tried multiple files of similar sizes and its definitely not a particular file issue. I've debugged the POST vars sent using Firebug, and the correct variables are still there in the header, together with the file. What could be going on here?

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  • What's your favorite programmable calculator?

    - by Pat Notz
    The HP-32S still holds a soft spot in my heart, even though it only had 4 registers. I have fond memories of writing a nonlinear solver for finding an azeotrope curve during a Thermodynamics final. Despite the increase in power, memory, pixels and features the HP-32G that followed never could steal my heart away. Here's to you, HP-32S. Let's hear it, what's your favorite programmable calculator? As with all poll type questions, do NOT submit a new answer unless your answer is not represented. Vote up your answer instead of adding yet another TI-85 or HP-49 to the list, and add comments to that answer if you want to relate specifics. EDIT: I moved my photo into an answer for polling.

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  • How to store the result of a JSP in a string?

    - by Spines
    I want to store the result of a JSP in a string. For example, I want to be able to call a function like: String result = ProcessJsp("/jspfile.jsp"); Also, this must be rather efficient. Making a url request to the jsp and then storing it would definitely be too slow. How could I do this? Here are my thoughts on how to do this, though I'm not sure if it would work, and I'm hoping there is something simpler: Do RequestDispatcher("/jspfile.jsp").include(hreq, hresp), but instead of putting the real HttpResponse object in there, you put your own where the getWriter() method returns something that writes to your String or a memory buffer, etc.

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  • Entity Framework ObjectContext Life-cycle

    - by Leonardo
    Hello, I'm developing a web application using asp.net 4.0 with Entity Framework. In my apllication I have a page DataEntry.aspx wich has 3 web user control.Each user control manage an entity and use a repository class to access data. The final user before save all the changes can add or remove entity in memory. My question is: how can i share the ObjectContext between the repositories? Basically I need a ObjectContext for the entire session working of DataEntry.aspx. How can I achive this? Thank you

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  • Splitting a string into new rows in R

    - by user3703195
    I have a data set like below: Country Region Molecule Item Code IND NA PB102 FR206985511 THAI AP PB103 BA-107603 / F000113361 / 107603 LUXE NA PB105 1012701 / SGP-1012701 / F041701000 IND AP PB106 AU206985211 / CA-F206985211 THAI HP PB107 F034702000 / 1010701 / SGP-1010701 BANG NA PB108 F000007970/25781/20009021 I want to split based the string values in ITEMCODE column on / and create a new row for each entry. For instance, the desired output will be: Country Region Molecule Item Code New row IND NA PB102 FR206985511 FR206985511 THAI AP PB103 BA-107603 / F000113361 / 107603 F000113361 107603 BA-107603 LUXE NA PB105 1012701 / SP-1012701 / F041701000 1012701 SP-1012701 F041701000 IND AP PB106 AU206985211 / CA-F206985211 AU206985211 CA-F206985211 THAI HP PB107 F034702000 / 1010701 / SP-1010701 F034702000 1010701 SP-1010701 BANG NA PB108 F000007970/25781/20009021 F000007970 25781 20009021 I tried the below code library(splitstackshape) df2=concat.split.multiple(df1,"Plant.Item.Code","/", direction="long") but got the Error "Error: memory exhausted (limit reached?)" When i tried strsplit() i got the below error message. Error in strsplit(df1$Plant.Item.Code, "/") : non-character argument Any help from you will be appreciated.

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  • Can't inherit from auto_ptr without problems

    - by fret
    What I want to do is this: #include <memory> class autostr : public std::auto_ptr<char> { public: autostr(char *a) : std::auto_ptr<char>(a) {} autostr(autostr &a) : std::auto_ptr<char>(a) {} // define a bunch of string utils here... }; autostr test(char a) { return autostr(new char(a)); } void main(int args, char **arg) { autostr asd = test('b'); return 0; } (I actually have a copy of the auto_ptr class that handles arrays as well, but the same error applies to the stl one) The compile error using GCC 4.3.0 is: main.cpp:152: error: no matching function for call to `autostr::autostr(autostr)' main.cpp:147: note: candidates are: autostr::autostr(autostr&) main.cpp:146: note: autostr::autostr(char*) I don't understand why it's not matching the autostr argument as a valid parameter to autostr(autostr&).

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  • CUDA driver installation on a laptop with nVidia NVS140M card

    - by stanigator
    I'm trying to first figure out if my computer contains a CUDA-enabled card. It has an nVidia NVS 140M card, but I can't seem to figure out if it is the 128 MB version or 256 MB version. On the laptop purchase receipt, I found out that I ordered the 128 MB version, but the control panel description of the card said otherwise as shown below: When I ran the CUDA driver from nVidia's site, it cannot find a hardware compatible with CUDA (even though the product series is CUDA-enabled, the card does not have 256 MB minimum of memory to do so). What would be your recommendations in this case with trying to use CUDA on this computer (I'm not sure if nothing can be done at this point)? Thanks in advance.

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  • Problem with running a program from flashdrive

    - by rajivpradeep
    I have a USB drive with two partitions in it, one hidden and one normal. I have an application which swaps the memory and runs the flash application in hidden zone. The problem is that the application works fine on Windows 7 and when run on Win XP, it swaps the partitions but doesn't run the flash applications but just keeps running in the background. I can see it in task manager. But, when I copy the application to desktop and run, it runs with no glitch. I was facing the same problem on Win 7 too, but it was running as required when I ran it using "Run in XP mode" and then I applied a SHIM and is running since then as required. The application is built using VC++ 2008. What might be the problem?

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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • Public static variables and Android activity life cycle management

    - by jsstp24n5
    According to the documentation the Android OS can kill the activity at the rear of the backstack. So, say for example I have an app and open the Main Activity (let's call it Activity A). In this public activity class I declare and initialize a public static variable (let's call it "foo"). In Activity A's onCreate() method I then change the value of "foo." From Activity A the user starts another activity within my app called Activity B. Variable "foo" is used in Activity B. Activity B is then paused after the user navigates to some other activities in other apps. Eventually, after a memory shortage occurs, Activity A then Activity B can be killed. After the user navigates back to my app it restarts (actually "recreates") activity B. What happens: 1) Will variable "foo" at this point have the value that was set to it when Activity A's onCreate() method ran? 2) Variable "foo" does not exist? 3) Variable "foo" exists and but is now the initialized value and not the value set in Activity A's onCreate() method?

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  • How do I implement .net plugins without using AppDomains?

    - by Abtin Forouzandeh
    Problem statement: Implement a plug-in system that allows the associated assemblies to be overwritten (avoid file locking). In .Net, specific assemblies may not be unloaded, only entire AppDomains may be unloaded. I'm posting this because when I was trying to solve the problem, every solution made reference to using multiple AppDomains. Multiple AppDomains are very hard to implement correctly, even when architected at the start of a project. Also, AppDomains didn't work for me because I needed to transfer Type across domains as a setting for Speech Server worfklow's InvokeWorkflow activity. Unfortunately, sending a type across domains causes the assembly to be injected into the local AppDomain. Also, this is relevant to IIS. IIS has a Shadow Copy setting that allows an executing assembly to be overwritten while its loaded into memory. The problem is that (at least under XP, didnt test on production 2003 servers) when you programmatically load an assembly, the shadow copy doesnt work (because you are loading the DLL, not IIS).

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  • Clojure closures and GC

    - by Ralph
    It is my understanding that the default ClassLoader used in Java (and thus, Clojure) holds on to pointers to any anonymous classes created, and thus, onto lambdas and closures. These are never garbage collected, and so represent a "memory leak". There is some investigation going on for Java 7 or 8 to adding an anonymous ClassLoader that will not retain references to these functions. In the mean time how are people dealing with writing long-running applications in languages like Clojure and Scala, that encourage the use of these constructs? Is there any possibility that Clojure could provide its own anonymous ClassLoader, extending the system one, but not holding onto created classes?

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