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• Why does C++ linking use virtually no CPU? (updated)

  - by John

  On a native C++ project, linking right now can take a minute or two, yet during this time CPU drops from 100% during compilation to virtually zero. Does this mean linking is primarily a disk activity? If so, is this the main area an SSD would make big changes? But, why aren't all my OBJ files (or as many as possible) kept in RAM after compilation to avoid this? With 4Gb of RAM I should be able to save a lot of disk access and make it CPU-bound again, no? update: so the obvious follow-up is, can VC++ compiler and linker talk together better to streamline things and keep OBJ files in memory, similar to how Delphi does?

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• overriding callbacks avoiding attribute pollution

  - by pygabriel

  I've a class that has some callbacks and its own interface, something like: class Service: def __init__(self): connect("service_resolved", self.service_resolved) def service_resolved(self, a,b c): ''' This function is called when it's triggered service resolved signal and has a lot of parameters''' the connect function is for example the gtkwidget.connect, but I want that this connection is something more general, so I've decided to use a "twisted like" approach: class MyService(Service): def my_on_service_resolved(self, little_param): ''' it's a decorated version of srvice_resolved ''' def service_resolved(self,a,b,c): super(MyService,self).service_resolved(a,b,c) little_param = "something that's obtained from a,b,c" self.my_on_service_resolved(little_param) So I can use MyService by overriding my_on_service_resolved. The problem is the "attributes" pollution. In the real implementation, Service has some attributes that can accidentally be overriden in MyService and those who subclass MyService. How can I avoid attribute pollution? What I've thought is a "wrapper" like approach but I don't know if it's a good solution: class WrapperService(): def __init__(self): self._service = service_resolved # how to override self._service.service_resolved callback? def my_on_service_resolved(self,param): ''' '''

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• How to define an array inside a function in C?

  - by Arunav Dev

  So in my source file I have the folowin function: void update(state* old_state, state* measurement, uint32_t size) { state new_state[size]; //some function using measurement and old_state and returning the result in newstate arm_fadd_32(measurement,old_state,newstate,size); // rest of the code } Now the compiler throws an error saying that error#28:expression must have a constant value. I think it's due to the fact that even though inside the method the size local variable is not changing the compiler is expecting a constant while defining the size. I have tried the following: int const a = size; and then tried to reinitialize it says constant value is not known. I did some research in internet and it appears that there is no easier way without using malloc, which I don't want to since I am using the code for some embedded application. Is there a way to avoid this problem without really using malloc? Thanks in advance guys!

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• Are C++ Templates just Macros in disguise?

  - by Roddy

  I've been programming in C++ for a few years, and I've used STL quite a bit and have created my own template classes a few times to see how it's done. Now I'm trying to integrate templates deeper into my OO design, and a nagging thought keeps coming back to me: They're just a macros, really... You could implement (rather UGLY) auto_ptrs using #defines, if you really wanted to. This way of thinking about templates helps me understand how my code will actually work, but I feel that I must be missing the point somehow. Macros are meant evil incarnate, yet "template metaprogramming" is all the rage. So, what ARE the real distinctions? and how can templates avoid the dangers that #define leads you into, like Inscrutable compiler errors in places where you don't expect them? Code bloat? Difficulty in tracing code? Setting Debugger Breakpoints?

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• How can I load an MP3 or similar music file for display and anaysis in wxWdigets?

  - by Jon Cage

  I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That shuold be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of it's amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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• 16 millisecond quantization when sending/receivingtcp packets

  - by MKZ

  Hi, I have a C++ application running on windows xp 32 system sending and receiving short tcp/ip packets. Measuring (accurately) the arrival time I see a quantization of the arrival time to 16 millisecond time units. (Meaning all packets arriving are at (16 )xN milliseconds separated from each other) To avoid packet aggregation I tried to disable the NAGLE algorithm by setting the IPPROTO_TCP option to TCP_NODELAY in the socket variables but it did not help I suspect that the problem is related to the windows schedular which also have a 16 millisecond clock.. Any idea of a solution to this problem ? Thanks

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• In few words, what can be said about Func<>

  - by Richard77

  Hello, I've been seing Func< for sometime now, and I've manage to avoid it (for now). But, now it looks like I can't dodge it forever. For instance, I tried Dynamic Linq, but almost everything was in terms of Func<. I've tried one of my book (C# 2008/Deitel&Deitel) and also MSDN but I'm not getting it yet. They all jump straight in the subject. What can be said (in few words) about Func< Can I get some links on the web that can get me started on that matter? Thanks for helping

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• Unusual conversion error (string to integer) asp.net

  - by Phil

  I have my repeater item template: <ItemTemplate> <tr><td><%#Container.DataItem("Category")%></td></tr> </ItemTemplate> Hooked up to: s = "SQL that works ok on server" x = New SqlCommand(s, c) x.Parameters.Add("@contentid", SqlDbType.Int) x.Parameters("@contentid").Value = contentid c.Open() r = x.ExecuteReader If r.HasRows Then Linksrepeater.DataSource = r Linksrepeater.DataBind() End If c.Close() r.Close() When I run the code I get: Invalid Cast Exception was not handled by user code (Conversion from string "category" to type 'Integer' is not valid.) I'm not sure how / why it is trying to convert "Category" to integer as in the db it is a string. Can you please tell me how to avoid this error? thanks.

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• How to access device settings on a S60 symbian based mobile phone?

  - by TheRHCP

  Hello everyone, I recently bought a Sony Ericsson mobile phone which embeds Symbian S60 and I would like to add a missing feature myself. In fact I cannot actually disable Internet connection in an easy way when roaming, which cost me a lot of money last time I moved away ... So I would like to develop a little application that would just replace the actual Internet configuration with a fake configuration to avoid auto-connections. So what I would like to know is how can I access programmatically to my phone settings? I believe that this is possible but I do not really have a clue where to start. I know that Sony Ericsson provides a SDK to run Java applications on its customised JVM but Symbian is also providing a SDK to develop applications for S60 devices in many languages. The real questions is which SDK will provide an API able to access phone settings. This is not well documented so I am asking this question with the hope that someone here already had experience with development for Sony Ericsson/Symbian devices. Thanks.

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• How do I ensure my abstract class's function can only operate on extenders of the same type as the c

  - by incrediman

  For example, let's say this is my abstract class: abstract class A{ int x; int y; void foo(A fooMe); } ...and B and C are two classes which extend A. What I want is for B to only be able to call foo() on other Bs, and for C to only be able to call foo() on other Cs. But I want this to be out of the hands of the programmer who's extending my A class - that is, I want a way to ensure this functionality within As code alone. What can I do? (If possible) I'd like to avoid any hack or generics solution that's too messy - I still want foo to be able to be called like this, for example: B b=new B(); B bb=new B(); bb.foo(b);

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• HTML chrome:// page with select box, onChange failing

  - by Noitidart

  I have a html page. It is chrome://. I have a select box. Giving it the oncommand attribute won't work. So I have to use onchange however you have the typical problem with onchange where it doesnt work if user uses the keyboard arrows, or letters of items to change things. Is there anyway to attach onCommand to my select box? I want to avoid to use onkeyup as then i have to to validation to see if it really changed (which would require me saving previous values).

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• h3 tag text/image replacement, does this hurt seo?

  - by Mike007

  I'm trying to "replace" text with an image in all of my h3 tags. I want the image to be in the html to avoid multiple h3 classes as this is being done for a portfolio and there will be about 10 h3 tags on the page. My question is, will this be viewed as an attempt to hide, stuff keywords by google for seo purposes? If it will then does anyone know a better way to accomplish this? CSS: h3 { display: block; width: 156px; height: 44px; overflow: hidden; } Html: <h3><img src="images/project001.png" alt="Recent Projects" />Recent Projects</h3>

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• Replace html tag with a certain class

  - by fire

  I am looking for suitable replacement code that allows me replace the content inside of any HTML tag that has a certain class e.g. $class = "blah"; $content = "new content"; $html = '<div class="blah">hello world</div>'; // code to replace, $html now looks like: // <div class="blah">new content</div> Bare in mind that: It wont necessarily be a div, it could be <h2 class="blah"> The class can have more than one class and still needs to be replaced e.g. <div class="foo blah green">hello world</div> I am thinking regular expressions should be able to do this, if not I am open to other suggestions such as using the DOM class (although I would rather avoid this if possible because it has to be PHP4 compatible).

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• On which Windows versions and configurations does my C++ app run?

  - by saas

  I've built a C++ application using MSVC 2010, default compile settings (note: Using "Multithreaded" instead of "Multithreaded DLL" to avoid the Microsoft C++ runtime being needed). I used only the STL and a few, old functions from the Win32 API (Windows.h). Where will my app run? (98-7?) Can the be any differences on how my app works on different PCs? As said: It's only a simple console app. I'd be glad if you could add some additional information if you have it!

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• The Scala way to use one actor per socket connection

  - by Stefan

  I am wondering how it is possible to avoid one socket connection pr. thread in Scala. I have thought a lot about it, but I always end up with some code which is listening for incoming data for each client connection. The problem is that I want to develop an application which should simultanously handle perhaps a couple of thousand connections. However I will of course not want to create a thread for each connection because of the lack of scalability and context switching. What would be the "right" way to do this. In my world it should be possible to have one actor for each connection without the need to block one thread per actor.

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• In-memory data structure that supports boolean querying

  - by sanity

  I need to store data in memory where I map one or more key strings to an object, as follows: "green", "blue" -> object1 "red", "yellow" -> object2 I need to be able to efficiently receive a list of objects, where the strings match some boolean criteria, such as: ("red" OR "green") AND NOT "blue" I'm working in Java, so the ideal solution would be an off-the-shelf Java library. I am, however, willing to implement something from scratch if necessary. Anyone have any ideas? I'd rather avoid the overhead of an in-memory database if possible, I'm hoping for something comparable in speed to a HashMap (or at least the same order of magnitude).

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• delete all records except the id I have in a python list

  - by jay_t

  Hi all, I want to delete all records in a mysql db except the record id's I have in a list. The length of that list can vary and could easily contain 2000+ id's, ... Currently I convert my list to a string so it fits in something like this: cursor.execute("""delete from table where id not in (%s)""",(list)) Which doesn't feel right and I have no idea how long list is allowed to be, .... What's the most efficient way of doing this from python? Altering the structure of table with an extra field to mark/unmark records for deletion would be great but not an option. Having a dedicated table storing the id's would indeed be helpful then this can just be done through a sql query... but I would really like to avoid these options if possible. Thanks,

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• OpenGL multitexture tessellation

  - by user1715296

  I have to tessellate some surface in OpenGL with rectangular textures. Let it be a single triangle for simplicity. The textures touch each other by sides, and do not overlap. That is done by setting GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T to GL_CLAMP_TO_BORDER and adjusting texture coords properly. Everything goes fine while GL_TEXTURE_MIN_FILTER and GL_TEXTURE_MAG_FILTER is set to GL_NEAREST, but when I want to apply GL_LINEAR filering and/or anisotropic filtering following arifact apperas: textures border pixel's alpha gradually fall to transparent, so that line of background color is visible between neighbouring textures. How can I avoid this artifact without merging multiple textures to one while linear filtering is preserved?

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• Mysterious different conversion to string[] of seemingly same input data

  - by Roman Kuzmin

  During investigation of some problem I found that the reason was unexpected different conversion to string[] of seemingly same input data. Namely, in the code below two commands both return the same two items File1.txt and File2.txt. But conversion to string[] gives different results, see the comments. Any ideas why is it? This might be a bug. If anybody also thinks so, I’ll submit it. But it would nice to understand what’s going on and avoid traps like that. # *** WARNING # *** Make sure you do not have anything in C:\TEMP\Test # *** The code creates C:\TEMP\Test with File1.txt, File2.txt # Make C:\TEMP\Test and two test files $null = mkdir C:\TEMP\Test -Force 1 | Set-Content C:\TEMP\Test\File1.txt 1 | Set-Content C:\TEMP\Test\File2.txt # This gets just file names [string[]](Get-ChildItem C:\TEMP\Test) # This gets full file paths [string[]](Get-ChildItem C:\TEMP\Test -Include *) # Output: # File1.txt # File2.txt # C:\TEMP\Test\File1.txt # C:\TEMP\Test\File2.txt

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• Remove margin between rows of overflowing inline elements

  - by Ian

  I'm creating a tile-based game and am using block rendering to update a large list of tiles. I'm attempting to do this in the most simple manner, so I've been trying to work with HTML's default layouts. Right now I'm creating 'inline-blocks', omitting whitespace between the elements to avoid horizontal spaces in between them but when the blocks overflow and create a new line there is some vertical margining in which I do not know how to remove. Example to make this a bit clearer: http://jsfiddle.net/mLa93/13/ (Pretty much I just need to remove the spacing between the block rows while retaining the simple markup.)

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• html5 offline storage for Windows Mobile 6.1 or an alternative?

  - by SimonNet

  I understand that there are no browsers currently which support offline storage for mobile 6.1. I am trying to find a web form based solution avoiding the loss of data when my device has no connectivity. Have ruled out Gears and would like to avoid a win forms application as the forms change so often. Are there any other approaches that I should look at which are viable in C#? Are there any estimated dates for when we might see a browser for mobile 6.1 which can offer offline storage? Thanks

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• Split query result by half in TSQL (obtain 2 resultsets/tables)

  - by rubdottocom

  I have a query that returns a large number of heavy rows. When I transform this rows in a list of CustomObject I have a big memory peak, and this transformation is made by a custom dotnet framework that I can't modify. I need to retrieve a less number of rows to do "the transform" in two passes and then avoid the momery peak. How can I split the result of a query by half? I need to do it in DB layer. I thing to do a "Top count(*)/2" but how to get the other half? Thank you!

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• PHP 5.3 Namespaces should i use every PHP function with backslash?

  - by lhwparis

  Hi, im now using namespaces in PHP 5.3 now there is a fallback mechanism for functions which dont exist in the namespace. so php every time checks if the function exists in namespace and then tries to load it from global space. So what about all php internal functions? strstr for example? Should i now use every php internal function with a \ ? to avoid php first checking the namespace? is this fallback a huge performance drop? what do you think?

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• Why can't I enforce derived classes to have parameterless constructors?

  - by FrisbeeBen

  I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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• How Do I Execute A Stored Procedure From A BizTalk SendPort?

  - by kgarske

  Hello, I would like to call a stored procedure from a SendPort. I want to avoid an orchestration and instead, create a subscription to the message box based on the receive port and message type. I also need to use attributes from the received message xml as parameters for my stored procedure. My assumption is that I should use WCF-SQL adapter. However, the only examples I have found require a 20 step process and some magic/luck... oh yeah, and an orchestration. Am I crazy for thinking this should be way simpler than it seems? Can anyone provide me with resources or advice?

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