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• Lucene's nested query evaluation regarding negation

  - by ponzao

  Hi, I am adding Apache Lucene support to Querydsl (which offers type-safe queries for Java) and I am having problems understanding how Lucene evaluates queries especially regarding negation in nested queries. For instance the following two queries in my opinion are semantically the same, but only the first one returns results. +year:1990 -title:"Jurassic Park" +year:1990 +(-title:"Jurassic Park") The simplified object tree in the second example is shown below. query : Query clauses : ArrayList [0] : BooleanClause "MUST" occur : BooleanClause.Occur "year:1990" query : TermQuery [1] : BooleanClause "MUST" occur : BooleanClause.Occur query : BooleanQuery clauses : ArrayList [0] : BooleanClause "MUST_NOT" occur : BooleanClause.Occur "title:"Jurassic Park"" query : TermQuery Lucene's own QueryParser seems to evaluate "AND (NOT" into the same kind of object trees. Is this a bug in Lucene or have I misunderstood Lucene's query evaluation? I am happy to give more information if necessary.

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• What is C's analogy to LabVIEW's Event Structure?

  - by SiegeX

  One programming construct I use quite a bit in LabVIEW is the Event Structure. This gives me the benefit of not having to needlessly waste CPU cycles via polling but only perform actions when an event I'm interested in is generated. As an experienced LabVIEW programmer with a decent understanding of C, I'm curious how one would go about emulating LabVIEW's event structure in C; preferably under Linux. A small code sample (like the one in the link above) illustrating how this might be done would be much appreciated. Also, if there already exists 3rd party libraries (for Linux) to add this event framework to C, that would be nice to know as well. Thanks.

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• java generics covariance

  - by soocracy42

  I am having trouble understanding the following article: http://www.ibm.com/developerworks/java/library/j-jtp01255.html Under, Generics are not covariant the author states, Because ln is a List, adding a Float to it seems perfectly legal. But if ln were aliased with li, then it would break the type-safety promise implicit in the definition of li -- that it is a list of integers, which is why generic types cannot be covariant. I can't understand the part where it says "if ln were aliased with li". What does the author means by alias?(reference?). The code snippet above the quoted line seems to illustrate WHAT is illegal in java and not WHY. It would be very helpful to me if somebody could explain with an example. Thanks in advance.

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• reinventing the wheels: Node.JS/Event-driven programming v.s. Functional Programming?

  - by ivanTheTerrible

  Now there's all the hype lately about Node.JS, an event driven framework using Javascript callbacks. To my limited understanding, its primary advantage seems to be that you don't have to wait step by step sequentially (for example, you can fetch the SQL results, while calling other functions too). So my question is: how is this different, or better than just functional languages, like CL, Haskell, Clojure etc? If not better, then why don't people just do functional languages then (instead of reinventing the wheel with Javascript)? Please note that I have none experience in either Node.JS nor functional programming. So some basic explanation can be helpful.

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• Selectively configuring Apache 2 mod_headers for Google Chrome Frame

  - by Adam Cobb

  I am currently evaluating Google Chrome Frame and so far i'm happy with it, but what i'd like to do is selectively use it for certain sections of my website. Some sections require ActiveX so need to be viewed in native IE, whereas others benefit greatly, and may end up requiring, Chrome Frame. I've currently got the following configured in my apache httpd.conf file - <IfModule mod_setenvif.c> <IfModule mod_headers.c> BrowserMatch chromeframe gcf Header append X-UA-Compatible "chrome=1" env=gcf </IfModule> </IfModule> This causes anything coming in via Apache to get the chrome frame stuff added to the headers. What I need is to make this only happen when a user visits particular URL's / particular pages, which i'm currently controlling via RewriteRules. Could anybody explain how I would go about this, as my understanding of the Apache config files isn't brilliant. Thanks.

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• Rails 3: What is the proper way to respond to REST-ful actions with JSON in rails?

  - by Damien Wilson

  Hello SO. I'm trying to make an API for my rails application using JSON responses to RESTful resource controllers. This is a new experience for me, so I'm looking for some guidance and pointers. To start things off: In a rails application, what is the "proper" way to respond with JSON to REST-ful controller methods? (create, update, destroy) Is there an idiomatic way to indicate success/failure through a JSON response? Additional information: I'm currently working with rails 3.0.beta2 I would like to avoid using a plugin or gem to do the grunt work, my goal is to gain a better understanding of how to make a rails 3 API. Links to places I could find more information on the topic would also be appreciated, some quick searching on google didn't do me much good.

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• Building webparts with Visual Studio 2010 Express

  - by MalphasWats

  Hi, I'm trying to get started with building my own webparts, planning to follow this MSDN article. I've downloaded Visual C# 2010 Express - I'm not quite at the point where I feel comfortable dropping 1000 big ones yet, and I installed Visual Web Developer 2010 Express via the WPInstaller. Following through the tutorial, aside from the fact that I don't get the option to create a "Web Control Library", a gap I filled with this article, I can't seem to find the sn.exe tool (or the "Visual Studio 2005 Command Prompt"!). I know it's not quite a direct programming related question, but I can't even get the thing going yet! Any help is appreciated. Thanks EDIT:- I think I may be jumping the gun quite considerably, I wrote a simple hello world example and tried to build it but it doesn't have any references to the Microsoft.SharePoint packages and they don't appear in my lists. Am I understanding some more research I've done (namely this) correctly, in that I have to actually have a full installation of actual SharePoint on the machine I'm developing on?

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• Why does MSBuild fail from the command line where VS2008 succeeds?

  - by sundeep

  I have an ASP.NET solution that builds just fine from within VS2008. However , it fails when i do this : MSBUILD.exe c:\path-to-sln It fails with a CS0006 error ("Metadata file 'dll_name' could not be found"). It also fails when I try with a .csproj of a project within the solution. What is VS2008 doing that MSBuild is missing ? It is my understanding that VS knows about inter assembly dependencies that MSBuild cant. Is there any way I can inform MSBuild of these? (I need MSBuild to work from the command line because I am calling it from an MSBuild-Task from within CruiseControl.Net.) Thanks in Advance. :3) (I have looked at http://stackoverflow.com/questions/280559/how-to-get-cmd-line-build-command-for-vs-solution , but still dont get it)

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• What are the use cases for closures/callback functions in Javascript?

  - by Christopher Altman

  I was listening to Crockford's talk on Javascript closures and am convinced of the benefit of information hiding, but I do not have a firm understanding of when to use callback functions. It is mostly a true statement that a person could accomplish the same functionality with or without callbacks. As someone who is writing code, what heuristics or cues should I keep in mind when determining when to use callbacks/closures? I am not looking for the blanket statement 'Closures make more secure code', rather a list of practical examples or rules of thumb for when callbacks are the right idea. Crockford's Presentation: http://www.yuiblog.com/blog/2010/04/08/video-crockonjs-5/

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• Can I redistribute Phing with non-free software?

  - by Matt1776

  I am having trouble understanding the terms of the LGPL in light of a program that is not written in C or C++. They speak of libraries being linked and 'derivitive' works. If I were to package a php program and sell it, but within the program the deployment mechanism used the phing package (full up with the entire contents as is and un modified) - would I be violating the terms of the LGPL? For example, If this was a C program that was compiled by linking the phing 'library' then the answer would be easier, it is a derivitive work and therefore unless released under the GPL will not be considered free and also a violation. But this situation is different. I am not linking and not producing a derivitive, i am simply using phing as a deployment tool to move files around and set up the enviornment. Can someone shed some light? Thank you!

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• Explain Python extensions multithreading

  - by Checkers

  Python interpreter has a Global Interpreter Lock, and it is my understanding that extensions must acquire it in a multi-threaded environment. But Boost.Python HOWTO page says the extension function must release the GIL and reacquire it on exit. I want to resist temptation to guess here, so I would like to know what should be GIL locking patterns in the following scenarios: Extension is called from python (presumably running in a python thread). And extension's background thread calls back into Py_* functions. And a final question is, why the linked document says the GIL should be released and re-acquired?

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• Unexpected behavior with AudioQueueServices callback while recording audio

  - by rcw3

  I'm recording a continuous stream of data using AudioQueueServices. It is my understanding that the callback will only be called when the buffer fills with data. In practice, the first callback has a full buffer, the 2nd callback is 3/4 full, the 3rd callback is full, the 4th is 3/4 full, and so on. These buffers are 8000 packets (recording 8khz audio) - so I should be getting back 1s of audio to the callback each time. I've confirmed that my audio queue buffer size is correct (and is somewhat confirmed by the behavior). What am I doing wrong? Should I be doing something in the AudioQueueNewInput with a different RunLoop? I tried but this didn't seem to make a difference... By the way, if I run in the debugger, each callback is full with 8000 samples - making me think this is a threading / timing thing.

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• security issue of Linux sudo command?

  - by George2

  Hello everyone, 1. I am using Red Hat Enterprise 5 Linux box. I find if a user is in /etc/sudoers file, then if the user run command with sudo, the user will run this command with root privilege (without knowing root password, the user runs sudo only need to input the user's own password in order to run a command with sudo). Is that correct understanding? 2. If yes, then is it a security hole? Since users other than root could run with root privilege? thanks in advance, George

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• Sync Framework,LINQ, and my DAL

  - by Refracted Paladin

  I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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• How do functional programming languages work?

  - by eSKay

  I was just reading this excellent post, and got some better understanding of what exactly object oriented programming is, how Java implements it in one extreme manner, and how functional programming languages are a contrast. What I was thinking is this: if functional programming languages cannot save any state, how do they do some simple stuff like reading input from a user (I mean how do they "store" it), or storing any data for that matter? For example - how would this simple C thing translate to any functional programming language, for example haskell? #include<stdio.h> int main() { int no; scanf("%d",&no); return 0; }

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• SQLCLR using the wrong version of the .NET Framework

  - by Tobias Rundbom

  During a recent restart of our development server the SQL Server started using .NET 4.0 for the SQLCLR. This means that nothing using the CLR in SQL works, or at least that's my understanding by reading these sources: http://software.intel.com/en-us/blogs/2009/10/16/sql-server-2008-sqlclr-net-framework-version/ www.sqlskills.com/BLOGS/BOBB/post/On-SQL-Server-and-NET-40.aspx All we get are error messages of this type: Msg 6517, Level 16, State 1, Line 1 Failed to create AppDomain "xxx.dbo[ddl].3". Method's type signature is not Interop compatible. Does anyone know how to solve this or how we can force SQL Server CLR to use an earlier version of the Framework?

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• Computing orientation of a square and displaying an object with the same orientation

  - by Robin

  Hi, I wrote an application which detects a square within an image. To give you a good understanding of how such an image containing such a square, in this case a marker, could look like: What I get, after the detection, are the coordinates of the four corners of my marker. Now I don't know how to display an object on my marker. The object should have the same rotation/angle/direction as the marker. Are there any papers on how to achieve that, any algorithms that I can use that proofed to be pretty solid/working? It doesn't need to be a working solution, it could be a simple description on how to achieve that or something similar. If you point me at a library or something, it should work under linux, windows is not needed but would be great in case I need to port the application at some point. I already looked at the ARToolkit but they you camera parameter files and more complex matrices while I only got the four corner points and a single image instead of a whole video / camera stream.

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• Dns.GetHostEntry returns multiple IP addresses

  - by spender

  This question probably highlights a lack of understanding of networking principals on my part, rather than a programming issue. I'm doing a lookup on a hostname using Dns.GetHostEntry This returns an IPHostEntry to me, which has an AddressList property which is an array of IPAddress. I always thought there is a 1 to 1 mapping between hostname and IP, but I'm finding that in some cases I get back several IPAddress(es) for the same host. This is a surprise to me. Which part of domain name resolution do I not understand?

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• Batch File input validation - Make sure user entered an integer

  - by B2Ben

  I'm experimenting with a DOS batch file to perform a simple operation which requires the user to enter a non-negative integer. I'm using simple batch-file techniques to get user input: @ECHO OFF SET /P UserInput=Please Enter a Number: The user can enter any text they want here, so I would like to add some routine to make sure what the user entered was a valid number. That is... they entered at least one character, and every character is a number from 0 to 9. I'd like something I can feed the UserInput into. At the end of the routine would be like an if/then that would run different statements based on whether or not it was actually a valid number. I've experimented with loops and substrings and such, but my knowledge and understanding is still slim... so any help would be appreciated. I could build an executable, and I know there are nicer ways to do things than batch files, but at least for this task I'm trying to keep it simple by using a batch file.

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• MIT vs. BSD vs. Dual License

  - by ryanve

  My understanding is that: MIT-licensed projects can be used/redistributed in BSD-licensed projects. BSD-licensed projects can be used/redistributed in MIT-licensed projects. The MIT and the BSD 2-clause licenses are essentially identical. BSD 3-clause = BSD 2-clause + the "no endorsement" clause Issuing a dual license allows users to choose from those licenses—not be bound to both. If all of the above is correct, then what is the point of using a dual MIT/BSD license? Even if the BSD refers to the 3-clause version, then can't a user legally choose to only abide by the MIT license? It seems that if you really want the "no endorsement" clause to apply then you have to license it as just BSD (not dual). If you don't care about the "no endorsement" clause, then MIT alone is sufficient and MIT/BSD is redundant. Similarly, since the MIT and BSD licenses are both "GPL-compatible" and can be redistributed in GPL-licensed projects, then dual licensing MIT/GPL also seems redundant.

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• The advantages and disadvantages of using ORM

  - by JHarley1

  Good Morning, I would like to discuss today the advantages and disadvantages of using ORM (such as ADO.NET). Advantages: Speeds-up Development - eliminates the need for repetitive SQL code. Reduces Development Time. Reduces Development Costs. Overcomes vendor specific SQL differences - the ORM knows how to write vendor specific SQL so you don't have to. Disadvantages: Loss in developer productivity whilst they learn to program with ORM. Developers loose understanding of what the code is actually doing - the developer is more in control using SQL. ORM has a tendency to be slow. ORM fail to compete against SQL queries for complex queries. In summary, I believe that the disadvantages of using an ORM (mainly the reduced time taken to perform repetitive tasks) is far outweighed by the disadvantages of ORM e.g. its difficulty to get to grips with. Can people point out were I am going wrong and suggest any further advantages/disadvantages. Many Thanks, J

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• Linux bash: when to use egrep instead of grep?

  - by Michael Mao

  Hi all : I am preparing for a Linux terminal assessment now, I tried to Google and found most resources are referring to the basic "grep" rather than the more powerful "egrep" -- well, that is at least what the professor said in lecture. I am always working with small samples so performance tuning is a thing too far away. So basically I'd like to know are there any areas where I must switch to egrep to do it in a better way? Is it safe to work with basic "grep" as for now? will there be potential risks? Sorry about my limited knowledge on Linux shell commands, the man page looks like a maze to me and honestly I haven't put much time in understanding all the features both command provide.

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• help converting sql to linq expression with count

  - by Philip

  I am trying to convert the following SQL into a LINQ expression SELECT COUNT(ID) AS Count, MyCode FROM dbo.Archive WHERE DateSent=@DateStartMonth AND DateSent<=@DateEndMonth GROUP BY MyCode and I have been trying to follow this webpage as an example http://stackoverflow.com/questions/606124/converting-sql-containing-top-count-group-and-order-to-linq-2-entities I got this so far but I am stuck on understanding the new part var res=(from p in db.Archives where (p.DateSent>= dateStartMonth) && (p.DateSent< dateToday) group p by p.MyCode into g select new { ??????MyCode = g.something?, MonthlyCount= g.Count() }); Thanks in advance for helping greatly appreciated Philip

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• Why is thread local storage so slow?

  - by dsimcha

  I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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• Building Visual studio like application, need inputs..

  - by akjoshi

  Hi, I am working on a Visual studio like application i.e. hava a tolbox, an editor and property grid similar to VS. ser can drag and drop the controls(custom and third party) to the editor window and perform operations like resize, move, align, group etc.; Properties of that control needs to be displayed in property grid and user can update them from there. As per my current understanding I will have to extend the Canvas to create my own editor and and Interface for controls which it supports; Each supported control will have to implemnt this interface so that it can be placed in our editor. Something similar to this - http://www.codeproject.com/KB/WPF/WPFDiagramDesigner_Part4.aspx Looking forward for any kind of help, comment or links.

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