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• Which .NET exception to throw for invalid database state?

  - by jslatts

  I am writing some data access code and I want to check for potentially "invalid" data states in the database. For instance, I am returning a widget out of the database and I only expect one. If I get two, I want to throw an exception. Even though referential integrity should prevent this from occurring, I do not want to depend on the DBAs never changing the schema. I would like to use the System.IO.InvalidDataException, except that I am not dealing with a file stream so it would be misleading. I ended up going with a generic applicationexception. Anyone have a better idea?

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• Fork to shell script and terminate original process with Haskell

  - by Neth

  I am currently writing a Haskell program that does some initialization work and then calls ncmpcpp. What I am trying to do is start ncmpcpp and terminate the Haskell program, so that only ncmpcpp is left (optionally, the program can keep running in the background, as long as it's unintrusive) However, even though I am able to start ncmpcpp, I cannot interact with it. I see its output, but input appears to be impossible. What I am currently doing is: import System.Process (createProcess, proc) ... spawnCurses :: [String] -> IO () spawnCurses params = do _ <- createProcess (proc "ncmpcpp" params) return () What am I doing wrong/What should I do differently?

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• Which of FILE* or ifstream has better memory usage?

  - by Viet

  I need to read fixed number of bytes from files, whose sizes are around 50MB. To be more precise, read a frame from YUV 4:2:0 CIF/QCIF files (~25KB to ~100KB per frame). Not very huge number but I don't want whole file to be in the memory. I'm using C++, in such a case, which of FILE* or ifstream has better (less/minimal) memory usage? Please kindly advise. Thanks! EDIT: I read fixed number of bytes: 25KB or 100KB (depending on QCIF/CIF format). The reading is in binary mode and forward-only. No seeking needed. No writing needed, only reading. EDIT: If identifying better of them is hard, which one does not require loading the whole file into memory?

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• Can a MAC address be used as a reliable part of a rights management (DRM) scheme?

  - by Jarrod Mosen

  We're currently writing some software that we want to protect. We thought that registering a user's MAC address in a database upon activation of the software seemed viable; we can profile and grab that with a Java applet, (is there a better way?) so getting it isn't too much of a problem. However, we want their computer to only run the application, and download application files/updates from the server when their MAC address has been verified with their one on-file. We understand that this means a lockdown to one computer, but special changes can be made on request. What would be the best way to verify their MAC address, to see if it exists in the database, and then serve them the files to run the application? (And to simply run it on subsequent requests, to prevent re-downloading.)

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• Porting library from Java to Python

  - by Mike Griffith

  I'm about to port a smallish library from Java to Python and wanted some advice (smallish ~ a few thousand lines of code). I've studied the Java code a little, and noticed some design patterns that are common in both languages. However, there were definitely some Java-only idioms (singletons, etc) present that are generally not-well-received in Python-world. I know at least one tool (j2py) exists that will turn a .java file into a .py file by walking the AST. Some initial experimentation yielded less than favorable results. Should I even be considering using an automated tool to generate some code, or are the languages different enough that any tool would create enough re-work to have justified writing from scratch? If tools aren't the devil, are there any besides j2py that can at least handle same-project import management? I don't expect any tool to match 3rd party libraries from one language to a substitute in another.

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• SQL LIKE question

  - by user176121

  I was wondering if there's a drawback (other than bad practice) to using something like this SELECT * FROM my_table WHERE id LIKE '1'; where id is an integer. I know you're supposed to use id=1 but I am writing a java program and if everything can use LIKE it'll be a lot easier for me. Also, so far, everything works fine; I get the correct query results, so if there is no drawback I will continue doing it like this. edit: I am using MySQL.

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• Maximum number of files in one ext3 directory while still getting acceptable performance?

  - by knorv

  I have an application writing to an ext3 directory which over time has grown to roughly three million files. Needless to say, reading the file listing of this directory is unbearably slow. I don't blame ext3. The proper solution would have been to let the application code write to sub-directories such as ./a/b/c/abc.ext rather than using only ./abc.ext. I'm changing to such a sub-directory structure and my question is simply: roughly how many files should I expect to store in one ext3 directory while still getting acceptable performance? What's your experience? Or in other words; assuming that I need to store three million files in the structure, how many levels deep should the ./a/b/c/abc.ext structure be? Obviously this is a question that cannot be answered exactly, but I'm looking for a ball park estimate.

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• Floating point Endianness?

  - by cake

  Hi I'm writing a client and a server for a realtime offshore simulator, and, as I have to send a lot of data through a socket, I'm using binary data to maximize the ammount of data I can send. I already know about integers endianness, and how to use htonl and ntohl to circumvent endianness issues, but my application, as almost all simulation software, deals with a lot of floats. My question is: Is there some issue of endianness whean dealing with binary formats of floating point numbers? I know that all the machines where my code will run use IEEE implementation of floating points, but is there some endianness issue when dealing with floats? Since I only have access to machines with the same endian, I cannot test this by myself. So, I'll be glad if someone can help me with this. Thanks in advance.

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• How to persist and load an object which conforms to NSCoding protocol?

  - by mystify

  I have made an class which conforms to the NSCoding protocol and does all the encode and decode stuff. For my app, I simply want to persist an object from that class to the device and the next time when the app launches, I want to load that object back into memory. Basically it's just an class which holds some user input information. For example the user starts writing a text but then quits the app. Next time I want to load that data object. I guess I need NSKeyedArchiver? Is there a good tutorial on this? How do I do that?

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• Why isn't this simple program working?

  - by user1445478

  I'm writing a very basic program that aims for the text view to display the phrase "Hello" after a button is pressed on the screen. However, I can't get this program to work; every time I run it, it says that the application has stopped unexpectedly. This is the program I wrote: public class EtudeActivityActivity extends Activity{ TextView tvResponse; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); final TextView tvResponse = (TextView) findViewById (R.id.tvResponse); } public void updateTV(View v) { tvResponse.setText("Hello"); } } Also, I inserted an android:onClick = "updateTV" into my main.xml file for the button. Thanks for any help!

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• How to copy files from local machine to server using SSH file transfer protocol?

  - by morpheous

  I have an Ubuntu 9.10 desktop machine which I use locally. I am setting up a server on a hosting provider. The server will run a very minimal version of Ubuntu server LTS (only LAMP and email server no GUI). I want to write a script (scheduled as a cron job) that will allow me to upload local files onto the server. I want to use [SFTP][1], for security reasons. I am new to shell scripting - but I guess shell scripting is the way to do this (unless I am mistaken). Can anyone provide me with the initial pointers on how to go about writing such a script, in order to SECURELY upload local files to the server? Ideally, I would like to compress the files before the transfer (to save on bandwidth) [1]: http://SSH file transfer protocol

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• Javascript/jQuery: Varying parameters on a custom function

  - by dclowd9901

  I'm writing a plugin that will allow parameters to 'set it up.' But I predict the user won't always want to set up every aspect of the function. function This_Function(a,b,c,d); For instance, maybe they'll only want to set up a and c, but not b and d (they'll just prefer to leave those as defaults). How do I write the function (or the parameters for that matter) so that the user can customize which functions they would prefer to pass? I have a feeling it involves parsing input, but I've seen many other functions with this capability. Thanks in advance for the help.

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• Force an object to be allocated on the heap

  - by Warren Seine

  A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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• Group and count in Rails

  - by alamodey

  I have this bit of code and I get an empty object. @results = PollRoles.find( :all, :select => 'option_id, count(*) count', :group => 'option_id', :conditions => ["poll_id = ?", @poll.id]) Is this the correct way of writing the query? I want a collection of records that have an option id and the number of times that option id is found in the PollRoles model. EDIT: This is how I''m iterating through the results: <% @results.each do |result| %> <% @option = Option.find_by_id(result.option_id) %> <%= @option.question %> <%= result.count %> <% end %>

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• What's the best way to implement one-dimensional collision detection?

  - by cyclotis04

  I'm writing a piece of simulation software, and need an efficient way to test for collisions along a line. The simulation is of a train crossing several switches on a track. When a wheel comes within N inches of the switch, the switch turns on, then turns off when the wheel leaves. Since all wheels are the same size, and all switches are the same size, I can represent them as a single coordinate X along the track. Switch distances and wheel distances don't change in relation to each other, once set. This is a fairly trivial problem when done through brute force by placing the X coordinates in lists, and traversing them, but I need a way to do so efficiently, because it needs to be extremely accurate, even when the train is moving at high speeds. There's a ton of tutorials on 2D collision detection, but I'm not sure the best way to go about this unique 1D scenario.

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• Advantages of using WCF to work with Sharepoint Services WSS3.0?

  - by val

  Hi folks, what is your opinion or better off your practical experience using WCF to work with WSS instead of SP web services? I am writing some custom library for our software to store and retrieve files from WSS document libraries using sharepoint web services. I am not entirely happy with the performance of the sp web services - a bit too slow in many cases. Now, microsoft claims a significant improvements in WCF over remoting and I am looking into a good way to use WCF for my file services. Any suggestions or ideas? Maybe a good source of coding practices or blogs? Thanks a lot, Val

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• What is a good reporting service for a simple database/hobbyist setup?

  - by Zombies

  I have a meager production environment running on my PC for a little application that I work on in my spare time. At this point I have the basics setup, MySQL, junit, svn... I am midway through development and I now need to generate various reports. These reports are based on what data is in the database.... Now, my question is this: Is there an existing reporting tool that accepts SQL and generates various reports (via: email, PDF, etc). Some tool which makes writing new reports easy, while also having a somewhat robust set of features. Does this software exist or must I write all of these reports myself?

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• VB.NET: SQLite to MSSQL

  - by user1736785

  I have a vb.net project that uses a SQLite database. I do this by using dataset/table adapters. The client is happy and all works well. However I have just heard that they plan on providing this product to another customer that wishes to use their MSSQL database. So I am writing this post so I can mentally prepare for this before I begin. I am not a database pro and have really enjoyed the simplicity of setting up and managing an SQLite database. So any ideas on the easiest way to support MSSQL as well? I am happy to run them parallel to each other. Can I just make a separate service / middleware that syncs the SQLite database to the MSSQL on a timer and does not care about what the main app is up to? Any pointers are appreciated.

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• natural sort of text and numbers, JavaScript

  - by ptrn

  I'm looking for the easiest way to sort an array that consists of numbers and text, and a combination of these. E.g. '123asd' '19asd' '12345asd' 'asd123' 'asd12' turns into '19asd' '123asd' '12345asd' 'asd12' 'asd123' This is going to be used in combination with the solution to another question I've asked here. The sorting function in itself works, what I need is a function that can say that that '19asd' is smaller than '123asd'. I'm writing this in JavaScript. Edit: as adormitu pointed out, what I'm looking for is a function for natural sorting

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• How do I test switching compilers from MSVS 6 to MSVS 2008?

  - by Leif

  When switching from MSVS 6 to MSVS 2008, what major differences should I look for when testing the software? I'm coming from more of a QA perspective. We have two programs that work closely together that were originally compiled in Visual C++ 6. Now one of the programs has been compiled in Visual C++ 2008 in order to use a specific CD writing routine. The other program is still compiled under MSVS 6. My manager is very concerned with this change and wants me to run tests specific to this change. Since I deal more with QA and less with development, I really have no idea where to start. I've looked for differences between the two, but nothing has given me a clear direction as far as testing is concerned. Any suggestions would be helpful.

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• How does compiling circular dependencies work?

  - by Fabio F.

  I've made the example in Java but I think (not tested) that it works in other (all?) languages. You have 2 files. First, M.java: public class MType { XType x; MType() {x = null;} } Second, another file (in the same directory), XType.java: public class XType { MType m; public XType(MType m) {this.m = m;} } Ok it's bad programming, but if you run javac XType it compiles: compiles even MType because XType needs it. But ... MType needs XType ... how does that work? How does the compiler know what is happening? Probably this is a stupid question, but I would like to know how the compiler (javac or any other compilers you know) manages that situation, not how to avoid it. I'm asking because i'm writing a precompiler and I would like to manage that situation.

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• C# filter results quarterly

  - by user339067

  Hello! I am writing a simple C# application that is handling bank savings. I want to be able to show the results on either, yearly, monthly or quarterly basic how can this be done? How can I loop through a set of results and only show every third post (if I am using quarterly) for example. In Python I can use range(1,31,3) but how is it done in C#? UPDATE 1 I want to loop 12 times (annually) and calculate the interest each loop but I only want to print the results every third loop (quarterly). How can I achieve this? Please help!

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• C# Unit Testing - Generating Mock DataContexts / LINQ -> SQL classes

  - by gav

  Hi All, I am loving the new world that is C#, I've come to a point with my toy programs where I want to start writing some unit tests. My code currently uses a database via a DatabaseDataContext object (*.dbml file), what's the best way to create a mock for this object? Given how easy it is to generate the database LINQ - SQL code and how common a request this must be I'm hoping that VS2010 has built in functionality to help with testing. If I'm way off and this must be done manually could you please enlighten me as to your preferred approach? Many Thanks, Gavin

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• Scaling a ruby script by launching multiple processes instead of using threads.

  - by Zombies

  I want to increase the throughput of a script which does net I/O (a scraper). Instead of making it multithreaded in ruby (I use the default 1.9.1 interpreter), I want to launch multiple processes. So, is there a system for doing this to where I can track when one finishes to re-launch it again so that I have X number running at any time. ALso some will run with different command args. I was thinking of writing a bash script but it sounds like a potentially bad idea if there already exists a method for doing something like this on linux.

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• how do I return to the same exact page after posting a form?

  - by William Calleja

  I'm posting data to a page called process.aspx that handles some business logic with the following code: <%@ Page Language="C#" %> <% MyData.process(Request); Response.Redirect("") %> this page I will be calling from a variety of pages. Is there some way of knowing from which page my form was submitted? I was thinking something along the lines of writing: <form id="frmSystem" method="post" action="process.aspx?page=<%= %>"> However I don't know what to write in between the <%= %> to get the current page name. Can anyone help please?

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