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  • dimension || pointer pointer

    - by gcc
    What are pointers to pointers (like char **p;) used for? Can there be char ***p; or char ****p;? What would they be used for? my real question is >>what is the main purpose of char **p; why we need to use that type one answer is char *p - one dimension char *p - 2 dimensions char **p - 3 dimensions i have asked you can give example but he havenot answer i am thinking can we use ? is p[i][j] to **p that is can we use it like for(;;) for(;;) scanf("....",p[i][j]);

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  • Null Pointer Exception on a 2D array (Java)

    - by user315156
    I have a class, "Tetris", in which one of the instance variables is "board". "board" is 2D array of Color objects. Upon the creation of a tetris object I call a method that sets the dimensions of board and then sets all of the Color objects to be the Default value, that is to say, Color.blue. public Tetris(int rows, int cols){ this.rows = rows; this.cols = cols; reset(rows, cols); } public void reset(int rows, int cols){ Color[][] board = new Color[rows][cols]; for(int i = 0; i Unfortunately, when I run the code (which obviously has not been posted in its entirety) I get a null pointer exception on the line: board[i][j] = DEFAULT_COLOR; // Color.blue; //DEFAULT-COLOR. Is there anything obviously wrong with what I am doing? (Sorry if there are glaring format issues, this is my first time on Stack Overflow)

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  • *** glibc detected *** perl: munmap_chunk(): invalid pointer

    - by sid_com
    At the and of a script-output (parsing a xhtml-site with XML::LibXML::Reader) I get this: * glibc detected * perl: munmap_chunk(): invalid pointer: 0x0000000000b362e0 * ======= Backtrace: ========= /lib64/libc.so.6[0x7fb84952fc76] /usr/lib64/libxml2.so.2[0x7fb848b75e17] /usr/lib64/libxml2.so.2(xmlHashFree+0xa6)[0x7fb848b691b6] ... ... ======= Memory map: ======== 00400000-0053d000 r-xp 00000000 08:01 182002 /usr/local/bin/perl 0073c000-0073d000 r--p 0013c000 08:01 182002 /usr/local/bin/perl 0073d000-00741000 rw-p 0013d000 08:01 182002 /usr/local/bin/perl 00741000-00c60000 rw-p 00000000 00:00 0 [heap] 7fb8482cd000-7fb8482e3000 r-xp 00000000 08:01 2404 /lib64/libgcc_s.so.1 ... ... Is this due a bug?

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  • Using a member function pointer within a class

    - by neuviemeporte
    Given an example class: class Fred { public: Fred() { func = &Fred::fa; } void run() { int foo, bar; *func(foo,bar); } double fa(int x, int y); double fb(int x, int y); private: double (Fred::*func)(int x, int y); }; I get a compiler error at the line calling the member function through the pointer "*func(foo,bar)", saying: "term does not evaluate to a function taking 2 arguments". What am I doing wrong?

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  • function pointer error

    - by Codeguru
    Can anybody help me with this simple code?? include using namespace std; void testFunction(){ cout<<"This is the test function 0"< void testFunction1(){ cout<<"This is the test function 1"< void testFunction2(){ cout<<"This is the test function 2"< int main(){ //fp=testFunction; (*fp[testFunction1])(); //cout<<"Addrees of the function pointer is:"<<*fp; } Iam getting the following error: error: invalid types `void (*[3])()[void ()()]' for array subscript|

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  • c++ defining a static member of a template class with type inner class pointer

    - by Jack
    I have a template class like here (in a header) with a inner class and a static member of type pointer to inner class template <class t> class outer { class inner { int a; }; static inner *m; }; template <class t> outer <t>::inner *outer <t>::m; when i want to define that static member i says "error: expected constructor, destructor, or type conversion before '*' token" on the last line (mingw32-g++ 3.4.5)

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  • pointer being freed was not allocated

    - by kudorgyozo
    Hello i have the following error: malloc: * error for object 0x2087000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug I have no idea what object that is. I don't know how to find it. Can anybody explain to me how (and where) to use malloc_history. I have set a breakpoint in malloc_error_break but i couldn't find out what object is at that address. I receive this after removing an object from an nsmutablearray and popping a view controller manually. If I comment out the line [reviewUpload.images removeObject: self.reviewUploadImg] it doesn't give me the error but of course it's not useful for me like that. - (void) removeImage { debugLog(@"reviewUploadImg %@", self.reviewUploadImg); debugLog(@"reviewUpload %@", self.reviewUpload); debugLog(@"reviewUploadImg thumb %@", self.reviewUploadImg.thumb); [reviewUpload.images removeObject: self.reviewUploadImg]; [self.navigationController popViewControllerAnimated:TRUE]; }

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  • Type Declaration - Pointer Asterisk Position

    - by sahs
    Hello, in C++, the following means "allocate memory for an int pointer": int* number; So, the asterisk is part of the variable type; without it, that would mean something else (that's why I usually don't separate the asterisk from the variable type). Then what is the reason the asterisk is considered something else, instead of being part of the type? For example, it seems better, if the following meant "allocate memory for two int pointers": int* number1, number2; Am I wrong?

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  • Activating "pointer-events:none" only on section of image that overlaps

    - by Buckers
    I'm using pointer-events:none; on the main photograph at the top of my site http://www.onedirection.net/, to allow the user to select the navigation behind the image. However, I'd like to let the user click on each member of the band to go to a separate page, but ONLY for the parts of the image that don't overlap into the navigation. I'm a bit stuck with this. Can it be done? I was thinking of using an image map, but can't get it working without the navigation becoming "less clickable".

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  • C++ private pointer "leaking"?

    - by jbu
    I'm going to create a class to hold a long list of parameters that will be passed to a function. Let's use this shorter example: class ParamList{ public: ParamList(string& a_string); string& getString(); //returns my_string private: string& my_string; } My question is this: my_string is private, yet I'm returning the reference to it. Isn't that called something like private pointer leaking in C++? Is this not good programming practice? I want callers of getString to be able to get the reference and also modify it. Please let me know. Thanks, jbu edit1: callers will use getString() and modify the string that was returned.

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  • C++ pointer, Beginner Question...

    - by BobAlmond
    Hi there, just want to ask a beginner question... here, I made some code, for understanding the concept/basic of pointer: int a=1; int *b=&a; int **c = &b; int ***d = &c; cout << &*(&*d) << endl; can someone explain to me, why the &*(&d) return address of "c" instead of address of "b"? I've also tried code like &(&(&(&*(&*d)))), but it keep return address of "c" Thanks a lot :)

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  • C++ pointer to functions, Beginner Question...

    - by BobAlmond
    Hi all, I want to ask about pointer in C++ I have some simple code: int add(int a, int b){ return a+b; } int runner(int x,int y, int (*functocall)(int, int)){ return (*functocall)(x,y); } now, suppose I call those functions using this way : cout<<runner(2,5,&add); or maybe cout<<runner(2,5,add); is there any difference? because when I tried, the result is the same and with no error. Thanks a lot

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  • Modifying a const through a non-const pointer

    - by jasonline
    I'm a bit confused what happened in the following code: const int e = 2; int* w = ( int* ) &e; // (1) cast to remove const-ness *w = 5; // (2) cout << *w << endl; // (3) outputs 5 cout << e << endl; // (4) outputs 2 cout << "w = " << w << endl; // (5) w points to the address of e cout << "&e = " << &e << endl; In (1), w points to the address of e. In (2), that value was changed to 5. However, when the values of *w and e were displayed, their values are different. But if you print value of w pointer and &e, they have the same value/address. How come e still contained 2, even if it was changed to 5? Were they stored in a separate location? Or a temporary? But how come the value pointed by w is still the address of e?

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  • Go: using a pointer to array

    - by Sean
    I'm having a little play with google's Go language, and I've run into something which is fairly basic in C but doesn't seem to be covered in the documentation I've seen so far When I pass a pointer to an array to a function, I presumed we'd have some way to access it as follows: func conv(x []int, xlen int, h []int, hlen int, y *[]int) for i := 0; i<xlen; i++ { for j := 0; j<hlen; j++ { *y[i+j] += x[i]*h[j] } } } But the Go compiler doesn't like this: sean@spray:~/dev$ 8g broke.go broke.go:8: invalid operation: y[i + j] (index of type *[]int) Fair enough - it was just a guess. I have got a fairly straightforward workaround: func conv(x []int, xlen int, h []int, hlen int, y_ *[]int) { y := *y_ for i := 0; i<xlen; i++ { for j := 0; j<hlen; j++ { y[i+j] += x[i]*h[j] } } } But surely there's a better way. The annoying thing is that googling for info on Go isn't very useful as all sorts of C\C++\unrelated results appear for most search terms.

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  • vector::erase with pointer member

    - by matt
    I am manipulating vectors of objects defined as follow: class Hyp{ public: int x; int y; double wFactor; double hFactor; char shapeNum; double* visibleShape; int xmin, xmax, ymin, ymax; Hyp(int xx, int yy, double ww, double hh, char s): x(xx), y(yy), wFactor(ww), hFactor(hh), shapeNum(s) {visibleShape=0;shapeNum=-1;}; //Copy constructor necessary for support of vector::push_back() with visibleShape Hyp(const Hyp &other) { x = other.x; y = other.y; wFactor = other.wFactor; hFactor = other.hFactor; shapeNum = other.shapeNum; xmin = other.xmin; xmax = other.xmax; ymin = other.ymin; ymax = other.ymax; int visShapeSize = (xmax-xmin+1)*(ymax-ymin+1); visibleShape = new double[visShapeSize]; for (int ind=0; ind<visShapeSize; ind++) { visibleShape[ind] = other.visibleShape[ind]; } }; ~Hyp(){delete[] visibleShape;}; }; When I create a Hyp object, allocate/write memory to visibleShape and add the object to a vector with vector::push_back, everything works as expected: the data pointed by visibleShape is copied using the copy-constructor. But when I use vector::erase to remove a Hyp from the vector, the other elements are moved correctly EXCEPT the pointer members visibleShape that are now pointing to wrong addresses! How to avoid this problem? Am I missing something?

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  • getting Null pointer exception

    - by Abhijeet
    Hi I am getting this message on emulator when I run my android project: The application MediaPlayerDemo_Video.java (process com.android.MediaPlayerDemo_Video) has stopped unexpectedly. Please try again I am trying to run the MediaPlayerDemo_Video.java given in ApiDemos in the Samples given on developer.android.com. The code is : package com.android.MediaPlayerDemo_Video; import android.app.Activity; import android.media.AudioManager; import android.media.MediaPlayer; import android.media.MediaPlayer.OnBufferingUpdateListener; import android.media.MediaPlayer.OnCompletionListener; import android.media.MediaPlayer.OnPreparedListener; import android.media.MediaPlayer.OnVideoSizeChangedListener; import android.os.Bundle; import android.util.Log; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.widget.Toast; public class MediaPlayerDemo_Video extends Activity implements OnBufferingUpdateListener, OnCompletionListener, OnPreparedListener, OnVideoSizeChangedListener, SurfaceHolder.Callback { private static final String TAG = "MediaPlayerDemo"; private int mVideoWidth; private int mVideoHeight; private MediaPlayer mMediaPlayer; private SurfaceView mPreview; private SurfaceHolder holder; private String path; private Bundle extras; private static final String MEDIA = "media"; // private static final int LOCAL_AUDIO = 1; // private static final int STREAM_AUDIO = 2; // private static final int RESOURCES_AUDIO = 3; private static final int LOCAL_VIDEO = 4; private static final int STREAM_VIDEO = 5; private boolean mIsVideoSizeKnown = false; private boolean mIsVideoReadyToBePlayed = false; /** * * Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.mediaplayer_2); mPreview = (SurfaceView) findViewById(R.id.surface); holder = mPreview.getHolder(); holder.addCallback(this); holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); extras = getIntent().getExtras(); } private void playVideo(Integer Media) { doCleanUp(); try { switch (Media) { case LOCAL_VIDEO: // Set the path variable to a local media file path. path = ""; if (path == "") { // Tell the user to provide a media file URL. Toast .makeText( MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity, " + "and set the path variable to your media file path." + " Your media file must be stored on sdcard.", Toast.LENGTH_LONG).show(); } break; case STREAM_VIDEO: /* * Set path variable to progressive streamable mp4 or * 3gpp format URL. Http protocol should be used. * Mediaplayer can only play "progressive streamable * contents" which basically means: 1. the movie atom has to * precede all the media data atoms. 2. The clip has to be * reasonably interleaved. * */ path = ""; if (path == "") { // Tell the user to provide a media file URL. Toast .makeText( MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity," + " and set the path variable to your media file URL.", Toast.LENGTH_LONG).show(); } break; } // Create a new media player and set the listeners mMediaPlayer = new MediaPlayer(); mMediaPlayer.setDataSource(path); mMediaPlayer.setDisplay(holder); mMediaPlayer.prepare(); mMediaPlayer.setOnBufferingUpdateListener(this); mMediaPlayer.setOnCompletionListener(this); mMediaPlayer.setOnPreparedListener(this); mMediaPlayer.setOnVideoSizeChangedListener(this); mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC); } catch (Exception e) { Log.e(TAG, "error: " + e.getMessage(), e); } } public void onBufferingUpdate(MediaPlayer arg0, int percent) { Log.d(TAG, "onBufferingUpdate percent:" + percent); } public void onCompletion(MediaPlayer arg0) { Log.d(TAG, "onCompletion called"); } public void onVideoSizeChanged(MediaPlayer mp, int width, int height) { Log.v(TAG, "onVideoSizeChanged called"); if (width == 0 || height == 0) { Log.e(TAG, "invalid video width(" + width + ") or height(" + height + ")"); return; } mIsVideoSizeKnown = true; mVideoWidth = width; mVideoHeight = height; if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) { startVideoPlayback(); } } public void onPrepared(MediaPlayer mediaplayer) { Log.d(TAG, "onPrepared called"); mIsVideoReadyToBePlayed = true; if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) { startVideoPlayback(); } } public void surfaceChanged(SurfaceHolder surfaceholder, int i, int j, int k) { Log.d(TAG, "surfaceChanged called"); } public void surfaceDestroyed(SurfaceHolder surfaceholder) { Log.d(TAG, "surfaceDestroyed called"); } public void surfaceCreated(SurfaceHolder holder) { Log.d(TAG, "surfaceCreated called"); playVideo(extras.getInt(MEDIA)); } @Override protected void onPause() { super.onPause(); releaseMediaPlayer(); doCleanUp(); } @Override protected void onDestroy() { super.onDestroy(); releaseMediaPlayer(); doCleanUp(); } private void releaseMediaPlayer() { if (mMediaPlayer != null) { mMediaPlayer.release(); mMediaPlayer = null; } } private void doCleanUp() { mVideoWidth = 0; mVideoHeight = 0; mIsVideoReadyToBePlayed = false; mIsVideoSizeKnown = false; } private void startVideoPlayback() { Log.v(TAG, "startVideoPlayback"); holder.setFixedSize(mVideoWidth, mVideoHeight); mMediaPlayer.start(); } } I think the above message is due to Null pointer exception , however I may be false. I am unable to find where the error is . So , Please someone help me out .

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  • High end mobile workstations with pointer stick

    - by Elijah Lynn
    I am looking for a list of higher end mobile workstations that run Ubuntu/Kubuntu well and also have a hardware pointer stick. Here's an illustration of one (from sciencesurvivalblog): I wouldn't mind getting a Macbook Pro and wiping it but they refuse to use pointer sticks and to me, they are extremely efficient. I see a lot of potential for Lenovo thinkpads as well. System 76 said they have no plans to implement a hardware pointer stick so that leaves them out as well. Any ideas?

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  • USB mouse pointer only moving horizontally on macbook 6.2 with 12.04

    - by Glyn Normington
    After installing Ubuntu 12.04 on a macbook pro 6.2, the touchpad and external USB mouse worked perfectly. After rebooting I can't get either touchpad or external USB mouse to work. Sometimes no mouse pointer is visible, but more often I can only move the mouse pointer horizontally five sixths of the way across the display (from the top left). I have uninstalled mouseemu. xinput list shows the USB mouse. xinput query-state for the USB mouse shows the following: ButtonClass button[1]=up ... button[16]=up ValuatorClass Mode=Relative Proximity=In valuator[0]=480 valuator[1]=2400 valuator[2]=0 valuator[3]=3 and re-issuing this command with the pointer at its right hand extreme displays the same except for: valuator[0]=1679 So the valuator[0] seems to be the x-coordinate of the pointer and the range of motion 480-1679 is indeed about five sixths of the display width (1440). valuator[1] is suspiciously large given the display height is 900. Perhaps this is a side-effect of having previously been using a dual monitor (although booting with that monitor connected does not help). There are other entries listed under xinput list: Virtual core XTEST pointer which seems stuck at position (840,1050). bcm5974 which seems stuck at position (837,6700). Removing the bcm5974 module using rmmod disables the toucpad as expected but does not fix the USB mouse problem. After adding the module back, it is stuck at position (840,1050) instead of (837,6700). /etc/X11/xorg.conf was generated by nvidia-settings and contains: Section "InputDevice" # generated from default Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/psaux" Option "ZAxisMapping" "4 5" although I don't know how plausible these settings are. Any suggestions?

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  • Mouse pointer hides at bad times after updating to 13.10

    - by Richard
    A bug, I think, though I can't even seem to find any information when searching for it. The mouse pointer hides itself, but it is still possible to use it. Whenever I start watching a video in VLC, or start playing KSP through Steam my mouse pointer disappears. It is not returned upon exiting the application. I have not tried with other games in Steam. The mouse pointer do not disappear when watching videos online through YouTube, though it properly hides itself after a few seconds. The bug came about after I updated to 13.10, it was not present with the same setup in 13.04. I have tried removing ~/.compiz and restarting the kernel module psmouse. Going to tty1 and back to the desktop reveals the pointer, though this fix is bothering me. How do I fix this problem?

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  • Is it any good to use binary arithmetic in a C++ code like "C style"?

    - by user827992
    I like the fact that the C language lets you use binary arithmetic in an explicit way in your code, sometimes the use of the binary arithmetic can also give you a little edge in terms of performance; but since I started studying C++ i can't really tell how much i have seen the explicit use of something like that in a C++ code, something like a pointer to pointer structure or an instruction for jumping to a specific index value through the binary arithmetic. Is the binary arithmetic still important and relevant in the C++ world? How i can optimize my arithmetic and/or an access to a specific index? What about the C++ and the way in which the bits are arranged according to the standard? ... or i have taken a look at the wrong coding conventions ... ?

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  • Go - Pointer to map

    - by nevalu
    Having some maps defined as: var valueToSomeType = map[uint8]someType{...} var nameToSomeType = map[string]someType{...} I would want a variable that points to the address of the maps (to don't copy all variable). I tried it using: valueTo := &valueToSomeType nameTo := &nameToSomeType but at using valueTo[number], it shows internal compiler error: var without type, init: new How to get it?

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  • How to avoid null pointer error

    - by Jessy
    I trying to find whether the elements of 2 arrayLists are match or not. But this code give me error Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException since some of the elements are null. How can I solved this problem? String level []={"High","High","High","High","High","High"}; ArrayList<Object> n = new ArrayList<Object>(Arrays.asList(level)); String choice []={null,"High","Low","High",null,"Medium"}; ArrayList<Object> m = new ArrayList<Object>(Arrays.asList(choice)); //Check if the two arrayList are identical for(int i=0; i<m.size(); i++){ if(!(m.get(i).equals(n.get(i)))){ result= true; break; } } return result; }

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  • Classes, constructor and pointer class members

    - by pocoa
    I'm a bit confused about the object references. Please check the examples below: class ListHandler { public: ListHandler(vector<int> &list); private: vector<int> list; } ListHandler::ListHandler(vector<int> &list) { this->list = list; } Here I would be wasting memory right? So the right one would be: class ListHandler { public: ListHandler(vector<int>* list); private: vector<int>* list; } ListHandler::ListHandler(vector<int>* list) { this->list = list; } ListHandler::~ListHandler() { delete list; }

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  • Use super class's address/pointer in initialization list

    - by JQ
    context 1: class D : public B1, public B2{}; context 2: B2 takes B1 to initialize: B2( B1 * ) //B2's constructor my question is in D's initialization list: D::D() : B1(), B2( ? )... What should be in ? I don't want to put " (B1*)this " in the ? place, because it's no good to use "this" in initialization list. And since B1 part has been initialized, it makes sense to use it. What should I do ?

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