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• Raspberry Pi broadcast serial port data to local network

  - by D051P0

  I didn't find anything to help me with this problem. What I want is: Serial device sends repeatedly some data to serial port. Raspberry Pi should get this data from RxD and stream it to local network via port 10001 without filtering it. So I can find this device on my pc. This should also work in other direction: Raspberry listen to port 10001 and forward all data from local network to TxD. I'm newbie in Linux World. How can I listen to some port on Raspberry Pi and send broadcast to the same port? I'm using Raspbian Wheezy with soft float. I have found a library Pi4j for Java, that I already use to get and write data from/to serial port. final Serial serial = SerialFactory.createInstance(); serial.addListener(new SerialDataListener() { public void dataReceived(SerialDataEvent event) { forward(event.getData()); } }); event.getData() is a String, which I want to broadcast in my local network. Is it generally a good Idea to use Java for that? I need also a String from port 10001, which I can forward to serial port.

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• How have your coding values changed since graduating?

  - by Matt

  We all walked out of school with the stars in our eyes and little experience in "real-world" programming. How have your opinions on programming as a craft changed since you've gained more experience away from academia? I've become more and more about design a la McConnell : wide use of encapsulation, quality code that gives you warm fuzzy feelings when you read it, maintainability over execution performance, etc..., whereas many of my co-workers have followed a different path of fewer middlemen layers getting in the way, code that is right out in the open and easier to locate, even if harder to read, and performance-centric designs. What have you learned about the craft of software design which has changed the way you approach coding since leaving the academic world?

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• .Net Hash Codes no longer persistent?

  - by RobV

  I have an API where various types have custom hash codes. These hash codes are based on getting the hash of a string representation of the object in question. Various salting techniques are used so that as far as possible Hash Codes do not collide and that Objects of different types with equivalent string representations have different Hash Codes. Obviously since the Hash Codes are based on strings there are some collisions (infinite strings vs the limited range of 32 bit integers). I use hashes based on string representations since I need the hashes to persist over sessions and particularly for use in database storage of objects. Suddenly today my code has started generating different hash codes for Objects which is breaking all kinds of things. It was working earlier today and I haven't touched any of the code involved in Hash Code generation. I'm aware that the .Net documentation allows for implementation of hash codes between .Net framework versions to change (and between 32 and 64 bit versions) but I haven't changed the framework version and there has been no framework updates recently as far as I can remember Any ideas because this seems really weird? Edit Hash Codes are generated like follows: //Compute Hash Code this._hashcode = (this._nodetype + this.ToString() + PlainLiteralHashCodeSalt).GetHashCode();

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• Objective-C Definedness

  - by Dan Ray

  This is an agonizingly rookie question, but here I am learning a new language and framework, and I'm trying to answer the question "What is Truth?" as pertains to Obj-C. I'm trying to lazy-load images across the network. I have a data class called Event that has properties including: @property (nonatomic, retain) UIImage image; @property (nonatomic, retain) UIImage thumbnail; in my AppDelegate, I fetch up a bunch of data about my events (this is an app that shows local arts event listings), and pre-sets each event.image to my default "no-image.png". Then in the UITableViewController where I view these things, I do: if (thisEvent.image == NULL) { NSLog(@"Going for this item's image"); UIImage *tempImage = [UIImage imageWithData:[NSData dataWithContentsOfURL: [NSURL URLWithString: [NSString stringWithFormat: @"http://www.mysite.com/content_elements/%@_image_1.jpg", thisEvent.guid]]]]; thisEvent.image = tempImage; } We never get that NSLog call. Testing thisEvent.image for NULLness isn't the thing. I've tried == nil as well, but that also doesn't work.

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• ActionListener isn't Implementing

  - by Nick Gibson

  JFrameWithPanel is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener public class JFrameWithPanel extends JFrame implements ActionListener I Don't get this code. Book and Java site tells me this is the syntax for the method, but again this error shows up constantly. import javax.swing.*; import javax.swing.JOptionPane; import java.awt.*; import java.awt.event.*; import java.lang.Math.*; import java.lang.Integer.*; import java.util.*; import java.util.Random; import java.io.*; import java.text.*; import java.text.DecimalFormat.*; public class JFrameWithPanel extends JFrame implements ActionListener { JButton button = new JButton("Exit"); public JFrameWithPanel() { super("JFrame with Panel"); JComboBox packageChoice = new JComboBox(); packageChoice.addItem("A+ Certification"); packageChoice.addItem("Network+ Certification "); packageChoice.addItem("Security+ Certifictation"); packageChoice.addItem("CIT Full Test Package"); packageChoice.addActionListener(this); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel pane = new JPanel(); pane.add(button); pane.add(packageChoice); setContentPane(pane); setSize(200,100); setVisible(true); } } then later public class CreateJFrameWithPanel { public static void main(String[] args) { JFrameWithPanel panel = new JFrameWithPanel(); } }

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• Transitioning from C++ to C#

  - by Jim

  I am very experienced in C and C++ but am having problems finding current opportunities. I decided to switch to C# but noticed that while the syntax is very similar, the programming styles are very different (we don't have IEnumerable etc in C). So the problem I am having now is having 20 years of experience but is only a junior when it comes to interviewing for a C# job. Most of the problems are me not being able to answer questions like 1) How do you do XYZ in Sql Server? 2) What's the use of in Spring.NET In other words, the phone interviewers don;t care if you know DB programming or not - they want to know if you know SQL Server. I am frustrated because the guys who are doing the interviews seem to be so narrow sighted in knowing ONLY C#, .NET and SQL Server, that I don't know how to get past them.

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• Socket select() Handling Abrupt Disconnections

  - by Genesis

  I am currently trying to fix a bug in a proxy server I have written relating to the socket select() call. I am using the Poco C++ libraries (using SocketReactor) and the issue is actually in the Poco code which may be a bug but I have yet to receive any confirmation of this from them. What is happening is whenever a connection abruptly terminates the socket select() call is returning immediately which is what I believe it is meant to do? Anyway, it returns all of the disconnected sockets within the readable set of file descriptors but the problem is that an exception "Socket is not connected" is thrown when Poco tries to fire the onReadable event handler which is where I would be putting the code to deal with this. Given that the exception is silently caught and the onReadable event is never fired, the select() call keeps returning immediately resulting in an infinite loop in the SocketReactor. I was considering modifying the Poco code so that rather than catching the exception silently it fires a new event called onDisconnected or something like that so that a cleanup can be performed. My question is, are there any elegant ways of determining whether a socket has closed abnormally using select() calls? I was thinking of using the exception message to determine when this has occured but this seems dirty to me.

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• What are some practical uses of generating all permutations of a list, such as ['a', 'b', 'c'] ?

  - by Jian Lin

  I was asked by somebody in an interview for web front end job, to write a function that generates all permutation of a string, such as "abc" (or consider it ['a', 'b', 'c']). so the expected result from the function, when given ['a', 'b', 'c'], is abc acb bac bca cab cba Actually in my past 20 years of career, I have never needed to do something like that, especially when doing front end work for web programming. What are some practical use of this problem nowadays, in web programming, front end or back end, I wonder? As a side note, I kind of feel that expecting a result in 3 minutes might be "either he gets it or he doesn't", especially I was thinking of doing it by a procedural, non-recursive way at first. After the interview, I spent another 10 minutes and thought of how to do it using recursion, but expecting it to be solved within 3 minutes... may not be a good test of how qualified he is, especially for front end work.

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• Ideas for using R to create a T-shirt design (for useR 2010) ?

  - by Tal Galili

  There is now a competition for creating a T-shirt design for useR2010. Someone proposed the idea to use R for creating the T-shirt image. Which leads me to my questions: What type of images do you think might be fitting for this? How would you suggest to use R to create the images ? Would anyone here want to have a go at it? (p.s: I understand this is not a pure "programming" question. Yet it involves R programming, the understanding of R aesthetics, and some caring for the R community. I also understand I am at the risk of annoying people here with this question, so in case that happens - I deeply apologies! My only justification is that I am acting in good faith and in the purpose of having nice things for R users to enjoy, while learning something in the process) Related thread I once opened: http://stackoverflow.com/questions/2162131/how-can-i-learn-to-create-beautiful-infographics-with-connection-to-my-r-knowled

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• Choosing approach for an IM client-server app

  - by John

  Update: totally re-wrote this to be more succint. I'm looking at a new application, one part of which will be very similar to standard IM clients, i.e text chat, ability to send attachments, maybe some real-time interaction like a multi-user whiteboard. It will be client-server, i.e all traffic goes through my central server. That means if I want to support cross-communication with other IM systems, I am still free to pick any protocol for my own client<--server communication - my server can use XMPP or whatever to talk to other systems. Clients are expected to include desktop apps, but probably also browser-based as well either through Flex/Silverlight or HTML/AJAX. I see 3 options for my own client-server communication layer: XMPP. The benefits are clients already exist as do open-source servers. However it requires the most up-front research/learning and also appears like it might raise legal issues due to GPL. Custom sockets. A server app makes connections with the clients, allowing any text/binary data to be sent very fast. However this approach requires building said server from scratch, and also makes a JS client tricky Servlets (or similar web server). Using tried and tested Java web-stack, clients send HTTP requests similar to AJAX-based websites. The benefit is the server is easy to write using well-established technologies, and easy to talk to. But what restrictions would this bring? Is it appropriate technology for real-time communication? Advice and suggests are welcome, especially what pros and cons surround using a web-server approach as compared to a socket-based approach.

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• Where can C debugger tutorials be found?

  - by Ricky

  Is there any tutorial about using debuggers, when doing C programming on Linux (console mode)?

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• Eror while showing returned value on parent window from chield (Dialog box) window using JSF Trinida

  - by Navnath

  Hi There, I am using Myfaces and Trinidad tld's for page design. In that, I am trying to implement Dialog box which will going to open on button click with tacking some value from parent window and return result to Parent window. Now the problem is I can send value to Dialog box and also get return from dialog box successfully, but there is problem to show return value on Parent window because parent window is not reflecting that value and ask for refresh page. When I refresh page, it again open the pop up, i.e. it resending the previous request. Here is my return code. private UIXInput input; public UIXInput getInput() { return input; } public void setInput(UIXInput input) { this.input = input; } public void returned(ReturnEvent event) { if (event.getReturnValue() != null) { getInput().setValue(event.getReturnValue()); RequestContext afContext = RequestContext.getCurrentInstance(); afContext.addPartialTarget(getInput()); } } Next is I have bind input variable with field which need to reflect return value. Here is .jspx code. I have download Trinidad dialog code and try to run on local system, but it not showing any dialog box. But once I remove partialSubmit="true" attribute from comment button which shows dialog box, Then I can see dialog box. Is this attribute making an above error? I hope I have explain my problem clearly. Please...Please let me know any any kind of solution, suggestion. I have spend almost a week to resolve this issue, but.......didn't succeed. Thank You in advance, Navnath Kumbhar.

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• Ajax Update Panel Not Displaying Updated Image in IE, Chrome and FireFox

  - by jmease

  I have a parent page with an Ajax Update Panel that contains an image and a button. There is a hyperlink that opens up a child page. When the child page is submitted, there is an onclientclick event that triggers a javascript function that clicks the button in the update panel on the parent page, the button's click event being the trigger for the panel as well as the event that updates the image URL. When I use this on my android tablet, it works perfectly. However, it doesn't work at all on any browser I've used on a PC (Windows XP). The Image URL updates, but the updated image doesn't display without refreshing the entire page. In IE, I can right click on the image and click Show Image and it updates. In Chrome and Firefox, I have to refresh the entire page. Why would an Ajax control only work properly on the Android OS and what could I be doing wrong that would cause the image not to redisplay on my PC without refreshing the page even though the image URL is clearly being updated properly. I suspect a caching issue, but don't know how to correct.

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• When did the idea of macros (user-defined code transformation) appear?

  - by Jay

  I have read McCarthy's 1960 paper on LISP and found no reference to anything that's similar to user-defined macros or normal order evaluation. I was wondering when marcos first appeared in programming language history (and also in Lisp history): When was the idea of user-defined code transformation (before interpretation or compilation) first described (theoretically)? What was the first programming language implementation to have Lisp-like macros (by "Lisp-like" I mean "using a readable Turing-complete language to do code-transformation")? (including non-Lisps -- Forth for example is quite old, but I'm not sure if the first Forth implementation already had "IMMEDIATE") What was the first Lisp dialect to have macros? Thank you!

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• Flex/Flash: Don't show 'bar' cursor when dragging over a TextField/TextArea?

  - by David Wolever

  As the title suggests, how can I prevent the "bar" cursor from appearing when I click-and-drag over a TextField? For example, consider this interaction: I'd like to prevent the cursor changing to the "bar" in step "2". How can I do that? I've tried fiddling with the selectable flag: protected static function fixMouseOverAfordance(field:TextField):void { var iOwnClick:Boolean = false; function handleMouseOver(event:MouseEvent):void { if (event.buttonDown) { field.selectable = iOwnClick; } else { field.selectable = true; iOwnClick = false; } } field.addEventListener(MouseEvent.MOUSE_OVER, handleMouseOver, false, EventPriority.CURSOR_MANAGEMENT+1); field.addEventListener(MouseEvent.ROLL_OVER, handleMouseOver, false, EventPriority.CURSOR_MANAGEMENT+1); field.addEventListener(MouseEvent.MOUSE_MOVE, handleMouseOver, false, EventPriority.CURSOR_MANAGEMENT+1); field.addEventListener(MouseEvent.MOUSE_DOWN, function(event:MouseEvent):void { iOwnClick = true; field.selectable = true; }); } But the "bar" cursor still appears the first time the mouse is moved over the text field (however, after it has been moved out then moved back in, it does the right thing).

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• Is Android reference at android.com good enough

  - by the100rabh

  Hi, I am a C++ developer, but have a fair idea of Java as I learnt it in college 5years ago. I have been trying to learn programming for android. But instead of rushing to buy books, I have tried to read through the Android Dev Guide and learn from there making use of the sample applications. Thats besides SO ofcourse. I am trying to make some apps based on ideas I have. So my question is, Is it suitable or possible to learn android programming this way. Or is there something that I will be missing in all this.

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• How do software events work internally?

  - by Duddle

  Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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• Does anybody know of a GUI DSL for Scala?

  - by kula

  hi all does anybody knows a scala dsl on gui programming. regards. kula

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• C# Timer -- measuring time slower

  - by Fassenkugel

  I'm writing a code where: I.) The user adds "events" during run-time. (To a flowlayoutpanel) These events are turning some LEDs on/off, after "x" time has elapsed and the LED-turning functions are written in a Led-function.cs class. i.e: 1) Turn left led on After 3500ms 2) Turn right led on After 4000ms II.) When the user hits start a timer starts. // Create timer. System.Timers.Timer _timer; _timer = new System.Timers.Timer(); _timer.Interval = (1); _timer.Elapsed += (sender, e) => { HandleTimerElapsed(LedObject, device, _timer); }; _timer.Start(); III.) The timer's tick event is raised every millisecond and checks if the user definied time has ellapsed. Im measuring the elapsed time with adding +1 to an integer at every tick event. (NumberOfTicks++;) //Timer Handle private void HandleTimerElapsed(Led_Functions LedObject, string device, System.Timers.Timer _timer) { NumberOfTicks++; if (NumberOfTicks >= Start_time[0]) { LedObject.LeftLED_ONnobutton(device); } } IV.) What I noticed was that when the tick was set to 1. (So the tick event is raised every millisecond) Even if I set 3000ms to the evet the LED actually flashed around 6 seconds. When the tick was set to 100. (So every 0,1s) then the flash was more accurate (3,5sec or so). Any Ideas why im having this delay in time? Or do you have any ideas how could I implement it better? Thank you!

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• What's the deal with all of the abstract stuff?

  - by JustVenting

  I see a lot of talk about MVVM, MVC, Design Patterns etc... You know, some guy has a blog, and he spent the last six months learning about one these things and desiging a program centered around that concept and then he goes on and on about it like its better than sliced bread. I read all of this crap and I wonder, whatever happened to simple logical programming? Not self-absorbed huge frameworks of design patterns and mvc and whatever else you can think of... just simple linear programming, perhaps a few classes to encapsulate things here and there.

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• Erlang Question - Time order of messages

  - by Aiden Bell

  Read (skimmed enough to get coding) through Erlang Programming and Programming Erlang. One question, which is as simple as it sounds: If you have a process Pid1 on machine m1 and a billion million messages are sent to Pid1, are messages handled in parallel by that process (I get the impression no) and(answered below) is there any guarantee of order when processing messages? ie. Received in order sent? If so, how is clock skew handled in high traffic situations for ordering? Coming from the whole C/Thread pools/Shared State background ... I want to get this concrete. I understand distributing an application, but want to ensure the 'raw bones' are what I expect before building processes and distributing workload. Also, am I right in thinking the whole world is currently flicking through Erlang texts ;)

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• jQuery how to set click on href in the div?

  - by faya

  Good day, I want to set click event on every anchor element in my div container. Here is an example what I want to do: ---HTML--- <div id="my-container"> <a href="page1.html">page1</a> <a href="page2.html">page2</a> <a href="page3.html">page3</a> </div> ---- jQuery ---- $("#my-container a").click(function() { var link = $(this).attr("href"); $("#my-container").load(link); }); What I want to do is to let me handle loading event of href clicks and load it to the same container. And this is must done without id, class attributes which aren't available for that hrefs. The problem is in this: $("#my-container a"). Any help would be appreciated! Thanks UPDATE People doesn't seem to get right what I wanted to ask. I repeat myself again. $("#my-container a") <---- doesn't add click events on href anchors. So how I can set click event?

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• Line by Line explanation of "Javascript: Good Parts" example?

  - by Matrym

  I'm reading "Javascript: The Good Parts" and am totally baffled by what's really going on here. A more detailed and/or simplified explanation would be greatly appreciated. // BAD EXAMPLE // Make a function that assigns event handler functions to an array of nodes the wrong way. // When you click on a node, an alert box is supposed to display the ordinal of the node. // But it always displays the number of nodes instead. var add_the_handlers = function (nodes) { var i; for (i = 0; i < nodes.length; i += 1) { nodes[i].onclick = function (e) { alert(i); } } }; // END BAD EXAMPLE The add_the_handlers function was intended to give each handler a unique number (i). It fails because the handler functions are bound to the variable i, not the value of the variable i at the time the function was made: // BETTER EXAMPLE // Make a function that assigns event handler functions to an array of nodes the right way. // When you click on a node, an alert box will display the ordinal of the node. var add_the_handlers = function (nodes) { var i; for (i = 0; i < nodes.length; i += 1) { nodes[i].onclick = function (i) { return function (e) { alert(i); }; }(i); } }; Now, instead of assigning a function to onclick, we define a function and immediately invoke it, passing in i. That function will return an event handler function that is bound to the value of i that was passed in, not to the i defined in add_the_handlers. That returned function is assigned to onclick.

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• Large Switch statements: Bad OOP?

  - by Mystere Man

  I've always been of the opinion that large switch statements are a symptom of bad OOP design. In the past, I've read articles that discuss this topic and they have provided altnerative OOP based approaches, typically based on polymorphism to instantiate the right object to handle the case. I'm now in a situation that has a monsterous switch statement based on a stream of data from a TCP socket in which the protocol consists of basically newline terminated command, followed by lines of data, followed by an end marker. The command can be one of 100 different commands, so I'd like to find a way to reduce this monster switch statement to something more manageable. I've done some googling to find the solutions I recall, but sadly, Google has become a wasteland of irrelevant results for many kinds of queries these days. Are there any patterns for this sort of problem? Any suggestions on possible implementations? One thought I had was to use a dictionary lookup, matching the command text to the object type to instantiate. This has the nice advantage of merely creating a new object and inserting a new command/type in the table for any new commands. However, this also has the problem of type explosion. I now need 100 new classes, plus I have to find a way to interface them cleanly to the data model. Is the "one true switch statement" really the way to go? I'd appreciate your thoughts, opinions, or comments.

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• undefined offset error in php

  - by user225269

  I don't know why but the code below is working when I have a different query: $result = mysql_query("SELECT * FROM student WHERE IDNO='".$_GET['id']."'") ?> <?php while ( $row = mysql_fetch_array($result) ) { ?> <?php list($year,$month,$day)=explode("-", $row['BIRTHDAY']); ?> <tr> <td width="30" height="35"><font size="2">Month:</td> <td width="30"><input name="mm" type="text" id="mm" onkeypress="return handleEnter(this, event)" value="<?php echo $month;?>"> <td width="30" height="35"><font size="2">Day:</td> <td width="30"><input name="dd" type="text" id="dd" maxlength="25" onkeypress="return handleEnter(this, event)" value="<?php echo $day;?>"> <td width="30" height="35"><font size="2">Year:</td> <td width="30"><input name="yyyy" type="text" id="yyyy" maxlength="25" onkeypress="return handleEnter(this, event)" value="<?php echo $year;?>"> And it works when this is my query: $idnum = mysql_real_escape_string($_POST['idnum']); mysql_select_db("school", $con); $result = mysql_query("SELECT * FROM student WHERE IDNO='$idnum'"); Please help, why do I get the undefined offset error when I use this query: $result = mysql_query("SELECT * FROM student WHERE IDNO='".$_GET['id']."'") I assume that the query is the problem because its the only thing that's different between the two.

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