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  • Why would a variable in Scala code mysteriously become null?

    - by Alex R
    I've isolated the problem down to this: Predef.println("the value of argv1 here is " + argv(1)); var n: $ = undef; n = argv(1); Predef.println("the value of argv1 here is " + argv(1)); Predef.println("the value of n here is " + n); Predef.println("the class of n here is " + n.getClass); Here's the definition of $: class $ { println("constructed a new $ of type: " + this.getClass); def value: $ = this; def toValue: Value = { new ConstStringValue(this.toString()) }; def -(sym: Symbol): $ = { println("looked up: " + sym); this } def -(sym: $): $ = { println("looked up: " + sym); this } def update(sym: Symbol, any: Any) { println("update called: " + sym + "=" + any); } def apply(sym: Symbol) = { this } def apply(obj: $) = { this } def apply() = { this } def +(o:$) = this.toValue.div(o.toValue) def *(o:$) = this.toValue.mul(o.toValue) def >(o:$) = this.toValue.gt(o.toValue) def <(o:$) = this.toValue.lt(o.toValue) def ++() = { this } def -=(o:$) = { this } } When run, the code prints: the value of argv1 here is 10 the value of argv1 here is 10 the value of n here is null java.lang.NullPointerException at test_1_php$.include(_tmp.scala:149) at php.script.main(php.scala:57) at test_1_php.main(_tmp.scala) [...] Why would n mysteriously lose its value (or fail to take one on)?

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  • Monitoring outgoing internet traffic

    - by Frane
    Is there a way to monitoring internet traffic programatically? I would like to log the pages users are visiting on the Internet. Can this be achieved with .NET code, is there a 3rd party .NET component that could be used to retrieved data. Information about Internet traffic must be stored to a database so I cannot use a plugin or something for IE. We are also looking to include this code into our existing product so we cannot use a 3rd party product that cannot be redistributed. It would be cool if this thing could monitor traffic for all browsers but monitoring IE traffic might also be sufficient.

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  • How to find minimum weight with maximum cost in 0-1 Knapsack algorithm?

    - by Nitin9791
    I am trying to solve a spoj problem Party Schedule the problem statement is- You just received another bill which you cannot pay because you lack the money. Unfortunately, this is not the first time to happen, and now you decide to investigate the cause of your constant monetary shortness. The reason is quite obvious: the lion's share of your money routinely disappears at the entrance of party localities. You make up your mind to solve the problem where it arises, namely at the parties themselves. You introduce a limit for your party budget and try to have the most possible fun with regard to this limit. You inquire beforehand about the entrance fee to each party and estimate how much fun you might have there. The list is readily compiled, but how do you actually pick the parties that give you the most fun and do not exceed your budget? Write a program which finds this optimal set of parties that offer the most fun. Keep in mind that your budget need not necessarily be reached exactly. Achieve the highest possible fun level, and do not spend more money than is absolutely necessary. Input The first line of the input specifies your party budget and the number n of parties. The following n lines contain two numbers each. The first number indicates the entrance fee of each party. Parties cost between 5 and 25 francs. The second number indicates the amount of fun of each party, given as an integer number ranging from 0 to 10. The budget will not exceed 500 and there will be at most 100 parties. All numbers are separated by a single space. There are many test cases. Input ends with 0 0. Output For each test case your program must output the sum of the entrance fees and the sum of all fun values of an optimal solution. Both numbers must be separated by a single space. Example Sample input: 50 10 12 3 15 8 16 9 16 6 10 2 21 9 18 4 12 4 17 8 18 9 50 10 13 8 19 10 16 8 12 9 10 2 12 8 13 5 15 5 11 7 16 2 0 0 Sample output: 49 26 48 32 now I know that it is an advance version of 0/1 knapsack problem where along with maximum cost we also have to find minimum weight that is less than a a given weight and have maximum cost. so I have used dp to solve this problem but still get a wrong awnser on submission while it is perfectly fine with given test cases. My code is typedef vector<int> vi; #define pb push_back #define FOR(i,n) for(int i=0;i<n;i++) int main() { //freopen("input.txt","r",stdin); while(1) { int W,n; cin>>W>>n; if(W==0 && n==0) break; int K[n+1][W+1]; vi val,wt; FOR(i,n) { int x,y; cin>>x>>y; wt.pb(x); val.pb(y); } FOR(i,n+1) { FOR(w,W+1) { if(i==0 || w==0) { K[i][w]=0; } else if (wt[i-1] <= w) { if(val[i-1] + K[i-1][w-wt[i-1]]>=K[i-1][w]) { K[i][w]=val[i-1] + K[i-1][w-wt[i-1]]; } else { K[i][w]=K[i-1][w]; } } else { K[i][w] = K[i-1][w]; } } } int a1=K[n][W],a2; for(int j=0;j<W;j++) { if(K[n][j]==a1) { a2=j; break; } } cout<<a2<<" "<<a1<<"\n"; } return 0; } Could anyone suggest what am I missing??

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  • PHP - Best practice to retain form values across postback

    - by Adam
    Hello, Complete PHP novice here, almost all my previous work was in ASP.NET. I am now working on a PHP project, and the first rock I have stumbled upon is retaining values across postback. For the most simple yet still realistic example, i have 10 dropdowns. They are not even databound yet, as that is my next step. They are simple dropdowns. I have my entire page inclosed in a tag. the onclick() event for each dropdown, calls a javascript function that will populate the corrosponding dropdowns hidden element, with the dropdowns selected value. Then, upon page reload, if that hidden value is not empty, i set the selected option = that of my hidden. This works great for a single postback. However, when another dropdown is changed, the original 1'st dropdown loses its value, due to its corrosponding hidden value losing its value as well! This draws me to look into using querystring, or sessions, or... some other idea. Could someone point me in the right direction, as to which option is the best in my situation? I am a PHP novice, however I am being required to do some pretty intense stuff for my skill level, so I need something flexable and preferribly somewhat easy to use. Thanks! -----edit----- A little more clarification on my question :) When i say 'PostBack' I am referring to the page/form being submitted. The control is passed back to the server, and the HTML/PHP code is executed again. As for the dropdowns & hiddens, the reason I used hidden variables to retain the "selected value" or "selected index", is so that when the page is submitted, I am able to redraw the dropdown with the previous selection, instead of defaulting back to the first index. When I use the $_POST[] command, I am unable to retrieve the dropdown by name, but I am able to retrieve the hidden value by name. This is why upon dropdown-changed event, I call javascript which sets the selected value from the dropdown into its corrosponding hidden.

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  • Sparse quadratic program solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an QP solver for large sparse matrices. Also, A is huge (around 2e6x2e6) but very sparse with <=4 elements per row. Any ideas/recommendations?

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  • How can I generate the Rowland prime sequence idiomatically in J?

    - by Gregory Higley
    If you're not familiar with the Rowland prime sequence, you can find out about it here. I've created an ugly, procedural monadic verb in J to generate the first n terms in this sequence, as follows: rowland =: monad define result =. 0 $ 0 t =. 1 $ 7 while. (# result) < y do. a =. {: t n =. 1 + # t t =. t , a + n +. a d =. | -/ _2 {. t if. d > 1 do. result =. ~. result , d end. end. result ) This works perfectly, and it indeed generates the first n terms in the sequence. (By n terms, I mean the first n distinct primes.) Here is the output of rowland 20: 5 3 11 23 47 101 7 13 233 467 941 1889 3779 7559 15131 53 30323 60647 121403 242807 My question is, how can I write this in more idiomatic J? I don't have a clue, although I did write the following function to find the differences between each successive number in a list of numbers, which is one of the required steps. Here it is, although it too could probably be refactored by a more experienced J programmer than I: diffs =: monad : '}: (|@({.-2&{.) , $:@}.) ^: (1 < #) y'

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  • Is it possible to change a exe's icon without recompiling it?

    - by Microkernel
    Hi all, I have lot of executable that I have compiled (long time back) for many of which I don't have sourcecode now. But when I compiled them I didn't put any icons for them, so they all look like same dull, bald default icon. So my questions are, (1) is it possible for me to write a software that can change the resources section of the exe and change its looks? If so, can anyone plz point me to the location where its explained? (I am a beginner, I have no idea on the exe format and all) Also its fun to keep changing Icons without having the pain of recompiling everything just for the icon change... (2) This is raises a natural converse question, Is it similarly possible to zap out the icon used by some file and use it for some other file? (If so, plz point me to location where I can get some details. I am a C/C++ developers and I am looking for solution on Windows Platform... Regards, MicroKernel

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  • How can i learn file name and create a folder?

    - by Phsika
    i try to make TCP/Ip Application to listen any other roemote computer to recieve any file. So i try to get files. i can do that. on the other hand every sample on google about giving SaveDialogBox to recived path folder.Forexample my old server.cs is that: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Net; using System.Net.Sockets; using System.Threading; namespace Server3 { public partial class Form1 : Form { Thread kanal; public Form1() { InitializeComponent(); try { kanal = new Thread(new ThreadStart(Dinle)); kanal.Start(); kanal.Priority = ThreadPriority.Normal; this.Text = "Kanal Çalisti"; } catch (Exception ex) { this.Text = "kanal çalismadi"; MessageBox.Show("hata:" + ex.ToString()); kanal.Abort(); throw; } } void Dinle() { TcpListener server = null; try { Int32 port = 51124; IPAddress localAddr = IPAddress.Parse("127.0.0.1"); server = new TcpListener(localAddr, port); server.Start(); Byte[] bytes = new Byte[1024 * 250000]; // string ReceivedPath = "C:/recieved"; while (true) { MessageBox.Show("Waiting for a connection... "); TcpClient client = server.AcceptTcpClient(); MessageBox.Show("Connected!"); NetworkStream stream = client.GetStream(); if (stream.CanRead) { saveFileDialog1.ShowDialog(); string pathfolder = saveFileDialog1.FileName; StreamWriter yaz = new StreamWriter(pathfolder); string satir; StreamReader oku = new StreamReader(stream); while ((satir = oku.ReadLine()) != null) { satir = satir + (char)13 + (char)10; yaz.WriteLine(satir); } oku.Close(); yaz.Close(); client.Close(); } } } catch (SocketException e) { Console.WriteLine("SocketException: {0}", e); } finally { // Stop listening for new clients. server.Stop(); } Console.WriteLine("\nHit enter to continue..."); Console.Read(); } private void Form1_Load(object sender, EventArgs e) { Dinle(); } } } i want to give automatically folder without SAVEDIALOGBOX. Also i want to learn my file name om my stream.Like that: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Net; using System.Net.Sockets; using System.Threading; namespace Server3 { public partial class Form1 : Form { Thread kanal; public Form1() { InitializeComponent(); try { kanal = new Thread(new ThreadStart(Dinle)); kanal.Start(); kanal.Priority = ThreadPriority.Normal; this.Text = "Kanal Çalisti"; } catch (Exception ex) { this.Text = "kanal çalismadi"; MessageBox.Show("hata:" + ex.ToString()); kanal.Abort(); throw; } } void Dinle() { TcpListener server = null; try { Int32 port = 51124; IPAddress localAddr = IPAddress.Parse("127.0.0.1"); server = new TcpListener(localAddr, port); server.Start(); Byte[] bytes = new Byte[1024 * 250000]; string ReceivedPath = "C:/recieved"; while (true) { MessageBox.Show("Waiting for a connection... "); TcpClient client = server.AcceptTcpClient(); MessageBox.Show("Connected!"); NetworkStream stream = client.GetStream(); if (stream.CanRead) { saveFileDialog1.ShowDialog(); string pathfolder = " i have to give property creating path and want to learn file name"; StreamWriter yaz = new StreamWriter(pathfolder); string satir; StreamReader oku = new StreamReader(stream); while ((satir = oku.ReadLine()) != null) { satir = satir + (char)13 + (char)10; yaz.WriteLine(satir); } oku.Close(); yaz.Close(); client.Close(); } } } catch (SocketException e) { Console.WriteLine("SocketException: {0}", e); } finally { // Stop listening for new clients. server.Stop(); } Console.WriteLine("\nHit enter to continue..."); Console.Read(); } private void Form1_Load(object sender, EventArgs e) { Dinle(); } } } Also i need : FileStream fs; FileInfo fi = new FileInfo(@"c:/recieved"); if (fi.Exists) fs = new FileStream(fi.FullName, FileMode.Append); else fs = new FileStream(fi.FullName, FileMode.Create); StreamWriter yazici = new StreamWriter(fs); How can i do that. Creating C:/recieved if it does not exist. And how can i learn File name on my network stream sending File Name.

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  • about python scripting

    - by kmitnick
    I have this code class HNCS (ThreadingTCPServer): def verify_request(self, request, client_address): for key in connections: if connections[key].client_address[0] == client_address[0]: if client_address[0] != '127.0.0.1': return False return True def welcome(self): return '''______________________________________________________ ------------------------------------------------------ %s ______________________________________________________ ------------------------------------------------------ * Server started %s * Waiting for connections on port %i ''' % (gpl, ctime(), PORT) I only can't figure out the line where it says if connections[key].client_address[0] == client_address[0] how come we used client_address as an attribute after dictionary???

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  • How to start the web cam by programmatically?

    - by Nitz
    Hello Guys How to start any web cam through programmatically? my main requirement is it should start webcam? and that should be any application - software not a website. we can use any language. So how can start the web cam using programing language? btw... [I am not talking about the power of the webcam][Any web cam means any companies web cam]

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  • Are there any modern platforms with non-IEEE C/C++ float formats?

    - by Patrick Niedzielski
    Hi all, I am writing a video game, Humm and Strumm, which requires a network component in its game engine. I can deal with differences in endianness easily, but I have hit a wall in attempting to deal with possible float memory formats. I know that modern computers have all a standard integer format, but I have heard that they may not all use the IEEE standard for floating-point integers. Is this true? While certainly I could just output it as a character string into each packet, I would still have to convert to a "well-known format" of each client, regardless of the platform. The standard printf() and atod() would be inadequate. Please note, because this game is a Free/Open Source Software program that will run on GNU/Linux, *BSD, and Microsoft Windows, I cannot use any proprietary solutions, nor any single-platform solutions. Cheers, Patrick

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  • what is pagecache page

    - by kumar
    /* * Each physical page in the system has a struct page associated with * it to keep track of whatever it is we are using the page for at the * moment. Note that we have no way to track which tasks are using * a page, though if it is a pagecache page, rmap structures can tell us * who is mapping it. */ include/linux/mm_types.h Here Please lemme know what is "pagecache page" means? Thanks!

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  • Reverse rendering of Urdu fonts

    - by Syed Muhammad Umair
    I am working on a project that is based on Urdu language in Ubuntu platform. I'm using Python language and have almost achieved my task. The problem is that, the Urdu text is rendered in reverse order. For example, consider the word ??? (which means work) consisting of the three letters: ? , ? , and ? The output is rendered in reverse order as ??? consisting of the three letters: ?, ?, and ? When copying this text to Open Office or opening the generated XML file in Firefox, the generated result is absolutely desired. I Am using Python 2.6 IDLE, its working perfect with Windows platform, which clearly shows its not the problem of IDLE. Am working on TKINTER GUI library. How can this problem be solved?

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  • Which languages are dynamically typed and compiled (and which are statically typed and interpreted)?

    - by Skilldrick
    In my reading on dynamic and static typing, I keep coming up against the assumption that statically typed languages are compiled, while dynamically typed languages are interpreted. I know that in general this is true, but I'm interested in the exceptions. I'd really like someone to not only give some examples of these exceptions, but try to explain why it was decided that these languages should work in this way.

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  • Mathematica equivalent of Ruby's inject

    - by Ben Alpert
    Is there a Mathematica function like inject in Ruby? For example, if I want the product of the elements in a list, in Ruby I can write: list.inject(1) { |prod,el| prod * el } I found I can just use Product in Mathematica: Apply[Product, list] However, this isn't general enough for me (like, if I don't just want the product or sum of the numbers). What's the closest equivalent to inject?

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  • What are all the disadvantages of using files as a means of communicating between two processes?

    - by Manny
    I have legacy code which I need to improve for performance reasons. My application comprises of two executables that need to exchange certain information. In the legacy code, one exe writes to a file ( the file name is passed as an argument to exe) and the second executable first checks if such a file exists; if does not exist checks again and when it finds it, then goes on to read the contents of the file. This way information in transferred between the two executables. The way the code is structured, the second executable is successful on the first try itself. Now I have to clean this code up and was wondering what are the disadvantages of using files as a means of communication rather than some inter-process communication like pipes.Is opening and reading a file more expensive than pipes? Are there any other disadvantages? And how significant do you think would be the performance degradation. The legacy code is run on both windows and linux.

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  • Getting "Illegal Seek" error after calling accept()

    - by Bilthon
    Well.. it's pretty much that, I seem to be getting a "Illegal Seek" error when checking my errno variable. The problem is that I have no idea of what that can mean. I know sockets are treated like files in unix, but I can't see how can this be related to sockets. What I'm doing exactly is: int sck = ::accept(m_socket, (struct sockaddr*)&client_address, (socklen_t*)&address_len); Then I get sck = -1 and errno = ESPIPE And the weird thing is that it happens randomly. I mean, sometimes the code works fine, and sometimes it just thows an exception. I'm working with threads so that's understandable. But I just would like to know what kind of behaviour makes the accept() call to set errno as ESPIPE so I could check the paramethers for instance. Thanks Nelson R. Pérez

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  • 0xDEADBEEF equivalent for 64-bit development?

    - by Peter Mortensen
    For C++ development for 32-bit systems (be it Linux, Mac OS or Windows, PowerPC or x86) I have initialised pointers that would otherwise be undefined (e.g. they can not immediately get a proper value) like so: int *pInt = reinterpret_cast<int *>(0xDEADBEEF); (To save typing and being DRY the right-hand side would normally be in a constant, e.g. BAD_PTR.) If pInt is dereferenced before it gets a proper value then it will crash immediately on most systems (instead of crashing much later when some memory is overwritten or going into a very long loop). Of course the behavior is dependent on the underlying hardware (getting a 4 byte integer from the odd address 0xDEADBEEF from a user process may be perfectly valid), but the crashing has been 100% reliable for all the systems I have developed for so far (Mac OS 68xxx, Mac OS PowerPC, Linux Redhat Pentium, Windows GUI Pentium, Windows console Pentium). For instance on PowerPC it is illegal (bus fault) to fetch a 4 byte integer from an odd address. What is a good value for this on 64-bit systems?

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  • How to flush DNS cache in Windows Mobile programmatically?

    - by Bounded
    Hello, My windows mobile application (written in C# with the compact framework) needs to know if a particular machine is active or not. To achieve this goal, I thought to use a ping mechanism. I tried to use the Ping class implemented in the opennetcf framework (the System.Net.NetworkInformation.Ping class for the .NET Framework is not part of the compact framework). Because I give to the Ping.Send function a host name, it first tries to resolve this host name and to retrieve an IP address. But i observe the following problem : If the first dns resolution fails (because the network is down at this moment), and if the application tries immediately again to send the ping, it fails too, even if the network is note down anymore. I check with a famous network protocol analyzer and i saw that only the requests concerning the first dns resolution are sent. The requests concerning the dns resolution of the second ping are not sent. Why is the second dns request not sent ? Is there any dns cache mechanism on such Windows Mobile devices ? If yes, can this mechanism beeing flushed programmatically ? EDIT : I gave up finding a solution to this DNS flush. I chose to ping an IP adress instead of a name machine. The problem of pinging an hard coded adress IP is that we have to be 100% sure that this IP will not change. The gateway IP can be used because it's always reachable (if it does not, it means the network is down).

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