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• When designing an event, is it a good idea to prevent listeners from being added twice?

  - by Matt

  I am creating an event-based API where a user can subscribe to an event by adding listener objects (as is common in Java or C#). When the event is raised, all subscribed listeners are invoked with the event information. I initially decided to prevent adding an event listener more than once. If a listener is added that already exists in the listener collection, it is not added again. However, after thinking about it some more, it doesn't seem that most event-based structures actually prevent this. Was my initial instinct wrong? I'm not sure which way to go here. I guess I thought that preventing addition of an existing listener would help to avoid a common programming error. Then again, it could also hide a bug that would lead to code being run multiple times when it shouldn't.

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• working with files on "start without debugging"

  - by user1472066

  I'm programming in C, and I have the following problem: I use fopen and try to read from a csv file, that is currently storred in the folder of the exe file of the program. the program works fine in debug mode and release mode, but when I try to run the program in "start without debugging" on visual studio 2008 express edition, the program stops working and windows is showing a message: "*.exe has stopped working. a program caused the program to stop working correctly. windows will close the program and notify you if a solution is available". I've tried running the program on several computers, and it's the same. another information I can give you is that if I enter the full path of the file (C:....file.csv) - then is works just fine, without any problem. I know I didn't write any code, but I hope someone will have an idea why this can happend. thanks is advance.

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• Are `return` and `break` useless inside a Ruby block when used as a callback?

  - by Skilldrick

  In Rails, blocks can be used as callbacks, e.g.: class User < ActiveRecord::Base validates_presence_of :login, :email before_create {|user| user.name = user.login.capitalize if user.name.blank?} end When a block is used like this, is there any use for break and return? I'm asking because normally in a block, break will break out of the loop, and return will return from the enclosing method. But in a callback context, I can't get my head round what that means. The Ruby Programming Language suggests that return could cause a LocalJumpError but I haven't been able to reproduce this in a Rails callback. Edit: with the following code I'd expect a LocalJumpError, but all the return does is stop the rest of the callback executing. class User < ActiveRecord::Base validates_presence_of :login, :email before_create do |user| return user.name = user.login.capitalize end

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• Looping in filemaker using a local variable

  - by Mike Davis

  Been programming in C# for a little bit - trying to use file maker and I cant believe it but I cant even get a simple for loop to work. What I want to do is simple: loop through for the amount of entries in my "amountOfRooms" field and create an entry in a table for each room. Sounds so simple, but I cant get it to work. Right now I have this: Set Variable[$cnt[Customers::AmountOfRooms]; value:1] Go to Layout["rooms"(Rooms)] Loop Exit Loop If[$cnt = Customers::AmountOfRooms] New Record / Request Set Variable[$cnt; Value: $cnt + 1] End Loop Exit Script No new records are created. I know the script is running because it does go to my layout, but doesnt create any new records. There is a "Repetition" field for my local variable - not sure how to use that or what it means? Any thoughts on how to do this simple loop? Thanks.

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• How to handle huge table ?

  - by misha-moroshko

  I would like to display to user a table which contains ~500,000 rows. The table should be calculated based on a file (i.e. the table is known at the beginning, and does not change). I guess that building the HTML text of this table is not a good idea in terms of memory performance. So how can I build such table ? I would like user to be able to scroll the table using a vertical scroll bar. Is it possible to build on the fly only the visible part of the table ? I'm afraid to see delays because of this. Is it a better idea to use server side programming rather than Javascript ? Any advise would be appreciated.

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• Could someone tell me if my C++ indent style is named? (example given)

  - by Maulrus

  I'm learning C++. For me, my programming style is just what looks the best; it doesn't seem to follow the rules of any one particular style. Here's an example void f(int x){ //no space between close-paren and bracket if (!x){ cout << "x is non-zero\n"; } //closing bracket indented to the same level as the original statement } It's only slightly different for something like a class or a namespace: class myClass {}; //space between class name and bracket, otherwise the same as functions K&R style does uses that kind of bracketing for statements, but my style uses it for everything. I'd like to know if there's a name for it so I can say simply what my indent style is without having to explain using examples like these.

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• Save the output of a command in a string in linux using python

  - by user1657901

  I am using Fedora 17 xfce and I am programming in Python 2.7.3. Fedora uses a package manager called yum. I have a python script that searches for packages like this: import os package = raw_input("Enter package name to search: ") os.system("yum list " + package) So I want python to check if in the output of this command exists the words "No matching packages to list". I checked a similar question and I tried some methods [http://stackoverflow.com/questions/2502833/python-store-output-of-subprocess-call-in-a-string][1] but the string contained only the first line of the output. Thanks in advance

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• Writing an AI for a turn-based board game

  - by Cyril

  Hi, i'm currently programming a board game (8x8) in which I need to develop an AI. I have read a lot of articles about AI in board games, minmax with or without alphabeta pruning, but I don't really know how to implements this, I don't know where to start... About my game, this is a turn-based game, each player has pieces on the board, they have to pick one and choose in moving this piece (1 or 2 cells max) or clone the piece (1 cell max). At the moment, I have a really stupid AI which choose a random piece then choose a random move to play... Could you please give me some clues, on how to implement this functionality ? Best regards

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• Opening up TCP Sockets in j2ee Webapplication

  - by Gvenez

  Hello, We have to communicate with a C++ component from a J2ee web application and my proposal involved using JMS server to communicate with the C++ component which is located on other machine. However the developer of the C++ component wants me to open up TCP/IP sockets from the webapplication and communicate over XML. My view is that socket programming in web application is error prone and will not scale well since there is a limited amount of sockets that can be opened up. Please let me have your architecture/design preference on using JMS vs TCP/IP sockets. Thank you

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• Trouble with SVN and Filename 'changes'.

  - by Stacey

  I am programming in Visual Studio 2010, using TortiseSVN and VisualSVN as my client to connect to SVN repositories. I am having a bit of a frequent problem though with the whole SVN thing in general. One thing that keeps cropping up is that if I make changes to files - namely filenames, or move them to new folders, etc, I end up getting all kinds of conflicts with the repository and it just causes all sorts of strange errors. I understand the importance of version control and check-in/check-out access like this, but what do most of you do to deal with this kind of thing? I mean, I've tried doing the whole 'Remove from Subversion', change my file, then 'Add to Subversion' thing, and it just doesn't seem to do the job very well. This is especially frustrating when working on web projects where filenames can change very frequently as a project evolves and becomes multifaceted. Are there any standard ways to deal with this kind of thing, or is it just one of the flaws of SVN in general?

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• Android how to call a method of MainActivity in SmsReceiver Class

  - by GeneticSmart

  I'm very new to Android Programming, It would be really great if someone can help me in this.My project contains two JAVA files. MainActivity.java extends Activity SMSReceiver.java extends Broadcastreceiver The SMSreceiver.java has the code which displays any incoming SMS in toast. Can you please tell me how to call a function in MainActivity whenever a particular SMS is received. For eg: when I receive sms called as starttemp it should call a function starttemp. I have searched a lot and found that intents are a way to do this and we cannot call these methods directly. Please can anyone help me in this? And it would be really great if someone can send me working code.

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• PHP: form input field names containing square brackets like field[index]

  - by gidireich

  Hi, I've seen lot of code that handle forms, which creates input fields with names containing square brackets. I understand that this is being somehow converted to PHP arrays when a PHP script examines the $_POST variable. My questions about this: What is the mechanism behind? At which point this names that merely contain brackets are converted to arrays? Is this a feature of the HTPP protocol? Of web servers? Of the PHP language? Continuing the previous question, is this a commonly used hack or a normal programming tool? What are (all) the rules of using brackets in input field names? Can multidimensional arrays be created this way? Thanks, Gidi

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• Starting Game dev on iPhone:iPad - learning path ??

  - by Tibi

  Hi there, I'm beginning in iPhone/iPad game dev and I'm searching to set up my learning path. The basic features I would like to learn (after the basic SDK iphone components programming) are : using a board like interface where I can move pawn with my fingers detect where the pawn was moved and triggers events in the game The board will be constitute by 6 tiles that may be organised randomly when starting the game : may i use an sdk component with a delegate and datasource to determine where the pawn was left and on which tile ? need to use dices (which kind of library may I use ?) ... Do you have any idea about where to start ? ;-) Many thanks, Tib.

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• Closed Source Java Applications

  - by Paul

  I am taking programming courses and we have been discussing Open Source and having a bit of an argument over the confusion. Just because Java is Open Source, the licensing on developed applications starts at the developer, correct? Someone is arguing about the use of code from a complete program just because "Java is Open Source". If I write a Java application, what are the limitations on how I can distribute it or how someone else can use it? Assume here that I DO NOT want someone having access to my source. Thanks

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• Are C++ Templates just Macros in disguise?

  - by Roddy

  I've been programming in C++ for a few years, and I've used STL quite a bit and have created my own template classes a few times to see how it's done. Now I'm trying to integrate templates deeper into my OO design, and a nagging thought keeps coming back to me: They're just a macros, really... You could implement (rather UGLY) auto_ptrs using #defines, if you really wanted to. This way of thinking about templates helps me understand how my code will actually work, but I feel that I must be missing the point somehow. Macros are meant evil incarnate, yet "template metaprogramming" is all the rage. So, what ARE the real distinctions? and how can templates avoid the dangers that #define leads you into, like Inscrutable compiler errors in places where you don't expect them? Code bloat? Difficulty in tracing code? Setting Debugger Breakpoints?

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• Array Related Doubt.......

  - by AGeek

  I have the following program........... int insert(int *array, int arraySize, int newElement) { array[arraySize + 1] = newElement; return (arraySize+1); // Return new Array size...... } int main() { int array[] = {1,2,3,4,5}; int arraySize = sizeof(array) / sizeof(int); insertInArray(array, arraySize,6); print(array); } I am trying to work out this program in C programming language... But when i print the array after insertion,,, it doesn't prints the desired output which is needed.. Please correct me if i am doing something wrong..... Thanks..

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• Tags php improving database speed and user experience

  - by Doodle

  How did stackOverFlow, excuse me if it wasn't the first implementation of this system. Decide what its initial tags where? I want to provide users with the best experience on my site and am implementing a tags system. I don't care about search engines or any of that. I just care about my users. Does any one have any advice about things that have failed or succeeded when they allowed users to tag things? Does any one know some good resources about the methodologies of user tagging? Does any one know some good resources about implementing a tags system from a programming perspective, database structures, theories, etc ? I'll give my check to who ever I feel points me in the best direction on the subject.

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• How to link .lib library in linux

  - by giga

  I'm pretty new to c programming and want to port a windows c application to linux. My code uses a .lib file va_g729.lib - is it possible to use the same library in Linux and compile it with gcc? All my .c and .h files along with the one .lib files are in the same directory. What I'm doing now is executing this command in the directory: gcc *.c -lm and I get following errors: lbcodec2.c:(.text+0xa6b): undefined reference to `va_g729a_init_encoder' lbcodec2.c:(.text+0xa83): undefined reference to `va_g729a_encoder' collect2: error: ld returned 1 exit status Is it possible to link the .lib file and compile with gcc? Thanks.

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• Variable pre-fixes, Visual Studio 2010 onwards?

  - by thedixon

  I'm a bit bewildered on this subject, as I relate variable prefixes to being a thing of the past now, but with Visual Studio 2010 onwards (I'm currently using 2012), do people still do this and why? I only ask because, these days, you can hover over any variable and it'll tell you the variable type and scope. There's literally no requirement for pre-fixing being there for readability. By this I mean: string strHello int intHello etc. And I'm being language/tool biased here - as Visual Studio takes a lot of the legwork out for you in terms of seeing exactly what type the variable is, including after conversions in the code. This is not a "general programming" question.

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• How to deal with multiple screensizes + dynamic controls in Android?

  - by chobo2

  Hi I am learning how to program on Android phone. However I am unsure how to make my application work for the different screen sizes and resolutions. I read the tutorial on the android site and still unsure how to do it. First I know there are different files so could make a layout for each of the sizes but my problem is most of the screen needs to be dynamically created so there would not be much to put in these files. So I am not sure how to android to re size dynamic controls based on the screen size. I have also read it is bad practice to make controls in anything but the xml file as it separates view logic and programming logic. However they never talk about if you need to make these controls dynamically what you should do. So is there some other way to do it that is considered good practice?

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• Wrapping a point-to-point link

  - by user3712955

  I'm using a pair of IP radios (non-WiFi) to bridge my office engineering LAN (172.0.0.0/8) to a lab in another building. The radios work fine, but they expose a web management interface I'd like to hide, and they also generate traffic (ARP, STP, and more) that I need to keep off my (very, very clean) LAN segments. I have some ARM-Linux boards (similar to Beagle/Panda/RasPi) running Ubuntu, and I've put one at each end of the link, between the radio and the LAN. Each of the boards has 2 wired Ethernet interfaces, eth0 and eth1. The LAN segments are connected to eth0, and the radios are connected to eth1. I'd like to accomplish the following: Keep radio-originated traffic off my LAN segments! Hide all services provided by the radio (web, ssh, etc.) Transparently pass all traffic between the LAN segments (including things like ARP). The above also applies to the ARM-Linux boards: No stray traffic my LAN from them either! I'd like the system to look like a switch: LAN packets arriving at one eth0 appear at the other. And neither eth0 should have an IP address: The working system should behave like a CAT6 cable with some latency (instead of ARM boards and radios). Unfortunately, I'm confused about how to properly configure the ARM Ubuntu systems. What I'm guessing I need is a bridge on each board (br0?) and a VLAN (vlan0 or eth0.0?) to isolate the LAN traffic from everything else as it passes through the ARM boards and the radios. Then I need some kind of a firewall to block sending anything out eth0 that isn't from the other eth0 (via the VLAN). I've looked at the ip and ebtables commands (especially -t broute). While the concepts sorta-kinda make sense, I'm completely lost in the details. Edit: In the perverse case that a system on one of my LAN segments has the same IP address as one of the radios, or as eth1 on the ARM-Ubuntu boards, a VLAN won't work. Which I believe means I need to tunnel all traffic between the two eth0 interfaces to get that "like a wire" behavior. Help? Finally, I'd like to have a way to temporarily expose services on the ARM boards (ssh) and the radios (web) for maintenance purposes. Ideally, it would expose an IP address with ssh available on port 22. Once connected, I figure I'd start an X11 session and run a browser on the ARM board to access the radios. Or something. I could login via the console to enable/disable this, or perhaps could use a GPIO to trigger a script. I feel I've identified most of the pieces needed to make all this happen, but I have no idea how to combine them to make a working system. Thanks!

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• how good do you have to be to claim you have X amount of experience with X language/platform/skill

  - by dfafa

  sometimes i see job requirements saying you need 5 years of LAMP experience or resumes listing years of experience for each language.... what would you need to prove you have 5 years of experience at something ? i mean what if you rested for a while from coding ? what if you were actually "learning" during the first few years ? i feel no confidence at all and although i have been learning web programming (lamp) since 4 years ago, i am uncertain whether my skills qualify as to those of someone who has "5 years of LAMP" experience, and how would i be able to find out ? i've written several web apps....but they haven't taken off as i hoped.

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• Computer/Application having trouble and getting slow while accessing Sql server through LAN, Network is fine

  - by user614297

  Hi, I have an web project in asp.net in one of my computers which are connected internally through LAN. The database is in Sql Server kept in another computer. The LAN is connected well. There is no connection error in my programming also. But sometimes in this particular system the page is taking long time to be open, sometime it is showing some exceptions(not everytime again and again). What can be the problem? How can it be solved? The same project is running good in other computers as well. My network seems ok, as I can acccess the computer hosting SQL server.

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• More swing design & actions

  - by takoi

  Im pretty new to gui programming so i've been reading through every post on this site about swing and design. Whats been answered over and over again is that one should have a class which handles all the action. Like this: (GUI being some JFrame) Now, this works great for one-way actions, like OpenDialog. But the actions for buttons in DialogA and B will have to have access to all the components (there will be many) in its dialog, and the controller. This is where im stuck. The only sane way i can see is to put it in DialogA/B but i would then need to pass the controller all the way down, through classes that dont even need it, and it'll get all spaghetti. Really dont want that. Someone must have encountered this problem before. So where should i put this Action? Or should i just drop the whole design?

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• Consolidating separate Loan, Purchase & Sales tables into one transaction table.

  - by Frank Computer

  INFORMIX-SE with ISQL 7.3: I have separate tables for Loan, Purchase & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.id [serial] = loan.foreign_id [integer]; = purchase.foreign_id [integer]; = sale.foreign_id [integer]; I would like to consolidate the three tables into one table called "transaction", where a column "transaction.trx_type" [char(1)] {L=Loan, P=Purchase, S=Sale} identifies the transaction type. Is this a good idea or is it better to keep them in separate tables? Storage space is not a concern, I think it would be easier programming & user=wise to have all types of transactions under one table.

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