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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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• Handler invocation speed: Objective-C vs virtual functions

  - by Kerido

  I heard that calling a handler (delegate, etc.) in Objective-C can be even faster than calling a virtual function in C++. Is it really correct? If so, how can that be? AFAIK, virtual functions are not that slow to call. At least, this is my understanding of what happens when a virtual function is called: Compute the index of the function pointer location in vtbl. Obtain the pointer to vtbl. Dereference the pointer and obtain the beginning of the array of function pointers. Offset (in pointer scale) the beginning of the array with the index value obtained on step 1. Issue a call instruction. Unfortunately, I don't know Objective-C so it's hard for me to compare performance. But at least, the mechanism of a virtual function call doesn't look that slow, right? How can something other than static function call be faster?

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• Setting the a caret in an JEditor Pane causes an exception.

  - by Elliott

  I have a JeditorPane which has some text in HTML format. When I execute the following command int len = editorPane.getText().length(); The value for len is 7473. But then I try to do the following: editorPane.setCaretPosition(4995); And I get the following exception: java.lang.IllegalArgumentException: bad position: 4995 My understanding is that I should only get this exception if the position at which I'm trying to set the caret is less than 0 or greater than the text length. It is neither. How can this be. Thank you, Elliott

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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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• How can I properly use environment variables encoded as Windows-1251 in Perl?

  - by Kartlee

  I have an environment variable set in Windows as TEST=abc£ which uses Windows-1252 code page. Now, when I run a Perl program test.pl this environment value comes properly. When I call another Perl code - test2.pl from test1.pl either by system(..) or Win32::Process, the environment comes garbled. Can someone provide information why this could be and way to resolve it? The version of perl I am using is 5.8. If my understanding is right, perl internally uses utf-8, so the initial process - test1.pl received it right from Windows-1252 → utf-8. When we call another process, should we convert back to Windows-1252 code page?

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• accessing $_SESSION when using file_get_contents in PHP

  - by hairdresser-101

  I am basic - intermediate developer using php and am a little stumped as to what I have found. I need some help in understanding how to alleviate this issue: I have a page called send.email.php which sends an email - pretty simple stuff - I pass an order id, it creates job request and sends it out. This works fine when used in the context I developed it (Use javascript to make an AJAX call to the URL and pass the order_id as a query parameter) I am now trying to reuse the exact same page in another application however I am calling it using php file_get_contents($base_url.'admin/send.email.php?order_id='.$order_id). When I call the page this way, the $_SESSION array is empty isempty() = 1. Is this because I am initiating a new session using file_get_contents and the values I stored in the $_SESSION on login are not available to me within there? Any help? Thanks

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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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• Redirecting http request to two different weblogic servers using the Weblogic proxy and Apache2

  - by Jhon

  Hello All, I've read previous posts like "Redirecting https requests to two different weblogic servers using the Weblogic proxy and Apache2". But I have a different situation and I don't think I'm understanding this to well. I have an Apache 2 server (server1) that will receive http request for my application. Then I have two more servers (server2 and server3) with Web Logic 9.2 runing on ports 7000 (server1) and 8000 (server2). I want the users to enter appname.domain.com and be redirected between the two web logic servers, always keeping appname.domain.com (this is hidding servername:port from URL). How can I manage to do that? Thanks in advanced! Jhon.

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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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• Entity Relationship Diagramming

  - by Ben Aston

  I'd like to improve my understanding of cardinality constraints in ER diagrams. I have two entities: User Location But, I want the relationship between these two entities to be many-to-many (a user can be in many locations and a location can have many users). To do this I need to introduce an association class UserLocation. Is it correct to say I now have 3 entities? If I were to draw an ER diagam of the above, would I draw in the UserLocation entity, and would the cardinality look like this? User 1 ------ * User Location * ------ 1 Location

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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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• 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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• 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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• 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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• 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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• 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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• 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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• SSRS 2008 - Textbox RTF

  - by Iceman

  Hello, We have rtf text stored in our database that looks like the following: {\rtf1\ansi\deff0{\fonttbl{\f0\fnil\fcharset0 MS Sans Serif;}{\f1\fnil MS Sans Serif;}} {\colortbl ;\red0\green0\blue0;} \viewkind4\uc1\pard\cf1\lang1033\f0\fs22 Some Text Here \f1 \par } It is my understanding that SSRS 2008 should be able to properly display this on a report. Has anyone been able to have this display correctly? Robert Bruckner's Advanced Reporting Services Blog A new feature of SSRS: Leverage the enhanced Textbox (aka "RichText") to define mixed formatting within the same textbox. In addition, HTML strings of text can be imported into the report from a database or other source. Any help is greatly appreciated.

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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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• 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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• setDelegate:self, how does it work?

  - by fuzzygoat

  I have a query regarding how delegates work. My understanding was that delegates take responsibility for doing certain tasks on behalf of another object. locationManager = [[CLLocationManager alloc] init]; [locationManager setDelegate:self]; [locationManager setDistanceFilter:kCLDistanceFilterNone]; [locationManager setDesiredAccuracy:kCLLocationAccuracyBest]; [locationManager startUpdatingLocation]; Am I right in thinking that in the example code above that the instance of CLLocationManager is created on a new thread so that it can get on with trying to find the location information it needs. When it completes its task (or encounters an error) it calls-back using the appropriate methods located in self e.g. locationManager:didUpdateToLocation:fromLocation: Essentially locationManager sends messages to self (which conforms to the correct delegate protocol) when things happen cheers gary

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• Base class for windows service

  - by user187020

  My new project has a design in which there are number windows services for performing different tasks. I have been given a task to create base class from which all of the windows service will inherit. This base class will perform common functions like creating instances of other windows services by iterating through the config file (may be like Activator.CreateInstance), do event logging on onStart, onStop etc. and may contain some more functionality. Before I start developing stuff, wondering if there is any pattern already in place or someone has good understanding of how to implement this kind of functionality. Any help appreciated.

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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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• free() on stack memory

  - by vidicon

  I'm supporting some c code on Solaris, and I've seen something weird at least I think it is: char new_login[64]; ... strcpy(new_login, (char *)login); ... free(new_login); My understanding is that since the variable is a local array the memory comes from the stack and does not need to be freed, and moreover since no malloc/calloc/realloc was used the behaviour is undefined. This is a real-time system so I think it is a waste of cycles. Am I missing something obvious?

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