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• Rotate 2d sprite towards pointer

  - by Phil

  I'm using Crafty.js and am trying to point a sprite towards the mouse pointer. I have a function for getting the degree between two points and I'm pretty sure it works mathematically (I have it under unit tests). At least it responds that the degree between { 0,0} and {1,1} is 45, which seems right. However, when I set the sprite rotation to the returned degree, it's just wrong all the time. If I manually set it to 90, 45, etc, it gets the right direction.. I have a jsfiddle that shows what I've done so far. Any ideas?

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• Problems after upgrading to 14.04 (only background and pointer after login)

  - by fabikw

  After upgrading from 12.04 to 14.04 I could log in to my X session (albeit with really low graphics). While trying to fix the graphics, I managed to break the X session. Now, after typing my password in the unity-greeter, the items disappear and I can only see the desktop background and the pointer. This happens for every user. I can still log in in tty's. How can I solve this? Also, I cannot seem to be able to install nvidia-current as it tries to install nvidia-304 and it depends on old video-abi libraries. Is there a way to tell the package manager that nvidia-current should use a newer version?

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• No Mouse Pointer - ubuntu 13.10

  - by Paul

  just installed 13.10 on my HP Envy M6 laptop and have no mouse pointer. My USB mouse does not work and neither does the track pad. When I booted from a USB key everything worked OK but once installed it seems to have broken the mouse. Unlike other posts, there is no flicker, it simply doesn't work at all. My laptop is an i5 with 6gb and dual Intel and AMD radeon graphics. Any help would be gratefully received as I really can't stand Windows 8 any longer. Thanks.

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• Question on passing a pointer to a structure in C to a function?

  - by worlds-apart89

  Below, I wrote a primitive singly linked list in C. Function "addEditNode" MUST receive a pointer by value, which, I am guessing, means we can edit the data of the pointer but can not point it to something else. If I allocate memory using malloc in "addEditNode", when the function returns, can I see the contents of first-next ? Second question is do I have to free first-next or is it only first that I should free? I am running into segmentation faults on Linux. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { int value; list_node_t *next; }; void addEditNode(list_node_t *node) { node->value = 10; node->next = (list_node_t*) malloc(sizeof(list_node_t)); node->next->value = 1; node->next->next = NULL; } int main() { list_node_t *first = (list_node_t*) malloc(sizeof(list_node_t)); first->value = 1; first->next = NULL; addEditNode(first); free(first); return 0; }

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• Mouse pointer strange problem...

  - by Paska

  Hi all, i have last ubuntu installed (10.10), but from an year and thousand updates, video drivers updates, an hundreds of tricks, the mouse pointer is showed like an UGLY square... These are the screenshots: First Second I have no idea what to do to solve this problem. Anyone of you have an idea to solve it? Edit: this problem was encountered from 8.10+! Edit 2, Video card specifications: paska@ubuntu:~$ hwinfo --gfxcard 35: PCI 100.0: 0300 VGA compatible controller (VGA) [Created at pci.318] UDI: /org/freedesktop/Hal/devices/pci_1106_3230 Unique ID: VCu0.QX54AGQKWeE Parent ID: vSkL.CP+qXDDqow8 SysFS ID: /devices/pci0000:00/0000:00:01.0/0000:01:00.0 SysFS BusID: 0000:01:00.0 Hardware Class: graphics card Model: "VIA K8M890CE/K8N890CE [Chrome 9]" Vendor: pci 0x1106 "VIA Technologies, Inc." Device: pci 0x3230 "K8M890CE/K8N890CE [Chrome 9]" SubVendor: pci 0x1043 "ASUSTeK Computer Inc." SubDevice: pci 0x81b5 Revision: 0x11 Memory Range: 0xd0000000-0xdfffffff (rw,prefetchable) Memory Range: 0xfa000000-0xfaffffff (rw,non-prefetchable) Memory Range: 0xfbcf0000-0xfbcfffff (ro,prefetchable,disabled) IRQ: 16 (10026 events) I/O Ports: 0x3c0-0x3df (rw) Module Alias: "pci:v00001106d00003230sv00001043sd000081B5bc03sc00i00" Driver Info #0: Driver Status: viafb is not active Driver Activation Cmd: "modprobe viafb" Config Status: cfg=new, avail=yes, need=no, active=unknown Attached to: #17 (PCI bridge) Primary display adapter: #35 paska@ubuntu:~$ thanks, A

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• September OTN Member Offers

  - by Cassandra Clark - OTN

  Oracle OpenWolrd and JavaOne are coming....so the OTN team is knee deep in planning the OTN Lounges that will be at each event this year (more info in another post soon), but we managed to work with our partners to offer a nice BIG list of NEW offers for September.  Visit Oracle Technology Network Member Discount page for codes and links to these great offers! Oracle Press Oracle Technology Network members get 40% off the newest Oracle Press title, Oracle Exalogic Elastic Cloud Handbook by Tom Plunkett! Mike Murach & Associates, Inc. Get 30% off and sample chapter of Murach’s SQL Server 2012 for Developers by Bryan Syverson and Joel Murach Manning - 41% off titles below and sample chapter of each. Making Java Groovy OCA Java SE 7 Programmer I Certification Guide Apress - Get 30% off on apress.com on Java 7 Recipes A Problem-Solution Approach Safari Books Online - OTN members get 30 days of free access + 20% off unlimited access to Safari Books Online for 6 months. Safari Books Online offers subscription access to more than 24,000 books and training videos about technology, digital media, business management and professional development from leading publishers such as Oracle Press, O'Reilly Media, Que, Addison-Wesley, Wrox, Cisco Press, Microsoft Press, McGraw Hill, Wiley, Apress, Adobe Press and many others. Already a customer? Come see us at Oracle OpenWorld (booth 537) or JavaOne (5110) and mention this to get a shirt!

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• White screen with pointer after removing Unity

  - by Sameer Pandit

  I have the same problem . I am a newbie. I added the repository with sudo add apt-get-repository ppa:canonical-dx-team/une then i went to ubuntu software center and installed "unity interface of ubuntu netbook edition" . after installing i found a problem with User interface as it kept on flashing when mouse points to side panel . so i decided to remove it . I removed it form Ubuntu software center . there were other unity related apps installed , but i did not remove then as i had no idea what they were about . Now i ended up with a blank white screen with mouse pointer whenever i login. though i m able to login using gdm , but the screen is blank white. I tried to these commands also sudo apt-get remove gnome-shell sudo apt-get remove unity sudo restart gdm but they did not work at all i also tried sudo dpkg-reconfigure xserver-xorg it too did not work. Note:I donot have any sort of graphics card or video card on my pc please help !!!

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• November New Member Offers

  - by Cassandra Clark - OTN

  Happy November!  OTN has worked with its partners to bring you more new offers or extend their existing ones.Oracle Press New Offer-Oracle Technology Network members get 40% off the newest Oracle Press titles by Oracle ACE Mark Rittman, Oracle Business Intelligence 11g Developers Guide and Oracle Exalytics Revealed  (ebook format only).Extended Offers - Oracle Store - Save 10% on Your Next Software Purchase from the Oracle StorePearson Publistiong - 35% off Hacker’s Delight Manning Publishing - 41% off the MEAP, eBook and print format of the following books: Making Java Groovy OCA Java SE 7 Programmer I Certification Guide Safari Books Online - OTN members get 30 days of free access + 20% off unlimited access to Safari Books Online for 6 months. Packt Publishing - 25% off the print books and 35% off the eBooks listed below: Getting Started with Oracle Data Integrator 11g: A Hands-On Tutorial Oracle Business Intelligence Enterprise Edition 11g: A Hands-On Tutorial  Oracle Certified Associate, Java SE 7 Programmer Study Guides. Murach  Publishing -  Get 30% off for OTN members - Murach’s SQL Server 2012 for Developers by Bryan Syverson and Joel Murach. Get all of this From the OTN Member Discount Page!

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• Bug: unable to handle kernel NULL pointer dereference at

  - by maria

  I have recently installed new system on my disc, Ubuntu 12.04. Installation proceeded without problems, I started installing additional software and put data from other discs. I had already two times bug report, it was quite long, and I have no idea how to acces to log file (which probably is somewhere saved) and since I had to switch off the computer using the button, anything else was possible, here is just a small part of it (what I've noted on paper) could not write bytes: Broken pipe speach dicpatcher disabled: edit etc/default/speach-dispatcher saned disabled: edit .... and than: BUG: unable to handle kernel NULL pointer dereference at 0000009c I've run Memory test in GRUB, everything is fine. First time it occured when I was using rsync, second time when I was trying to install texlive. Should I install whole system once again? Or can it be hardware problem? Or something else? If there is any hardware details which may be relevant, please ask, since I have no idea what is happening, I don't know what kind of information could be useful. Thanks P.S. dmesg output:

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• Potential issues using member's "from" address and the "sender" header

  - by Paul Burney

  Hi all, A major component of our application sends email to members on behalf of other members. Currently we set the "From" address to our system address and use a "Reply-to" header with the member's address. The issue is that replies from some email clients (and auto-replies/bounces) don't respect the "Reply-to" header so get sent to our system address, effectively sending them to a black hole. We're considering setting the "From" address to our member's address, and the "Sender" address to our system address. It appears this way would pass SPF and Sender-ID checks. Are there any reasons not to switch to this method? Are there any other potential issues? Thanks in advance, -Paul Here are way more details than you probably need: When the application was first developed, we just changed the "from" address to be that of the sending member as that was the common practice at the time (this was many years ago). We later changed that to have the "from" address be the member's name and our address, i.e., From: "Mary Smith" <[email protected]> With a "reply-to" header set to the member's address: Reply-To: "Mary Smith" <[email protected]> This helped with messages being mis-categorized as spam. As SPF became more popular, we added an additional header that would work in conjunction with our SPF records: Sender: <[email protected]> Things work OK, but it turns out that, in practice, some email clients and most MTA's don't respect the "Reply-To" header. Because of this, many members send messages to [email protected] instead of the desired member. So, I started envisioning various schemes to add data about the sender to the email headers or encode it in the "from" email address so that we could process the response and redirect appropriately. For example, From: "Mary Smith" <[email protected]> where the string after "messages" is a hash representing Mary Smith's member in our system. Of course, that path could lead to a lot of pain as we need to develop MTA functionality for our system address. I was looking again at the SPF documentation and found this page interesting: http://www.openspf.org/Best_Practices/Webgenerated They show two examples, that of evite.com and that of egreetings.com. Basically, evite.com is doing it the way we're doing it. The egreetings.com example uses the member's from address with an added "Sender" header. So the question is, are there any potential issues with using the egreetings method of the member's from address with a sender header? That would eliminate the replies that bad clients send to the system address. I don't believe that it solves the bounce/vacation/whitelist issue since those often send to the MAIL FROM even if Return Path is specified.

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• How does dereferencing of a function pointer happen?

  - by eSKay

  Why and how does dereferencing a function pointer just "do nothing"? This is what I am talking about: #include<stdio.h> void hello() { printf("hello"); } int main(void) { (*****hello)(); } From a comment over here: function pointers dereference just fine, but the resulting function designator will be immediately converted back to a function pointer And from an answer here: Dereferencing (in way you think) a function's pointer means: accessing a CODE memory as it would be a DATA memory. Function pointer isn't suppose to be dereferenced in that way. Instead, it is called. I would use a name "dereference" side by side with "call". It's OK. Anyway: C is designed in such a way that both function name identifier as well as variable holding function's pointer mean the same: address to CODE memory. And it allows to jump to that memory by using call () syntax either on an identifier or variable. How exactly does dereferencing of a function pointer work?

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• What type can hold member-function-pointers of difference classes in C++?

  - by Zach

  Hi all, I need an array to hold member-function-pointers of different classes. How can I define the array? The code should look like this : arr[0] = &CMyClass::FuncX; arr[1] = &CYourClass::FuncY; arr[2] = &CHerClass::FuncZ; I tried void*, but it doesn't work. Thanks. Best regards, Zach@Shine

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• Is it possible to get all member variables in flash(AS3)?

  - by Parris

  Hi, I am trying grab all the member variables in AS3, and then foreach one i would like to process it in various ways. I would need the name and then if it is a collection of some type I would like to loop through that collection as well. I am attempting to essentially serialize in a somewhat custom fashion. Thanks!

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• In actionscript, why is my static class member variable not the same when accessed from different pa

  - by Ryan M

  I have an actionscript class with a static member variable defined. public class A { public static var x:int; } When I try to access it from different parts in my code I don't get the same value in each spot. A.x I am accessing the variable in different modules that are loaded, so they are all in their own separate .swf file. Could this by why?

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• MiniMax function throws null pointer exception

  - by Sven

  I'm working on a school project, I have to build a tic tac toe game with the AI based on the MiniMax algorithm. The two player mode works like it should. I followed the code example on http://ethangunderson.com/blog/minimax-algorithm-in-c/. The only thing is that I get a NullPointer Exception when I run the code. And I can't wrap my finger around it. I placed a comment in the code where the exception is thrown. The recursive call is returning a null pointer, what is very strange because it can't.. When I place a breakpoint on the null return with the help of a if statement, then I see that there ARE still 2 to 3 empty places.. I probably overlooking something. Hope someone can tell me what I'm doing wrong. Here is the MiniMax code (the tic tac toe code is not important): /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package MiniMax; import Game.Block; import Game.Board; import java.util.ArrayList; public class MiniMax { public static Place getBestMove(Board gameBoard, Block.TYPE player) { Place bestPlace = null; ArrayList<Place> emptyPlaces = gameBoard.getEmptyPlaces(); Board newBoard; //loop trough all the empty places for(Place emptyPlace : emptyPlaces) { newBoard = gameBoard.clone(); newBoard.setBlock(emptyPlace.getRow(), emptyPlace.getCell(), player); //no game won and still room to move if(newBoard.getWinner() == Block.TYPE.NONE && newBoard.getEmptyPlaces().size() > 0) { //is an node (has children) Place tempPlace = getBestMove(newBoard, invertPlayer(player)); //ERROR is thrown here! tempPlace is null. emptyPlace.setScore(tempPlace.getScore()); } else { //is an leaf if(newBoard.getWinner() == Block.TYPE.NONE) { emptyPlace.setScore(0); } else if(newBoard.getWinner() == Block.TYPE.X) { emptyPlace.setScore(-1); } else if(newBoard.getWinner() == Block.TYPE.O) { emptyPlace.setScore(1); } //if this move is better then our prev move, take it! if((bestPlace == null) || (player == Block.TYPE.X && emptyPlace.getScore() < bestPlace.getScore()) || (player == Block.TYPE.O && emptyPlace.getScore() > bestPlace.getScore())) { bestPlace = emptyPlace; } } } //This should never be null, but it does.. return bestPlace; } private static Block.TYPE invertPlayer(Block.TYPE player) { if(player == Block.TYPE.X) { return Block.TYPE.O; } return Block.TYPE.X; } }

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• Android - Force Close - Null Pointer on Canvas?

  - by user22241

  Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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• CEN/CENELEC Lacks Perspective

  - by trond-arne.undheim

  Over the last few months, two of the European Standardization Organizations (ESOs), CEN and CENELEC have circulated an unfortunate position statement distorting the facts around fora and consortia. For the benefit of outsiders to this debate, let's just say that this debate regards whether and how the EU should recognize standards and specifications from certain fora and consortia based on a process evaluating the openness and transparency of such deliverables. The topic is complex, and somewhat confusing even to insiders, but nevertheless crucial to the European economy. As far as I can judge, their positions are not based on facts. This is unfortunate. For the benefit of clarity, here are some of the observations they make: a)"Most consortia are in essence driven by technology companies making hardware and software solutions, by definition very few of the largest ones are European-based". b) "Most consortia lack a European presence, relevant Committees, even those that are often cited as having stronger links with Europe, seem to lack an overall, inclusive set of participants". c) "Recognising specific consortia specifications will not resolve any concrete problems of interoperability for public authorities; interoperability depends on stringing together a range of specifications (from formal global bodies or consortia alike)". d) "Consortia already have the option to have their specifications adopted by the international formal standards bodies and many more exercise this than the two that seem to be campaigning for European recognition. Such specifications can then also be adopted as European standards." e) "Consortium specifications completely lack any process to take due and balanced account of requirements at national level - this is not important for technologies but can be a critical issue when discussing cross-border issues within the EU such as eGovernment, eHealth and so on". f) "The proposed recognition will not lead to standstill on national or European activities, nor to the adoption of the specifications as national standards in the CEN and CENELEC members (usually in their official national languages), nor to withdrawal of conflicting national standards. A big asset of the European standardization system is its coherence and lack of fragmentation." g) "We always miss concrete and specific examples of where consortia referencing are supposed to be helpful." First of all, note that ETSI, the third ESO, did not join the position. The reason is, of course, that ETSI beyond being an ESO, also has a global perspective and, moreover, does consider reality. Secondly, having produced arguments a) to g), CEN/CENELEC has the audacity to call a meeting on Friday 25 February entitled "ICT standardization - improving collaboration in Europe". This sounds very nice, but they have not set the stage for constructive debate. Rather, they demonstrate a striking lack of vision and lack of perspective. I will back this up by three facts, and leave it there. 1. Since the 1980s, global industry fora and consortia, such as IETF, W3C and OASIS have emerged as world-leading ICT standards development organizations with excellent procedures for openness and transparency in all phases of standards development, ex post and ex ante. - Practically no ICT system can be built without using fora and consortia standards (FCS). - Without using FCS, neither the Internet, upon which the EU economy depends, nor EU institutions would operate. - FCS are of high relevance for achieving and promoting interoperability and driving innovation. 2. FCS are complementary to the formally recognized standards organizations including the ESOs. - No work will be taken away from the ESOs should the EU recognize certain FCS. - Each FCS would be evaluated on its merit and on the openness of the process that produced it. ESOs would, with other stakeholders, have a say. - ESOs could potentially educate and assist European stakeholders to engage more actively and constructively with FCS. - ETSI, also an ESO, seems to clearly recognize these facts. 3. Europe and its Member States have a strong voice in several of the most relevant global industry fora and consortia. - W3C: W3C was founded in 1994 by an Englishman, Sir Tim Berners-Lee, in collaboration with CERN, the European research lab. In April 1995, INRIA (Institut National de Recherche en Informatique et Automatique) in France became the first European W3C host and in 2003, ERCIM (European Research Consortium in Informatics and Mathematics), also based in France, took over the role of European W3C host from INRIA. Today, W3C has 326 Members, 40% of which are European. Government participation is also strong, and it could be increased - a development that is very much desired by W3C. Current members of the W3C Advisory Board includes Ora Lassila (Nokia) and Charles McCathie Nevile (Opera). Nokia is Finnish company, Opera is a Norwegian company. SAP's Claus von Riegen is an alumni of the same Advisory Board. - OASIS: its membership - 30% of which is European - represents the marketplace, reflecting a balance of providers, user companies, government agencies, and non-profit organizations. In particular, about 15% of OASIS members are governments or universities. Frederick Hirsch from Nokia, Claus von Riegen from SAP AG and Charles-H. Schulz from Ars Aperta are on the Board of Directors. Nokia is a Finnish company, SAP is a German company and Ars Aperta is a French company. The Chairman of the Board is Peter Brown, who is an Independent Consultant, an Austrian citizen AND an official of the European Parliament currently on long-term leave. - IETF: The oversight of its activities is by the Internet Architecture Board (IAB), since 2007 chaired by Olaf Kolkman, a Dutch national who lives in Uithoorn, NL. Kolkman is director of NLnet Labs, a foundation chartered to develop open source software and open source standards for the Internet. Other IAB members include Marcelo Bagnulo whose affiliation is the University Carlos III of Madrid, Spain as well as Hannes Tschofenig from Nokia Siemens Networks. Nokia is a Finnish company. Siemens is a German company. Nokia Siemens is a European joint venture. - Member States: At least 17 European Member States have developed Interoperability Frameworks that include FCS, according to the EU-funded National Interoperability Framework Observatory (see list and NIFO web site on IDABC). This also means they actively procure solutions using FCS, reference FCS in their policies and even in laws. Member State reps are free to engage in FCS, and many do. It would be nice if the EU adjusted to this reality. - A huge number of European nationals work in the global IT industry, on European soil or elsewhere, whether in EU registered companies or not. CEN/CENELEC lacks perspective and has engaged in an effort to twist facts that is quite striking from a publicly funded organization. I wish them all possible success with Friday's meeting but I fear all of the most important stakeholders will not be at the table. Not because they do not wish to collaborate, but because they just have been insulted. If they do show up, it would be a gracious move, almost beyond comprehension. While I do not expect CEN/CENELEC to line up perfectly in favor of fora and consortia, I think it would be to their benefit to stick to more palatable observations. Actually, I would suggest an apology, straightening out the facts. This works among friends and it works in an organizational context. Then, we can all move on. Standardization is important. Too important to ignore. Too important to distort. The European economy depends on it. We need CEN/CENELEC. It is an important organization. But CEN/CENELEC needs fora and consortia, too.

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• Coupling/Cohesion

  - by user559142

  Hi All, Whilst there are many good examples on this forum that contain examples of coupling and cohesion, I am struggling to apply it to my code fully. I can identify parts in my code that may need changing. Would any Java experts be able to take a look at my code and explain to me what aspects are good and bad. I don't mind changing it myself at all. It's just that many people seem to disagree with each other and I'm finding it hard to actually understand what principles to follow... package familytree; /** * * @author David */ public class Main { /** * @param args the command line arguments */ public static void main(String[] args) { // TODO code application logic here KeyboardInput in = new KeyboardInput(); FamilyTree familyTree = new FamilyTree(in, System.out); familyTree.start(); } } package familytree; import java.io.PrintStream; /** * * @author David */ public class FamilyTree { /** * @param args the command line arguments */ private static final int DISPLAY_FAMILY_MEMBERS = 1; private static final int ADD_FAMILY_MEMBER = 2; private static final int REMOVE_FAMILY_MEMBER = 3; private static final int EDIT_FAMILY_MEMBER = 4; private static final int SAVE_FAMILY_TREE = 5; private static final int LOAD_FAMILY_TREE = 6; private static final int DISPLAY_ANCESTORS = 7; private static final int DISPLAY_DESCENDANTS = 8; private static final int QUIT = 9; private KeyboardInput in; private Family family; private PrintStream out; public FamilyTree(KeyboardInput in, PrintStream out) { this.in = in; this.out = out; family = new Family(); } public void start() { out.println("\nWelcome to the Family Tree Builder"); //enterUserDetails(); initialise(); while (true) { displayFamilyTreeMenu(); out.print("\nEnter Choice: "); int option = in.readInteger(); if (option > 0 && option <= 8) { if (quit(option)) { break; } executeOption(option); } else { out.println("Invalid Choice!"); } } } //good private void displayFamilyTreeMenu() { out.println("\nFamily Tree Menu"); out.println(DISPLAY_FAMILY_MEMBERS + ". Display Family Members"); out.println(ADD_FAMILY_MEMBER + ". Add Family Member"); out.println(REMOVE_FAMILY_MEMBER + ". Remove Family Member"); out.println(EDIT_FAMILY_MEMBER + ". Edit Family Member"); out.println(SAVE_FAMILY_TREE + ". Save Family Tree"); out.println(LOAD_FAMILY_TREE + ". Load Family Tree"); out.println(DISPLAY_ANCESTORS + ". Display Ancestors"); out.println(DISPLAY_DESCENDANTS + ". Display Descendants"); out.println(QUIT + ". Quit"); } //good private boolean quit(int opt) { return (opt == QUIT) ? true : false; } //good private void executeOption(int choice) { switch (choice) { case DISPLAY_FAMILY_MEMBERS: displayFamilyMembers(); break; case ADD_FAMILY_MEMBER: addFamilyMember(); break; case REMOVE_FAMILY_MEMBER: break; case EDIT_FAMILY_MEMBER: break; case SAVE_FAMILY_TREE: break; case LOAD_FAMILY_TREE: break; case DISPLAY_ANCESTORS: displayAncestors(); break; case DISPLAY_DESCENDANTS: displayDescendants(); break; default: out.println("Not a valid option! Try again."); break; } } //for selecting family member for editing adding nodes etc private void displayFamilyMembers() { out.println("\nDisplay Family Members"); int count = 0; for (FamilyMember member : family.getFamilyMembers()) { out.println(); if (count + 1 < 10) { out.println((count + 1) + ". " + member.getFirstName() + " " + member.getLastName()); out.println(" " + member.getDob()); out.println(" Generation: " + member.getGeneration()); } else { out.println((count + 1) + ". " + member.getFirstName() + " " + member.getLastName()); out.println(" " + member.getDob()); out.println(" Generation: " + member.getGeneration()); } count++; } } private int selectRelative() { out.println("\nSelect Relative"); out.println("1. Add Parents"); out.println("2. Add Child"); out.println("3. Add Partner"); out.println("4. Add Sibling"); out.print("\nEnter Choice: "); int choice = in.readInteger(); if (choice > 0 && choice < 5) { return choice; } return (-1); } private void addFamilyMember() { int memberIndex = selectMember(); if (memberIndex >= 0) { FamilyMember member = family.getFamilyMember(memberIndex); int relative = selectRelative(); if (relative > 0) { out.println("\nAdd Member"); //if choice is valid switch (relative) { case 1: //adding parents if (member.getFather() == null) { FamilyMember mum, dad; out.println("Enter Mothers Details"); mum = addMember(relative, "Female"); out.println("\nEnter Fathers Details"); dad = addMember(relative, "Male"); member.linkParent(mum); member.linkParent(dad); mum.linkPartner(dad); mum.setGeneration(member.getGeneration() - 1); dad.setGeneration(member.getGeneration() - 1); sortGenerations(); } else { out.println(member.getFirstName() + " " + member.getLastName() + " already has parents."); } break; case 2: //adding child if (member.getPartner() == null) { FamilyMember partner; if (member.getGender().equals("Male")) { out.println("Enter Mothers Details"); partner = addMember(1, "Female"); } else { out.println("Enter Fathers Details"); partner = addMember(1, "Male"); } //create partner member.linkPartner(partner); partner.setGeneration(member.getGeneration()); out.println(); } out.println("Enter Childs Details"); FamilyMember child = addMember(relative, ""); child.linkParent(member); child.linkParent(member.getPartner()); child.setGeneration(member.getGeneration() + 1); sortGenerations(); break; case 3: //adding partner if (member.getPartner() == null) { out.println("Enter Partners Details"); FamilyMember partner = addMember(relative, ""); member.linkPartner(partner); partner.setGeneration(member.getGeneration()); } else { out.println(member.getFirstName() + " " + member.getLastName() + " already has a partner."); } break; case 4: //adding sibling FamilyMember mum, dad; if (member.getFather() == null) { out.println("Enter Mothers Details"); mum = addMember(1, "Female"); out.println("\nEnter Fathers Details"); dad = addMember(1, "Male"); member.linkParent(mum); member.linkParent(dad); mum.linkPartner(dad); mum.setGeneration(member.getGeneration() - 1); dad.setGeneration(member.getGeneration() - 1); sortGenerations(); out.println("\nEnter Siblings Details"); } else { out.println("Enter Siblings Details"); } FamilyMember sibling = addMember(relative, ""); //create mum and dad mum = member.getMother(); dad = member.getFather(); sibling.linkParent(mum); sibling.linkParent(dad); sibling.setGeneration(member.getGeneration()); break; } } else { out.println("Invalid Option!"); } } else { out.println("Invalid Option!"); } } private int selectMember() { displayFamilyMembers(); out.print("\nSelect Member: "); int choice = in.readInteger(); if (choice > 0 && choice <= family.getFamilyMembers().size()) { return (choice - 1); } return -1; } private FamilyMember addMember(int option, String gender) { out.print("Enter First Name: "); String fName = formatString(in.readString().trim()); out.print("Enter Last Name: "); String lName = formatString(in.readString().trim()); if (option != 1) { //if not adding parents out.println("Select Gender"); out.println("1. Male"); out.println("2. Female"); out.print("Enter Choice: "); int gOpt = in.readInteger(); if (gOpt == 1) { gender = "Male"; } else if (gOpt == 2) { gender = "Female"; } else { out.println("Invalid Choice"); return null; } } String dob = enterDateOfBirth(); lName = formatString(lName); FamilyMember f = family.getFamilyMember(family.addMember(fName, lName, gender, dob)); f.setIndex(family.getFamilyMembers().size() - 1); return (f); } private String formatString(String s){ String firstLetter = s.substring(0, 1); String remainingLetters = s.substring(1, s.length()); s = firstLetter.toUpperCase() + remainingLetters.toLowerCase(); return s; } private String enterDateOfBirth(){ out.print("Enter Year Of Birth (0 - 2011): "); String y = in.readString(); out.print("Enter Month Of Birth (1-12): "); String m = in.readString(); if (Integer.parseInt(m) < 10) { m = "0" + m; } m += "-"; out.print("Enter Date of Birth (1-31): "); String d = in.readString(); if (Integer.parseInt(d) < 10) { d = "0" + d; } d += "-"; String dob = d + m + y; while(!DateValidator.isValid(dob)){ out.println("Invalid Date. Try Again:"); dob = enterDateOfBirth(); } return (dob); } private void displayAncestors() { out.print("\nDisplay Ancestors For Which Member: "); int choice = selectMember(); if (choice >= 0) { FamilyMember node = family.getFamilyMember(choice ); FamilyMember ms = findRootNode(node, 0, 2, -1); FamilyMember fs = findRootNode(node, 1, 2, -1); out.println("\nPrint Ancestors"); out.println("\nMothers Side"); printDescendants(ms, node, ms.getGeneration()); out.println("\nFathers Side"); printDescendants(fs, node, fs.getGeneration()); } else { out.println("Invalid Option!"); } } private void displayDescendants() { out.print("\nDisplay Descendants For Which Member: "); int choice = selectMember(); if (choice >= 0) { FamilyMember node = family.getFamilyMember(choice); out.println("\nPrint Descendants"); printDescendants(node, null, 0); } else { out.println("Invalid Option!"); } } private FamilyMember findRootNode(FamilyMember node, int parent, int numGenerations, int count) { FamilyMember root; count++; if (node.hasParents() && count < numGenerations) { if (parent == 0) { node = node.getMother(); root = findRootNode(node, 1, numGenerations, count); } else { node = node.getFather(); root = findRootNode(node, 1, numGenerations, count); } return root; } return node; } private int findHighestLeafGeneration(FamilyMember node) { int gen = node.getGeneration(); for (int i = 0; i < node.getChildren().size(); i++) { int highestChild = findHighestLeafGeneration(node.getChild(i)); if (highestChild > gen) { gen = highestChild; } } return gen; } private void printDescendants(FamilyMember root, FamilyMember node, int gen) { out.print((root.getGeneration() + 1) + " " + root.getFullName()); out.print(" [" + root.getDob() + "] "); if (root.getPartner() != null) { out.print("+Partner: " + root.getPartner().getFullName() + " [" + root.getPartner().getDob() + "] "); } if (root == node) { out.print("*"); } out.println(); if (!root.getChildren().isEmpty() && root != node) { for (int i = 0; i < root.getChildren().size(); i++) { for (int j = 0; j < root.getChild(i).getGeneration() - gen; j++) { out.print(" "); } printDescendants(root.getChild(i), node, gen); } } else { return; } } //retrieve highest generation public int getRootGeneration(){ int min = family.getFamilyMember(0).getGeneration(); for(int i = 0; i < family.getFamilyMembers().size(); i++){ min = Math.min(min, family.getFamilyMember(i).getGeneration()); } return Math.abs(min); } public void sortGenerations(){ int amount = getRootGeneration(); for (FamilyMember member : family.getFamilyMembers()) { member.setGeneration(member.getGeneration() + amount); } } //test method - temporary private void initialise() { family.addMember("Bilbo", "Baggins", "Male", "23-06-1920"); } } package familytree; import java.util.ArrayList; import java.util.Date; /** * * @author David */ public class Family { //family members private ArrayList<FamilyMember> family; //create Family public Family() { family = new ArrayList<FamilyMember>(); } //add member to the family public int addMember(String f, String l, String g, String d) { family.add(new FamilyMember(f, l, g, d)); return family.size()-1; } //remove member from family public void removeMember(int index) { family.remove(index); } public FamilyMember getFamilyMember(int index) { return family.get(index); } //return family public ArrayList <FamilyMember> getFamilyMembers() { return family; } public void changeFirstName(int index, String f) { family.get(index).setFirstName(f);//change to setfirstname and others } public void changeLastName(int index, String l) { family.get(index).setLastName(l); } public void changeAge(int index, int a) { family.get(index).setAge(a); } public void changeDOB() { //implement } } package familytree; import java.util.ArrayList; import java.util.Collections; /** * * @author David */ public class FamilyMember extends Person { private FamilyMember mother; private FamilyMember father; private FamilyMember partner; private ArrayList<FamilyMember> children; private int generation; private int index; //initialise family member public FamilyMember(String f, String l, String g, String d) { super(f, l, g, d); mother = null; father = null; partner = null; children = new ArrayList<FamilyMember>(); generation = 0; index = -1; } public void linkParent(FamilyMember parent) { if (parent.getGender().equals("Female")) { this.setMother(parent); } else { this.setFather(parent); } parent.addChild(this); } public void linkPartner(FamilyMember partner) { partner.setPartner(this); this.setPartner(partner); } public boolean hasParents() { if (this.getMother() == null && this.getFather() == null) { return false; } return true; } public FamilyMember getMother() { return mother; } public FamilyMember getFather() { return father; } public FamilyMember getPartner() { return partner; } public FamilyMember getChild(int index) { return children.get(index); } public int getGeneration() { return generation; } public int getIndex() { return index; } public ArrayList<FamilyMember> getChildren() { return children; } public void setMother(FamilyMember f) { mother = f; } public void setFather(FamilyMember f) { father = f; } public void setPartner(FamilyMember f) { partner = f; } public void addChild(FamilyMember f) { children.add(f); //add child if(children.size() > 1){ //sort in ascending order Collections.sort(children, new DateComparator()); } } public void addChildAt(FamilyMember f, int index) { children.set(index, f); } public void setGeneration(int g) { generation = g; } public void setIndex(int i){ index = i; } } package familytree; /** * * @author David */ public class Person{ private String fName; private String lName; private String gender; private int age; private String dob; public Person(String fName, String lName, String gender, String dob){ this.fName = fName; this.lName = lName; this.gender = gender; this.dob = dob; } public String getFullName(){ return (this.fName + " " + this.lName); } public String getFirstName(){ return (fName); } public String getLastName(){ return (lName); } public String getGender(){ return (gender); } public String getDob(){ return dob; } public int getAge(){ return age; } public void setFirstName(String fName){ this.fName = fName; } public void setLastName(String lName){ this.lName = lName; } public void setGender(String gender){ this.gender = gender; } public void setAge(int age){ this.age = age; } }

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• F#: any way to use member functions as unbound functions?

  - by gatoatigrado

  Is there a way to extract member functions, and use them as F# functions? I'd like to be able to write the following: mystring |> string.Split '\n' |> Array.filter (string.Length >> (=) 0 >> not) The code above works if you [let] let mystring = "a c\nb\n" let stringSplit (y:char) (x:string) = x.Split(y) let stringLength (x:string) = x.Length mystring |> stringSplit '\n' |> Array.filter (stringLength >> (=) 0 >> not)

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• X11: How do I REALLY grab the mouse pointer?

  - by Drew Hall

  I've implemented a horizontal splitter widget in Xlib. I'm trying to grab the mouse when the user clicks & drags on the splitter bar (so that the user can dynamically move the split & thus resize the windows on either side of the splitter bar). I've used XGrabPointer() after receiving a left click, in hopes that all future mouse motion (dragging) will be diverted to the splitter window until the left button is released. Unfortuntately, it doesn't seem to work like that. If the user drags too quickly and the mouse pointer enters one of the windows on either side of the split, the MotionEvent messages are diverted to that (child) window rather than the splitter window. What have I done wrong? My XGrabPointer() call is as follows: ::XGrabPointer(mDisplay, window, True, ButtonPressMask | ButtonReleaseMask | PointerMotionMask | FocusChangeMask | EnterWindowMask | LeaveWindowMask, GrabModeAsync, GrabModeAsync, RootWindow(mDisplay, DefaultScreen(mDisplay)), None, CurrentTime);

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• Is there performance to be gained by moving storage allocation local to a member function to its cla

  - by neuviemeporte

  Suppose I have the following C++ class: class Foo { double bar(double sth); }; double Foo::bar(double sth) { double a,b,c,d,e,f a = b = c = d = e = f = 0; /* do stuff with a..f and sth */ } The function bar() will be called millions of times in a loop. Obviously, each time it's called, the variables a..f have to be allocated. Will I gain any performance by making the variables a..f members of the Foo class and just initializing them at the function's point of entry? On the other hand, the values of a..f will be dereferenced through this-, so I'm wondering if it isn't actually a possible performance degradation. Is there any overhead to accessing a value through a pointer? Thanks!

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• How to get a float value the pointer points to?

  - by aleluja

  Hello, In my app, i've created the TList type list where i store the pointers to 1 string and 2 float(real) values for every 3 items. aList.Add(@sName); //string aList.Add(@x1); //float aList.Add(@x2); //float Then, i want to get the values out from the list, but i could only do that for string sStr := string(lList.items[i]); But i couldn't get the float values as a := real(lList...) will result in an invalid typecast error. So what do i do to get the float values? Of course i have a question if that string casting will actually give me the string value. I'm not good at pointer stuff so i don't know how to do it.

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• "ID 046d:c50e Logitech, Inc. Cordless Mouse Receiver" wheel-click is wrong

  - by sputnick

  I use this mouse under archlinux x86_64 with 3.2.8-1-ARCH kernel. I have some problems to select and then paste with the wheel-click in some applications like konversation, not in a terminal nor an editor. I don't know if it's a hardware problem or a software one. $ lsusb -v Bus 002 Device 110: ID 046d:c50e Logitech, Inc. Cordless Mouse Receiver Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x046d Logitech, Inc. idProduct 0xc50e Cordless Mouse Receiver bcdDevice 25.10 iManufacturer 1 Logitech iProduct 2 USB RECEIVER iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 34 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0xa0 (Bus Powered) Remote Wakeup MaxPower 70mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 3 Human Interface Device bInterfaceSubClass 1 Boot Interface Subclass bInterfaceProtocol 2 Mouse iInterface 0 HID Device Descriptor: bLength 9 bDescriptorType 33 bcdHID 1.11 bCountryCode 0 Not supported bNumDescriptors 1 bDescriptorType 34 Report wDescriptorLength 95 Report Descriptors: ** UNAVAILABLE ** Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 10 Device Status: 0x0000 (Bus Powered) When I see what's happens in xev, the output is different compared to another mouse My buggy Logitech mouse : ButtonPress event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170350700, (48,52), root:(1491,75), state 0x10, button 11, same_screen YES EnterNotify event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x0, time 170350700, (48,52), root:(1491,75), mode NotifyGrab, detail NotifyInferior, same_screen YES, focus YES, state 16 KeymapNotify event, serial 40, synthetic NO, window 0x0, keys: 90 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ButtonPress event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170350716, (48,52), root:(1491,75), state 0x10, button 6, same_screen YES ButtonRelease event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170350716, (48,52), root:(1491,75), state 0x10, button 6, same_screen YES ButtonRelease event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170350988, (48,52), root:(1491,75), state 0x10, button 11, same_screen YES LeaveNotify event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x0, time 170350988, (48,52), root:(1491,75), mode NotifyUngrab, detail NotifyInferior, same_screen YES, focus YES, state 16 a working mouse (dell) : ButtonPress event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170245131, (46,32), root:(1489,55), state 0x10, button 2, same_screen YES EnterNotify event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x0, time 170245131, (46,32), root:(1489,55), mode NotifyGrab, detail NotifyInferior, same_screen YES, focus YES, state 528 KeymapNotify event, serial 40, synthetic NO, window 0x0, keys: 90 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ButtonRelease event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x4400002, time 170245411, (46,32), root:(1489,55), state 0x210, button 2, same_screen YES LeaveNotify event, serial 40, synthetic NO, window 0x4400001, root 0x15a, subw 0x0, time 170245411, (46,32), root:(1489,55), mode NotifyUngrab, detail NotifyInferior, same_screen YES, focus YES, state 16 A demo of the problem when I use konversation (IRC) : http://www.youtube.com/watch?v=lhmr92M7NCc I tried to modify the button map with xmodmap like this with no success (one at a time) : xmodmap -e "pointer = 1 0 3" xmodmap -e "pointer = 1 1 3" xmodmap -e "pointer = 1 2 3" xmodmap -e "pointer = 1 3 3" xmodmap -e "pointer = 1 4 3" xmodmap -e "pointer = 1 5 3" xmodmap -e "pointer = 1 6 3" xmodmap -e "pointer = 1 7 3" xmodmap -e "pointer = 1 8 3" xmodmap -e "pointer = 1 9 3" xmodmap -e "pointer = 1 10 3" xmodmap -e "pointer = 1 11 3" xmodmap -e "pointer = 1 12 3" xmodmap -e "pointer = 1 13 3" xmodmap -e "pointer = 1 14 3" xmodmap -e "pointer = 1 15 3" xmodmap -e "pointer = 1 16 3" xmodmap -e "pointer = 1 17 3" xmodmap -e "pointer = 1 18 3" xmodmap -e "pointer = 1 19 3" xmodmap -e "pointer = 1 20 3" xmodmap -e "pointer = 1 21 3" xmodmap -e "pointer = 1 22 3" xmodmap -e "pointer = 1 23 3" xmodmap -e "pointer = 1 24 3" xmodmap -e "pointer = 1 25 3" Any clue ? I would like to avoid buying a new mouse just for a paste problem.

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• Why does perl crash with "*** glibc detected *** perl: munmap_chunk(): invalid pointer"?

  - by sid_com

  #!/usr/bin/env perl use warnings; use strict; use 5.012; use XML::LibXML::Reader; my $reader = XML::LibXML::Reader->new( location => 'http://www.heise.de/' ) or die $!; while ( $reader->read ) { say $reader->name; } At the end of the output from this script I get this error-messages: * glibc detected * perl: munmap_chunk(): invalid pointer: 0x0000000000b362e0 * ======= Backtrace: ========= /lib64/libc.so.6[0x7fb84952fc76] ... ======= Memory map: ======== 00400000-0053d000 r-xp 00000000 08:01 182002 /usr/local/bin/perl ... Is this due a bug? perl -V: Summary of my perl5 (revision 5 version 12 subversion 0) configuration: Platform: osname=linux, osvers=2.6.31.12-0.2-desktop, archname=x86_64-linux uname='linux linux1 2.6.31.12-0.2-desktop #1 smp preempt 2010-03-16 21:25:39 +0100 x86_64 x86_64 x86_64 gnulinux ' config_args='-Dnoextensions=ODBM_File' hint=recommended, useposix=true, d_sigaction=define useithreads=undef, usemultiplicity=undef useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef use64bitint=define, use64bitall=define, uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64', optimize='-O2', cppflags='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion='', gccversion='4.4.1 [gcc-4_4-branch revision 150839]', gccosandvers='' intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16 ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8 alignbytes=8, prototype=define Linker and Libraries: ld='cc', ldflags =' -fstack-protector -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/lib64 libs=-lnsl -ldl -lm -lcrypt -lutil -lc perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc libc=/lib/libc-2.10.1.so, so=so, useshrplib=false, libperl=libperl.a gnulibc_version='2.10.1' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E' cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector' Characteristics of this binary (from libperl): Compile-time options: PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP USE_64_BIT_ALL USE_64_BIT_INT USE_LARGE_FILES USE_PERLIO USE_PERL_ATOF Built under linux Compiled at Apr 15 2010 13:25:46 @INC: /usr/local/lib/perl5/site_perl/5.12.0/x86_64-linux /usr/local/lib/perl5/site_perl/5.12.0 /usr/local/lib/perl5/5.12.0/x86_64-linux /usr/local/lib/perl5/5.12.0 .

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• Is there a practical benefit to casting a NULL pointer to an object and calling one of its member fu

  - by zdawg

  Ok, so I know that technically this is undefined behavior, but nonetheless, I've seen this more than once in production code. And please correct me if I'm wrong, but I've also heard that some people use this "feature" as a somewhat legitimate substitute of a lacking aspect of the current C++ standard, namely, the inability to obtain the address (well, offset really) of a member function. For example, this is out of a popular implementation of a PCRE (Perl-compatible Regular Expression) library: #ifndef offsetof #define offsetof(p_type,field) ((size_t)&(((p_type *)0)->field)) #endif One can debate whether the exploitation of such a language subtlety in a case like this is valid or not, or even necessary, but I've also seen it used like this: struct Result { void stat() { if(this) // do something... else // do something else... } }; // ...somewhere else in the code... ((Result*)0)->stat(); This works just fine! It avoids a null pointer dereference by testing for the existence of this, and it does not try to access class members in the else block. So long as these guards are in place, it's legitimate code, right? So the question remains: Is there a practical use case, where one would benefit from using such a construct? I'm especially concerned about the second case, since the first case is more of a workaround for a language limitation. Or is it? PS. Sorry about the C-style casts, unfortunately people still prefer to type less if they can.

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