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• VSFTPD does not allow upload with virtual users

  - by Mr. Squig

  I am attempting to setup VSFTPD with virtual users on a server running Ubuntu 12.04. I have configured the server to allow for virtual users to login, but I am having trouble getting it to allow uploads. My vsftpd.conf is as follows: listen=YES anonymous_enable=NO local_enable=YES write_enable=YES local_umask=022 anon_upload_enable=YES dirmessage_enable=YES use_localtime=YES xferlog_enable=YES connect_from_port_20=YES chroot_local_user=YES virtual_use_local_privs=YES guest_enable=YES guest_username=virtual user_sub_token=$USER local_root=/var/www/$USER hide_ids=YES secure_chroot_dir=/var/run/vsftpd/empty pam_service_name=vsftpd rsa_cert_file=/etc/ssl/private/vsftpd.pem /etc/pam.d/vsftpd contains: auth required pam_pwdfile.so pwdfile /etc/vsftpd.passwd crypt=hash account required pam_permit.so crypt=hash I have two virtual users set up, one of which has the same name as a local user. They each have a directory in /var/www/ owned by 'virtual'. As I understand it, when a virtual user logs in this way they will appear to the system as the user virtual. Using this configuration user can log on, but cannot upload files. The error given in /var/log/vsftpd.log is: Tue Nov 20 19:49:00 2012 [pid 2] CONNECT: Client "96.233.116.53" Tue Nov 20 19:49:07 2012 [pid 1] [zac] OK LOGIN: Client "96.233.116.53" Tue Nov 20 19:49:11 2012 [pid 2] CONNECT: Client "96.233.116.53" Tue Nov 20 19:49:11 2012 [pid 1] [zac] OK LOGIN: Client "96.233.116.53" Tue Nov 20 19:49:11 2012 [pid 3] [zac] FAIL CHMOD: Client "96.233.116.53", "/test.ppm 644" I have tried changing the permissions of these directories in all sorts of ways, but nothing seem to work. I have a feeling that it is something simple related to permissions. Any ideas?

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• Reasons to Use a VM For Development

  - by George Stocker

  Background: I work at a start-up company, where one team uses Virtual Machines to connect to a remote server to do their development, and another team (the team I'm on) uses local IIS/SQL Server 2005/Visual Studio installations to conduct work. Team VM is located about 1000 miles from Team Non-VM, and the servers the VMs run off of are located near Team VM (Latency, for those that are wondering, is about 50ms). A person high in the company is pushing for Team Non-VM to use virtual machines for programming, development, and testing. The latter point we agree on -- we want Virtual Machines to test configurations and various aspects of the web application in a 'clean' state. The Problem: What we don't agree on is having developers using RDP to connect to a desktop remotely that contains Visual Studio, SQL Server, and IIS to do the same development we could do locally on our laptops. I've tried the VM set-up, and besides the color issue, there is a latency issue that is rather noticeable, not to mention that since we're a start-up, a good number of employees work from home on occasion with our work laptops, and this move would cut off the laptops. They'd be turned in. Reasons to Use Remote VMs for Development (Not Testing!): Here are the stated reasons that this person wants us to use VMs: They work for TeamVM. They keep the source code "safe". If we want to work from home, we could just use our home PCs. Licenses (I don't know what the argument is, only that it's been used). Reasons not to use Remote VMs for Development: Here are the stated reasons why we don't want to use VMs: We like working from home. We get a lot done on our own time. We're not going to use our Home PCs to do work related stuff. The Latency is noticeable. Support for the VMs (if they go down, or if we need a new VM) takes a while. We don't have administrative privileges on the VM, and are unable to change settings as needed. What I'm looking for from the community is this: What reasons would you give for not using VMs for development? Keep in mind these are remote VMs -- this isn't a VM running on a local desktop. It's using the laptop (or a desktop) as a thin client for a remote VM. Also, on the other side of the coin: Is there something we're missing that makes VMs more palatable for development? Edit: I think 'safe' is used in term of corporate espionage, or more correctly if the Laptop gets stolen, the person who stole would have access to our source code. The former (as we've pointed out, is always going to be a possibility -- companies stop that with litigation, there isn't a technical solution (so far as I can see)). The latter point is ( though I don't know its usefulness in a corporate scenario) mitigated by Truecrypt'ing the entire volume.

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• VMWare-Tools Installation fails

  - by Ajay

  I am trying to install VMwareTools-8.4.6-385536.tar.gz (VMWare Tools) on the following operating system: Ubuntu 11.04 Linux ubuntu 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:50 UTC 2011 i686 i686 i386 GNU/Linux I am using VMPlayer version 3.1.4 - build 385536 After starting the installation I am getting the following errors: What is the directory that contains the init scripts? [/etc/init.d] Error opening No such file or directory Distribution provided drivers for Xorg X server are used. Skipping X configuration because X drivers are not included. Creating a new initrd boot image for the kernel.<br> update-initramfs: Generating /boot/initrd.img-2.6.38-8-generic Starting VMware Tools services in the virtual machine: Switching to guest configuration: done Blocking file system: done Guest operating system daemon: failed Virtual Printing daemon: done Unable to start services for VMware Tools Can somebody help in this?

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• Virtual Machine Network Architecture, Isolating Public and Private Networks

  - by Mark

  I'm looking for some insight into best practices for network traffic isolation within a virtual environment, specifically under VMWARE ESXi. Currently I have (in testing) 1 hardware server running ESXi but i expect to expand this to multiple pieces of hardware. The current setup is as follows: 1 pfsense VM, this VM accepts all outside (WAN/internet) traffic and performs firewall/port forwarding/NAT functionality. I have multiple public IP addresses sent to the this VM that are used for access to individual servers (via per incoming IP port forwarding rules). This VM is attached to the private (virtual) network that all other VMs are on. It also manages a VPN link into the private network with some access restrictions. This isn't the perimeter firewall but rather the firewall for this virtual pool only. I have 3 VMs that communicate with each other, as well as have some public access requirements: 1 LAMP server running an eCommerce site, public internet accessible 1 accounting server, access via windows server 2008 RDS services for remote access by users 1 inventory/warehouse management server, VPN to client terminals in warehouses These servers constantly talk with each other for data synchronization. Currently all the servers are on the same subnet/virtual network and connected to the internet through the pfsense VM. The pfsense firewall uses port forwarding and NAT to allow outside access to the servers for services and for server access to the internet. My main question is this: Is there a security benefit to adding a second virtual network adapter to each server and controlling traffic such that all server to server communication is on one separate virtual network, while any access to the outside world is routed through the other network adapter, through the firewall, and on the the internet. This is the type of architecture i would use if these were all physical servers, but i'm unsure if the networks being virtual changes the way i should approach locking down this system. Thank you for any thoughts or direction to any appropriate literature.

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• Windows Server 2008 R2 Virtual Network Setup

  - by jpearl01

  Hi all, Some background: I'm very much new to networking in general, and virtualization in particular. I'm trying to set up a series of VMs as we are transitioning to a thin client setup. I have been supplied a limited number of static ip addresses. The server is located in an offsite building which houses the network we use to connect to the internet, share folders etc. The setup I've been trying to go for is this: The host OS (Windows Server 2008 R2) is bound to one nic using one of the static ips (say, Nic1 and ip 10.255.6.61). I've set up another external virtual network attached to another physical nic , and a virtual private network attached to no nic. There is one VM running the same os (as the host). This VM is connected to both the external virtual network (and uses another static ip say Nic2 and ip 10.255.6.62) and also to the virtual private network (I gave it a static random ip 192.168.88.1 subnet mask 255.255.255.0). This virtual private network is connected to all the other VMs. I'd like to share the internet connection with all the other VMs on the private virtual network, and so I installed the RRAS role on the server connected to Nic2, and selected the option to share the internet over the vpn. I've run through the RRAS wizard a few times, trying different configurations, but none of them seem to be letting the other vms connect to the 'net. The vms seem to connect to the virtual private network fine, they are assigned an ip address and everything, but no internet, and no rest of the network either. The other problem is in general I connect to the vms with RDP. Will that be possible with a setup like this? i.e. will the vms show up as computers on the network? If not, what are my other options? Thanks! ~josh

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• "Imprinting" as a language feature?

  - by MKO

  Idea I had this idea for a language feature that I think would be useful, does anyone know of a language that implements something like this? The idea is that besides inheritance a class can also use something called "imprinting" (for lack of better term). A class can imprint one or several (non-abstract) classes. When a class imprints another class it gets all it's properties and all it's methods. It's like the class storing an instance of the imprinted class and redirecting it's methods/properties to it. A class that imprints another class therefore by definition also implements all it's interfaces and it's abstract class. So what's the point? Well, inheritance and polymorphism is hard to get right. Often composition gives far more flexibility. Multiple inheritance offers a slew of different problems without much benefits (IMO). I often write adapter classes (in C#) by implementing some interface and passing along the actual methods/properties to an encapsulated object. The downside to that approach is that if the interface changes the class breaks. You also you have to put in a lot of code that does nothing but pass things along to the encapsulated object. A classic example is that you have some class that implements IEnumerable or IList and contains an internal class it uses. With this technique things would be much easier Example (c#) [imprint List<Person> as peopleList] public class People : PersonBase { public void SomeMethod() { DoSomething(this.Count); //Count is from List } } //Now People can be treated as an List<Person> People people = new People(); foreach(Person person in people) { ... } peopleList is an alias/variablename (of your choice)used internally to alias the instance but can be skipped if not needed. One thing that's useful is to override an imprinted method, that could be achieved with the ordinary override syntax public override void Add(Person person) { DoSomething(); personList.Add(person); } note that the above is functional equivalent (and could be rewritten by the compiler) to: public class People : PersonBase , IList<Person> { private List<Person> personList = new List<Person>(); public override void Add(object obj) { this.personList.Add(obj) } public override int IndexOf(object obj) { return personList.IndexOf(obj) } //etc etc for each signature in the interface } only if IList changes your class will break. IList won't change but an interface that you, someone in your team, or a thirdparty has designed might just change. Also this saves you writing a whole lot of code for some interfaces/abstract classes. Caveats There's a couple of gotchas. First we, syntax must be added to call the imprinted classes's constructors from the imprinting class constructor. Also, what happends if a class imprints two classes which have the same method? In that case the compiler would detect it and force the class to define an override of that method (where you could chose if you wanted to call either imprinted class or both) So what do you think, would it be useful, any caveats? It seems it would be pretty straightforward to implement something like that in the C# language but I might be missing something :) Sidenote - Why is this different from multiple inheritance Ok, so some people have asked about this. Why is this different from multiple inheritance and why not multiple inheritance. In C# methods are either virtual or not. Say that we have ClassB who inherits from ClassA. ClassA has the methods MethodA and MethodB. ClassB overrides MethodA but not MethodB. Now say that MethodB has a call to MethodA. if MethodA is virtual it will call the implementation that ClassB has, if not it will use the base class, ClassA's MethodA and you'll end up wondering why your class doesn't work as it should. By the terminology sofar you might already confused. So what happens if ClassB inherits both from ClassA and another ClassC. I bet both programmers and compilers will be scratching their heads. The benefit of this approach IMO is that the imprinting classes are totally encapsulated and need not be designed with multiple inheritance in mind. You can basically imprint anything.

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• Transferring an SQL Processor License to a virtual hosted environment

  - by Andrew Shepherd

  My company is currently hosting a service in-house, and we want to move to an externally hosted environment. We would then be using a virtual server. I understand that this might be spread across multiple machines, but from my perspective as a customer, this layer is abstracted away - I shouldn't know or care about the hardware that the OS is hosted on. We have a licensed edition of SQL Server 2008. This is one Processor license. Will it be a violation of the licensing agreement to use this in a virtual environment. From the reference guide here it says When licensed Per Processor With Workgroup, Web, and Standard editions, for each server to which you have assigned the required number of per processor licenses, you may run, at any one time, any number of instances of the server software in physical and virtual operating system environments on the licensed server. However, the total number of physical and virtual processors used by those operating system environments cannot exceed the number of software licenses assigned to that server For enterprise edition there is an added option: if all physical processors in a machine have been licensed, then you may run unlimited instances of SQL server 2008 in one physical and an unlimited number of virtual operating environments on that same machine. I'm having trouble getting my head around this. Would I theoretically have to get a license for every processor in this virtual environment (which is effectively impossible because I have no way of knowing how many processors there actually are)? Or can I just say that it's hosted on one "virtual" server, so that's OK?

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• Windows Server 2008 R2 Virtual Network Setup

  - by jpearl01

  Some background: I'm very much new to networking in general, and virtualization in particular. I'm trying to set up a series of VMs as we are transitioning to a thin client setup. I have been supplied a limited number of static ip addresses. The server is located in an offsite building which houses the network we use to connect to the internet, share folders etc. The setup I've been trying to go for is this: The host OS (Windows Server 2008 R2) is bound to one nic using one of the static ips (say, Nic1 and ip 10.255.6.61). I've set up another external virtual network attached to another physical nic , and a virtual private network attached to no nic. There is one VM running the same os (as the host). This VM is connected to both the external virtual network (and uses another static ip say Nic2 and ip 10.255.6.62) and also to the virtual private network (I gave it a static random ip 192.168.88.1 subnet mask 255.255.255.0). This virtual private network is connected to all the other VMs. I'd like to share the internet connection with all the other VMs on the private virtual network, and so I installed the RRAS role on the server connected to Nic2, and selected the option to share the internet over the vpn. I've run through the RRAS wizard a few times, trying different configurations, but none of them seem to be letting the other vms connect to the 'net. The vms seem to connect to the virtual private network fine, they are assigned an ip address and everything, but no internet, and no rest of the network either. The other problem is in general I connect to the vms with RDP. Will that be possible with a setup like this? i.e. will the vms show up as computers on the network? If not, what are my other options? Thanks! ~josh

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• Reasons to Use a VM For Development

  - by George Stocker

  Background: I work at a start-up company, where one team uses Virtual Machines to connect to a remote server to do their development, and another team (the team I'm on) uses local IIS/SQL Server 2005/Visual Studio installations to conduct work. Team VM is located about 1000 miles from Team Non-VM, and the servers the VMs run off of are located near Team VM (Latency, for those that are wondering, is about 50ms). A person high in the company is pushing for Team Non-VM to use virtual machines for programming, development, and testing. The latter point we agree on -- we want Virtual Machines to test configurations and various aspects of the web application in a 'clean' state. The Problem: What we don't agree on is having developers using RDP to connect to a desktop remotely that contains Visual Studio, SQL Server, and IIS to do the same development we could do locally on our laptops. I've tried the VM set-up, and besides the color issue, there is a latency issue that is rather noticeable, not to mention that since we're a start-up, a good number of employees work from home on occasion with our work laptops, and this move would cut off the laptops. They'd be turned in. Reasons to Use Remote VMs for Development (Not Testing!): Here are the stated reasons that this person wants us to use VMs: They work for TeamVM. They keep the source code "safe". If we want to work from home, we could just use our home PCs. Licenses (I don't know what the argument is, only that it's been used). Reasons not to use Remote VMs for Development: Here are the stated reasons why we don't want to use VMs: We like working from home. We get a lot done on our own time. We're not going to use our Home PCs to do work related stuff. The Latency is noticeable. Support for the VMs (if they go down, or if we need a new VM) takes a while. We don't have administrative privileges on the VM, and are unable to change settings as needed. What I'm looking for from the community is this: What reasons would you give for not using VMs for development? Keep in mind these are remote VMs -- this isn't a VM running on a local desktop. It's using the laptop (or a desktop) as a thin client for a remote VM. Also, on the other side of the coin: Is there something we're missing that makes VMs more palatable for development? Edit: I think 'safe' is used in term of corporate espionage, or more correctly if the Laptop gets stolen, the person who stole would have access to our source code. The former (as we've pointed out, is always going to be a possibility -- companies stop that with litigation, there isn't a technical solution (so far as I can see)). The latter point is ( though I don't know its usefulness in a corporate scenario) mitigated by Truecrypt'ing the entire volume.

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• Java: "Dynamic Language Support on the Java Virtual Machine"

  New features offer better support for dynamically typed languages.

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• Is it necessary that each machine code can only map to one assembly code?

  - by Mask

  Suppose these two are essensially the same: push 1 and 0x1231 Which says each assembly instruction maps to a machine code. But is it necessary that each machine code can only map to one assembly code?

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• Moving windows-2003 hdd into virtual machine - with HDD shrink

  - by jm666

  Before you vote to close as exact duplicate, please read the full question. I was already read: Can I make a virtual machine out of a Windows XP physical machine? Disk2vhd,convert my PC to Hyper-V Virtual Machine Creating a Windows Virtual PC image from a Physical machine physical machine to virtual machine and place into VirtualBox BSOD trying to migrate Windows XP from a physical to a virtual machine http://en.wikipedia.org/wiki/Physical-to-Virtual and all other similiar questions here and several external sites too Unfortunately, don't find answer for my problem. I have an physical machine with 500GB HDD, on what is installed old Windows-2003 server with one server application. The application is like the windows itself, too old, no support for it today, haven't installation media and so on.. ;( On the HDD it is used only approx. 100MB (maybe less when will delete all unnecessary files). Want convert the the machine into the VirtualBox, and the VirtualBox should run on the same machine. Is possible to do this with the next steps? I can attach another HDD (via USB or internally) Boot an live Linux from CD, mount HDDs Run "something" on the Linux (the above wikipedia article have many pointer for the SW) for the conversion and store the image on the USB HDD - unfortunately, many of tools uses some specialty what exists in Windows-XP and above. No informations about Windows-2003 server, so what is an working solution for Windows-2003? try boot the virtual image with VirtualBox when it will run ok, remove the old installation, install Linux on the old 500GB hdd, copy the image and run.. The above should works (i hope), but the problems: i currently have only 320GB external USB hdd. (ofc, i can remove it from a box and enter it as internal HDD too) so, for the conversion I looking for the on the fly HDD shrink, so while moving the physical 500GB HDD need shrink it into smaller HDD - as i told above, only 100MB is used Exists something for this? (free) - or the only way is buying and larger 1TB hdd and using it for the conversion? Another question are: is anybody have real experience with windows-2003 conversion into VirtualBox? Looking for an answer from someone who really doing it and can figure out real pitfalls. (googling can do myself). exists here better approach for the solution?

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• Windows 7 Ultimate Restore From Another Machine

  - by Guy Thomas

  The situation I have an old machine running Windows Server 2008. I make a backup of selected directories. New Machine: I install Windows 7 Ultimate (and Windows Server 2008 [dual boot]) I cannot restore those files that I backed-up on the old machine. On the New machine neither the Windows 7 or Windows Server 2008 Restore (Recovery) can 'see' the backup files even though they are on the local machine. Is this behaviour (non-behaviour) 'by design' or am I missing something?

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• Internal Linux machine with Apache that I can access by IP address but not computer name

  - by Parris

  I have an Ubuntu machine running LAMP. While on the machine I can type localhost or the computers name to access htdocs. From another machine I can only access the machine via its IP Address. This just started happening recently when someone rearranged the network cables and removed a hub sitting between the machine and the network, which makes me think it wasn't all the stable to begin with anyways. Any suggestions on where I should start looking?

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• How do you find a functions virtual call address in assembly?

  - by Daniel

  I've googled around but i'm not sure i am asking the right question or not and i couldn't find much regardless, perhaps a link would be helpful. I made a c++ program that shows a message box, then I opened it up with Ollydbg and went to the part where it calls MessageBoxW. The call address of MessageBoxW changes each time i run the app as windows is updating my Imports table to have the correct address of MessageBoxW. So my question is how do i find the virtual addres of MessageBoxW to my imports table and also how can i use this in ollydbg? Basically I'm trying to make a code cave in assembly to call MessageBoxW again. I got fairly close once by searching the executable with a hex editor and found the position of the call, and I think I found the virtual address. But when i call that virtual address in olly and saved it to the executable, the next time i opened it the call was replaced with a bunch of DB xyz (which looked like the virtual address but why did the call get removed? Sorry if my terminology is off as i'm new to this so i'm not quite sure what to call things.

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• How Can I assign an IP address to my virtual Windows Server, so that I can start using it almost as a VPS?

  - by Nelson Symonds

  We are a small office set up with two PC's out of which one of my PCs runs 24hrs. Its almost equivalent to a small server, but right now we're in need of a server which is why I am planning to keep my machine as well as a server into a single PC. I've used VMware Workstation to create a powerful Windows Server 2008 within my PC and I want to attach it to my Network Switch through the same PC where I am hosting it. I want to use it almost like a physical server with an IP address and everything so that I can connect from one Pc to the Server directly or my applications can connect to Server straight with the IP address. How should I do this? Step by step instructions would be appreciated. Thanks in Advance, Best regards Nelson

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• Should a newcomer to Perl learn both Perl 5 and 6?

  - by M. Joanis

  Hello! I have started playing around with Perl 5 lately, and it seems very interesting. I would like to spend some time learning it more in depth when I can. My question, since Perl 6 is slowly taking place (I believe...) and is said to break backward compatibility, is this: am I better learning Perl 5 and then Perl 6, or is learning Perl 6 directly a better time investment according to you? If the changes from Perl 5 to 6 are making it hard to understand Perl 5, I should certainly start with Perl 5 to be able to read "old" scripts, then check Perl 6. There is also the "Perl 6 is not yet completely released" problem. I know there's an early adopter implementation for Perl 6, but if Perl 6 isn't officially released before some more years, I'll stick to 5 for now. I would certainly like some insight on this. Feel free to discuss related stuff. My interest in scripting languages is fairly new. Thanks!

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• Python productivity VS Java Productivity

  - by toc777

  Over on SO I came across a question regarding which platform, Java or Python is best for developing on Google AppEngine. Many people were boasting of the increased productivity gained from using Python over Java. One thing I would say about the Python vs Java productivity argument, is Java has excellent IDE's to speed up development where as Python is really lacking in this area because of its dynamic nature. So even though I prefer to use Python as a language, I don't believe it gives quite the productivity boost compared to Java especially when using a new framework. Obviously if it were Java vs Python and the only editor you could use was VIM then Python would give you a huge productivity boost but when IDE's are brought into the equation its not as clear cut. I think Java's merits are often solely evaluated on a language level and often on out dated assumptions but Java has many benefits external to the language itself, e.g the JVM (often criticized but offers huge potential), excellent IDE's and tools, huge numbers of third party libraries, platforms etc.. Question, Does Python/related dynamic languages really give the huge productivity boosts often talked about? (with consideration given to using new frameworks and working with medium to large applications).

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• Python productivity VS Java Productivity

  - by toc777

  Over on SO I came across a question regarding which platform, Java or Python is best for developing on Google AppEngine. Many people were boasting of the increased productivity gained from using Python over Java. One thing I would say about the Python vs Java productivity argument, is Java has excellent IDE's to speed up development where as Python is really lacking in this area because of its dynamic nature. So even though I prefer to use Python as a language, I don't believe it gives quite the productivity boost compared to Java especially when using a new framework. Obviously if it were Java vs Python and the only editor you could use was VIM then Python would give you a huge productivity boost but when IDE's are brought into the equation its not as clear cut. I think Java's merits are often solely evaluated on a language level and often on out dated assumptions but Java has many benefits external to the language itself, e.g the JVM (often criticized but offers huge potential), excellent IDE's and tools, huge numbers of third party libraries, platforms etc.. Question, Does Python/related dynamic languages really give the huge productivity boosts often talked about? (with consideration given to using new frameworks and working with medium to large applications).

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• Declarative programming vs. Imperative programming

  - by EpsilonVector

  I feel very comfortable with Imperative programming. I never have trouble expressing algorithmically what I want the computer to do once I figured out what is it that I want it to do. But when it comes to languages like SQL or Relational Algebra I often get stuck because my head is too used to Imperative programming. For example, suppose you have the relations band(bandName, bandCountry), venue(venueName, venueCountry), plays(bandName, venueName), and I want to write a query that says: all venueNames such that for every bandCountry there's a band from that country that plays in venue of that name. In my mind I immediately go "for each venueName iterate over all the bandCountries and for each bandCountry get the list of bands that come from it. If none of them play in venueName, go to next venueName. Else, at the end of the bandCountries iteration add venueName to the set of good venueNames". ...but you can't talk like that in SQL and I actually need to think about how to formulate this, with the intuitive Imperative solution constantly nagging in the back of my head. Did anybody else had this problem? How did you overcome this? Did you figured out a paradigm shift? Made a map from Imperative concepts to SQL concepts to translate Imperative solutions into Declarative ones? Read a good book? PS I'm not looking for a solution to the above query, I did solve it.

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• Mission critical embedded language

  - by Moe

  Maybe the question sounds a bit strange, so i'll explain a the background a little bit. Currently i'm working on a project at y university, which will be a complete on-board software for an satellite. The system is programmed in c++ on top of a real-time operating system. However, some subsystems like the attitude control system and the fault detection and a space simulation are currently only implemented in Matlab/Simulink, to prototype the algorithms efficiently. After their verification, they will be translated into c++. The complete on-board software grew very complex, and only a handful people know the whole system. Furthermore, many of the students haven't program in c++ yet and the manual memory management of c++ makes it even more difficult to write mission critical software. Of course the main system has to be implemented in c++, but i asked myself if it's maybe possible to use an embedded language to implement the subsystem which are currently written in Matlab. This embedded language should feature: static/strong typing and compiler checks to minimize runtime errors small memory usage, and relative fast runtime attitude control algorithms are mainly numerical computations, so a good numeric support would be nice maybe some sort of functional programming feature, matlab/simulink encourage you to use it too I googled a bit, but only found Lua. It looks nice, but i would not use it in mission critical software. Have you ever encountered a situation like this, or do you know any language, which could satisfies the conditions? EDIT: To clarify some things: embedded means it should be able to embed the language into the existing c++ environment. So no compiled languages like Ada or Haskell ;)

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• What language should I use for making a cross platform library?

  - by Andrei

  I want to build a SyncML parsing library (no UI) which should be able to build up messages based on information provided by the host application, fed in by the library's methods. Also, the library should to be able to do callbacks to methods in the host application. I want to be able to compile this and have it available on as many platforms as possible: Windows, Windows Phone 7 OS, OSX, iOS, Linux, Android, BlackBerry. Basically as many platforms as possible. The priority is to have this available on mobile devices. Questions: What setup should I use? (programming languages, compilers, IDE etc.) How would I compile this library for these different platforms and how would I connect to it? Any other info? e.g. articles that cover the subject of cross-platform development? I haven't done this sort of a cross-platform project before, so any available information to put me in the right direction would be welcomed. Myself, I have a background in C#/.NET and Objective-C.

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• How can I compare between web development technologies?

  - by Steve

  I would like experts to explain for me how can I compare between web development tools or technologies in order to be able to choose the right one. I'm tired from searching always in the regular way: X Technology vs Y Technology. I'm tired from peoples' biased opinions and usually I don't find a fair comparison. I have decided to put my question here about how can I compare them so you may identify to me the main standards for comparisons so I can compare them by myself and becoming able to choose the technology that is appropriate for the project I will develop. Note: in web development technologies I mean server side languages (e.g. PHP). One important requirement for me that can be defined as major one is cost efficiency and I mean that I don't care about the cost in the near future or the current cost, but what is more important for me is the cost in the future. If, for example, the site becomes one of the most 100 visited sites.   So, how can I compare the cost of different technologies for a future status of a site (such as being very famous site) so I can scale my option easily without missing a good technology like what happened with some sites when they chose not the most effective tool.

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• Unit Tests as a learning tool - a good idea?

  - by Ekkehard.Horner

  I'm interested in ways and means for learning (a) programming language(s) efficiently. I believe that using Unit Test concepts and infrastructure early in that process is a good thing, even better than starting with "Hello world". Why: To write a decent program even for a toy/restricted problem in a new language, you'll have to master many heterogenous concepts (control flow & variables & IO ...), you are tempted to glance over details just to get your program 'to work'. Putting (your understanding of) the facts about the new language in assertions with good descriptions (=success messages) enforces thinking thru/clearness/precision. Grouping topics and adding assertions to such groups is much easier than incorporation features from the 2. chapter of your "Learning X" book to your chapter 1 program. Why not: 'Real' Unit Tests are meant to output "1234 tests ok; 1 failure: saveWorld() chokes on negative input"; 'didactic' Unit Tests should output relevant facts about the new language like perl6 10-string.t # ### p5chop ... ok 13 - p5chop( "cbä" ) returns "ä" ok 14 - after that, victim is changed to "cb" # ### (p6) chop ... ok 27 - (p6) chop( "cbä" ) returns chopped copy: "cb" ok 18 - after that, victim is unchanged: "cbä" # ### chomp ... So (mis?)using Unit Tests may be counterproductive - practicing actions while learning you wouldn't use professionally. How: Writing 'didactic' Unit Tests in languages with lightweight testing systems (Perl 5/6) is easy; (mis?)using more elaborate systems (JUnit, CppUnit) may be not worth the effort or not suitable for a person just starting with a new language. So Is using Unit Tests as a learning tool a bad idea? Can the Unit Test tool(s) of your favourite language(s) used didactically? Should implementation details (eventually) be discussed here or over at stackoverflow.com?

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• What is the correlation between programming language and experience/skills of their users?

  - by Petr Pudlák

  I'm sure there is such a correlation, because experience and skill leads good programmers to picking languages that are better for them, in which they're more productive, and working in a language forms how programmers think and influences their methods and skills. Is there any research or some statistical data of this phenomenon? Perhaps this is not a purely academic question. For example, if someone is starting a new project, it could be worth considering a language (among other criteria of course) for which there is a higher chance of finding or attracting experienced programmers. Update: Please don't fixate on the last paragraph. It's not my intention to choose a language based on this criterion, and I know there are other far more important ones. My interested is mostly academic. It comes from the (subjective) observation and I wonder if someone has researched it a bit. Also, I'm talking about a correlation, not about a rule. Sure there are both great and terrible programmers in every language. Just that in general it seems to me there is a correlation.

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