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  • Alternatives to Java for Android development?

    - by paul.meier
    Hey all, I've started developing Android apps a couple of months ago, and have a few under my belt. While I can tolerate Java enough to keep developing, I was wondering what success the community has had getting other languages to run. I've done some investigation as to how other JVM languages work, and it appears Dalvik messes them up pretty hard. Clojure seems unable to run, Scala seems to be one of the most successful. JRuby has also had some luck, but they caution against anything major. I've also checked out Scheme via Moby and Kawa, both of which seem to have some promise. What luck have any of you had? Languages I'm missing, misrepresenting? Any non-"Hello World" apps you've written in non-Java? Any snags in trying to get another language to run (e.g. "as long as you don't use continuations, you're fine in X Scheme"). Any particular snags in developing apps non-Java, once you get them to run? Thanks, hope you well ^_^

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  • When to use closure?

    - by shahkalpesh
    I have seen samples of closure from - http://stackoverflow.com/questions/36636/what-is-a-closure Can anyone provide simple example of when to use closure? Specifically, scenarios in which closure makes sense? Lets assume that the language doesn't have closure support, how would one still achieve similar thing? Not to offend anyone, please post code samples in a language like c#, python, javascript, ruby etc. I am sorry, I do not understand functional languages yet.

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  • Haskell Parsec Numeration

    - by Martin
    I'm using Text.ParserCombinators.Parsec and Text.XHtml to parse an input like this: - First type A\n -- First type B\n - Second type A\n -- First type B\n --Second type B\n And my output should be: <h11 First type A\n</h1 <h21.1 First type B\n</h2 <h12 Second type A\n</h2 <h22.1 First type B\n</h2 <h22.2 Second type B\n</h2 I have come to this part, but I cannot get any further: title1= do{ ;(count 1 (char '-')) ;s <- many1 anyChar newline ;return (h1 << s) } title2= do{ ;(count 2 (char '--')) ;s <- many1 anyChar newline ;return (h1 << s) } text=do { ;many (choice [try(title1),try(title2)]) } main :: IO () main = do t putStr "Error: " print err Right x - putStrLn $ prettyHtml x This is ok, but it does not include the numbering. Any ideas? Thanks!

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  • WebSocket for HTML5

    - by Sareuon
    Introduction: I am going to develop the instance messaging that is run on the browser. Problem: Unfortunately I can not find and no idea what are the browser that is support with web-socket. Question: What are the browser that support web-socket?

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  • Can I ran 2 or more Tcp Sever applications on one computer?

    - by Samvel Siradeghyan
    Hi all. I have a client-server Silverlight application, which is use Socets. I have server appliaction on may computer(Win Form application) and client applucation as web site(Silverlight application). I use policy server which open port 943. Everything works fine on this application. But now I need to write another client-server application. Server for that application olso use port 943 for policy connection. When I try to run this 2 server applications on the same compyeter an excepten is thrown which says that only one application can work on port 943. How can I solve this problem? Thanks.

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  • Polygon packing 2D

    - by Ilnur
    Hi! I have problem of packing 2 arbitrary polygons. I.e. we have 2 arbitrary polygons. We are to find such placement of this polygons (we could make rotations and movements), when rectangle, which circumscribes this polygons has minimal area. I know, that this is a NP-complete problem. I want to choose an efficient algorithm for solving this problem. I' looking for No-Fit-Polygon approach. But I could't find anywhere the simple and clear algorithm for finding the NFP of two arbitrary polygons.

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  • Cross-platform (microcontroller-PC) algorithm development

    - by Kyr
    Hello people! I was asked to develop a algorithm for network application on C. This project will be developed on Linux for PC and then it will be transferred to a more portable platform, something that will include a microcontroller. There are many microcontroller/companies out there that provide very nice and large libraries for TCP/IP. This software will hold statistics on the network performance. The whole idea of a cross platform (uC - PC) seems rubbish to me cause eventually the code should be written in a more platform specific way for the microcontroller, but I am not expert to judge anyway. Is there any clever way of doing this or is there a anyone that did this before? My brainstorming has "Wrapper library" and "Matlab"... Any ideas? Thx!

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  • How do I test OpenCL on GPU when logged in remotely on Mac?

    - by Christopher Bruns
    My OpenCL program can find the GPU device when I am logged in at the console, but not when I am logged in remotely with ssh. Further, if I run the program as root in the ssh session, the program can find the GPU. The computer is a Snow Leopard Mac with a GeForce 9400 GPU. If I run the program (see below) from the console or as root, the output is as follows (notice the "GeForce 9400" line): 2 devices found Device #0 name = GeForce 9400 Device #1 name = Intel(R) Core(TM)2 Duo CPU P8700 @ 2.53GHz but if it is just me, over ssh, there is no GeForce 9400 entry: 1 devices found Device #0 name = Intel(R) Core(TM)2 Duo CPU P8700 @ 2.53GHz I would like to test my code on the GPU without having to be root. Is that possible? Simplified GPU finding program below: #include <stdio.h> #include <OpenCL/opencl.h> int main(int argc, char** argv) { char dname[500]; size_t namesize; cl_device_id devices[10]; cl_uint num_devices; int d; clGetDeviceIDs(0, CL_DEVICE_TYPE_ALL, 10, devices, &num_devices); printf("%d devices found\n", num_devices); for (d = 0; d < num_devices; ++d) { clGetDeviceInfo(devices[d], CL_DEVICE_NAME, 500, dname, &namesize); printf("Device #%d name = %s\n", d, dname); } return 0; } EDIT: I found essentially the same question being asked on nvidia's forums. Unfortunately, the only answer was of the form "this is the wrong forum".

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  • How to solve a deallocated connection in iPhone SDK 3.1.3? - Streams - CFSockets

    - by Christian
    Hi everyone, Debugging my implementation I found a memory leak issue. I know where is the issue, I tried to solve it but sadly without success. I will try to explain you, maybe someone of you can help with this. First I have two classes involved in the issue, the publish class (where publishing the service and socket configuration is done) and the connection (where the socket binding and the streams configuration is done). The main issue is in the connection via native socket. In the 'publish' class the "server" accepts a connection with a callback. The callback has the native-socket information. Then, a connection with native-socket information is created. Next, the socket binding and the streams configuration is done. When those actions are successful the instance of the connection is saved in a mutable array. Thus, the connection is established. static void AcceptCallback(CFSocketRef socket, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { Publish *rePoint = (Publish *)info; if ( type != kCFSocketAcceptCallBack) { return; } CFSocketNativeHandle nativeSocketHandle = *((CFSocketNativeHandle *)data); NSLog(@"The AcceptCallback was called, a connection request arrived to the server"); [rePoint handleNewNativeSocket:nativeSocketHandle]; } - (void)handleNewNativeSocket:(CFSocketNativeHandle)nativeSocketHandle{ Connection *connection = [[[Connection alloc] initWithNativeSocketHandle:nativeSocketHandle] autorelease]; // Create the connection if (connection == nil) { close(nativeSocketHandle); return; } NSLog(@"The connection from the server was created now try to connect"); if ( ! [connection connect]) { [connection close]; return; } [clients addObject:connection]; //save the connection trying to avoid the deallocation } The next step is receive the information from the client, thus a read-stream callback is triggered with the information of the established connection. But when the callback-handler tries to use this connection the error occurs, it says that such connection is deallocated. The issue here is that I don't know where/when the connection is deallocated and how to know it. I am using the debugger, but after some trials, I don't see more info. void myReadStreamCallBack (CFReadStreamRef stream, CFStreamEventType eventType, void *info) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; Connection *handlerEv = [[(Connection *)info retain] autorelease]; // The error -[Connection retain]: message sent to deallocated instance 0x1f5ef0 (Where 0x1f5ef0 is the reference to the established connection) [handlerEv readStreamHandleEvent:stream andEvent:eventType]; [pool drain]; } void myWriteStreamCallBack (CFWriteStreamRef stream, CFStreamEventType eventType, void *info){ NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init]; Connection *handlerEv = [[(Connection *)info retain] autorelease]; //Sometimes the error also happens here, I tried without the pool, but it doesn't help neither. [handlerEv writeStreamHandleEvent:eventType]; [p drain]; } Something strange is that when I run the debugger(with breakpoints) everything goes well, the connection is not deallocated and the callbacks work fine and the server is able to receive the message. I will appreciate any hint!

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  • Web Sockets: Browser won't receive the message, complains about it not starting with 0x00 (byte)

    - by giggsey
    Here is my code: import java.net.*; import java.io.*; import java.util.*; import org.jibble.pircbot.*; public class WebSocket { public static int port = 12345; public static ArrayList<WebSocketClient> clients = new ArrayList<WebSocketClient>(); public static ArrayList<Boolean> handshakes = new ArrayList<Boolean>(); public static ArrayList<String> nicknames = new ArrayList<String>(); public static ArrayList<String> channels = new ArrayList<String>(); public static int indexNum; public static void main(String args[]) { try { ServerSocket ss = new ServerSocket(WebSocket.port); WebSocket.console("Created socket on port " + WebSocket.port); while (true) { Socket s = ss.accept(); WebSocket.console("New Client connecting..."); WebSocket.handshakes.add(WebSocket.indexNum,false); WebSocket.nicknames.add(WebSocket.indexNum,""); WebSocket.channels.add(WebSocket.indexNum,""); WebSocketClient p = new WebSocketClient(s,WebSocket.indexNum); Thread t = new Thread( p); WebSocket.clients.add(WebSocket.indexNum,p); indexNum++; t.start(); } } catch (Exception e) { WebSocket.console("ERROR - " + e.toString()); } } public static void console(String msg) { Date date = new Date(); System.out.println("[" + date.toString() + "] " + msg); } } class WebSocketClient implements Runnable { private Socket s; private int iAm; private String socket_res = ""; private String socket_host = ""; private String socket_origin = ""; protected String nick = ""; protected String ircChan = ""; WebSocketClient(Socket socket, int mynum) { s = socket; iAm = mynum; } public void run() { String client = s.getInetAddress().toString(); WebSocket.console("Connection from " + client); IRCclient irc = new IRCclient(iAm); Thread t = new Thread( irc ); try { Scanner in = new Scanner(s.getInputStream()); PrintWriter out = new PrintWriter(s.getOutputStream(),true); while (true) { if (! in.hasNextLine()) continue; String input = in.nextLine().trim(); if (input.isEmpty()) continue; // Lets work out what's wrong with our input if (input.length() > 3 && input.charAt(0) == 65533) { input = input.substring(2); } WebSocket.console("< " + input); // Lets work out if they authenticate... if (WebSocket.handshakes.get(iAm) == false) { checkForHandShake(input); continue; } // Lets check for NICK: if (input.length() > 6 && input.substring(0,6).equals("NICK: ")) { nick = input.substring(6); Random generator = new Random(); int rand = generator.nextInt(); WebSocket.console("I am known as " + nick); WebSocket.nicknames.set(iAm, "bo-" + nick + rand); } if (input.length() > 9 && input.substring(0,9).equals("CHANNEL: ")) { ircChan = "bo-" + input.substring(9); WebSocket.console("We will be joining " + ircChan); WebSocket.channels.set(iAm, ircChan); } if (! ircChan.isEmpty() && ! nick.isEmpty() && irc.started == false) { irc.chan = ircChan; irc.nick = WebSocket.nicknames.get(iAm); t.start(); continue; } else { irc.msg(input); } } } catch (Exception e) { WebSocket.console(e.toString()); e.printStackTrace(); } t.stop(); WebSocket.channels.remove(iAm); WebSocket.clients.remove(iAm); WebSocket.handshakes.remove(iAm); WebSocket.nicknames.remove(iAm); WebSocket.console("Closing connection from " + client); } private void checkForHandShake(String input) { // Check for HTML5 Socket getHeaders(input); if (! socket_res.isEmpty() && ! socket_host.isEmpty() && ! socket_origin.isEmpty()) { send("HTTP/1.1 101 Web Socket Protocol Handshake\r\n" + "Upgrade: WebSocket\r\n" + "Connection: Upgrade\r\n" + "WebSocket-Origin: " + socket_origin + "\r\n" + "WebSocket-Location: ws://" + socket_host + "/\r\n\r\n",false); WebSocket.handshakes.set(iAm,true); } return; } private void getHeaders(String input) { if (input.length() >= 8 && input.substring(0,8).equals("Origin: ")) { socket_origin = input.substring(8); return; } if (input.length() >= 6 && input.substring(0,6).equals("Host: ")) { socket_host = input.substring(6); return; } if (input.length() >= 7 && input.substring(0,7).equals("Cookie:")) { socket_res = "."; } /*input = input.substring(4); socket_res = input.substring(0,input.indexOf(" HTTP")); input = input.substring(input.indexOf("Host:") + 6); socket_host = input.substring(0,input.indexOf("\r\n")); input = input.substring(input.indexOf("Origin:") + 8); socket_origin = input.substring(0,input.indexOf("\r\n"));*/ return; } protected void send(String msg, boolean newline) { byte c0 = 0x00; byte c255 = (byte) 0xff; try { PrintWriter out = new PrintWriter(s.getOutputStream(),true); WebSocket.console("> " + msg); if (newline == true) msg = msg + "\n"; out.print(msg + c255); out.flush(); } catch (Exception e) { WebSocket.console(e.toString()); } } protected void send(String msg) { try { WebSocket.console(">> " + msg); byte[] message = msg.getBytes(); byte[] newmsg = new byte[message.length + 2]; newmsg[0] = (byte)0x00; for (int i = 1; i <= message.length; i++) { newmsg[i] = message[i - 1]; } newmsg[message.length + 1] = (byte)0xff; // This prints correctly..., apparently... System.out.println(Arrays.toString(newmsg)); OutputStream socketOutputStream = s.getOutputStream(); socketOutputStream.write(newmsg); } catch (Exception e) { WebSocket.console(e.toString()); } } protected void send(String msg, boolean one, boolean two) { try { WebSocket.console(">> " + msg); byte[] message = msg.getBytes(); byte[] newmsg = new byte[message.length+1]; for (int i = 0; i < message.length; i++) { newmsg[i] = message[i]; } newmsg[message.length] = (byte)0xff; // This prints correctly..., apparently... System.out.println(Arrays.toString(newmsg)); OutputStream socketOutputStream = s.getOutputStream(); socketOutputStream.write(newmsg); } catch (Exception e) { e.printStackTrace(); } } } class IRCclient implements Runnable { protected String nick; protected String chan; protected int iAm; boolean started = false; IRCUser irc; IRCclient(int me) { iAm = me; irc = new IRCUser(iAm); } public void run() { WebSocket.console("Connecting to IRC..."); started = true; irc.setNick(nick); irc.setVerbose(false); irc.connectToIRC(chan); } void msg(String input) { irc.sendMessage("#" + chan, input); } } class IRCUser extends PircBot { int iAm; IRCUser(int me) { iAm = me; } public void setNick(String nick) { this.setName(nick); } public void connectToIRC(String chan) { try { this.connect("irc.appliedirc.com"); this.joinChannel("#" + chan); } catch (Exception e) { WebSocket.console(e.toString()); } } public void onMessage(String channel, String sender,String login, String hostname, String message) { // Lets send this message to me WebSocket.clients.get(iAm).send(message); } } Whenever I try to send the message to the browser (via Web Sockets), it complains that it doesn't start with 0x00 (which is a byte). Any ideas? Edit 19/02 - Added the entire code. I know it's real messy and not neat, but I want to get it functioning first. Spend last two days trying to fix.

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  • Linux Kernel - Red/Black Trees

    - by CodeRanger
    I'm trying to implement a red/black tree in Linux per task_struct using code from linux/rbtree.h. I can get a red/black tree inserting properly in a standalone space in the kernel such as a module but when I try to get the same code to function with the rb_root declared in either task_struct or task_struct-files_struct, I get a SEGFAULT everytime I try an insert. Here's some code: In task_struct I create a rb_root struct for my tree (not a pointer). In init_task.h, macro INIT_TASK(tsk), I set this equal to RB_ROOT. To do an insert, I use this code: rb_insert(&(current-fd_tree), &rbnode); This is where the issue occurs. My insert command is the standard insert that is documented in all RBTree documentation for the kernel: int my_insert(struct rb_root *root, struct mytype *data) { struct rb_node **new = &(root->rb_node), *parent = NULL; /* Figure out where to put new node */ while (*new) { struct mytype *this = container_of(*new, struct mytype, node); int result = strcmp(data->keystring, this->keystring); parent = *new; if (result < 0) new = &((*new)->rb_left); else if (result > 0) new = &((*new)->rb_right); else return FALSE; } /* Add new node and rebalance tree. */ rb_link_node(&data->node, parent, new); rb_insert_color(&data->node, root); return TRUE; } Is there something I'm missing? Some reason this would work fine if I made a tree root outside of task_struct? If I make rb_root inside of a module this insert works fine. But once I put the actual tree root in the task_struct or even in the task_struct-files_struct, I get a SEGFAULT. Can a root node not be added in these structs? Any tips are greatly appreciated. I've tried nearly everything I can think of.

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  • accelerating Wheel - psychtoolbox in matlab

    - by ariel
    Hi I am trying to write a code that will show an acceleration wheel. as long as the user press 'a' the wheel should accelerate counterclock wize. the thing is that it turn in the right direction but it doesn't accelerate. This is the code I am using . PTB-3 windows XP. img=imread('c:\images.jpg'); [yimg,ximg,z]=size(img); rot_spd = 1; larrow = KbName('a'); % modify this for Windows rarrow = KbName('b'); [w,rect]=Screen('OpenWindow',0,[0 0 0]); sx = 400; % desired x-size of image (pixels) sy = yimg*sx/ximg; % desired y-size--keep proportional t = Screen('MakeTexture',w,img); bdown=0; th = 0; % initial rotation angle (degrees) HideCursor while(~any(bdown)) % exit loop if mouse button is pressed [x,y,bdown]=GetMouse; [keyisdown,secs,keycode] = KbCheck; if(keycode(larrow)) th = th - rot_spd-1; % accelerate counterclockwise th end if(keycode(rarrow)) th = th + rot_spd+1; % accelerate clockwise th end destrect=[x-sx/2,y-sy/2,x+sx/2,y+sy/2]; Screen('DrawTexture',w,t,[],destrect,th); Screen('Flip',w); end Screen('Close',w) ShowCursor If anyone has an odea why it doesn't accelerate I'd appriciate it very much. Ariel

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  • Why not allow mutation of the this binding?

    - by gnucom
    Hi Everyone, I'm building a interpreter/compiler for a school project (well now its turning into a hobby project) and an instructor warned me not to allow mutation of the 'this' binding (he said it was gross and made a huge deal about it) but I never learned why this is so... dangerous or bad. I'm very curious about why this is so bad. I figured this sort of feature could be useful in some way or another. I'm wondering if anyone familiar with building languages can tell me what sort of problems mutation on the 'this' binding can cause, and if they know of any cool or useful tricks that one could do if it actually was allowed. Do any languages that you're aware of allow mutation of 'this'? Thanks,

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  • Choosing a non microsoft language for web development?

    - by Luke Lowrey
    I am resonably experienced with asp.net and would like to learn a new language with a focus on web development. Licensing and hosting costs are why I would like to use something not reliant on microsoft so something based on open source technologies is a plus. I have had a tiny bit of experience with php and did not like it but I guess I could be convinced otherwise. Basically I'd like to know peoples opinion on the the best language for future web development with regards to longivity, resources, frameworks, hosting etc.

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  • Reference for proper handling of PID file on Unix

    - by bignose
    Where can I find a well-respected reference that details the proper handling of PID files on Unix? On Unix operating systems, it is common practice to “lock” a program (often a daemon) by use of a special lock file: the PID file. This is a file in a predictable location, often ‘/var/run/foo.pid’. The program is supposed to check when it starts up whether the PID file exists and, if the file does exist, exit with an error. So it's a kind of advisory, collaborative locking mechanism. The file contains a single line of text, being the numeric process ID (hence the name “PID file”) of the process that currently holds the lock; this allows an easy way to automate sending a signal to the process that holds the lock. What I can't find is a good reference on expected or “best practice” behaviour for handling PID files. There are various nuances: how to actually lock the file (don't bother? use the kernel? what about platform incompatibilities?), handling stale locks (silently delete them? when to check?), when exactly to acquire and release the lock, and so forth. Where can I find a respected, most-authoritative reference (ideally on the level of W. Richard Stevens) for this small topic?

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  • Bad File descriptor

    - by Luke
    Does anyone see a problem with this, its not working saying bad file descriptor not sure why? pipe(pipefd[0]); if ((opid = fork()) == 0) { dup2(pipefd[0][1],1);/*send to output*/ close(pipefd[0][0]); close(pipefd[0][1]); execlp("ls","ls","-al",NULL); } if((cpid = fork())==0){ dup2(pipefd[0][1],0);/*read from input*/ close(pipefd[0][0]); close(pipefd[1][1]); execlp("grep","grep",".bak",NULL); } close(pipefd[0][0]); close(pipefd[0][1]);

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  • Why don't purely functional languages use reference counting?

    - by Zifre
    In purely functional languages, data is immutable. With reference counting, creating a reference cycle requires changing already created data. It seems like purely functional languages could use reference counting without worrying about the possibility of cycles. Am is right? If so, why don't they? I understand that reference counting is slower than GC in many cases, but at least it reduces pause times. It would be nice to have the option to use reference counting in cases where pause times are bad.

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  • Cartesian product in Scheme

    - by John Retallack
    I've been trying to do a function that returns the Cartesian Product of n sets,in Dr Scheme,the sets are given as a list of lists,I've been stuck at this all day,I would like a few guidelines as where to start,I've wrote a pice of code but it dosen't work. (define cart-n(?(l) (if (null? l) '(()) (map (?(lst) (cons (car ( car(l))) lst)) (cart-n (cdr l) )))))

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  • Timing the Linux Kernel boot-time optimisation

    - by CVS-2600Hertz-wordpress-com
    I am trying to optimise the boot-up time of linux on an embedded device (not PC) Currently to profile the boot-up sequence, I have enabled the timing info on printk logs. Is this the most optimum way? If not, how do i profile the boot-up sequence (with timing) with minimum overhead? PS: I have a terminal (of the device) over a serial-connection & I use TeraTerm over windows-XP to access it.

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  • What language has the longest "Hello world" program?

    - by Kip
    In most scripting languages, a "Hello world!" application is very short: print "Hello world" In C++, it is a little more complicated, requiring at least 46 non-whitespace characters: #include <cstdio> int main() { puts("Hello world"); } Java, at 75 non-whitespace characters, is even more verbose: class A { public static void main(String[] args) { System.out.print("Hello world"); } } Are there any languages that require even more non-whitespace characters than Java? Which language requires the most? Notes: I'm asking about the length of the shortest possible "hello world" application in a given language. A newline after "Hello world" is not required. I'm not counting whitespace, but I know there is some language that uses only whitespace characters. If you use that one you can count the whitespace characters.

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