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• What is best practice as far as using perl-isms (idiomatic expressions) in Perl?

  - by DVK

  A couple of years back I participated in writing the best practices/coding style for our (fairly large and often Perl-using) company. It was done by a committee of "senior" Perl developers. As anything done by consensus, it had parts which everyone disagreed with. Duh. The part that rubbed wrong the most was a strong recommendation to NOT use many Perlisms (loosely defined as code idioms not present in, say C++ or Java), such as "Avoid using '... unless X;' constructs". The main rationale posited for such rules as this one was that non-Perl developers would have much harder time with the Perl code base otherwise. The assumption here I guess is that Perl code jockeys are rarer breed overall - and among new hires to the company - than non-Perlers. I was wondering whether SO has any good arguments to support or reject this logic... it is mostly academic curiosity at this point as the company's Perl coding standard is ossified and will never be revised again as far as I'm aware. P.S. Just to be clear, the question is in the context I noted - the answer for an all-Perl smaller development shop is obviously a resounding "use Perl to its maximum capability".

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• VB6 ImageList Frm Code Generation

  - by DAC

  Note: This is probably a shot in the dark, and its purely out of curiosity that I'm asking. When using the ImageList control from the Microsoft Common Control lib (mscomctl.ocx) I have found that VB6 generates FRM code that doesn't resolve to real property/method names and I am curious as to how the resolution is made. An example of the generated FRM code is given below with an ImageList containing 3 images: Begin MSComctlLib.ImageList ImageList1 BackColor = -2147483643 ImageWidth = 100 ImageHeight = 45 MaskColor = 12632256 BeginProperty Images {2C247F25-8591-11D1-B16A-00C0F0283628} NumListImages = 3 BeginProperty ListImage1 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":0054 Key = "" EndProperty BeginProperty ListImage2 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":3562 Key = "" EndProperty BeginProperty ListImage3 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":6A70 Key = "" EndProperty EndProperty End From my experience, a BeginProperty tag typically means a compound property (an object) is being assigned to, such as the Font object of most controls, for example: Begin VB.Form Form1 Caption = "Form1" ClientHeight = 10950 ClientLeft = 60 ClientTop = 450 ClientWidth = 7215 BeginProperty Font Name = "MS Serif" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = -1 'True Strikethrough = 0 'False EndProperty End Which can be easily seen to resolve to VB.Form.Font.<Property Name>. With ImageList, there is no property called Images. The GUID associated with property Images indicates type ListImages which implements interface IImages. This type makes sense, as the ImageList control has a property called ListImages which is of type IImages. Secondly, properties ListImage1, ListImage2 and ListImage3 don't exist on type IImages, but the GUID associated with these properties indicates type ListImage which implements interface IImage. This type also makes sense, as IImages is in fact a collection of IImage. What doesn't make sense to me is how VB6 makes these associations. How does VB6 know to make the association between the name Images - ListImages purely because of an associated type (provided by the GUID) - perhaps because it's the only property of that type? Secondly, how does it resolve ListImage1, ListImage2 and ListImage3 into additions to the collection IImages, and does it use the Add method? Or perhaps the ControlDefault property? Perhaps VB6 has specific knowledge of this control and no logical resolution exists?

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• What are the reasons to use dos batch programs in Windows?

  - by DVK

  Question What would be a good (ideally, technical) reason to ever program some non-trivial task in dos batch language on a modern Windows system as opposed to downloading either PowerShell, or ActiveState Perl? To be more specific, I make the following two assumptions for the duration of this question: anyone technical enough to be able to write a medium-complexity batch script is technical enough to install either of the scripting interpreters. Neither of those two present enough of a learning curve for basic batch replacement tasks that said curve would outweigh the pain of doing any remotely-non-trivial task in batch. Notes "You need a batch program for autoexec.bat" is not a valid reason. Your autoexec.bat may consist of simply calling non-batch script. If you disagree with either of my 2 assumptions above, that's fine, and I may be wrong. But my question is specifically "assuming those 2 assumptions are correct, what would be the reason to still stick with batch?" If it makes it easier to suspend disbelief (in case you disagree with me), add in a 3rd assumption that the question is limited to people who already posess at least some modicum of PowerShell or Perl experience. To re-iterate - this is not meant to be a subjective question about how easy it is to learn PSh or ASPerl compared to doing advanced batch coding. That is a separate question that is too subjective to be bothered with in this post. Background: I used to do some fairly complicated batch programming back in the elder days, and remember batch as one of the worst possble programming languages I had encountered. The idea for this question came after seeing a bunch of batch questions on SO, and trying to grok the answer of one of them out of sheer curiosity and giving up in pain after a minute, exclaiming mentally "why would anyone go through this pain instead of doing that in 1 line of Perl?" :) My own plausible answer I assume there may be an an likely DOS-compatible system, which has DOS interpreter but has no compatible PowerShell or Perl... I'm not aware of one but not completely impossible.

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• PHP Mystery Theatre - HTML Element doesn't display when served with php5, restart server with php4 a

  - by togglemedia

  Get this...I start the server in php5 and a specific HTML element ('a' element with a background image) is nowhere to be seen, I reboot the server in php4 and the HTML element is displaying properly. I boot back and forth between php5 and php4 with absolute consistent results, not displaying in php5 and displaying in php4. The thing that blows my mind is that: the HTML is consistent between boots of php5/4, so both scenarios have the necessary HTML elements the CSS is consistent between boots of php5/4, so both scenarios have the necessary CSS definitions there is an identically styled sibling element, with different class name that displays properly the problem is reproducible between browsers, between platforms. I've tested it on every possible config, Mac/Windows, IE6,7,8, FireFox, Safari etc... When the server is booted in php5 there is one HTML element that just doesn't display/render. A stab in the dark, I turned on PHP error reporting in php5 (to see if there would be any clues there) and low and behold the HTML element is now rendering in php5. I turn off PHP error reporting, and restart php5 and the HTML element is still rendering in php5, and the problem has been fixed...and I can't get the problem to reproduce. This is why my curiosity has brought me here. I just spent about four hours scratching my head trying to figure out how this could be. And now, I ask any php web dev gurus out there...what the heck was this all about?

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• Subsonic Access To App.Config Connection Strings From Referenced DLL in Powershell Script

  - by J Wynia

  I've got a DLL that contains Subsonic-generated and augmented code to access a data model. Actually, it is a merged DLL of that original assembly, Subsonic itself and a few other referenced DLL's into a single assembly, called "PowershellDataAccess.dll. However, it should be noted that I've also tried this referencing each assembly individually in the script as well and that doesn't work either. I am then attempting to use the objects and methods in that assembly. In this case, I'm accessing a class that uses Subsonic to load a bunch of records and creates a Lucene index from those records. The problem I'm running into is that the call into the Subsonic method to retrieve data from the database says it can't find the connection string. I'm pointing the AppDomain at the appropriate config file which does contain that connection string, by name. Here's the script. $ScriptDir = Get-Location [System.IO.Directory]::SetCurrentDirectory($ScriptDir) [Reflection.Assembly]::LoadFrom("PowershellDataAccess.dll") [System.AppDomain]::CurrentDomain.SetData("APP_CONFIG_FILE", "$ScriptDir\App.config") $indexer = New-Object LuceneIndexingEngine.LuceneIndexGenerator $indexer.GeneratePageTemplateIndex("PageTemplateIndex"); I went digging into Subsonic itself and the following line in Subsonic is what's looking for the connection string and throwing the exception: ConfigurationManager.ConnectionStrings[connectionStringName] So, out of curiosity, I created an assembly with a single class that has a single property that just runs that one line to retrieve the connection string name. I created a ps1 that called that assembly and hit that property. That prototype can find the connection string just fine. Anyone have any idea why Subsonic's portion can't seem to see the connection strings?

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• Explicit Type Conversion and Multiple Simple Type Specifiers

  - by James McNellis

  To value initialize an object of type T, one would do something along the lines of one of the following: T x = T(); T x((T())); My question concerns types specified by a combination of simple type specifiers, e.g., unsigned int: unsigned int x = unsigned int(); unsigned int x((unsigned int())); Visual C++ 2008 and Intel C++ Compiler 11.1 accept both of these without warnings; Comeau 4.3.10.1b2 and g++ 3.4.5 (which is, admittedly, not particularly recent) do not. According to the C++ standard (C++03 5.2.3/2, expr.type.conv): The expression T(), where T is a simple-type-specifier (7.1.5.2) for a non-array complete object type or the (possibly cv-qualified) void type, creates an rvalue of the specified type, which is value-initialized 7.1.5.2 says, "the simple type specifiers are," and follows with a list that includes unsigned and int. Therefore, given that in 5.2.3/2, "simple-type-specifier" is singular, and unsigned and int are two type specifiers, are the examples above that use unsigned int invalid? (and, if so, the followup is, is it incorrect for Microsoft and Intel to support said expressions?) This question is more out of curiosity than anything else; for all of the types specified by a combination of multiple simple type specifiers, value initialization is equivalent to zero initialization. (This question was prompted by comments in response to this answer to a question about initialization).

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• Advice for Future Programmers?

  - by Nate Zaugg

  I have a buddy that is going to be giving some presentations to high-schoolers. Specifically he asked: What would you be looking for if they approached you about work? Perhaps you are in that age group right now. What do you want to know? Perhaps you are just a few years into the workforce. What do you wish someone had told you but never did? Perhaps you have children, relatives or friends in or soon to be in that age group. What are you worried they don't know about? I'm sure there are other perspectives and questions I'm not even thinking about. I'd like to hear what you have to say about it. Here was my list: Don't be afraid to try! Don't let the perception that something is too difficult stop you from experimenting. Curiosity may have killed the cat, but an un-inquisitive person is mostly useless. Stolen from Einstein: You don't really understand something until you can explain it to your grandmother. It's never enough to be smart, you also have to work well with others. Before you can be really smart, you must learn how to learn. There will always be someone smarter than you are -- Become their buddy! Get to know great minds and learn all you can. Some knowledge can only be expressed this way. Communication, Communication, Communication! Projects rarely fail because of technical reasons and the difference between good programmers and outstanding programmers is how well they communicate. A good work ethic never goes unnoticed. Know when to ask for help and when to figure something out for yourself.

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• Mutability design patterns in Objective C and C++

  - by Mac

  Having recently done some development for iPhone, I've come to notice an interesting design pattern used a lot in the iPhone SDK, regarding object mutability. It seems the typical approach there is to define an immutable class NSFoo, and then derive from it a mutable descendant NSMutableFoo. Generally, the NSFoo class defines data members, getters and read-only operations, and the derived NSMutableFoo adds on setters and mutating operations. Being more familiar with C++, I couldn't help but notice that this seems to be a complete opposite to what I'd do when writing the same code in C++. While you certainly could take that approach, it seems to me that a more concise approach is to create a single Foo class, mark getters and read-only operations as const functions, and also implement the mutable operations and setters in the same class. You would then end up with a mutable class, but the types Foo const*, Foo const& etc all are effectively the immutable equivalent. I guess my question is, does my take on the situation make sense? I understand why Objective-C does things differently, but are there any advantages to the two-class approach in C++ that I've missed? Or am I missing the point entirely? Not an overly serious question - more for my own curiosity than anything else.

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• Draw on screen border in Commodore 64

  - by Stefano Borini

  Ok. I hope it does not get closed because I have this curiosity since 25 years and I would love to understand the trick. In the commodore 64 the border was not addressable by the 6569 VIC. All you could do was to draw pixels in the central area, the one where the cursor moved. The border was always uniform, although you could change its color with poke 53280,color if i remember correctly. Nevertheless I clearly remember games intros where the border was featured with graphics, like it was fully addressable. I tried to understand how it worked but never got to the point. legends say it was a clever use of sprites, which could, under some circumstances, be drawn on the border, but I don't know if it's an urban legend. edit: just read this from one of the provided links Sprites were multiplexed across vertical raster lines (over 8 sprites, sometimes up to 120 sprites). Until the Group Crest released Krestage 3 in May 2007 there was the common perception that no more than 8 sprites could appear at one raster line, but assigning new Y coordinates made it reappear further down the screen. This is evil.... you beat the raster and reposition the sprite before it gets there...

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• Java: How do you really force a GC using JVMTI's ForceGargabeCollection?

  - by WizardOfOdds

  I'm not looking for the usual "you can only hint the GC in Java using System.gc()" answers, this is not at all what this question is about. My questions is not subjective and is based on a reality: GC can be forced in Java for a fact. A lot of programs that we use daily do it: IntelliJ IDEA, NetBeans, VisualVM. They all can force GC to happen. How is it done? I take it they're all using JVMTI and more specifically the ForceGarbabeCollection (notice the "Force") but how can I try it for myself? http://java.sun.com/javase/6/docs/platform/jvmti/jvmti.html#ForceGarbageCollection Also note that this question is not about "why" I'd want to do this: the "why" may be "curiosity" or "we're writing a program similar to VisualVM", etc. The question is really "how do you force a GC using JVMTI's ForceGarbageCollection"? Does the JVM needs to be launched with any special parameters? Is any JNI required? If so, what code exactly? Does it only work on Sun VMs? Any complete and compilable example would be most welcome.

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• Retrieve 2 last posts for each category.

  - by Savageman

  Hello, Lets say I have 2 tables: blog_posts and categories. Each blog post belongs to only ONE category, so there is basically a foreign key between the 2 tables here. I would like to retrieve the 2 lasts posts from each category, is it possible to achieve this in a single request? GROUP BY would group everything and leave me with only one row in each category. But I want 2 of them. It would be easy to perform 1 + N query (N = number of category). First retrieve the categories. And then retrieve 2 posts from each category. I believe it would also be quite easy to perform M queries (M = number of posts I want from each category). First query selects the first post for each category (with a group by). Second query retrieves the second post for each category. etc. I'm just wondering if someone has a better solution for this. I don't really mind doing 1+N queries for that, but for curiosity and general SQL knowledge, it would be appreciated! Thanks in advance to whom can help me with this.

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• Visual Studio expression containing a term named "by" cannot be evaluated in the watch window

  - by Andrei Pana

  Consider my C++ code below: int _tmain(int argc, _TCHAR* argv[]) { int by = 10; printf("%d\n", by); int bx = 20; printf("%d\n", (by + bx)); return 0; } which works fine. The funny thing is with the "by" variable. If I try to add a watch for a simple expression that contains by, the result will be CXX0030: Error: expression cannot be evaluated. For example, on a breakpoint on return 0, if I add the following watches I get the results mentioned: by : 10 bx : 20 by + 5 : CXX0030: Error: expression cannot be evaluated bx + 5 : 25 by + bx : CXX0030: Error: expression cannot be evaluated (by) + bx : 30 by + (bx) : CXX0030: Error: expression cannot be evaluated bx + (by) : CXX0014: Error: missing operrand This happens on VS2010, VS2008 on multiple computers. So, more out of curiosity, what is happening with "by"? Is it some kind of strange operator? Why doesn't bx get the same treatment? (I've tried google on this but it is quite difficult to get some relevant hits with terms like "by")

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• HTML Element doesn't display when served with php5, restart server with php4 and Element displays.

  - by togglemedia

  Get this...I start the server in php5 and a specific HTML element ('a' element with a background image) is nowhere to be seen, I reboot the server in php4 and the HTML element is displaying properly. I boot back and forth between php5 and php4 with absolute consistent results, not displaying in php5 and displaying in php4. The thing that blows my mind is that: the HTML is consistent between boots of php5/4, so both scenarios have the necessary HTML elements the CSS is consistent between boots of php5/4, so both scenarios have the necessary CSS definitions there is an identically styled sibling element, with different class name that displays properly the problem is reproducible between browsers, between platforms. I've tested it on every possible config, Mac/Windows, IE6,7,8, FireFox, Safari etc... When the server is booted in php5 there is one HTML element that just doesn't display/render. A stab in the dark, I turned on PHP error reporting in php5 (to see if there would be any clues there) and low and behold the HTML element is now rendering in php5. I turn off PHP error reporting, and restart php5 and the HTML element is still rendering in php5, and the problem has been fixed...and I can't get the problem to reproduce. This is why my curiosity has brought me here. I just spent about four hours scratching my head trying to figure out how this could be. And now, I ask any php web dev gurus out there...what the heck was this all about?

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• How to bind a table in a dataset to a WPF datagrid in C# and XAML

  - by Jim Thomas

  I have been searching to hours for something very simple: bind a WPF datagrid to a datatable in order to see the columns at design-time. I can’t get any of the examples to work for me. Here is the C# code to populate the datatable InfoWork inside the dataset info: info = new Info(); InfoTableAdapters.InfoWorkTableAdapter adapter = new InfoTableAdapters.InfoWorkTableAdapter(); adapter.Fill(info.InfoWork); The problem is no matter how I declare ‘info’ or ‘infoWork’ Visual Studio/XAML can’t find it. I have tried: <Window.Resources> <ObjectDataProvider x:Key="infoWork" ObjectType="{x:Type local:info}" /> </Window.Resources> I have also tried this example from wpf.codeplex, but XAML doesn’t even like the “local:” keyword! <Window.Resources> <local:info x:Key="infoWork"/> </Window.Resources> There are really two main questions here: 1) How do I declare the table InfoWork in C# so that XAML can see it? I tried declaring it Public in the window class that XAML exists in with no success. 2) How do I declare the windows resource in XAML, specifcally the datatable inside the dataset? Out of curiosity, is there a reason that ItemsSource just doesn't show up as a property that be set in the properties design window?

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• Image File In Text Editor - What Are The Characters? What's the Process?

  - by TheDarkIn1978

  i'm currently in the process of conceptualizing an art piece for a gallery show next year, so this bizarre question of mine is more than just simple curiosity. if i open up an image file (a .PNG) with Text Edit or Note Pad, the file is presented in textual characters. something like this except: æº"í=™?0Ù:Ã,ÏI8^?K¯pmDHƒÃ?;wÔlD DDF›ä™èÜE[E˜ƒê?¯ƒºäeèçã?'ów+æ1ï‡ê0òHõñ?ò$úîù¥{WÎn}2*Ÿ!y(Ö!%2e9U2µ i4Õ(?=ù(›7}:É?##„G¶VfcVñ[÷D6gvrˆvéZN›=Ù=ó{púp…p?Ók‹oÃvŒÛ»{ùœóüôøW†W–VH\P?P$VTPt^lQ‹_B_S=Q™\Z[Ü)s/{]Œ_û]~¯¿¯Awu˜ùä’JÖ Í*tï[’ÎáÔ=<Æ6?~ZCWSÛpVµ?±ØŒ?nÆ^¨æ??™¡?a¥ë£1µÒÁ#?Gè)G<^mRl™m?jˆj~€"“R–Úª’?u?çO-•m˜â?ìéväˆàˆOä5ùXùûù”]¬]?]›V›œ{X{Óˆ|Ô’Èm{J?4‰Èáæõ}??~Á?óºYáœåüuRFÆ>W|^3Ñ5‰94=,<ú?|1b=2< >ö:?sÃ`¨{úf<f|ÛÖ?ãÊ íâ–âè/_÷O¬}Â?Í›§Ãd’kÃkØ?sSíS? ??øy;-6]ˆ?÷ÌÌÙåËLÈ,l÷uvzNtÆt6Ô6?O ?P?_t_|°N¸]Ÿ{ƒ{è˜3KK> ?x~ò[ñ\ÆXA?x?Ãî?X? ?…°”¸™‘jÂzÕkm~]jObµ·p1°Y‚s?&b”}s?ãËóí-»ñ”÷‰?‡v?ˆ˜WõØ£??æe~;¸n?Ooáa'aÁÎÌ-ª$ª!ª~ ?¨‹CÏpÏO/Á›œ/?80<Ë<§8 can anyone explain what is happening here? are the characters some form translation of pixel data by the text editor? maybe it is completely meaningless / an error? if not, is there a name for this type of data conversion or process?

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• Is functional GUI programming possible?

  - by eman

  I've recently caught the FP bug (trying to learn Haskell), and I've been really impressed with what I've seen so far (first-class functions, lazy evaluation, and all the other goodies). I'm no expert yet, but I've already begun to find it easier to reason "functionally" than imperatively for basic algorithms (and I'm having trouble going back where I have to). The one area where current FP seems to fall flat, however, is GUI programming. The Haskell approach seems to be to just wrap imperative GUI toolkits (such as GTK+ or wxWidgets) and to use "do" blocks to simulate an imperative style. I haven't used F#, but my understanding is that it does something similar using OOP with .NET classes. Obviously, there's a good reason for this--current GUI programming is all about IO and side effects, so purely functional programming isn't possible with most current frameworks. My question is, is it possible to have a functional approach to GUI programming? I'm having trouble imagining what this would look like in practice. Does anyone know of any frameworks, experimental or otherwise, that try this sort of thing (or even any frameworks that are designed from the ground up for a functional language)? Or is the solution to just use a hybrid approach, with OOP for the GUI parts and FP for the logic? (I'm just asking out of curiosity--I'd love to think that FP is "the future," but GUI programming seems like a pretty large hole to fill.)

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• Link click does nothing after ajax switching?

  - by Neil

  An odd case I'm trying to figure out here. I'm trying to design a mailbox system, and making some of the options ajax-y. Here's the scenario: We have a page with 2 tabs, inbox and compose. Inbox is a essentially a list of links of the form mailbox.php?msg=xxx. Clicking on the inbox or compose tabs does an ajax switch. So, let's say we're on an message page: mailbox.php?msg=123 I click on "compose" - it ajax switches to a compose form. I change my mind, click on "inbox" - it goes back to a list of messages. Note, the url has not changed at this point (all has been done through ajax). I click on the same message as before. It should go back into that message. However, nothing happens! The url it should go to (mailbox.php?msg=123) IS the url showing in the address bar, but, due to the earlier ajax activity, it's showing the inbox. Thoughts on how to resolve this? And, out of curiosity, an explanation? Normally, clicking on a link that takes you to a page you're already on will reload the page. Thanks!

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• Can a class inherit from LambdaExpression in .NET? Or is this not recommended?

  - by d.

  Consider the following code (C# 4.0): public class Foo : LambdaExpression { } This throws the following design-time error: Foo does not implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) There's absolutely no problem with public class Foo : Expression { } but, out of curiosity and for the sake of learning, I've searched in Google System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) and guess what: zero results returned (when was the last time you saw that?). Needless to say, I haven't found any documentation on this method anywhere else. As I said, one can easily inherit from Expression; on the other hand LambdaExpression, while not marked as sealed (Expression<TDelegate> inherits from it), seems to be designed to prevent inheriting from it. Is this actually the case? Does anyone out there know what this method is about? EDIT (1): More info based on the first answers - If you try to implement Accept, the editor (C# 2010 Express) automatically gives you the following stub: protected override Expression Accept(System.Linq.Expressions.ExpressionVisitor visitor) { return base.Accept(visitor); } But you still get the same error. If you try to use a parameter of type StackSpiller directly, the compiler throws a different error: System.Linq.Expressions.Compiler.StackSpiller is inaccessible due to its protection level. EDIT (2): Based on other answers, inheriting from LambdaExpression is not possible so the question as to whether or not it is recommended becomes irrelevant. I wonder if, in cases like this, the error message should be Foo cannot implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) because [reasons go here]; the current error message (as some answers prove) seems to tell me that all I need to do is implement Accept (which I can't do).

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• What does flushing thread local memory to global memory mean?

  - by Jack Griffith

  Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• Why doesn't gcc remove this check of a non-volatile variable?

  - by Thomas

  This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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• Oracle - Getting Select Count(*) from ... as an output parameter in System.Data.OracleClient

  - by cbeuker

  Greetings all, I have a question. I am trying to build a parametrized query to get me the number of rows from a table in Oracle. Rather simple. However I am an Oracle newbie.. I know in SQL Server you can do something like: Select @outputVariable = count(*) from sometable where name = @SomeOtherVariable and then you can set up an Output parameter in the System.Data.SqlClient to get the @outputVariable. Thinking that one should be able to do this in Oracle as well, I have the following query Select count(*) into :theCount from sometable where name = :SomeValue I set up my oracle parameters (using System.Data.OracleClient - yes I know it will be deprecated in .Net 4 - but that's what I am working with for now) as follows IDbCommand command = new OracleCommand(); command.CommandText = "Select count(*) into :theCount from sometable where name = :SomeValue"); command.CommandType = CommandType.Text; OracleParameter parameterTheCount = new OracleParameter(":theCount ", OracleType.Number); parameterTheCount .Direction = ParameterDirection.Output; command.Parameters.Add(parameterTheCount ); OracleParameter parameterSomeValue = new OracleParameter(":SomeValue", OracleType.VarChar, 40); parameterSomeValue .Direction = ParameterDirection.Input; parameterSomeValue .Value = "TheValueToLookFor"; command.Parameters.Add(parameterSomeValue ); command.Connection = myconnectionObject; command.ExecuteNonQuery(); int theCount = (int)parameterTheCount.Value; At which point I was hoping the count would be in the parameter parameterTheCount that I could readily access. I keep getting the error ora-01036 which http://ora-01036.ora-code.com tells me to check my binding in the sql statement. Am I messing something up in the SQL statement? Am I missing something simple elsewhere? I could just use command.ExecuteScaler() as I am only getting one item, and am probably going to end up using that, but at this point, curiosity has got the better of me. What if I had two parameters I wanted back from my query (ie: select max(ColA), min(ColB) into :max, :min.....) Thanks..

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• Any high-level languages that can use c libraries?

  - by Isaiah

  I know this question could be in vain, but it's just out of curiosity, and I'm still much a newb^^ Anyways I've been loving python for some time while learning it. My problem is obviously speed issues. I'd like to get into indie game creation, and for the short future, 2d and pygame will work. But I'd eventually like to branch into the 3d area, and python is really too slow to make anything 3d and professional. So I'm wondering if there has ever been work to create a high-level language able to import and use c libraries? I've looked at Genie and it seems to be able to use certain libraries, but I'm not sure to what extent. Will I be able to use it for openGL programing, or in a c game engine? I do know some lisp and enjoy it a lot, but there aren't a great many libraries out there for it. Which leads to the problem: I can't stand C syntax, but C has libraries galore that I could need! And game engines like irrlicht. Is there any language that can be used in place of C around C? Thanks so much guys

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• Accessing functions in a swf-file through javascript [chatroulette.com]

  - by RadiantHeart

  Lately I have been interested in the code behind chatroulette.com. As you probably know it is a peer-to-peer webcam-chat-service written in actionscript, as I understand. What i have been wondering about is weather its possible to extract the ip-address of whomever you are currently communicating with. I have seen services that do that, but they require that you install a program that runs alongside on your computer sniffing UDP-packages. I was wondering if there was a simpler method. What I do know is that the javascript on the page communicates with the application via "ExternalInterface". On this area I am pretty much a novice but according to my limited understanding you cant get information from the flash-application unless you have configured a listener for a call from javascript and then attach a callback to that event. Is this correct or can you access public functions and variables directly through javascript? There is for example a public function like this: public function get outgoingAddress():String{ return (this.__info.outgoingAddress); } Can it be accessed directly through javascript? If it cant be done so easily, is it possible to decompile the .swf-file, change it (add some functions) and recompile it and run it instead? I am hoping someone can satisfy my curiosity here. Here are two links to a decompiled version of the swf-file. The first with line numbering and one without. With line numbering ˜ 3.5 Mbyte Without line numbering ˜ 2.1 Mbyte

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• ASP.Net MVC 2 - How to set up a Cancel button with client side navigation

  - by arame3333

  Thanks to a previous question I found a useful link on multiple buttons. http://weblogs.asp.net/dfindley/archive/2009/05/31/asp-net-mvc-multiple-buttons-in-the-same-form.aspx What I want to do is have a cancel button on my page, similar to this; <button name="button" type="button" onclick="document.location.href=$('#cancelUrl').attr('href')">Cancel</button> <a id="cancelUrl" href="<%: Url.Action("Index", "Home") %>" style="display:none;"></a> However although this code works, I really want to go back to the previous page. For Web Forms I could use the javascript Back() or Go(-1) functions, but they relied on postbacks. I could of course hard code the previous page and controller as I have done above. However I am struggling to find links that explain to me how Url.Action works. Because if I do this, I also need to include an index parameter, and I am not clear how the syntax works for that. It seems odd the amount of coding to do this. Out of curiosity, I am also wondering how you TDD client side code like this.

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