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  • Where does the compiler store methods for C++ classes?

    - by Mashmagar
    This is more a curiosity than anything else... Suppose I have a C++ class Kitty as follows: class Kitty { void Meow() { //Do stuff } } Does the compiler place the code for Meow() in every instance of Kitty? Obviously repeating the same code everywhere requires more memory. But on the other hand, branching to a relative location in nearby memory requires fewer assembly instructions than branching to an absolute location in memory on modern processors, so this is potentially faster. I suppose this is an implementation detail, so different compilers may perform differently. Keep in mind, I'm not considering static or virtual methods here.

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  • C++ code generation for repeted task

    - by sateesh
    Hi, I have something like below which will get repeated many times based on the function that get called for e.g acceptfunction() { inserter["quantity"] = sdd.getfloat(quantity); inserter["prodtype"] = sdd.getstring(prodtype); : : so on } Like accept above there are 20 more functions(reject,cancel etc) which will do the similar thing.But the parameteres they insert can differ based on function called. How can I automate this kind of code.So that I dont need to write new function from scratch.Basically what I need is if i provide parametres like ("quantity",prodtype) through some text file or xml, it should generate the required function with the input parametres. Is this task can be handled through C++ tempalte Meta programming or someother code generation tool will help me to do this?

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  • C++: Switching from MSVC to G++: Global Variables

    - by feed the fire
    I recently switched to Linux and wanted to compile my Visual Studio 2010 C++ source code, which uses only the STL, on G++. My Linux machine currently isn't available but I can try to tell you what is going on, first: As I try to compile my project, all global variables I use in main and which perfectly work on MSVC result in myGlobalVar is not defined in this scope errors. My project is built nearly the same as the example below: // myclass.h class myClass { // .... }; extern myClass globalInstance; // myclass.cpp #include "myclass.h" // myClass functions located here myClass globalInstance; // main.cpp #include "myclass.h" int main( ) { // Accessing globalInstance results in an error: Not defined in this scope } What am I doing wrong? Where are the differences between G++ and MSVC in terms of global variables?

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  • What frameworks should we consider for a custom web application?

    - by justkevin
    A client is looking for a custom web application, which will eventually include lots of interconnected components, but the main features are: Subscription based membership as well as virtual/digital product sales Members have their own public web cookie-cutter directories (e.g., storefronts, pages, etc.) and personal member admin area. Site administrators will need both common tools (member admin, password changes, etc.) and custom tools that can be readily developed or integrated with 3rd party solutions. What frameworks should we be looking at? PHP/MySQL is preferable unless something really outstanding is available in another stack.

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  • How to give 'Everybody' full rights to a file (programmatically)

    - by egrunin
    I'm modifying an old C++ program to run on Vista. It does not require Admin privileges. I've changed the code to put logfiles in \ProgramData\MyApp\. These logfiles are written with the stdio functions (fopen, fprintf, fclose). Here's the problem: UserA runs the program first, it creates \ProgramData\MyApp\MyLogFile.txt UserB runs the program next, it tries to append to MyLogFile.txt and gets access denied. I tried creating a null SECURITY_DESCRIPTOR and passing that to CreateFile(). That does create a file with "no permissions assigned", but it seems as if the first user to write to the file takes ownership and afterwards all the other non-admin users are out of luck. It's important that all users share the same logfiles, but it's also important that I change as little code as possible.

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  • Possible to convert list of #defines into strings (C++)

    - by brandonC
    Suppose I have a list of #defines in a header file for an external library. These #defines represent error codes returned from functions. I want to write a conversion function that can take as an input an error code and return as an output a string literal representing the actual #define name. As an example, if I have #define NO_ERROR 0 #define ONE_KIND_OF_ERROR 1 #define ANOTHER_KIND_OF_ERROR 2 I would like a function to be able to called like int errorCode = doSomeLibraryFunction(); if (errorCode) writeToLog(convertToString(errorCode)); And have convertToString() be able to auto-convert that error code without being a giant switch-case looking like const char* convertToString(int errorCode) { switch (errorCode) { case NO_ERROR: return "NO_ERROR"; case ONE_KIND_OF_ERROR: return "ONE_KIND_OF_ERROR"; ... ... ... I have a feeling that if this is possible, it would be possible using templates and metaprogramming, but that would only work the error codes were actually a type and not a bunch of processor macros. Thanks

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  • OpenGL "out of memory" on glReadPixels()

    - by spurserh
    Hello, I am running into an "out of memory" error from OpenGL on glReadPixels() under low-memory conditions. I am writing a plug-in to a program that has a robust heap mechanism for such situations, but I have no idea whether or how OpenGL could be made to use it for application memory management. The notion that this is even possible came to my attention through this [albeit dated] thread on a similar issue under Mac OS X: http://lists.apple.com/archives/Mac-opengl/2001/Sep/msg00042.html I am using Windows XP, and have seen it on multiple NVidia cards. I am also interested in any work-arounds I might be able to relay to users (the thread mentions "increasing virtual memory"). Thanks, Sean

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  • overloading new operator in c++

    - by Angus
    I have a code for best fit algorithm. I want to try to use the best fit algorithm using the operator new. Every time I create an object I should give it from the already allocated memory say, 1]20 2]12 3]15 4]6 5]23 respectively. which ever minimum amount fits to the objects size(eg.21) I wanted to do it for different object types, so I need to write the overloaded operator new to be common functionality for all the class objects. Can I do it through friend functions, or is there any possible way to do it.

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  • jQuery - How do I make the menu fadeout when the user clicks anywhere else in the document besides the menu itself?

    - by GirlGoneMad
    Hi, I have a link that functions similar to a drop down menu in that it fades in a list of links below it when clicked. Currently, the list fades back out when the link is clicked again, but I'd like for it to also fade out if the user clicks elsewhere on the page. I'm not sure how to add the $(document).click(function()... that handles this, or if this is even the right approach. Here is my code: $('#show_button').click( function(){ if(!$('#list').is(':visible')){ var pos = $('#show_button').offset(); $('#list').css({'left':pos.left - 11, 'top': pos.top+14}).fadeIn(); } else{ $('#list').fadeOut(); } }); I am trying to add something like this to make the list fade out when the user clicks anywhere else in the page: if($('#list').is(':visible')){ $(document).click(function() { $('#list').fadeOut(); }); } Thanks in advance - I would appreciate any help on this one :)

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  • Lots of pointer casts in QGraphicsView framework and performance

    - by kleimola
    Since most of the convenience functions of QGraphicsScene and QGraphicsItem (such as items(), collidingItems(), childItems() etc.) return a QList you're forced to do lots of qgraphicsitem_cast or static_cast and QGraphicsItem::Type() checks to get hold of the actual items when you have lots of different type of items in the scene. I thought doing lots of subclass casts were not a desirable coding style, but I guess in this case there are no other viable way, or is there? QList<QGraphicsItem *> itemsHit = someItem->collidingItems(Qt::IntersectsItemShape); foreach (QGraphicsItem *item, itemsHit) { if (item->type() == QGraphicsEllipseItem::type()) { QGraphicsEllipseItem *ellipse = qgraphicsitem_cast<QGraphicsEllipseItem *>(item); // do something } else if (item->type() == MyItemSubclass::type()) { MyItemSubClass *myItem = qgraphicsitem_cast<MyItemSubClass *>(item); // do something } // etc } The above qgraphicsitem_cast could be replaced by static_cast since correct type is already verified. When doing lots of these all the time (very dynamic scene), will the numerous casting affect performance beyond the normal if-else evaluation?

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  • MySql returning multiple rows from stored procedure / function

    - by pistacchio
    Hi, I need to make a stored procedure or function that returns a set of rows. I've noted that in a stored procedure i can SELECT * FROM table with success. If i fetch rows in a loop and SELECT something, something_other FROM table once per loop execution, I only get one single result. What I need to do is looping, doing some calculations and returning a rowset. What's the best way to do this? A temporary table? Stored functions? Any help appreciated.

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  • Running Firefox in the Windows service mode

    - by Leonid
    I'm writing a server running as a Windows service that by request invokes Firefox to generate a pdf snapshot of a webpage. I know it is a bad idea to run a GUI program in service mode, but the server nature of my program restricts from running it in the user mode. Running a user-level 'proxy' also is not an option, since there might be no interactive user logged-in on the machine with the server running. In my experiments Firefox successfully produced pdf when the service was running under a user account that was already logged-in. Obviously it didn't work in other cases: for Local System and user accounts that weren't logged-in. Under LocalSystem with 'Allow service to interact with desktop' option enabled I could see the Firefox started that reports that it's unable to find a printer. Since it wouldn't be practical to require an opened user session for the pdf server to run, is there any workaround for this except running the whole thing from a virtual machine?

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  • save state of external running program

    - by SuitUp
    Hi, my goal is to save state of running process and later start from this point. This is not necessary need to be state from this exact moment, let's say save after 5 seconds is good too. Problem is, i can't alter in code of this external program, i am even don't aware of it's architecture. I have resources to save whole program to disk from memory, but i need some tips, where to start. I can't use any VM like Virtual Box to save state of whole operating system, and program can be written in c++ or c or c#...

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  • Document/Scripts management for R code

    - by harshsinghal
    Hi useRs, I am looking for a solution that allows me to keep a track of a multitude of R scripts that I create for various projects and purposes. Some scripts are easily tracked to specific projects, whereas others are "convenience" functions created to serve a set of tasks. Is there a way I can create a central DB and query it to find which scripts match most appropriately? I could create a system using a DBMS manually, but are users aware of anything in general or specific to R, that comes in the form of a software tool (maybe FOSS) ?

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  • ORA-00937 error during select subquery

    - by RedRaven
    I am attempting to write a query that returns the the number of employees, the average salary, and the number of employees paid below the average. The query I have so far is: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select count(salary) from employees where salary < (select avg(salary) from employees) ) UnderPaid from employees; But when I run this I get the ora-00937 error in the subquery. I had thought that maybe the "count" function is what is causing the issue, but even running a simpler sub query such as: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select avg(salary) from employees ) UnderPaid from employees; still returns the same error. As both AVG and COUNT seem to be aggregate functions, I'm not sure why I'm getting the error? Thanks

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  • VB.NET logical expression evaluator

    - by Tim
    I need to test a logical expression held in a string to see if it evaluate to TRUE or FALSE.(the strig is built dynamically) For example the resulting string may contain "'dog'<'cat' OR (14 AND 4<6)". There are no variables in the string, it will logically evaluate. It will only contain simple operators = < < = <= and AND , OR and Open and Close Brackets, string constants and numbers. (converted to correct syntax && || etc.) I currently acheive this by creating a jscipt function and compiling it into a .dll. I then reference the .dll in my VB.NET project. class ExpressionEvaluator { function Evaluate(Expression : String) { return eval(Expression); } } Is there a simpler method using built in .NET functions or Lamdba expressions.

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  • it is possible to "group by" without losing the original rows?

    - by toPeerOrNotToPeer
    i have a query like this: ID | name | commentsCount 1 | mysql for dummies | 33 2 | mysql beginners guide | 22 SELECT ..., commentsCount // will return 33 for first row, 22 for second one FROM mycontents WHERE name LIKE "%mysql%" also i want to know the total of comments, of all rows: SELECT ..., SUM(commentsCount) AS commentsCountAggregate // should return 55 FROM mycontents WHERE name LIKE "%mysql%" but this one obviously returns a single row with the total. now i want to merge these two queries in one single only, because my actual query is very heavy to execute (it uses boolean full text search, substring offset search, and sadly lot more), then i don't want to execute it twice is there a way to get the total of comments without making the SELECT twice? !! custom functions are welcome !! also variable usage is welcome, i never used them...

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  • Syncronizing indices of function pointer table to table contents

    - by Thomas Matthews
    In the embedded system I'm working on, we are using a table of function pointers to support proprietary Dynamic Libraries. We have a header file that uses named constants (#define) for the function pointer indices. These values are used in calculating the location in the table of the function's address. Example: *(export_table.c)* // Assume each function in the table has an associated declaration typedef void (*Function_Ptr)(void); Function_Ptr Export_Function_Table[] = { 0, Print, Read, Write, Process, }; Here is the header file: *export_table.h* #define ID_PRINT_FUNCTION 1 #define ID_READ_FUNCTION 2 #define ID_WRITE_FUNCTION 3 #define ID_PROCESS_FUNCTION 4 I'm looking for a scheme to define the named constants in terms of their location in the array so that when the order of the functions changes, the constants will also change. (Also, I would like the compiler or preprocessor to calculate the indices to avoid human mistakes like typeo's.)

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  • Unexpected result from reduce function

    - by StackedCrooked
    I would like to get the smallest element from a vector. For this I use combine the reduce and min functions. However, when providing my own implementation of min I get unexpected results: user=> (reduce (fn [x y] (< x y) x y) [1 2 3 2 1 0 1 2]) 2 user=> (reduce min [1 2 3 2 1 0 1 2 3]) 0 The reduce with standard min returns 0 as expected. However, when I provide my own implementation it returns 2. What am I doing wrong?

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  • Hudson build fails when a user logs out of RDP session

    - by sjohnston
    We are using Hudson to build mixed C++/Java projects with an Ant script. It is running in Tomcat 6, on a Win XP virtual machine. I have noticed recently that when a user logs off the machine (from a remote desktop session), builds that are currently running tend to suddenly fail without an error message. Has anyone encountered anything similar or have an idea what might be causing this effect? I can post additional information about our setup if needed, I'm just not sure what's relevant in this case.

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  • c++ polymorphism and other function question

    - by aharont
    i have got this code: class father{ public: virtual void f() { cout<<1;} }; class son:public father{ public: void f() {cout<<2;} }; void test (father x){x.f();} int main(){ son s; test(s); } the question says: the output is '1', what is the rule about polymorphism that the programmer forgot and how can i fix it so the output would be '2'? there is another rule that the programmer forgot when he wrote the father class, and he need to add an empty function to avoid problems from other sons of the father class. what is the rule and what is the missing function? another question write the g function so the next code would run with no crashes int x=11; g(x)=22;

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  • matrix = *((fxMatrix*)&d3dMatrix); //Evil?

    - by Xilliah
    I've been using matrix = *((fxMatrix*)&d3dMatrix); for quite a while. It worked fine until my screen turned black and received a bucket of frustration on my desk. fxMatrix contains 4 fxVectors. fxVector used to be 16 bytes, but now it was suddenly 20. This was because it inherited fxStreamable, which added the vTable. So one solution is of course just to not inherit fxStreamable, and leave a comment saying that it must always be 16 bytes and never more. Another solution would be to make conversion functions, and copy the matrix completely. This makes it more secure, but has an impact on the performance. I suppose this is the best idea. Another solution is to not convert at all, and stick to D3DXMATRIX, but this makes the engine inconsistent and I personally really dislike this idea. What is your opinion?

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  • NSPredicate aggregate function [SIZE] gives 'unsupported function expression' error

    - by jinglesthula
    iOS 4: I have entities in Core Data (using SQLite, which is a requirement) of: Request Response (which has a property personId) Revision Relationships are: Request <-- Revision Request <-- Response Revision <-- Response (e.g. each request may have many responses; each request/response pair may have many revisions) I'm trying to do a predicate to get all Responses with a given personId that have zero Revisions. Using: (personId == %d) && (Request.Revision[SIZE] == 0) in my predicate string gives me a runtime exception "Unsupported function expression Request.Revision[SIZE]" The documentation seems pretty sparse on aggregate functions, only noting that they exist, but with no syntax or examples. Not sure if it's my syntax or if the SIZE function really isn't supported in iOS.

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  • Assign grid.arrange to object

    - by Tyler Rinker
    I want to arrange plots with grid.arrange to make more complex coplots and then use grid.arrange to combine these complex coplots. I am using the following solution (http://stackoverflow.com/a/13295880/1000343) in this task to arrange mutliple plots and ensure they have equal widths. Here is a demo of the code: library(ggplot2); library(gridExtra) gA <- ggplotGrob(A) gB <- ggplotGrob(B) maxWidth = grid::unit.pmax(gA$widths[2:5], gB$widths[2:5]) gA$widths[2:5] <- as.list(maxWidth) gB$widths[2:5] <- as.list(maxWidth) x <- grid.arrange(gA, gB, ncol=1) y <- grid.arrange(gA, gB, ncol=1) grid.arrange(x, y, ncol=2) To be clear in my case x and y are slightly different plots with different values. I know grid.arrange isn't returning the plot as other grid based functions.

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  • How to OrderBy on a generic IEnumerable (IEnumerable<T>) using LINQ in C#?

    - by Jeffrey
    In my generic repository I have below method: public virtual IEnumerable<T> GetAll<T>() where T : class { using (var ctx = new DataContext()) { ctx.ObjectTrackingEnabled = false; var table = ctx.GetTable<T>().ToList().AsReadOnly(); return table; } } T is a Linq to Sql class and I want to be able to OrderBy on a particular property. Say if T has property name "SortOrder" then do OrderBy on this property. But I am not sure how I can achieve this. So I need some helps. Thank you!

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