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• ANSI C++: Diferences between delete and delete[]

  - by Sunscreen

  I was looking a snipset of code: int* ip; ip = new int[100]; delete ip; The example above states that: "This code will work with many compilers, but it should instead read:" int* ip; ip = new int[100]; delete [] ip; Is this indeed the case? I use the compiler "Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 11.00.7022 for 80x86" and does not complain (first example) while compiling. At runtime the pointer is set to NULL. Other compilers behave diferrently? Can a compiler not compain and issues can appear at runtime? Thanks, Sun

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• Extract data from uint8 to double

  - by HADJ AMOR HASSEN

  I have a C function receiving a uint8 pointer with another parameter which is its size (number of bytes). I want to extract double data from this buffer. Here is my code: Write(uint8* data, uint8 size) /* data and size are given by a callback to my function)*/ { double d; for (i = 0; i < size; i++) { d = ((double*)&data)[i]; printf(" d = %d\n"); } } The problem is that I am not receiving what I am sending within an external hardware. I guess that my cast is wrong. I tried other methods but without any good result. I am still not able to get what I send.

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• question abouut string sort

  - by davit-datuashvili

  i have question from programming pearls problem is following show how to use lomuto's partitioning scheme to sort varying length bit strings in time proportional to the sum oof their length and algorithm is following each record in x[0..n-1] has an integer length and pointer to the array bit[0..length-1] code void bsort(l,u,depth){ if (l>=u) return; for (int i=l;i<u;i++) if (x[i].length<depth) swap(i,l++); m=l; if (x[i].bit[depth] ==0) swap(i,m++); bsort(l,m-1,depth+1); bsort(m,u,depth+1); please help me i need following things 1. how this algorith works 2.how implement in java?

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• C++ syntax of constructors " 'Object1 a (1, Object1(2))''

  - by osgx

  Hello I have a such syntax in program class Object1 : BaseClass { BaseClass *link; int i; public: Object1(int a){i=a;} Object1(int a, Object1 /*place1*/ o) {i=a; link= &o;} }; int main(){ Object1 a(1, /*place2*/ Object1(2)); ... } What do I need in place1? I want to save a link (pointer) to the second object in the first object. Should I use in place1 reference "&"? What type will have "Object1(2)" in place2? Is it a constructor of the anonymous object? Will it have a "auto" storage type?

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• freeing malloc and checkin it is empty or not

  - by gcc

  char *p; p="kjkjk"; . .//there are codes which are checking another command . if(.....)//i used pointer p in only that area free(p); . . //there are codes which are checking another command . if(p==NULL) //i check whether is empty .... if(p==-1) //can we use "EOF==p " in if statement ... //are there any usage like that EOF==p else .... I think there is big error , but where?

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• Need guidance for my first Android application: how many activities should I use?

  - by jul

  Hi, I'm starting Android doing an application for searching restaurants, and some guidance would be welcome! On the first screen I'd like to have a search field with a submit button (I get the data from a web service), and below a list with the results of the search. When clicking on one of the items of the list it will show a screen with the restaurant details as well as a map showing its location. My questions are: Can I do everything in one single activity or should I do an activity for the search, one for the result list, one for the restaurant description, and another for the map? Would doing one single activity make the application more responsive? How can I use a list and a map within a normal activity (without ListActivity and MapActivity)? Any help, pointer, example application or sample code is very appreciated! Thank you Jul

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• How can Java assignment be made to point to an object instead of making a copy?

  - by Matthew Piziak

  In a class, I have: private Foo bar; public Constructor(Foo bar) { this.bar = bar; } Instead of creating a copy of bar from the object provided in the parameter, is it possible to include a pointer to bar in the constructor such that changing the original bar changes the field in this object? Another way of putting it: int x = 7; int y = x; x = 9; System.out.print(y); //Prints 7. It is possible to set it up so that printing y prints 9 instead of 7?

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• Best way to access nested data structures?

  - by Blackshark

  I would like to know what the best way (performance wise) to access a large data structure is. There are about hundred ways to do it but what is the most accessible for the compiler to optimize? One can access a value by foo[someindex].bar[indexlist[i].subelement[j]].baz[0] or create some pointer aliases like sometype_t* tmpfoo = &foo[someindex]; tmpfoo->bar[indexlist[i].subelement[j]].baz[0] or create reference aliases like sometype_t &tmpfoo = foo[someindex]; tmpfoo.bar[indexlist[i].subelement[j]].baz[0] and so forth...

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• Method to register method to be called when event is raised

  - by zaidwaqi

  I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share.

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• CUDA Global Memory, Where is it?

  - by gamerx

  I understand that in CUDA's memory hierachy, we have things like shared memory, texture memory, constant memory, registers and of course the global memory which we allocate using cudaMalloc(). I've been searching through whatever documentations I can find but I have yet to come across any that explicitly explains what is the global memory. I believe that the global memory allocated is on the GDDR of graphics card itself and not the RAM that is shared with the CPU since one of the documentations did state that the pointer cannot be dereferenced by the host side. Am I right?

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• Layout of popup components changes while moving

  - by Le_Coeur

  I have designed some popup moving menu with JQuery, it looks perfekt in webkit browsers, but i have one problem in mozilla, when i move my popup window, layout of some components in this window changes! For example button add changes from: to: or to: , and it's absolutly random. What can it be? This image is in span: <span class="sw_link_add"></span> .sw_link_add { background:url("/img/confirm_new.png") no-repeat scroll right center transparent; cursor:pointer; padding-right:30px; padding-top:2px; }

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• Button border radius and cursor

  - by noober

  CSS border radius does affect button rendering (I see it's round form), but does not affect how it interacts with the user (I still can click button outside its border). How should I fix it? I see the behavior in Chrome. button { cursor: pointer; outline: none; background-size: 100% 100%; background-color: red; /*transparent;*/ /* It's actually red and ROUND. */ background-position: center center; background-repeat: no-repeat; border: 0px; -webkit-border-top-left-radius: 73px; -webkit-border-top-right-radius: 73px; -webkit-border-bottom-left-radius: 73px; -webkit-border-bottom-right-radius: 73px; width: 146px; height: 146px; background-image: url('leftarrow.png'); } Regards,

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• How does the stream manipulators work?

  - by Narek

  It is well known that the user can define stream manipulators like this: ostream& tab(ostream & output) { return output<< '\t'; } And this can be used in main() like this: cout<<'a'<<tab<<'b'<<'c'<<endl; Please explain me how does this all work? If operator<< assumes as a second parameter a pointer to the function that takes and returns ostream &, then please explain my why it is necessary? What would be wrong if the function does not take and return ostream & but it was void instead of ostream &? Also it is interesting why “dec”, “hex” manipulators take effect until I don’t change between them, but user defined manipulators should be always used in order to take effect for each streaming?

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• Memory allocated with malloc does not persist outside function scope?

  - by PM

  Hi, I'm a bit new to C's malloc function, but from what I know it should store the value in the heap, so you can reference it with a pointer from outside the original scope. I created a test program that is supposed to do this but I keep getting the value 0, after running the program. What am I doing wrong? int f1(int * b) { b = malloc(sizeof(int)); *b = 5; } int main() { int * a; f1(a); printf("%d\n", a); return 0; }

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• C++ Vector of vectors

  - by xbonez

  I have a class header file called Grid.h that contains the following 2 private data object: vector<int> column; vector<vector<int>> row; And a public method whose prototype in Grid.h is such: int getElement (unsigned int& col, unsigned int& row); The definition of above mentioned function is defined as such in Grid.cpp: int getElement (unsigned int& col, unsigned int& row) { return row[row][col] ; } When I run the program, I get this error: error C2109: subscript requires array or pointer type Whats going wrong?

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• Array-size macro that rejects pointers

  - by nneonneo

  The standard array-size macro that is often taught is #define ARRAYSIZE(arr) (sizeof(arr) / sizeof(arr[0])) or some equivalent formation. However, this kind of thing silently succeeds when a pointer is passed in, and gives results that can seem plausible at runtime until things mysteriously fall apart. It's all-too-easy to make this mistake: a function that has a local array variable is refactored, moving a bit of array manipulation into a new function called with the array as a parameter. So, the question is: is there a "sanitary" macro to detect misuse of the ARRAYSIZE macro in C, preferably at compile-time? In C++ we'd just use a template specialized for array arguments only; in C, it seems we'll need some way to distinguish arrays and pointers. (If I wanted to reject arrays, for instance, I'd just do e.g. (arr=arr, ...) because array assignment is illegal).

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• .NET Regex - need matching string for parsing...

  - by TomTom

  Hello, I am a regex idiot and never found a good tutorial (links welcome, as well as a pointer to an interactive VS2010 integrated editor). I need to parse strings in the following form: [a/b]:c/d a, b: double with "." as possible separator. CAN be empty c: double with "." as separator d: integer, positive I.e. valid strings are: [/]:0.25/2 [-0.5/0.5]:0.05/2 [/0.1]:0.05/2 ;) Anyone can help? Thanks

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• seg violation using pycapsule_new

  - by user1733051

  I am trying some simple c API, where I am using PyCapsule_New to encapsulate a pointer. I am running into segment violation, can some body help me. mystruct *func1(int streamno, char mode,unsigned int options) { char * s; s=malloc(100); return s; } PyObject *Wrapper_func1(PyObject *self, PyObject *args) { int streamno; char mode; unsigned int options; mystruct* result; if (!PyArg_ParseTuple(args,"icI",&streamno,&mode,&options)) return NULL; result = func1(streamno,mode,options); return PyCapsule_New( result,NULL,NULL); }

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• Are unspecified and undefined behavior required to be consistent between compiles?

  - by sharptooth

  Let's pretend my program contains a specific construct the C++ Standard states to be unspecified behavior. This basically means the implementation has to do something reasonable but is allowed not to document it. But is the implementation required to produce the same behavior every time it compiles a specific construct with unspecified behavior or is it allowed to produce different behavior in different compiles? What about undefined behavior? Let's pretend my program contains a construct that is UB according to the Standard. The implementation is allowed to exhibit any behavior. But can this behavior differ between compiles of the same program on the same compiler with same settings in the same environment? In other words, if I dereference a null pointer on line 78 in file X.cpp and the implementation formats the drive in such case does it mean that it will do the same after the program is recompiled?

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• Help with implementing a function to change size of dynamic array

  - by iRobot

  I'm trying to write a function that will change the size of a dynamic array to a new size. In my header file, I have: Image **images; //pointer to a dynamic array of image pointers int maximum; //size I want to do this by allocating a new array and copying the values over without changing their indices. If there are non-null pointers outside the range newmax, then we cant do this. So heres what I have: There are no compilation or runtime errors. However, I find that the new array isnt getting sized right. When I run the following test case: I should get an index out of bounds error, but instead the system lets it slide. Can anyone see the mistake? I've looked for hours but cant find anything.

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• Break the limit of threading, segmentation fault

  - by user353573

  use pthread_create to create limited number of threads running concurrently Successfully compile and run However, after adding function pointer array to run the function, Segmentation fault Where is wrong? workserver number: 0 Segmentation fault void* workserver(void arg) { int status; while(true) { printf("workserver number: %d\n", (int)arg); ( job_queue[(int)arg])(); sleep(3); status = pthread_mutex_lock(&data.mutex); if(status != 0) printf("%d lock mutex", status); data.value = 1; status = pthread_cond_signal(&data.cond); if(status != 0) printf("%d signal condition", status); status = pthread_mutex_unlock(&data.mutex); if(status != 0) printf("%d unlock mutex", status); } }

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• C++ Inheritance Question

  - by shaz

  I have a base class MessageHandler and 2 derived classes, MessageHandler_CB and MessageHandler_DQ. The derived classes redefine the handleMessage(...) method. MH_DQ processes a message and puts the result in a deque while MH_CB processes the message and then executes a callback function. The base class has a static callback function that I pass along with a this pointer to a library which calls the static callback when a new message is available for processing. My problem comes when I am in the static callback with a void * pointing to either a MH_DQ or a MH_CB. If I cast it to the base class the empty MessageHandler::handleMessage(...) method is called, rather than the version in the appropriate derived class. What is the best way to address this situation from a design perspective and/or what language features might help me to implement a solution to my problem? Thanks in advance!

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• between syntax, are there any equal function

  - by gcc

  /* char **mainp=malloc(sizeof(char *)*2); mainp[0]=malloc(sizeof(char)*300); mainp[1]=malloc(sizeof(char )*300); */ *I have some input about propositional calculus *After calculating some math funtion-removing paranthesis-changing"&" with ","-replacing "|" with"," I have >> (1) P,-Q,Q,-R is stored in mainp[0] R,A,P,B,F is stored in mainp[1] *My question is: Between comma , I have want to compare two pointer array. If there is any equal two or more functions(Q,-R is function representation) ,function which you will show me how to write must return int. According to example (1),function will return 1 (I expect like that) /*I have som thought://which function should I have use:*/ in for loop if( strspn(mainp[0][i])==1 ) increment d; continue; or in for loop srtcmp(mainp[0][i],mainp[1]);

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• Shift from Java to c++

  - by zengr

  Hello, I have been developing applications based on C# (.net) and Java (J2EE) from the last 3 years. But, now I feel, Java, C# makes you lame (from learning point of view) and you can develop your apps quickly but you fail to understand the basic underlying concepts of programming. So, I am trying to learn C++, but I find it a little "confusing" due to pointer, multiple inheritance, some conventions and other concepts of C++ which don't exist in Java. So, what do you guys suggest? How should I got about it? Thanks PS: I am a student, so have all the time in the world and actually shift.

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• Abstract class and operator!= in c++

  - by Alessandro Teruzzi

  Hi All, I have problem implementing the operator!= in a set class deriving from an abstact one. The code looks like this: class Abstract { public: //to make the syntax easier let's use a raw pointer virtual bool operator!=(const Abstract* other) = 0; }; class Implementation { SomeObject impl_; //that already implement the operator!= public: bool operator!=(const Abstract* other) { return dynamic_cast<Implementation*>(other)->impl_ != this->impl_; } }; This code works but it has the drawback to use dynamic_cast and I need to handle error in casting operation. This is a generic problem that occur when a function of a concrete class it is trying to using some internal information (not available at the abstract class level) to perform a task. Is there any better way to solve this kind of problem? Cheers

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