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  • Writing a VM - well formed bytecode?

    - by David Titarenco
    Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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  • C# functional quicksort is failing

    - by Rubys
    I'm trying to implement quicksort in a functional style using C# using linq, and this code randomly works/doesn't work, and I can't figure out why. Important to mention: When I call this on an array or list, it works fine. But on an unknown-what-it-really-is IEnumerable, it goes insane (loses values or crashes, usually. sometimes works.) The code: public static IEnumerable<T> Quicksort<T>(this IEnumerable<T> source) where T : IComparable<T> { if (!source.Any()) yield break; var pivot = source.First(); var sortedQuery = source.Skip(1).Where(a => a.CompareTo(source.First()) <= 0).Quicksort() .Concat(new[] { pivot }) .Concat(source.Skip(1).Where(a => a.CompareTo(source.First()) > 0).Quicksort()); foreach (T key in sortedQuery) yield return key; } Can you find any faults here that would cause this to fail?

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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 "exotic" language feature do you use every day?

    - by fmark
    For most programmers using procedural or object-oriented languages there is a language-feature lowest common denominator: variables, procedures, standard control structures, and classes. However, almost all languages add features on top of this. Recent C# versions have LINQ and delegates. C++ has template metaprogramming. Java has annotations. What features such as these do you use every day?

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  • Why is Visual Basic bad?

    - by Mike
    Why do programmers consider Visual Basic a bad language? Putting aside any gripes with Microsoft or with proprietary/non-free software in general, and looking the language itself. Syntax, style, etc. I have just started using it, and find the syntax rather terrible. But I'm wondering what are the most common specific problems.

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  • what do you do while code is compiling

    - by Jacob
    I'm looking for the best idea for what to do while code is compiling or tests are running. Typically around 5 minutes of thumb twiddling. Only so many cups of coffee can be made and drunk in a day, and I don't want to be seen always in the kitchen or bothering other people.

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  • Parallel processing via multithreading in Java

    - by Robz
    There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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  • Java compilers or JVM languages that support goto?

    - by unknown
    Is there a java compiler flag that allows me to use goto as a valid construct? If not, are there any third-party java compilers that supports goto? If not, are there any other languages that support goto while at the same time can easily call methods written in Java? The reason is I'm making a language that is implemented in Java. Gotos are an important part of my language; I want to be able to compile it to native or JVM bytecode, although it has to be able to easily use Java libraries (ie. C supports goto, but to use it I'd have to rewrite the libraries in C). I want to generate C or Java, etc source files, and not bytecode or machine code. I'm using a third-party compiler to do that.

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  • assembly of pdp-11(simulator)

    - by lego69
    I have this code on pdp-11 tks = 177560 tkb = 177562 tps = 177564 tpb = 177566 lcs = 177546 . = torg + 2000 main: mov #main, sp mov #kb_int, @#60 mov #200, @#62 mov #101, @#tks mov #clock, @#100 mov #300, @#102 mov #100, @#lcs loop: mov @#tks,r2 aslb r2 bmi loop halt clock: tst bufferg beq clk_end mov #msg,-(sp) jsr pc, print_str tst (sp)+ clr bufferg bic #100,@#tks clr @#lcs clk_end:rti kb_int: mov r1,-(sp) jsr pc, read_char movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr end_kb_int: mov (sp)+,r1 rti ;############################# read_char: tstb @#tks bpl read_char movb @#tkb, r1 rts pc ;############################# print_char: tstb @#tps bpl print_char movb r1, @#tpb rts pc ;############################# print_str: mov r1,-(sp) mov r2,-(sp) mov 6(sp),r2 str_loop: movb (r2)+,r1 beq pr_str_end jsr pc, print_char br str_loop pr_str_end: mov (sp)+,r2 mov (sp)+,r1 rts pc . = torg + 3000 msg:.ascii<Something is wrong!> .byte 0 .even buff_ptr: .word buffer buffer: .blkw 3 bufferg: .word 0 Can somebody please explain how this part is working, thanks in advance movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr

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  • Support Open Source Projects via T-Shirts

    - by The MYYN
    Can we get a list of free and open source projects, which can be supported through purchasing branded garment? Free Software Foundation http://shop.fsf.org/ OpenBSD https://https.openbsd.org/cgi-bin/order Mozilla http://store.mozilla.org/ ps. I know this is extremly off-topic. But I'd like to buy clothing and support open source at the same time. And I'd like to know, where this is possible.

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  • Is PHP still basically Procedural Overall?

    - by coffeeaddict
    I know PHP 5 has some object oriented similarities but it's not a true OOP environment still right? Also does it have a true compiler? I see compiling of scripts which still means procedural. I assume it's not a real compiler in that any PHP compilers out there do not create assemblies?

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  • How is GUID pronounced?

    - by Roberto Sebestyen
    Is it pronounced "Gewid" or is it prononced "G.U.I.D" by spelling out the letters. It seems inconsistently used. What is the proper pronountiaton? Same story goes for SQL. It seems more people say "S.Q.L." than "Sequel".

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  • Where is the Open Source alternative to WPF?

    - by Evan Plaice
    If we've learned anything from HTML/CSS it's that, declarative languages (like XML) work best to describe User Interfaces because: It's easy to build code preprocessors that can template the code effectively. The code is in a well defined well structured (ideally) format so it's easy to parse. The technology to effectively parse or crawl an XML based source file already exists. The UIs scripted code becomes much simpler and easier to understand. It simple enough that designers are able to design the interface themselves. Programmers suck at creating UIs so it should be made easy enough for designers. I recently took a look at the meat of a WPF application (ie. the XAML) and it looks surprisingly familiar to the declarative language style used in HTML. It's blindingly apparent to me that the current state of desktop UI development is largely fractionalized, otherwise there wouldn't be so much duplicated effort in the domain of user interfaces (IE. GTK, XUL, Qt, Winforms, WPF, etc). There are 45 GUI platforms for Python alone It's painfully obvious to me that there should be a general purpose, open source, standardized, platform independent, markup language for designing desktop GUIs. Much like what the W3C made HTML/CSS into. WPF, or more specifically XAML seems like a pretty likely step in the right direction. Why hasn't anyone in the Open Source community (AFAIK) even scratched the surface of this issue. Now that the 'browser wars' are over should we look forward to a future of 'desktop gui wars?' Note: This topic is relatively subjective in the attempt to be 'future-thinking.' I think that desktop GUI development in its current state sucks ((really)hard) and, even though WPF is still in it's infancy, it presents a likely solution to the problem. Has no one in the OS community looked into developing something similar because they don't see the value, or because it's not worth the effort?

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  • Is transmitted bytes event exist in Linux kernel?

    - by alnet
    I need to write a rate limiter, that will perform some stuff each time X bytes were transmitted. The straightforward is to check the length of each transmitted packet, but I think it will be to slow for me. Is there a way to use some king of network event, that will be triggered by transmitted packets/bytes?

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  • Definition of the job titles involved in a software development process.

    - by Rafael Romão
    I have seen many job titles for people involved in a software development process, but never found a consensus about they mean. I know many of them are equivalent, and found some other questions about that here in SO, but I would like to know your definitions and comments about them. I want not only to know if there is really a consensus, but also to know if what I suppose to be a Software Architect, is really a Software Architect, and so on. The job titles I mean are: Developer; System Analyst; Programmer; Analyst Programmer; Software Engineer; Software Architect; Designer; Software Designer; Business Manager; Business Analyst; Program Manager; Project Manager; Development Manager; Tester; Support Analyst; Please, feel free to add more titles to this list in your answers. It would be very helpful.

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  • The behavior of send() and recv() in socket communication

    - by gc
    The following is the setup: Server Client | | accept connect | | v | send msg1- | | | v v recv <- send | | v v send msg2- recv | | v v close Here is my question: 1. Client actually receives msg1 before it closes, why is it like this? 2. send msg2 returns normally. Since client closes after receiving msg1, why is send msg2 successful?

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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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  • How to get an internship with a low GPA?

    - by Jason Baker
    A lot of changed majors and some other mitigating circumstances have left me with a pretty low GPA. My GPA in the last couple of semesters hasn't been stellar, but my grades have gotten a LOT better. I want to try and start putting in some resumes to get a good internship this summer. I do think that I have some decent experience for someone at my level, but I see my GPA being a pretty big potential stumbling block. Is there anything I can do to help my chances of getting a good internship? (For the record, the mitigating circumstances aren't something I'd feel comfortable discussing with a potential employer. I'd prefer getting a job by proving my merit, not making excuses.)

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