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• How to check if the internal typedef struct of a typedef struct is NULL ?

  - by watchloop

  typedef struct { uint32 item1; uint32 item2; uint32 item3; uint32 item4; <some_other_typedef struct> *table; } Inner_t; typedef struct { Inner_t tableA; Inner_t tableB; } Outer_t; Outer_t outer_instance = { {NULL}, { 0, 1, 2, 3, table_defined_somewhere_else, } }; My question is how to check if tableA is NULL just like the case for outer_instance. It tried: if ( tmp->tableA == NULL ). I get "error: invalid operands to binary =="

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• Define and return a struct in c

  - by nevan

  I'm trying to convert some code from Javascript to c. The function creates an array (which always has a fixed number of items) and then returns the array. I've learned that in c it's not straightforward to return an array, so I'd like to return this as a struct instead. My c is not all that great, so I'd like to check that returning a struct is the right thing to do in this situation, and that I'm doing it the right way. Thanks. typedef struct { double x; double y; double z; } Xyz; Xyz xyzPlusOne(Xyz addOne) { Xyz xyz; xyz.x = addOne.x + 1; xyz.y = addOne.y + 1; xyz.z = addOne.z + 1; return xyz; }

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• Static initialization of a struct with class members

  - by JS Bangs

  I have a struct that's defined with a large number of vanilla char* pointers, but also an object member. When I try to statically initialize such a struct, I get a compiler error. typedef struct { const char* pszA; // ... snip ... const char* pszZ; SomeObject obj; } example_struct; // I only want to assign the first few members, the rest should be default example_struct ex = { "a", "b" }; SomeObject has a public default constructor with no arguments, so I didn't think this would be a problem. But when I try to compile this (using VS), I get the following error: error C2248: 'SomeObject::SomeObject' : cannot access private member declared in class 'SomeObject' Any idea why?

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• C++ vector and struct problem win32

  - by ~james2432

  I have a structure defined in my header file: struct video { wchar_t* videoName; std::vector<wchar_t*> audio; std::vector<wchar_t*> subs; }; struct ret { std::vector<video*> videos; wchar_t* errMessage; }; struct params{ HWND form; wchar_t* cwd; wchar_t* disk; ret* returnData; }; When I try to add my video structure to a vector of video* I get access violation reading 0xcdcdcdc1 (videoName is @ 0xcdcdcdcd, before I allocate it) //extract of code where problem is video v; v.videoName = (wchar_t*)malloc((wcslen(line)+1)*sizeof(wchar_t)); wcscpy(v.videoName,line); p->returnData->videos.push_back(&v); //error here

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• Struct like objects in Java

  - by cdv

  Is it completely against the Java way to create struct like objects? class SomeData1 { public int x; public int y; } I can see a class with accessors and mutators being more Java like. class SomeData2 { int getX(); void setX(int x); int getY(); void setY(int y); private int x; private int y; } The class from the first example is notationally convenient. // a function in a class public int f(SomeData1 d) { return (3 * d.x) / d.y; } This is not as convenient. // a function in a class public int f(SomeData2 d) { return (3 * d.getX()) / d.getY(); }

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• Returning a struct from a class method

  - by tree

  I have a header file that looks something like the following: class Model { private: struct coord { int x; int y; } xy; public: .... coord get() const { return xy; } }; And in yet another file (assume ModelObject exists): struct c { int x; int y; void operator = (c &rhs) { x = rhs.x; y = rhs.y; }; } xy; xy = ModelObject->get(); The compiler throws an error that says there is no known covnersion from coord to c. I believe it is because it doesn't know about coord type because it is declared inside of a class header. I can get around that by declaring the struct outside of the class, but I was wondering if it is possible to do the way I am, or is this generally considered bad practice

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• Dynamic loading a class in java with a different package name

  - by C. Ross

  Is it possible to load a class in Java and 'fake' the package name/canonical name of a class? I tried doing this, the obvious way, but I get a "class name doesn't match" message in a ClassDefNotFoundException. The reason I'm doing this is I'm trying to load an API that was written in the default package so that I can use it directly without using reflection. The code will compile against the class in a folder structure representing the package and a package name import. ie: ./com/DefaultPackageClass.class // ... import com.DefaultPackageClass; import java.util.Vector; // ... My current code is as follows: public Class loadClass(String name) throws ClassNotFoundException { if(!CLASS_NAME.equals(name)) return super.loadClass(name); try { URL myUrl = new URL(fileUrl); URLConnection connection = myUrl.openConnection(); InputStream input = connection.getInputStream(); ByteArrayOutputStream buffer = new ByteArrayOutputStream(); int data = input.read(); while(data != -1){ buffer.write(data); data = input.read(); } input.close(); byte[] classData = buffer.toByteArray(); return defineClass(CLASS_NAME, classData, 0, classData.length); } catch (MalformedURLException e) { throw new UndeclaredThrowableException(e); } catch (IOException e) { throw new UndeclaredThrowableException(e); } }

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• making class accessible from class path in dynamic class loading

  - by Noona

  I have a project created in Eclipse, and I defined an interface and a class for dynamic class loading, the class is in the project directory, so I have this code in my project: if (handlerClassName != null) { TypeHandler typeHandler = null; try { typeHandler = (TypeHandler) (Class.forName(handlerClassName).newInstance()); but I get this exception: java.lang.ClassNotFoundException: "handlerClassName" what should I do to make the JVM recognize the class "handlerClassName" in my project? thanks

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• Java code generation from class diagram

  - by Sanjay

  I'm on the way developing a Java application where user can provide a class diagram and get the corresponding Java code. I don't know how can I let the user interactively draw a class diagram in Java. I am currently getting the required parameters like attributes, functions directly from the user, and then I render a class diagram for him. I show the class diagram on a jdialog. Is there a better way to do this? This is an example of a class diagram, I need to generate this from a Java program, given the values and relationship.

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• Question about casting a class in Java with generics

  - by Florian F

  In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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• Switching from abstract class to interface

  - by nischayn22

  I have an abstract class which has all abstract methods except one which constructs objects of the subclasses. Now my mentor asked me to move this abstract class to an interface. Having an interface is no problem except with the method used to construct subclass objects. Where should this method go now? Also, I read somewhere that interfaces are more efficient than abstract classes. Is this true? Here's an example of my classes abstract class Animal { //many abstract methods getAnimalobject(some parameter) { return //appropriate subclass } } class Dog extends Animal {} class Elephant extends Animal {}

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• Use Struct as a Ptr/class? Need a fix .NET

  - by acidzombie24

  I wrote a bunch of code and i would like to fix it the fastest way possible. I'll describe my problem in a easier way. I have apples and oranges, they are both Point and in the list apples, oranges. I create a PictureBox and draw the apple/oranges on screen and move them around and update the Point via Tag. The problem now is since its a struct the tag is a copy so the original elements in the list are not update. So, how do i update them? I consider using Point? But those seem to be readonly. So the only solution i can think of is Clear the list, iterate through all the controls then check the picturebox property to check if the image is a apple or orange then add it to a list I really only thought of this solution typing this question, but my main question is, is there a better way? Is there some List<Ptr<Point>> class i can use so when i update the apples or oranges through the tag the element in the list will update as a class would?

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• C# Cast Class to Overridden Class

  - by Nathan Tornquist

  I have a class Application that I need to override with INotifyPropertyChanged events. I have written the logic to override the original class and ended up creating SuperApplication I am pulling the data from a library though, and cannot change the loading logic. I just need a way to get the data from the original class into my superClass. I've tried things like superClass = (SuperApplication)standardClass; but it hasn't worked. How would I go about doing this? If it helps, this is the code I'm using to override the original class: public class SuperCreditApplication : CreditApplication { public SuperCreditApplicant Applicant { get; set; } public SuperCreditApplicant CoApplicant { get; set; } } public class SuperCreditApplicant : CreditApplicant { public SuperProspect Prospect { get; set; } } public class SuperProspect : Prospect, INotifyPropertyChanged { public State DriverLicenseState { get { return DriverLicenseState; } set { DriverLicenseState = value; OnPropertyChanged("DriverLicenseState"); } } public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } }

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• C++ Using a class from a header within a class

  - by Kotsuzui

  I'm having a bit of trouble with classes used within classes, from header files. I have an class time in time.h: class Time { private: int hour, second, minute; public: . . . int getHour(int h); etc. setHour(); etc. void print24hour(); // Prints time in 24 hour format } And then, main.cpp: #include "time.h" class Class { private: string name; double grade; Time startTime; Time endTime; public: Class(); ~Class(); void setName(); void setGrade(); etc. } int main() { //Need to print time in 24 hour format, but I don't know how. class[i].startTime.print24(getStartTime()); // ??? I'm rather lost } I get quite a few "hour, second, minute, etc." are private errors, I'm guessing I'm doing something simple in a rather wrong way. Please help.

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• abstract class extends abstract class in php?

  - by user151841

  I am working on a simple abstract database class. In my usage of this class, I'll want to have some instance be a singleton. I was thinking of having a abstract class that is not a singleton, and then extend it into another abstract class that is a singleton. Is this possible? Recommended?

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• Sizeof struct in GO

  - by Homer J. Simpson

  I'm having a look at Go, which looks quite promising. I am trying to figure out how to get the size of a go struct, for example something like type Coord3d struct { X, Y, Z int64 } Of course I know that it's 24 bytes, but I'd like to know it programmatically.. Do you have any ideas how to do this ?

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• When to use a namespace or a struct?

  - by Justen

  I was just reading a little bit on them from http://www.cplusplus.com/doc/tutorial/namespaces/ and it seems like a struct is capable of the same things? Or even a class for that matter. Maybe someone here can better define what a namespace is, and how it differs from a struct/class?

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• Deriving a class from an abstract class (C++)

  - by cemregoksu

  I have an abstract class with a pure virtual function f() and i want to create a class inherited from that class, and also override function f(). I seperated the header file and the cpp file. I declared the function f(int) in the header file and the definition is in the cpp file. However, the compiler says the derived class is still abstract. How can i fix it?

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• How to make a struct of structs in C++

  - by Phenom

  Can a struct contain other structs? I would like to make a struct that holds an array of four other structs. Is this possible? What would the code look like?

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• Struct with pointer to a function

  - by user354021

  Hello, In a C struct I have defined a function pointer as follows: typedef struct _sequence_t { const int seq[3]; typedef void (* callbackPtr)(); } sequence_t; I want to initialize a var of that type globally with: sequence_t sequences[] = { { { 0, 1, 2 }, toggleArmament }, }; And I keep getting error telling me that there are too many initializers. How to work it out?

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• C# vector class - Interpolation design decision

  - by Benjamin

  Currently I'm working on a vector class in C# and now I'm coming to the point, where I've to figure out, how i want to implement the functions for interpolation between two vectors. At first I came up with implementing the functions directly into the vector class... public class Vector3D { public static Vector3D LinearInterpolate(Vector3D vector1, Vector3D vector2, double factor) { ... } public Vector3D LinearInterpolate(Vector3D other, double factor { ... } } (I always offer both: a static method with two vectors as parameters and one non-static, with only one vector as parameter) ...but then I got the idea to use extension methods (defined in a seperate class called "Interpolation" for example), since interpolation isn't really a thing only available for vectors. So this could be another solution: public class Vector3D { ... } public static class Interpolation { public static Vector3D LinearInterpolate(this Vector3D vector, Vector3D other, double factor) { ... } } So here an example how you'd use the different possibilities: { var vec1 = new Vector3D(5, 3, 1); var vec2 = new Vector3D(4, 2, 0); Vector3D vec3; vec3 = vec1.LinearInterpolate(vec2, 0.5); //1 vec3 = Vector3D.LinearInterpolate(vec1, vec2, 0.5); //2 //or with extension-methods vec3 = vec1.LinearInterpolate(vec2, 0.5); //3 (same as 1) vec3 = Interpolation.LinearInterpolation(vec1, vec2, 0.5); //4 } So I really don't know which design is better. Also I don't know if there's an ultimate rule for things like this or if it's just about what someone personally prefers. But I really would like to hear your opinions, what's better (and if possible why ).

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• postgreSQL vs Cassandra vs MongoDB vs Voldemart ?

  - by ramonrails

  Which database to decide upon? Any comparisions? Existing: postgresql Issues Not easily scalable horizontal. Needs sharding etc Clustering does not solve the data growth problem Looking for: Any database that is easily horizontally scalable Cassandra (Twitter uses that?) MongoDB (rapidly gaining popularity) Voldemart Other? Why? Data growing with snowball effect existing postgresql locks table etc for vaccuum tasks periodically Archiving data is tideous currently Human interaction involved in existing archive, vaccuum, ... process periodically Need a 'set it. forget it. just add another server when data grows more.' type of solution

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• wire colors: color vs black vs white (positive vs negative voltage)

  - by David Oneill

  I'm working on building a computer (first time for me). There are several plugs that I need to connect to the motherboard (Power LED, reset switch, etc). Of the two wires, they are either: Color and white (reset switch, power LED, HDD LED) red and black (speaker, power switch) The manual for the motherboard has a nice diagram of where to plug them in, but has them labeled + or -. Which colors are positive, and which are negative?

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• Cannot create class diagram for simple dll class in Visual Studio 2010

  - by xenn_33

  Hi, It seems that there is a really annoying issue in Class Diagram designer in VS (my version is 2010 Ultimate, but the issue is also observed in VS 2008). When I'm trying to create a class diagram for particular simple class from DLL I'm getting the following error: "Some of the selected type(s) cannot be added to the class diagram. Check the code for errors and ensure that all required assemblies ... blah-blah-blah" My code doesn't contain any error. I have multiple class and interface definitions in one separate .cs file, but these classes are really simple - even no calls to unmanaged/interop. Any solution for this?

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• Redhat cluster Vs Pacemaker Vs Gluster Vs Sheepdog

  - by chandank

  Changing the entire question as earlier one was very confusing. I have been exploring different clustering system to run Virtual machines on two different machines on LAN with high availability. Currently I am already using DRBD resource on two different machines on Primary/Secondary mode. In case the primary fails I manually promote the secondary to Primary and start the VM. I also explored Gluster and looks good, however, I would rather prefer clustering over Gluster (user space FS). So if anyone has idea which one would be better from ease of use prospective please I would be interested in. Moreover, sheepdog project appears good, however, could not find much documentations/Howtos. I am using Centos 6.

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