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• A question about some code from TBB book, Thanks.

  - by Jackie

  I am reading the book: Intel Threading Building Blocks. I often have difficulties understanding them. For example,the following code is from the book(page 112): Node* AllocateNode() { Node* n; FreeListMutexType::scoped_lock lock; lock.acquire(FreeListMutex); n=FreeList; if(n) Freelist=n->next; lock.release(); if(!n) n=new Node(); return n; } There is other introduction regarding this code. I can not understand it. What does it means? How can I understand this book better? Thanks.

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• How do laziness and I/O work together in Haskell?

  - by Bill

  I'm trying to get a deeper understanding of laziness in Haskell. I was imagining the following snippet today: data Image = Image { name :: String, pixels :: String } image :: String -> IO Image image path = Image path <$> readFile path The appeal here is that I could simply create an Image instance and pass it around; if I need the image data it would be read lazily - if not, the time and memory cost of reading the file would be avoided: main = do image <- image "file" putStrLn $ length $ pixels image But is that how it actually works? How is laziness compatible with IO? Will readFile be called regardless of whether I access pixels image or will the runtime leave that thunk unevaluated if I never refer to it? If the image is indeed read lazily, then isn't it possible I/O actions could occur out of order? For example, what if immediately after calling image I delete the file? Now the putStrLn call will find nothing when it tries to read.

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• Adding text before footer in wordpress

  - by jake

  I've been reading the wordpress codex and it seems that if I want to add some text just before the footer shows up I should use code like this in my functions.php add_action('wp_footer', 'your_function'); function your_function() { $content = 'This is inserted at the bottom'; echo $content; } It is my understanding that the $content should show up just before the footer, but it does not show up at all. Is there another way to show up my code just before the footer ? I am with WP 2.8 but this should not matter

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• ado.net managing connections

  - by madlan

  Hi, I'm populating a listview with a list of databases on a selected SQL instance, then retrieving a value from each database (It's internal product version, column doesn't always exist) I'm calling the below function to populate the second column of the listview: item.SubItems.Add(DBVersionCheck(serverName, database.Name)) Function DBVersionCheck(ByVal SelectedInstance As String, ByVal SelectedDatabase As String) Dim m_Connection As New SqlConnection("Server=" + SelectedInstance + ";User Id=sa;Password=password;Database=" + SelectedDatabase) Dim db_command As New SqlCommand("select Setting from SystemSettings where [Setting] = 'version'", m_Connection) Try m_Connection.Open() Return db_command.ExecuteScalar().trim m_Connection.Dispose() Catch ex As Exception 'MessageBox.Show(ex.Message) Return "NA" Finally m_Connection.Dispose() End Try End Function This works fine except it's creating a connection to each database and leaving it open. My understanding is the close()\dispose() releases only the connection from the pool in ado rather than the actual connection to sql. How would I close the actual connections after I've retrieved the value? Leaving these open will create hundreds of connections to databases that will probably not be used for that session.

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• How to play Sound and Animations in MVVM

  - by user275561

  I have read alot of blogs about the best way to play sound/Animation but if possible I would like to see a simplified example on how this is done so I understand better. So to my understanding in MVVM The View--Sound and Animation The ViewModel--If some value is true, i would like to play the Sound and Animation on the view. Now How would I go about doing this. I was told to use interfaces like ISoundService and IAnimationService. Implement in the View and then do what? If possible, a workable bare bone example will help alot.

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• Using a Loader for a string of QML

  - by Robbert

  In Qt 5.3 I've been using the Loader QML element for loading screens. Now I'm trying to load a string of QML dynamically. Qt.createQmlObject enables me to do so, but I can't seem to get the Loader element to play along. Seems like Loader only takes a URL (QUrl) or component (QQmlComponent), but Qt.createQmlObject creates an object (QObject). I'm new to QML, but from my understanding components are reusable elements, similar to classes, and objects are the instances of those classes. I thus can't seem to wrap my head around why Loader wouldn't work with objects. How can I show a loading screen while (asynchronously) parsing and initializing a string of QML? Example QML code: Item { Rectangle {id: content} Loader {id: loader} Component.onCompleted: { var obj = Qt.createQmlObject('import QtQuick 2.3; Rectangle {}', content); loader.source = obj; // Throws error. } }

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• Where to start with Direct2d?

  - by ShrimpCrackers

  Interested in learning Direct2d to create a Windows 8 app, but after 2 hours of research I'm thoroughly confused. Samples like this (Creating a Simple Direct2D Application) seem to assume you know what an HWND and HRESULT is, and how the Windows API works in general. My question is this: do you need an understanding of the Win API, COM, OLE, and all this other Windows stuff in order to get a good grasp on Direct2d/3d? All the other barebones tutorials assume that you know all this stuff and I don't really know where to start. The startup D2D project in VS 2012 gives you a bunch of files but there's no main or WinMain... How does this program even start?

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• Expression Tree

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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• DurandalJS vs AngularJS?

  - by Zach

  I'm looking for a JS framework to build an SPA and found DurandalJS and AngularJS. Can anyone compare these two frameworks? I did find many articles that compares AngularJS and KnockoutJS, and they say AngularJS is more than data binding, so I think DurandalJS may be the one to compare. I did a little research on AngularJS, it is good but one thing is bad: the $ prefix does not work when minified, although there is an ugly workaround. And someone said Twitter Bootstrap does not work well with it (I didn't check). For DurandalJS, I still cannot find the samples (http://durandaljs.com/documentation/Understanding-the-Samples/), so it's hard to say. PS: are they working well with TypeScript? Best regards, Zach

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• How does this ruby custom accessor work

  - by ennuikiller

  So the method below in class_eval dynamically creates accessors for attributes defined at runtime. It can be used, for example, to create configuration objects with attributes read from a config file (and unknown until runtime). I understanding all of it except for the else branch. If I am correct the else branch returns the attribute value (val[0]) if there is one value passed in *val. However the way its written I would expect it to return an array (val) if there is more then one value passed in *var. In particular, if I have something like the following: value = 5 then from reading the code I would expect "#{@value}" to be [=,5]. However "#{@value}" returns 5 and not the array [=,5]. How is this possible? class Module def dsl_accessor(*symbols) symbols.each do |sym| class_eval %{ def #{sym}(*val) if val.empty? @#{sym} else @#{sym} = val.size == 1 ? val[0] : val end end } end end end

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• Can someone explain me implicit parameters in Scala?

  - by Oscar Reyes

  And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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• Don't see Clean solution option in Visual Studio

  - by user102533

  For one of the solutions, I don't see the Clean Solution option neither in the context menu when I right click on the solution name in the Solution Explorer nor in the Build menu. When I make any changes to the project and debug, VS never hits the break point and I get the "The breakpoint will not currently be hit. The source code is different from the original version." message. My understanding is that I need to clean the solution. For other solutions, I do see the Clean solution and I don't have the same issue.

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• copying a jar file in Apache Ant

  - by synchronicity

  I need to copy a jar file from one directory to another when my project is built. Placing the statement: <copy file="${test.dir}/MyFirstTest.jar" todir="${share.path}"/> works fine when the project is built alone, but if I clean and build the project I get a warning informing me that the ${test.dir}/ directory hasn't been created yet. If I'm understanding properly I should be able to create a 'target' and specify a dependency for this operation but I'm unsure of what dependency to specify. What series of statements do I need to use to ensure this copy will occur whether I clean and build or just build the project? Please let me know if any further clarification is needed. FYI I am using Netbeans 6.8 to build my project.

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• Compiling a C program with a specific architecture

  - by Marplesoft

  I was recently fighting some problems trying to compile an open source library on my Mac that depended on another library and got some errors about incompatible library architectures. Can somebody explain the concept behind compiling a C program for a specific architecture? I have seen the -arch compiler flag before and have seen values passed to it such as ppc, i386 and x86_64 which I assume maps to the CPU "language", but my understanding stops there. If one program uses a particular architecture, do all libraries that it loads need to be on the same architecture as well? How can I tell what architecture a given program/process is running under?

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• SlideDown then call custom function

  - by user275074

  Hi, Having difficulty understanding why my function is being called twice. I'm trying to detect when a radio button is called (intRev_yes), check if a div is empty, slide down another div and then call a custome function which dynamically creates a date field. if(this.id=="intRev_yes"){ if($('div#mainField').is(':empty')){ $('.intRevSections').slideDown('slow',function(){ current=-1; addIrField(); }); } } When I alert out at each stage, after getting to the end (i.e. addIrField()), the script seems to go back to the slideDown() section and recalls addIrField(). I can't understand why, there are no loops. current is used as an index for the date field.

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• grails metaprogramming

  - by Don

  Hi, My understanding is that there are two obvious places in a Grails app where one can do meta-programming: The init closure of Bootstrap.groovy The doWithDynamicMethods closure of a plugin The meta-programming I'm referring to here should be visible throughout the metaprogramming, typical examples include adding (or replacing) methods of 3rd party classes. String.metaClass.myCustomMethod = { /* implementation omitted */ } The disadvantage of (1), is that the metaprogramming won't be applied when the application is dynamically reloaded. The disadvantage of (2) is that I need to create and maintain an entire plugin just for the sake of a little metaprogramming. Is there a better place to do this kind of metaprogramming? Thanks, Don

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• PHP app with cookie less session does not work

  - by iama

  I am trying to use PHP session without using cookies. I have enabled session.use_trans_sid and disabled session.use_cookies in my php.ini file. I have also disabled cookies in my firefox browser. Now, when I browse my home page, I do not see the HTTP set cookie header in the server response to my page request (using Live HTTP headers). My understanding is that PHP will append session IDs to my request URL when cookies are disabled. Am I doing something wrong? BTW, I am aware using session IDs is not a recommended approach.

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• Using comet with PHP?

  - by ryeguy

  I was thinking of implementing real time chat using a PHP backend, but I ran across this comment on a site discussing comet: My understanding is that PHP is a terrible language for Comet, because Comet requires you to keep a persistent connection open to each browser client. Using mod_php this means tying up an Apache child full-time for each client which doesn’t scale at all. The people I know doing Comet stuff are mostly using Twisted Python which is designed to handle hundreds or thousands of simultaneous connections. Is this true? Or is it something that can be configured around?

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• django app organization

  - by iHeartDucks

  I have been reading some django tutorial and it seems like all the view functions have to go in a file called "views.py" and all the models go in "models.py". I fear that I might end up with a lot of view functions in my view.py file and the same is the case with models.py. Is my understanding of django apps correct? Django apps lets us separate common functionality into different apps and keep the file size of views and models to a minimum? For example: My project can contain an app for recipes (create, update, view, and search) and a friend app, the comments app, and so on. Can I still move some of my view functions to a different file? So I only have the CRUD in one single file?

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• Filtering A MySQL Result Set Based On The Return Value Of A Function

  - by Joshua

  I'm a SQL noob, and I need a little bit of help understanding the big picture of if it is possible, and if so how to go about filtering a result set based on the return value of a function which is passed one of the fields of the record. Let's say I have a table called "Numbers" with just one field: "Value". How could I correctly specify the following "pseudo-sql"?: SELECT Value FROM numbers WHERE IsPrime(Value)=true Can I accomplish such a thing, and if so, where/how do I put/store "IsPrime"? I'm using MySQL.

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• How safe am I signing into Google Spreadsheets with yeroon.net/ggplot2

  - by Farrel

  I am impressed by what I have seen of yeroon.net/ggplot2 which is a web interface for Hadley Wickham's R package ggplot2. I want to try it out on my own data. The part that has me very excited is that one can use data stored in one's own Google spreadsheet as the data. One just signs into their Google Account so that yeroon.net/ggplot2 can access the spreadsheet list. I have been hesitant to do it. If I sign in whilst on yeroon.net am I handing over my username and password to a third party? It would not be wise of me to divulge my google password to third parties since Google is fast becoming my repository of everything. How do I know if Jeroon's application is using ClientLogin or OAuth? My understanding is very basic and may be wrong but nevertheless here it is. OAuth would be better since it does not actually pass the password onto the third party application.

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• Difference between "traditional" COM and COM+ (in Component Services)

  - by kizzx2

  By the "traditional" way I mean registering the DLL in registry. There seems to be another method to set up it by going to mmc-Component Services-COM+ Applications and adding the .tlb file. I have a COM library that supports both methods. When it installs, it registers itself in the registry as a COM component and it works fine. However, when I added the .tlb file using the Component Services method, the behavior seems to be different and it starts giving out errors. I suspect it has something to do with marshaling and inter-process object transfer? (Sorry, I'm really a noob in the COM area) Can anyone point me to a good resource to clear my understanding?

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• Using MS Anti XSS library for sanitizing HTML

  - by user102533

  In the intent of preventing XSS attacks, I am updating a page in which we have a textbox that accepts HTML, stores it in a database and retrieves and renders it at a later time. My understanding is that I can sanitize the HTML using AntiXSS.GetSafeHtmlFragment() method. As long as I do this before storing the HTML in the database, am I covered? Do I need to do anything when the HTML is outputted on a web page? Also, it appears that the white list is kind of a black box. Is there a way to update this based on our requirements?

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• Windows code pages, what are they?

  - by Mike D

  I'm trying to gain a basic understanding of what is meant by a Windows code page. I kind of get the feeling it's a translation between a given 8 bit value and some 'abstraction' for a given character graphic. I made the following experiment. I created a "" character literal with two versions of the letter u with an umlaut. One created using the ALT 129 (uses code page 437) value and one using the ALT 0252 (uses code page 1252) value. When I examined the literal both characters had the value 252. Is 252 the universal 8 bit abstraction for u with an umlaut? Is it the Unicode value? Aside from keyboard input are there any library routines or system calls that use code pages? For example is there a function to translate a string using a given code table (as above for the ALT 129 value)?

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• Accessing structure elements using pointers

  - by Arun Nadesh

  Hi Everybody, Greetings! I got surprised when the following program did not crash. typedef struct _x{ int a; char b; int c; }x; main() { x *ptr=0; char *d=&ptr->b; } As per my understanding the -> operator has higher precedence over & operator. So I expected the program to crash at the below statement when we try to dereference the NULL pointer tr. char *d=&ptr->b; But the statement &ptr->b evaluates to a valid address. Could somebody please explain where I'm wrong? Thanks & Regards, Arun

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