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• Is it possible to apply inheritance to a Singleton class?

  - by Bragaadeesh

  Hi, Today I faced one question in interview. Is it possible to apply inheritance concept on Singleton Classes. I said since the constructor is private, we cannot extend that Singleton class (can someone please validate this). Next thing he asked me is to apply inheritance on that Singleton class. So, I made the Singleton's constructor as protected thinking that child's constructor also has be protected. But I was wrong the child can have a modifier either equal to or higher than that. So, I asked him to give a real world example on such a case. He was not able to give me one and said that I cant ask questions and wanted me to tell whether this scenario is possible or not. I went kind of blank. My question here is, Is this possible? Even if its possible, what is the use of it? What real world scenario would demand such a use. Thanks

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• Select all rows where there is not a specific value in a different table

  - by JMC Creative

  This is a wordpress installation, but I think the question is more of a general sql question. First off, my sql skills are not great (I don't even know if I'm following the correct format for illustrating the db). I've got two tables: wp_posts : ID (pk) | post_name | ... ---------------------------- 45 | "Hello" 91 | "Funny" 16 | "Wheat" wp_postmeta : post_id (fk) | meta_key | meta_value | ... ------------------------------------------------ 45 | "_edit_lock" | 5789789834 45 | "fizzbizz" | "foobar" 91 | "_something" | "teve" 16 | "_edit_lock" | 8798756 I would to select all rows in wp_posts where there is NO corresponding row in wp_postmeta where meta_key = "fizzbizz" I originally had this query, but someone pointed out that it would not retrive ID = '16' in the above case. How would I correctly write the query? $pageposts = $wpdb->get_results(" SELECT * FROM wp_posts p JOIN wp_postmeta m ON p.ID = m.post_id WHERE m.meta_key <> 'fizzbizz' ORDER BY p.post_date DESC; ");

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• Retain Delimiters when Splitting String

  - by JoeC

  Edit: OK, I can't read, thanks to Col. Shrapnel for the help. If anyone comes here looking for the same thing to be answered... print_r(preg_split('/([\!|\?|\.|\!\?])/', $string, null, PREG_SPLIT_DELIM_CAPTURE)); Is there any way to split a string on a set of delimiters, and retain the position and character(s) of the delimiter after the split? For example, using delimiters of ! ? . !? turning this: $string = 'Hello. A question? How strange! Maybe even surreal!? Who knows.'; into this array('Hello', '.', 'A question', '?', 'How strange', '!', 'Maybe even surreal', '!?', 'Who knows', '.'); Currently I'm trying to use print_r(preg_split('/([\!|\?|\.|\!\?])/', $string)); to capture the delimiters as a subpattern, but I'm not having much luck.

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• Where does one enter the JavaScript code in CRM Dynamics?

  - by Konrad Viltersten

  I've started to play with CRM Dynamics yesterday so this question should be seen as a very basic one. I've been coding for many years but CRM D is news to me. Apparently, one is supposed to be able to enter JavaScript code to customize the behavior of the application. I've understood that there's an API for that and that touching DOM directly or playing with jQuery is a no-no. Question: Where is the JS-code supposed to be entered? I've gone through all the menus but as far I can see, there's no spot where I could plug-in my custom code. E.g.: Where do I get to define a validation for the last name of a contact currently being defined?

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• Best way to search for a saturation value in a sorted list

  - by AB Kolan

  A question from Math Battle. This particular question was also asked to me in one of my job interviews. " A monkey has two coconuts. It is fooling around by throwing coconut down from the balconies of M-storey building. The monkey wants to know the lowest floor when coconut is broken. What is the minimal number of attempts needed to establish that fact? " Conditions: if a coconut is broken, you cannot reuse the same. You are left with only with the other coconut Possible approaches/strategies I can think of are Binary break ups & once you find the floor on which the coconut breaks use upcounting from the last found Binary break up lower index. Window/Slices of smaller sets of floors & use binary break up within the Window/Slice (but on the down side this would require a Slicing algorithm of it's own.) Wondering if there are any other way to do this.

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• RFC Repository of programming RFC's with ability to direct-link sections or even lines?

  - by Lasse V. Karlsen

  Forgive me if this is the wrong place to ask this, I feel like the question is slightly off-topic even though it is also about programming. I am inputting todo-tasks for my WebDAV-project into my issue tracker, as I read through the relevant RFC's, and it would be nice to be able to add a link in my issue text directly to the relevant text, instead of just a link to the RFC file with a section number in the issue text, and then I have to use the find function to find it. For instance, a link like this: http://ieft.org/rfc2518.txt#1000 <-- line 1000 http://ieft.org/rfc2518.txt#9.8.3 <-- section 9.8.3 Neither of these two works, since they just post the full text files, so my question is this: Does anyone know of hosted versions of the RFC documents that contains such links?

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• Are there any platforms where using structure copy on an fd_set (for select() or pselect()) causes p

  - by Jonathan Leffler

  The select() and pselect() system calls modify their arguments (the 'struct fd_set *' arguments), so the input value tells the system which file descriptors to check and the return values tell the programmer which file descriptors are currently usable. If you are going to call them repeatedly for the same set of file descriptors, you need to ensure that you have a fresh copy of the descriptors for each call. The obvious way to do that is to use a structure copy: struct fd_set ref_set_rd; struct fd_set ref_set_wr; struct fd_set ref_set_er; ... ...code to set the reference fd_set_xx values... ... while (!done) { struct fd_set act_set_rd = ref_set_rd; struct fd_set act_set_wr = ref_set_wr; struct fd_set act_set_er = ref_set_er; int bits_set = select(max_fd, &act_set_rd, &act_set_wr, &act_set_er, &timeout); if (bits_set > 0) { ...process the output values of act_set_xx... } } My question: Are there any platforms where it is not safe to do a structure copy of the struct fd_set values as shown? I'm concerned lest there be hidden memory allocation or anything unexpected like that. (There are macros/functions FD_SET(), FD_CLR(), FD_ZERO() and FD_ISSET() to mask the internals from the application.) I can see that MacOS X (Darwin) is safe; other BSD-based systems are likely to be safe, therefore. You can help by documenting other systems that you know are safe in your answers. (I do have minor concerns about how well the struct fd_set would work with more than 8192 open file descriptors - the default maximum number of open files is only 256, but the maximum number is 'unlimited'. Also, since the structures are 1 KB, the copying code is not dreadfully efficient, but then running through a list of file descriptors to recreate the input mask on each cycle is not necessarily efficient either. Maybe you can't do select() when you have that many file descriptors open, though that is when you are most likely to need the functionality.) There's a related SO question - asking about 'poll() vs select()' which addresses a different set of issues from this question.

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• Aren't passwords written in inputbox vulnerable through a stack trace ?

  - by loursonwinny

  Hello, I am not a guru of the stack tracing, at all. I even don't know how to get some. Anyway, I am wondering if entering a password entered in an inputbox is safe. Can't it be retrieved by getting a stack trace ? A password entered that way will be found in many places : Caption property of the TEdit Result of the function which creates the inputbox probably, a variable that stores the Result of the InputBox Command etc... If the answer is "yes, it is a vulnerability", then my world collapses :p. What can be done to avoid that vulnerability hole ? NOTE : The InputBox is an example but it can be with a "homebrewed" login prompt. InputBox is a Delphi command but I haven't tagged the question with the Delphi tag because I suppose that the question concerns any language. Thanks for reading

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• MS Access 07 - Q re lookup column vs many-to-many; Q re checkboxes in many-to-many forms

  - by TBinLondon

  Hello, I'm creating a database with Access. This is just a test database, similar to my requirements, so I can get my skills up before creating one for work. I've created a database for a fictional school as this is a good playground and rich data (many students have many subjects have many teachers, etc). Question 1 What is the difference, if any, between using a Lookup column and a many-to-many associate table? Example: I have Tables 'Teacher' and 'Subject'. Many teachers have many subjects. I can, and have, created a table 'Teacher_Subject' and run queries with this. I have then created a lookup column in teachers table with data from subjects. The lookup column seems to take the place of the teacher_subject table. (though the data on relationships is obviously duplicated between lookup table and teacher_subject and may vary). Which one is the 'better' option? Is there a snag with using lookup tables? (I realize that this is a very 'general' question. Links to other resources and answers saying 'that depends...' are appreciated) Question 2 What attracts me to lookup tables is the following: When creating a form for entering subjects for teachers, with lookup I can simply create checkboxes and click a subject for a teacher 'on' or 'off'. Each click on/off creates/removes a record in the lookup column (which replaces teacher_subject). If I use a form from a query from teacher subject with teacher as main form and subject as subform I run into this problem: In the subform I can either select each subject that teacher has in a bombo box, i.e. click, scroll down, select, go to next row, click, scroll down, etc. (takes too long) OR I can create a list box listing all available subjects in each row but allowing me to select only one. (takes up too much space). Is it possible to have a click on/off list box for teacher_subject, creating/removing a record there with each click? Note - I know zero SQL or VB. If the correct answer is "you need to know SQL for this" then that's cool. I just need to know. Thanks!

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• Why does std::map operator[] create an object if the key doesn't exist?

  - by n1ck

  Hi, I'm pretty sure I already saw this question somewhere (comp.lang.c++? Google doesn't seem to find it there either) but a quick search here doesn't seem to find it so here it is: Why does the std::map operator[] create an object if the key doesn't exist? I don't know but for me this seems counter-intuitive if you compare to most other operator[] (like std::vector) where if you use it you must be sure that the index exists. I'm wondering what's the rationale for implementing this behavior in std::map. Like I said wouldn't it be more intuitive to act more like an index in a vector and crash (well undefined behavior I guess) when accessed with an invalid key? Refining my question after seeing the answers: Ok so far I got a lot of answers saying basically it's cheap so why not or things similar. I totally agree with that but why not use a dedicated function for that (I think one of the comment said that in java there is no operator[] and the function is called put)? My point is why doesn't map operator[] work like a vector? If I use operator[] on an out of range index on a vector I wouldn't like it to insert an element even if it was cheap because that probably mean an error in my code. My point is why isn't it the same thing with map. I mean, for me, using operator[] on a map would mean: i know this key already exist (for whatever reason, i just inserted it, I have redundancy somewhere, whatever). I think it would be more intuitive that way. That said what are the advantage of doing the current behavior with operator[] (and only for that, I agree that a function with the current behavior should be there, just not operator[])? Maybe it give clearer code that way? I don't know. Another answer was that it already existed that way so why not keep it but then, probably when they (the ones before stl) choose to implement it that way they found it provided an advantage or something? So my question is basically: why choose to implement it that way, meaning a somewhat lack of consistency with other operator[]. What benefit do it give? Thanks

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• Rewriting .each() loop as for loop to optimize, how to replicate $(this).attr()

  - by John B

  I running into some performance issues with a jquery script i wrote when running in ie so I'm going through it trying to optimize any way possible. Apparently using for loops is way faster than using the jQuery .each method. This has led me to a question regarding the equivalent of $(this) inside a for loop. I'm simplifying what I'm doing in my loop down to just using an attr() function as it gets across my main underlying question. Im doing this with each(simplified) var existing = $('#existing'); existing.each(function(){ console.log($(this).attr('id')); }); And I've tried rewriting it as a for loop as such: var existing = $('#existing'); for(var i = 0;i < existing.length;i++) { console.log(existing[i].attr('id')); } Its throwing an error saying: Uncaught TypeError: Object #<HTMLDivElement> has no method 'attr' Thanks.

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• How to use sound and images in a Java applet?

  - by Click Upvote

  Question 1: How should I structure my project so the sound and images files can be loaded most easily? Right now, I have the folder: C:\java\pacman with the sub-directory C:\java\pacman\src containing all the code, and C:\java\pacman\assets containing the images and .wav files. Is this the best structure or should I put the assets somewhere else? Question 2: What's the best way to refer to the images/sounds without using the full path e.g C:\java\pacman\assets\something.png to them? If I use the getCodeBase() function it seems to refer to the C:\java\pacman\bin instead of C:\java\pacman\. I want to use such a function/class which would work automatically when i compile the applet in a jar as well as right now when I test the applet through eclipse. Question 3: How should I load the images/sounds? This is what I'm using now: 1) For general images: import java.awt.Image; public Image getImg(String file) { //imgDir in this case is a hardcoded string containing //"C:\\java\\pacman\\assets\\" file=imgDir + file; return new ImageIcon(file).getImage(); } The images returned from this function are used in the drawImage method of the Graphics class in the paint method of the applet. 2) For a buffered image, which is used to get subImages and load sprites from a sprite sheet: public BufferedImage getSheet() throws IOException { return ImageIO.read(new File(img.getPath("pacman-sprites.png"))); } Later: public void loadSprites() { BufferedImage sheet; try { sheet=getSheet(); redGhost.setNormalImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setUpImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setDownImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setLeftImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setRightImg(sheet.getSubimage(60, 60, 20, 20)); } catch (IOException e) { System.out.println("Couldnt open file!"); System.out.println(e.getLocalizedMessage()); } } 3) For sound files: import sun.audio.*; import java.io.*; public synchronized void play() { try { InputStream in = new FileInputStream(filename); AudioStream as = new AudioStream(in); AudioPlayer.player.start(as); } catch (IOException e) { e.printStackTrace(); } }

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• What are the exact versions of stuff you have to install in order to be able to step-debug a Scala p

  - by Alex R

  How do YOU debug a Scala program? I mean YOU as in the person posting the Answer :) Please answer only from personal experience, not from stuff you've heard or read on the Internet. You should not believe everything you read on the Internet, especially tales of complex open-source software configurations that actually work :-) The are many Java tools which claim to support Scala in some way or another, but I have so far struck out in trying to get any one of them to actually let me set a breakpoint in Scala code and step through it. These are big, major open-source IDEs I'm talking about here. The main problem in getting a debugger to work seems to be the "version hell" with fast-changing IDEs, Plug-Ins, JDKs, and the Scala language itself. Hence, the more detailed re-statement of the question is appropriate: What is the exact version number of the IDE, Plug-In, JDK, Scala, and even Operating System, that you are successfully using? My question is related to this one, but wider in scope: http://stackoverflow.com/questions/2272705/how-to-debug-scala-code-when-outside-of-an-ide Thanks

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• Trouble understanding Java map Entry sets

  - by Jake Sellers

  I'm looking at a java hangman game here: https://github.com/leleah/EvilHangman/blob/master/EvilHangman.java The code in particular is this: Iterator<Entry<List<Integer>, Set<String>>> k = partitions.entrySet().iterator(); while (k.hasNext()) { Entry<?, ?> pair = (Entry<?, ?>)k.next(); int sizeOfSet = ((Set<String>)pair.getValue()).size(); if (sizeOfSet > biggestPartitionSize) { biggestPartitionSize = sizeOfSet; } } Now my question. My google foo is weak I guess, I cannot find much on Entry sets other than the java doc itself. Is is just a temporary copy of the map? And I cannot find any info at all on the syntax: Entry<?, ?> Can anyone explain or point me toward an explanation of what is going on with those question marks? Thanks in advanced.

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• When to use <strong> and when to use <b>?

  - by metal-gear-solid

  When to use <strong> and when to use <b> or other ways to give look of bold? strong has semantic value ( and useful for screen reader while b is presentation (and even valid in HTML 5). my question is not what is the difference between strong and b. The question is when to use semantic tag and when to use just to make text bold Should I always use <strong> if client's content files (MS word files) has some words bold in content paragraphs? How can we know when client want to give emphasis to text and when he just want to make text bold for presentation/aesthetic purpose? If it's client job to tell us, then how to explain this scenario to client to give us clear info on "when he just want to make text bold for presentation/aesthetic purpose" ?

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• How do I output an individual character when using char *[] = "something"

  - by Matt

  I've been playing with pointers to better understand them and I came across something I think I should be able to do, but can't sort out how. The code below works fine - I can output "a", "dog", "socks", and "pants" - but what if I wanted to just output the 'o' from "socks"? How would I do that? char *mars[4] = { "a", "dog", "sock", "pants" }; for ( int counter = 0; counter < 4; counter++ ) { cout << mars[ counter ]; } Please forgive me if the question is answered somewhere - there are 30+ pages of C++ pointer related question, and I spent about 90 minutes looking through them, as well as reading various (very informative) articles, before deciding to ask.

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• What are the z-coordinates in Cocoa mouse events for?

  - by gf

  Interestingly i didn't find the answer for this seemingly trivial question - Cocoas mouse events have z-coordinates - what are they for?

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• Why is writing a compiler in a functional language so efficient and easier?

  - by wvd

  Hello all, I've been thinking of this question very long, but really couldn't find the answer on Google as well a similar question on Stackoverflow. If there is a duplicate, I'm sorry for that. A lot of people seem to say that writing compilers and other language tools in functional languages such as OCaml and Haskell is much more efficient and easier then writing them in imperative languages. Is this true? And if so -- why is so efficient and easy to write them in functional languages instead of in an imperative language, like C? Also -- isn't a language tool in a functional language slower then in some low-level language like C? Thanks in advance, William v. Doorn

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• Problem executing with Python+MySQL

  - by Satya

  Hi, I am not getting the reason why my python script is not working though I hv put all the things correctly as my knowledge.The below test I did and it worked fine.But when I import the MySQLdb in my script it gives error as no module name MySQLdb. **C:\Python26python Python 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. import MySQLdb ** Kindly let me know the reason for this error. And all the development is going on in windows XP, python 2.6, mysql 4.0.3 Earlier 1 hour back I have posted the question but some mistake was there in the question itself..

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• How to refer to object in JavaScript event handler?

  - by George Edison

  Note: This question uses jQuery but the question has nothing to do with jQuery! Okay so I have this object: var box = new BigBox(); This object has a method named Serialize(): box.AddToPage(); Here is the method AddToPage(): function AddToPage() { $('#some_item').html("<div id='box' onclick='this.OnClick()'></div>"); } The problem above is the this.OnClick() (which obviously does not work). I need the onclick handler to invoke a member of the BigBox class. How can I do this? How can an object refer to itself in an event handler?

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• Better way of coding this if statment?

  - by HadlowJ

  Hi. I have another question for you very helpful people. I use a lot of if statements many of which are just repeated and im sure could be shortened. This is my current bit of code if (Globals.TotalStands <= 1) { ScoreUpdate.StandNo2.Visible = false; ScoreUpdate.ScoreStand2.Visible = false; ScoreUpdate.ScoreOutOf2.Visible = false; } if (Globals.TotalStands <= 2) { ScoreUpdate.StandNo3.Visible = false; ScoreUpdate.ScoreStand3.Visible = false; ScoreUpdate.ScoreOutOf3.Visible = false; } if (Globals.TotalStands <= 3) { ScoreUpdate.StandNo4.Visible = false; ScoreUpdate.ScoreStand4.Visible = false; ScoreUpdate.ScoreOutOf4.Visible = false; } if (Globals.TotalStands <= 4) { ScoreUpdate.StandNo5.Visible = false; ScoreUpdate.ScoreStand5.Visible = false; ScoreUpdate.ScoreOutOf5.Visible = false; } if (Globals.TotalStands <= 5) { ScoreUpdate.StandNo6.Visible = false; ScoreUpdate.ScoreStand6.Visible = false; ScoreUpdate.ScoreOutOf6.Visible = false; } if (Globals.TotalStands <= 6) { ScoreUpdate.StandNo7.Visible = false; ScoreUpdate.ScoreStand7.Visible = false; ScoreUpdate.ScoreOutOf7.Visible = false; } if (Globals.TotalStands <= 7) { ScoreUpdate.StandNo8.Visible = false; ScoreUpdate.ScoreStand8.Visible = false; ScoreUpdate.ScoreOutOf8.Visible = false; } as you can see there is a huge amount of code to do something simple (which i do on a few other forms as well and im sure there must be a better way of coding this that gets the same result? Im a code noob so please be gentle, code is c# and software is visual studio 2008 pro. Thanks

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• How to trigger code on two different servers in a WAS cluster?

  - by Dean J

  I have an administrative page in a web application that resets the cache, but it only resets the cache on the current JVM. The web application is deployed as a cluster to two WAS servers. Any way that I can elegantly have the "clear cache" button on each server trigger the method on both JVMs? Edit: The original developer just wrote a singleton holding a HashMap to be the cache in question. Lightweight and (previously) worked just fine for the requirements. It caches content pulled from six or seven web services for specified amounts of time. Edit: The entire application in question is three pages, so the elegant solution might well be the lightest solution.

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• Is MySQL Replication Appropriate in this case?

  - by MJB

  I have a series of databases, each of which is basically standalone. It initially seemed like I needed a replication solution, but the more I researched it, the more it felt like replication was overkill and not useful anyway. I have not done MySQL replication before, so I have been reading up on the online docs, googling, and searching SO for relevant questions, but I can't find a scenario quite like mine. Here is a brief description of my issue: The various databases almost never have a live connection to each other. They need to be able to "sync" by copying files to a thumb drive and then moving them to the proper destination. It is OK for the data to not match exactly, but they should have the same parent-child relationships. That is, if a generated key differs between databases, no big deal. But the visible data must match. Timing is not critical. Updates can be done a week later, or even a month later, as long as they are done eventually. Updates cannot be guaranteed to be in the proper order, or in any order for that matter. They will be in order from each database; just not between databases. Rather than a set of master-slave relationships, it is more like a central database (R/W) and multiple remote databases (also R/W). I won't know how many remote databases I have until they are created. And the central DB won't know that a database exists until data arrives from it. (To me, this implies I cannot use the method of giving each its own unique identity range to guarantee uniqueness in the central database.) It appears to me that the bottom line is that I don't want "replication" so much as I want "awareness". I want the central database to know what happened in the remote databases, but there is no time requirement. I want the remote databases to be aware of the central database, but they don't need to know about each other. WTH is my question? It is this: Does this scenario sound like any of the typical replication scenarios, or does it sound like I have to roll my own? Perhaps #7 above is the only one that matters, and given that requirement, out-of-the-box replication is impossible. EDIT: I realize that this question might be more suited to ServerFault. I also searched there and found no answers to my questions. And based on the replication questions I did find both on SO and SF, it seemed that the decision was 50-50 over where to put my question. Sorry if I guessed wrong.

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• Filtering out unique rows in MySQL

  - by jpatokal

  So I've got a large amount of SQL data that looks basically like this: user | src | dst 1 | 1 | 1 1 | 1 | 1 1 | 1 | 2 1 | 1 | 2 2 | 1 | 1 2 | 1 | 3 I want to filter out pairs of (src,dst) that are unique to one user (even if that user has duplicates), leaving behind only those pairs belonging to more than one user: user | src | dst 1 | 1 | 1 1 | 1 | 1 2 | 1 | 1 In other words, pair (1,2) is unique to user 1 and pair (1,3) to user 2, so they're dropped, leaving behind only all instances of pair (1,1). Any ideas? The answers to the question below can find the non-unique pairs, but my SQL-fu doesn't suffice to handle the complication of requiring that they belong to multiple users as well. [SQL question] How to select non "unique" rows

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• Codesample with bufferoverflow (gets method). Why does it not behave as expected?

  - by citronas

  This an extract from an c program that should demonstrate a bufferoverflow. void foo() { char arr[8]; printf(" enter bla bla bla"); gets(arr); printf(" you entered %s\n", arr); } The question was "How many input chars can a user maximal enter without a creating a buffer overflow" My initial answer was 8, because the char-array is 8 bytes long. Although I was pretty certain my answer was correct, I tried a higher amount of chars, and found that the limit of chars that I can enter, before I get a segmentation fault is 11. (Im running this on A VirtualBox Ubuntu) So my question is: Why is it possible to enter 11 chars into that 8 byte array?

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