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  • Strange difference between optimized/non optimized microsoft c++ code

    - by Anders Forsgren
    I have a c++ program with a method that looks something like this: int myMethod(int* arr1, int* arr2, int* index) { arr1--; arr2--; int val = arr1[*index]; int val2 = arr2[val]; doMoreThings(val); } With optimizations enabled (/O2) the first line where the first pointer is decremented is not executed. I assume the compiler believes that the arr1 array is not used since it thinks it can remove the decrement. Am I violating some convention in the above code? What could cause this behavior? It is a very old piece of f2c-translated code, the pointer decrement is due to the 1-based indexing of the original code.

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  • Best way to build an application based on R?

    - by Prasad Chalasani
    I'm looking for suggestions on how to go about building an application that uses R for analytics, table generation, and plotting. What I have in mind is an application that: displays various data tables in different tabs, somewhat like in Excel, and the columns should be sortable by clicking. takes user input parameters in some dialog windows. displays plots dynamically (i.e. user-input-dependent) either in a tab or in a new pop-up window/frame Note that I am not talking about a general-purpose fron-end/GUI for exploring data with R (like say Rattle), but a specific application. Some questions I'd like to see addressed are: Is an entirely R-based approach even possible ( on Windows ) ? The following passage from the Rattle article in R-Journal intrigues me: It is interesting to note that the first implementation of Rattle actually used Python for implementing the callbacks and R for the statistics, using rpy. The release of RGtk2 allowed the interface el- ements of Rattle to be written directly in R so that Rattle is a fully R-based application If it's better to use another language for the GUI part, which language is best suited for this? I'm looking for a language where it's relatively "painless" to build the GUI, and that also integrates very well with R. From this StackOverflow question How should I do rapid GUI development for R and Octave methods (possibly with Python)? I see that Python + PyQt4 + QtDesigner + RPy2 seems to be the best combo. Is that the consensus ? Anyone have pointers to specific (open source) applications of the type I describe, as examples that I can learn from?

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  • Java Beginner Question : What is wrong with the code below ?

    - by happysoul
    public class Function { public static void main(String args[]) { System.out.println(power(3,2)); System.out.println(power(3,2)); System.out.println(power(2)); } public long power(int m) { return m*m; } public long power(int m,int n) { long product=1; for(int i=1;i<=n;i++) { product=product*m; } return product; } } Compiler displays this error :- Function.java:5: non-static method power(int,int) cannot be referenced from a static context

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  • My Delphi 7 application halts on Application.Initialize and does not return to next line

    - by m-abdi
    I have created an application on Delphi 7. my app had running fine since yesterday. I don't know what's happened yesterday which cause my application halts on Application.Initialize line in source code and does not return to next line when i trace the program. I can't run the created executable file from widows niether while the generated file does run on another machine correctly. here is the code where the compiler stops on it: program Info_Kiosk; uses SysUtils, Forms, ... (some other units) ; {$R *.res} begin Application.Initialize; Application.CreateForm(Tfrm_Main, frm_Main); any help would be appreciated

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  • How can I dynamically set the default namespace declaration of an XSLT transformation's output XML?

    - by Paralife
    I can do it, but not for the default namespace, using the <xsl:namespace>. If I try to do it for the default namespace: <xsl:namespace name="" select"myUri"/> it never works. It demands that I explicitly define the namespace of the element to be able to use the above null prefix declaration. The reason I want this is because I have a task to transform an input XML file to another output xml. The output XML has many elements and i dont want to have to explicitly set the namespace for every element. Thats why I want to set the default and never bother again. But the default must be computed from some data in the source XML. It does not change during the whole transformation, but it is dependent on input XML data. Any solution? EDIT 1: To sup up: I want to create a namespace dynamically and set it to be the default namespace of the output xml document. The uri of the namespace is derived from some data in the input XML. If I use <xsl:namespace> in my root output element, I cannot create a default namespace for it, only a prefixed one. And even with the prefixed one, it does not propagate to children.

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  • What's the best way to build software that doesn't require the newest glibc?

    - by ZorbaTHut
    I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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  • Using module include in OCaml

    - by Geoff
    In OCaml 3.11, I want to "extend" an existing module using the include directive, like so: module MyString = struct include String let trim s = ... end No problem. But now I want to expose this module's type explicitly (i.e. in a .mli file). I want something like this: module MyString : sig include String val trim : string -> string end But the include syntax is not correct because String refers to a module, not a module type (and the compiler does indeed barf). How can I refer to the module type for String here (without having write it out explicitly in a sig expression)? Thanks!

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  • Precision problems of real numbers in Fortran

    - by saladoil
    I've been trying to use Fortran for my research project, with the GNU Fortran compiler (gfortran), latest version, but I've been encountering some problems in the way it processes real numbers. If you have for example the code: program test implicit none real :: y = 23.234, z z = y * 100000 write(*,*) y, z end program You'll get as output: 23.23999 2323400.0. I find this really strange. Can someone tell me what's exactly happening here? Looking at z I can see that y does retain its precision, so for calculations that shouldn't be a problem I suppose. But why is the output of y not exactly the same as the value that I've specified, and what can I do to make it exactly the same?

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  • ToList()-- Does it Create a New List?

    - by Ngu Soon Hui
    Let's say I have a class public class MyObject { public int SimpleInt{get;set;} } And I have a List<MyObject>, and I ToList() it and then change one of the SimpleInt, will my change be propagated back to the original list. In other words, what would be the output of the following method? public void RunChangeList() { var objs = new List<MyObject>(){new MyObject(){SimpleInt=0}}; var whatInt = ChangeToList(objs ); } public int ChangeToList(List<MyObject> objects) { var objectList = objects.ToList(); objectList[0].SimpleInt=5; return objects[0].SimpleInt; } Why? P/S: I'm sorry if it seems obvious to find out. But I don't have compiler with me now...

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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • When destroying one record, another one gets destroyed

    - by normalocity
    Products (like an iPod Classic) :has_many = :listings, :dependent = :destroy Listings (like "My name is Joe, and I have an iPod for sale) :belongs_to = :product So, if I delete a given Product, all the listings that point to it get deleted. That makes sense, and is by design. However, I am writing a "merge" function, where you merge two Products into one, and combine their Listings. So, let's say my two products are "iPod Color" and "iPod Classic", and I want to merge the two. What I want to do is say, "iPod Color, merge into iPod Classic", and result should be that: All the iPod Color Listings are re-pointed to the iPod Classic product After the product_id change, the Listing(s) are saved I then delete the "iPod Color" product Well, that should all work fine, without deleting any Listings. However, I've got this controller, and for whatever reason when I destroy the "iPod Color" Product, even after confirming that the Listings have been moved to "iPod Classic" and saved to the database, the Listings that were previously pointed to "iPod Color" get destroyed as well, and I can't figure out why. It's as if they are retaining some kind of link to the destroyed product, and therefore begin destroyed themselves. What painfully obvious thing am I missing? def merge merging_from = Product.find(params[:id]) merging_to = Product.find_by_model(params[:merging_to]) unless merging_to.nil? unless merging_from.nil? unless merging_from == merging_to # you don't want to merge something with itself merging_from.listings.each do |l| l.product = merging_to l.save end # through some debugging, I've confirmed that my missing Listings are disappearing as a result of the following destroy call merging_from.destroy end end end

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  • functions in assembler

    - by stupid_idiot
    hi, i have philosophised about the purpose of stack a little bit and after some coding i figured out what is it's strength. The only thing that lies in my stomache is how does it work with functions? I tried to make some easy function for adding two numbers using universal registers but I suppose that's not how does it work in C for example.. where are all the parameters, local variables and where is the result stored? how would you rewrite this to assembler?(how would compiler for C rewrite it?) int function(int a, int &b, int *c){ return a*(b++)+(*c); } i know this example kinda sucks.. but this way i can understand all the possibilities

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  • C++/g++: Concurrent programm

    - by phimuemue
    Hi, I got a C++ program (source) that is said to work in parallel. However, if I compile it (I am using Ubuntu 10.04 and g++ 4.4.3) with g++ and run it, one of my two CPU cores gets full load while the other is doing "nothing". So I spoke to the one who gave me the program. I was told that I had to set specific flags for g++ in order to get the program compiled for 2 CPU cores. However, if I look at the code I'm not able to find any lines that point to parallelism. So I have two questions: Are there any C++-intrinsics for multithreaded applications, i.e. is it possible to write parallel code without any extra libraries (because I did not find any non-standard libraries included)? Is it true that there are indeed flags for g++ that tell the compiler to compile the program for 2 CPU cores and to compile it so it runs in parallel (and if: what are they)?

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  • How can I force the text go to the button of the panel?

    - by Roman
    At the moment I have the following code which works fine. label = new JLabel(panelLabel,SwingConstants.CENTER); outputPanel.add(label,BorderLayout.CENTER); I get the text in the center of the panel (in terms of the left-right position as well as in terms of the top-bottom). Now I want to set the position to the bottom (and center in terms of "left-right"). I tried to use SOUTH instead of the CENTER in the first line. Compiler does not complains but during the execution i get IllegalArgumentException: HorizontalAlignment. What is that?

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  • Why Can't I import a UITableViewCell subclass ? That's weird....

    - by user320064
    It's like this, I created a UITableViewCell subclass called NewsItemCell, then I wanna use it in my FirstViewController.m, then I tried to import it, but the compiler keeps telling me this Below is my code, it is driving me mad, thank you if you can help. import "NewsItemCell.h" import "FirstViewController.h" @implementation FirstViewController @synthesize computers; (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"NewsItemCellIdentifier"; NewsItemcell *cell = (NewsItemcell *)[tableView dequeueReusableCellWithIdentifier: CellIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"NewsItemCell" owner:self options:nil]; for (id oneObject in nib) if ([oneObject isKindOfClass:[NewsItemcell class]]) cell = (NewsItemcell *)oneObject; } NSUInteger row = [indexPath row]; NSDictionary *rowData = [self.computers objectAtIndex:row]; cell.newsTitle.text = [rowData objectForKey:@"Color"]; cell.newsDate.text = [rowData objectForKey:@"Name"]; return cell; } Jason

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  • Linking Error: undefined reference to `MPI_Init' on Windows 7

    - by fatpipp
    I am using OpenMPI library to write a program to run on Windows 7. I compile and build with C Free 4.0, Mingw. Compiling is Ok but when the compiler links object, errors "undefined reference to ..." occurs. I have set the environment already: I added OpenMPI lib, include and bin folder into C Free Build Directories. I added them into Windows environment variables too. But the error still occurs. Can anyone tell me how to fix it? Thanks a lot.

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  • Why "constructor-way" of declaring variable in "for-loop" allowed but in "if-statement" not allowed?

    - by PiotrNycz
    Consider this simple example: /*1*/ int main() { /*2*/ for (int i(7); i;){break;} /*3*/ if (int i(7)) {} /*4*/ } Why line-2 compiles just fine, whilst line-3 gives the error? This is little strange to me why if-statement is in this aspect treated worse than for-loop? If this is compiler specific - I tested with gcc-4.5.1: prog.cpp: In function 'int main()': prog.cpp:3:7: error: expected primary-expression before 'int' prog.cpp:3:7: error: expected ')' before 'int' I was inspired by this question [UPDATE] I know this compiles just fine: /*1*/ int main() { /*2*/ for (int i = 7; i;){break;} /*3*/ if (int i = 7) {} /*4*/ }

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  • Asynchronous SQL Operations

    - by Paul Hatcherian
    I've got a problem I'm not sure how best to solve. I have an application which updates a database in response to ad hoc requests. One request in particular is quite common. The request is an update that by itself is quite simple, but has some complex preconditions. For this request the business layer first requests a set of data from the data layer. The business logic layer evaluated the data from the database and parameters from the request, from this the action to be performed is determined, and the request's response message(s) are created. The business layer now executes the actual update command that is the purpose of the request. This last step is the problem, this command is dependent on the state of the database, which might have changed since the business logic ran. Locking down the data read in this operation across several round-trips to the database doesn't seem like a good idea either. Is there a 'best-practice' way to accomplish something like this? Thanks!

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  • Does C++ require a destructor call for each placement new?

    - by Josh Haberman
    I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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  • Using a class with const data members in a vector

    - by Max
    Given a class like this: class Foo { const int a; }; Is it possible to put that class in a vector? When I try, my compiler tells me it can't use the default assignment operator. I try to write my own, but googling around tells me that it's impossible to write an assignment operator for a class with const data members. One post I found said that "if you made [the data member] const that means you don't want assignment to happen in the first place." This makes sense. I've written a class with const data members, and I never intended on using assignment on it, but apparently I need assignment to put it in a vector. Is there a way around this that still preserves const-correctness?

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  • c++ when to put method out side the class

    - by user63898
    i saw that some times in c++ applications using only namespace declarations with header and source file like this : #ifndef _UT_ #define _UT_ #include <string> #include <windows.h> namespace UT { void setRootPath(char* program_path, char* file_path); char * ConvertStringToCharP(std::string str); }; #endif //and then in UT.cpp #include "UT.h" namespace UT { char * ConvertStringToCharP(std::string str) { char * writable = new char[str.size() + 1]; std::copy(str.begin(), str.end(), writable); writable[str.size()] = '\0'; return writable; } void setRootPath(char* program_path, char* file_path) { //... } } is it better then defining classic class with static methods? or just simple class ? dose this method has something better for the compiler linker ? the methods in this namespace are called allot of times .

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  • How to catch any exception (System.Exception) without a warning in F#?

    - by LLS
    I tried to catch an Exception but the compiler gives warning: This type test or downcast will always hold let testFail () = try printfn "Ready for failing..." failwith "Fails" with | :? System.ArgumentException -> () | :? System.Exception -> () The question is: how to I do it without the warning? (I believe there must be a way to do this, otherwise there should be no warning) Like C# try { Console.WriteLine("Ready for failing..."); throw new Exception("Fails"); } catch (Exception) { }

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  • Strange behaviour when collapsing lines in XML bound WPF Datagrid

    - by Flossn
    i am using a wpf datagrid with a xml file as DataContext. All working good except for iterating thorough the table and collapsing individual rows. There are several checkboxes where the user can decide which kinds of rows he wants to see, dependent on their error level string. If a checkbox is checked, some of the rows are collapsed, others not. You need to uncheck the checkbox and check it again to collapse the ones of the first try and some of the others. If you recheck it again more rows are collapsed every time. I guess it has something to do with how much of the list is actually visible and how much not because of the window size. Thanks in advance. foreach (DataGridRow r in rows) { bool showRow = true; var tb = Datagrid.GetCell(dataGridEvents, r, 2).Content; string level = ((TextBlock)tb).Text; switch (level) { case "Warning": showRow = checkBoxWarnings.IsChecked.HasValue ? checkBoxWarnings.IsChecked.Value : false; break; case "Critical": showRow = checkBoxCritical.IsChecked.HasValue ? checkBoxCritical.IsChecked.Value : false; break; case "OK": showRow = checkBoxOK.IsChecked.HasValue ? checkBoxOK.IsChecked.Value : false; break; case "Unknown": showRow = checkBoxUnknown.IsChecked.HasValue ? checkBoxUnknown.IsChecked.Value : false; break; } r.Visibility = showRow ? Visibility.Visible : Visibility.Collapsed; }

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  • Is It Safe to Cast Away volatile?

    - by Yan Cheng CHEOK
    Most of the time, I am doing this way. class a { public: ~ a() { i = 100; // OK delete (int *)j; // Compiler happy. But, is it safe? // Error : delete j; } private: volatile int i; volatile int *j; }; int main() { a aa; } However, I saw an article here: https://www.securecoding.cert.org/confluence/display/seccode/EXP32-C.+Do+not+access+a+volatile+object+through+a+non-volatile+reference Casting away volatile allows access to an object through a non-volatile reference. This can result in undefined and perhaps unintended program behavior. So, what will be the workaround for my above code example?

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  • Will Windows Update modify anything in Visual Studio?

    - by Martin
    (Note: Yes, the technical side of this question seems to be rather SuperUser, but the implications are more relevant for StackOverflow readers.) As the title says, we are wondering if (fully) enabling automated Windows Updates on our developer machines will have implications for MS Visual Studio. That is, will any fixes to any components (be it libraries, UI/IDE, compiler, ...) ever be updated through Windows Update? We want to have 100% exact and reproducible development environments (wrt C++) on all developer machines, and so we are concerned that automated Windows updates may introduce some uncontrolled updates into our development chain.

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