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• Mercurial Subrepos, how to control which changeset I want to use for a subrepo?

  - by Lasse V. Karlsen

  I am reading up on subrepos, and have been running some tests locally, seems to work OK so far, but I have one question. How do I specify/control which changeset I want to use for a particular subrepo? For instance, let's say I have the following two projects: class library application o fourth commit o second commit, added a feature | | o third commit o initial commit | | o second commit |/ o initial commit Now, I want the class library as a subrepo of my application, but due to the immaturity of the longest branch (the one ending up as fourth commit), I want to temporarily use the "second commit" tip. How do I go about configuring that, assuming it is even possible? Here's a batch file that sets up the above two repos + adds the library as a subrepo. If you run the batch file, it will output: [C:\Temp] :test ... v4 As you can see from that last line there, it verifies the contents of the file in the class library, which is "v4" from the fourth commit. I'd like it to be "v2", and persist as "v2" until I'm ready to pull down a newer version from the class library repository. Can anyone tell me if it is possible to do what I want, and if so, what I need to do in order to lock my subrepo to the right changeset? Batch-file: @echo off if exist app rd /s /q app if exist lib rd /s /q lib if exist app-clone rd /s /q app-clone rem == app == hg init app cd app echo program>main.txt hg add main.txt hg commit -m "initial commit" echo program+feature1>main.txt hg commit -m "second commit, added a feature" cd .. rem == lib == hg init lib cd lib echo v1>lib.txt hg add lib.txt hg commit -m "initial commit" echo v2>lib.txt hg commit -m "second commit" hg update 0 echo v3>lib.txt hg commit -m "third commit" echo v4>lib.txt hg commit -m "fourth commit" cd .. rem == subrepos == cd app hg clone ..\lib lib echo lib = ..\lib >.hgsub hg add .hgsub hg commit -m "added subrepo" cd .. rem == clone == hg clone app app-clone type app-clone\lib\lib.txt

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• Is it getting to be time for C# to support compile-time macros?

  - by Robert Rossney

  Thus far, Microsoft's C# team has resisted adding formal compile-time macro capabilities to the language. There are aspects of programming with WPF that seem (to me, at least) to be creating some compelling use cases for macros. Dependency properties, for instance. It would be so nice to just be able to do something like this: [DependencyProperty] public string Foo { get; set; } and have the body of the Foo property and the static FooProperty property be generated automatically at compile time. Or, for another example an attribute like this: [NotifyPropertyChanged] public string Foo { get; set; } that would make the currently-nonexistent preprocessor produce this: private string _Foo; public string Foo { get { return _Foo; } set { _Foo = value; OnPropertyChanged("Foo"); } } You can implement change notification with PostSharp, and really, maybe PostSharp is a better answer to the question. I really don't know. Assuming that you've thought about this more than I have, which if you've thought about it at all you probably have, what do you think? (This is clearly a community wiki question and I've marked it accordingly.)

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• TCP/IP RST being sent differently in different browsers.

  - by Brian

  On Mac OS X (10.6), if I start a YouTube video download and pull the Ethernet cable for 5 or so seconds, then plug it back in, I get varying results depending on the browser. With Opera and Chrome, after I plug the cable back in the video continues to load. But with Safari and Firefox, it never does. Using Wireshark to look at the traffic, I found that Opera and Chrome simply ACK the first packet from YouTube after the cable has been plugged back in, but Safari and Firefox set the RST flag (0x4) in the TCP header and no more traffic follows. I can put a HUB in between the machine and the internet connection, the problem goes away and all four browsers continue loading the video when the cable is plugged back into the HUB. Again, looking at the Wireshark logs, it's evident that the machine doesn't see the Mulitcast connection close and there is simply a delay in the packets flowing through. So it seems that if Safari and Firefox sees a Multicast connection close, and then later see data on that same connection, they will send a RST. My question is why? What is the correct course of action, and why are 2/4 browsers doing it one way, while the other 2/4 are doing it another way? Is there somewhere in the code that I can see where this is happening in Firefox, for instance? Thank you very much.

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• Python logging in Django

  - by Jeff

  I'm developing a Django app, and I'm trying to use Python's logging module for error/trace logging. Ideally I'd like to have different loggers configured for different areas of the site. So far I've got all of this working, but one thing has me scratching my head. I have the root logger going to sys.stderr, and I have configured another logger to write to a file. This is in my settings.py file: sviewlog = logging.getLogger('MyApp.views.scans') view_log_handler = logging.FileHandler('C:\\MyApp\\logs\\scan_log.log') view_log_handler.setLevel(logging.INFO) view_log_handler.setFormatter(logging.Formatter('%(asctime)s %(name)-12s %(levelname)-8s %(message)s')) sviewlog.addHandler(view_log_handler) Seems pretty simple. Here's the problem, though: whatever I write to the sviewlog gets written to the log file twice. The root logger only prints it once. It's like addHandler() is being called twice. And when I put my code through a debugger, this is exactly what I see. The code in settings.py is getting executed twice, so two FileHandlers are created and added to the same logger instance. But why? And how do I get around this? Can anyone tell me what's going on here? I've tried moving the sviewlog logger/handler instantiation code to the file where it's used (since that actually seems like the appropriate place to me), but I have the same problem there. Most of the examples I've seen online use only the root logger, and I'd prefer to have multiple loggers.

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• how to fetch more than 1000 entities NON keybased?

  - by user291071

  If I should be approaching this problem through a different method, please suggest so. I am creating an item based collaborative filter. I populate the db with the LinkRating2 class and for each link there are more than a 1000 users that I need to call and collect their ratings to perform calculations which I then use to create another table. So I need to call more than 1000 entities for a given link. For instance lets say there are over a 1000 users rated 'link1' there will be over a 1000 instances of this class for the given link property that I need to call. How would I complete this example? class LinkRating2(db.Model): user = db.StringProperty() link = db.StringProperty() rating2 = db.FloatProperty() query =LinkRating2.all() link1 = 'link string name' a = query.filter('link = ', link1) aa = a.fetch(1000)##how would i get more than 1000 for a given link1 as shown? ##keybased over 1000 in other post example i need method for a subset though not key class MyModel(db.Expando): @classmethod def count_all(cls): """ Count *all* of the rows (without maxing out at 1000) """ count = 0 query = cls.all().order('__key__') while count % 1000 == 0: current_count = query.count() if current_count == 0: break count += current_count if current_count == 1000: last_key = query.fetch(1, 999)[0].key() query = query.filter('__key__ > ', last_key) return count

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• On counting pairs of words that differ by one letter

  - by Quintofron

  Let us consider n words, each of length k. Those words consist of letters over an alphabet (whose cardinality is n) with defined order. The task is to derive an O(nk) algorithm to count the number of pairs of words that differ by one position (no matter which one exactly, as long as it's only a single position). For instance, in the following set of words (n = 5, k = 4): abcd, abdd, adcb, adcd, aecd there are 5 such pairs: (abcd, abdd), (abcd, adcd), (abcd, aecd), (adcb, adcd), (adcd, aecd). So far I've managed to find an algorithm that solves a slightly easier problem: counting the number of pairs of words that differ by one GIVEN position (i-th). In order to do this I swap the letter at the ith position with the last letter within each word, perform a Radix sort (ignoring the last position in each word - formerly the ith position), linearly detect words whose letters at the first 1 to k-1 positions are the same, eventually count the number of occurrences of each letter at the last (originally ith) position within each set of duplicates and calculate the desired pairs (the last part is simple). However, the algorithm above doesn't seem to be applicable to the main problem (under the O(nk) constraint) - at least not without some modifications. Any idea how to solve this?

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• Silverlight: Button template with texttrimming cut off

  - by dex3703

  I'm replacing the default Button template's ContentPresenter with a TextBlock, so the text can be trimmed when it's too long. Works fine in WPF. In Silverlight the text gets pushed to one edge and cut off on the left, even when there's space on the right: Template is nothing special, just replaced the ContentPresenter with the TextBlock: <Border x:Name="bdrBackground" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" /> <Rectangle x:Name="rectMouseOverVisualElement" Opacity="0"> <Rectangle.Fill> <SolidColorBrush x:Name="rectMouseOverColor" Color="{StaticResource MouseOverItemBgColor}"/> </Rectangle.Fill> </Rectangle> <Rectangle x:Name="rectPressedVisualElement" Opacity="0" Style="{TemplateBinding Tag}"/> <TextBlock x:Name="textblock" Text="{TemplateBinding Content}" TextTrimming="WordEllipsis" TextWrapping="NoWrap" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> <Rectangle x:Name="rectDisabledVisualElement" Opacity="0" Style="{StaticResource RectangleDisabledStyle}"/> <Rectangle x:Name="rectFocusVisualElement" Opacity="0" Style="{StaticResource RectangleFocusStyle}"/> </Grid> </ControlTemplate> How do I fix this? More info: With the latest comment about HorizontalAlignment, it's clear that SL's implementation of TextTrimming differs from WPF's. In SL, TextTrimming only really works if the text is aligned left. SL isn't smart enough to align the text the way WPF does. For instance: WPF button: SL button with the textblock horizontalalignment = left: SL button with textblock horizontalalignment = center:

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• Create SQL parameters programmatically

  - by Neo

  Another annoying one for me but probably something simple. I have a number of possible where clauses for a query based on user input, my question is how can I add these programmatically? For instance: wherequery = @"WHERE fieldname = @p_FieldName AND "; if (txtValue.textLength > 0){ wherequery += "fieldname2 = @p_FieldName2 AND "; } query = @"SELECT * FROM tabe" + wherequery; sql = connection.CreateCommand(); sql.CommandText = query; How would I go about doing the parameters for that? I've tried ArrayLists, Dictionaries and a few other methods but can't find a way of doing it. Ideally I'd want to do something like this: SqlParameter[] sqlparams; wherequery = @"WHERE fieldname = @p_FieldName AND "; if (txtValue.textLength > 0){ wherequery += "fieldname2 = @p_FieldName2 AND "; sqlparams.Parameters.Add("@p_FieldName2 ", SqlDbType.VarChar).Value = txtValue.text; } query = @"SELECT * FROM tabe" + wherequery; sql = connection.CreateCommand(); sql.CommandText = query; sql.Parameters.Add(sqlparams);

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• google app engine atomic section???

  - by bokertov

  hi, Say you retrieve a set of records from the datastore (something like: select * from MyClass where reserved='false'). how do i ensure that another user doesn't set the reserved is still false? I've looked in the Transaction documentation and got shocked from google's solution which is to catch the exception and retry in a loop. Any solution that I'm missing - it's hard to believe that there's no way to have an atomic operation in this environment. (btw - i could use 'syncronize' inside the servlet but i think it's not valid as there's no way to ensure that there's only one instance of the servlet object, isn't it? same applies to static variable solution) Any idea on how to solve??? (here's the google solution: http://code.google.com/appengine/docs/java/datastore/transactions.html#Entity_Groups look at: Key k = KeyFactory.createKey("Employee", "k12345"); Employee e = pm.getObjectById(Employee.class, k); e.counter += 1; pm.makePersistent(e); This requires a transaction because the value may be updated by another user after this code fetches the object, but before it saves the modified object. Without a transaction, the user's request will use the value of counter prior to the other user's update, and the save will overwrite the new value. With a transaction, the application is told about the other user's update. If the entity is updated during the transaction, then the transaction fails with an exception. The application can repeat the transaction to use the new data. THANKS!

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• A generic C++ library that provides QtConcurrent functionality?

  - by Lucas

  QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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• Extremely Difficult Problem with ASP.Net 4.0 WebForms app using Routing

  - by dudeNumber4

  I have a completed app running in a QA environment. Everything works fine under most circumstances. If you hit a plain URL (no identifying information in the URL), you see an intro page with a button (generated by an asp LinkButton control) that posts back and directs you to another page. The markup looks the same when it fails and when it doesn't. When such a URL is followed from, e.g., Word and the default browser is IE, the intro page loads fine, but clicking the button causes an error. When not debugging, this behavior occurs every time. While debugging, the error occurs only ~ 1 in 10 times (closing the browser instance and starting over every time). When the error occurs, the intro page Page_Load fires and IsPostBack is false. Somehow, instead of a post, a get is being issued. When I run fiddler to try to analyze the actual calls (can't use firebug because it never happens using Firefox), everything works every time. I don't know whether this issue has anything to do with routing, and I've no idea even what to look at next. The strange thing is, when I debug, the intro page doesn't fully load every time. Only about 1 in 3 times does it fully load even if I've just cleared browser cache. When I run it through fiddler, it fully loads and works fine every time.

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• Is Safari on iOS 6 caching $.ajax results?

  - by user1684978

  Since the upgrade to iOS 6, we are seeing Safari's web view take the liberty of caching $.ajax calls. This is in the context of a PhoneGap application so it is using the Safari WebView. Our $.ajax calls are POST methods and we have cache set to false {cache:false}, but still this is happening. We tried manually adding a timestamp to the headers but it did not help. We did more research and found that Safari is only returning cached results for web services that have a function signature that is static and does not change from call to call. For instance, imagine a function called something like: getNewRecordID(intRecordType) This function receives the same input parameters over and over again, but the data it returns should be different every time. Must be in Apple's haste to make iOS 6 zip along impressively they got too happy with the cache settings. Has anyone else seen this behavior on iOS 6? If so, what exactly is causing it? The workaround that we found was to modify the function signature to be something like this: getNewRecordID(intRecordType, strTimestamp) and then always pass in a timestamp parameter as well, and just discard that value on the server side. This works around the issue. I hope this helps some other poor soul who spends 15 hours on this issue like I did!

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• Reordering fields in Django model

  - by Alex Lebedev

  I want to add few fields to every model in my django application. This time it's created_at, updated_at and notes. Duplicating code for every of 20+ models seems dumb. So, I decided to use abstract base class which would add these fields. The problem is that fields inherited from abstract base class come first in the field list in admin. Declaring field order for every ModelAdmin class is not an option, it's even more duplicate code than with manual field declaration. In my final solution, I modified model constructor to reorder fields in _meta before creating new instance: class MyModel(models.Model): # Service fields notes = my_fields.NotesField() created_at = models.DateTimeField(auto_now_add=True) updated_at = models.DateTimeField(auto_now=True) class Meta: abstract = True last_fields = ("notes", "created_at", "updated_at") def __init__(self, *args, **kwargs): new_order = [f.name for f in self._meta.fields] for field in self.last_fields: new_order.remove(field) new_order.append(field) self._meta._field_name_cache.sort(key=lambda x: new_order.index(x.name)) super(TwangooModel, self).__init__(*args, **kwargs) class ModelA(MyModel): field1 = models.CharField() field2 = models.CharField() #etc ... It works as intended, but I'm wondering, is there a better way to acheive my goal?

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• GADTs and Scrap your Boilerplate

  - by finnsson

  I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing GADTs. I got the GADT data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine GADTs with Scrap your Boilerplate? If so: how do you implement gunfold for a GADT?

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• Error compiling basic java code

  - by Michael Younani

  New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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• UDP security and identifying incoming data.

  - by Charles

  I have been creating an application using UDP for transmitting and receiving information. The problem I am running into is security. Right now I am using the IP/socketid in determining what data belongs to whom. However, I have been reading about how people could simply spoof their IP, then just send data as a specific IP. So this seems to be the wrong way to do it (insecure). So how else am I suppose to identify what data belongs to what users? For instance you have 10 users connected, all have specific data. The server would need to match the user data to this data we received. The only way I can see to do this is to use some sort of client/server key system and encrypt the data. I am curious as to how other applications (or games, since that's what this application is) make sure their data is genuine. Also there is the fact that encryption takes much longer to process than unencrypted. Although I am not sure by how much it will affect performance. Any information would be appreciated. Thanks.

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• Looking for resources to explain a security risk.

  - by Dave

  I've a developer which has given users the ability to download a zip archive which contains an html document which references a relative javascript file and flash document. The flash document accepts as one of it's parameters a url which is embedded in the html document. I believe that this archive is meant to be used as a means to transfer an advertisement to someone who would use the source to display the ad on their site, however the end user appears to want to view it locally. When one opens the html document the flash document is presented and when the user clicks on the flash document it redirects to this embedded url. However, if one extracts the archive on the desktop and opens the html document in a browser and clicks the flash object, nothing observable happens, they will not be redirected to the external url. I believe this is a security risk because one is transferring from the local computer zone to an external zone. I'm trying to determine the best way to explain this security risk in the simplest of terms to a very end user. They simply believe it's "broken" when it's not broken, they're being protected from a known vulnerability. The developer attempted to explain how to copy the files to a local iis instance, which I highly doubt is running on the users machine, and I do not consider this to be a viable explanation.

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• The best way to predict performance without actually porting the code?

  - by ardiyu07

  I believe there are people with the same experience with me, where he/she must give a (estimated) performance report of porting a program from sequential to parallel with some designated multicore hardwares, with a very few amount of time given. For instance, if a 10K LoC sequential program was given and executes on Intel i7-3770k (not vectorized) in 100 ms, how long would it take to run if one parallelizes the code to a Tesla C2075 with NVIDIA CUDA, given that all kinds of parallelizing optimization techniques were done? (but you're only given 2-4 days to report the performance? assume that you didn't know the algorithm at all. Or perhaps it'd be safer if we just assume that it's an impossible situation to finish the job) Therefore, I'm wondering, what most likely be the fastest way to give such performance report? Is it safe to calculate solely by the hardware's capability, such as GFLOPs peak and memory bandwidth rate? Is there a mathematical way to calculate it? If there is, please prove your method with the corresponding problem description and the algorithm, and also the target hardwares' specifications. Or perhaps there already exists such tool to (roughly) estimate code porting? (Please don't the answer: 'kill yourself is the fastest way.')

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• NUll exception in filling a querystring by mocing framework

  - by user564101

  There is a simple controller that a querystring is read in constructor of it. public class ProductController : Controller { parivate string productName; public ProductController() { productName = Request.QueryString["productname"]; } public ActionResult Index() { ViewData["Message"] = productName; return View(); } } Also I have a function in unit test that create an instance of this Controller and I fill the querystring by a Mock object like below. [TestClass] public class ProductControllerTest { [TestMethod] public void test() { // Arrange var querystring = new System.Collections.Specialized.NameValueCollection { { "productname", "sampleproduct"} }; var mock = new Mock<ControllerContext>(); mock.SetupGet(p => p.HttpContext.Request.QueryString).Returns(querystring); var controller = new ProductController(); controller.ControllerContext = mock.Object; // Act var result = controller.Index() as ViewResult; // Assert Assert.AreEqual("Index", result.ViewName); } } Unfortunately Request.QueryString["productname"] is null in constructor of ProductController when I run test unit. Is ther any way to fill a querystrin by a mocking and get it in constructor of a control?

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• Can foreground threads be aborted on application shutdown in C#.Net?

  - by Cartman

  I inherited a c# winforms app (.NET 2.0) which creates a thread upon startup in a singleton class. This thread handles messages from a messaging topic (Tibco EMS). When the app is shutdown, the thread doesn't remain the the background? How is this possible? Is there something else happening that can abort this thread? Code snippet: public class Startup { public static void main(string [] args) { MySingletonClass.Instance.Init(); // do other things below Application.Run(new MainForm()); } public class MySingletonClass { // singleton code //.. //.. private Thread t; public void Init() { t = new Thread(new ThreadStart(poll)); } private void poll() { while(true} { // listen for messages and process but there is no break clause // exceptions are also handled within to ensure control doesnt go out } } Pls. don't write to tell me this is bad code. I know it and i was going to refactor it when i realised that the app actually shutdowns correctly inspite of this aberration. So i want to understand how this is possible. Thanks for your help

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• How can I spot subtle Lisp syntax mistakes?

  - by Marius Andersen

  I'm a newbie playing around with Lisp (actually, Emacs Lisp). It's a lot of fun, except when I seem to run into the same syntax mistakes again and again. For instance, here's something I've encountered several times. I have some cond form, like (cond ((foo bar) (qux quux)) ((or corge (grault warg)) (fred) (t xyzzy))) and the default clause, which returns xyzzy, is never carried out, because it's actually nested inside the previous clause: (cond ((foo bar) (qux quux)) ((or corge (grault warg)) (fred)) (t xyzzy)) It's difficult for me to see such errors when the difference in indentation is only one space. Does this get easier with time? I also have problems when there's a large distance between the (mal-)indented line and the line it should be indented against. let forms with a lot of complex bindings, for example, or an unless form with a long conditional: (defun test () (unless (foo bar (qux quux) (or corge (grault warg) (fred)))) xyzzy) It turns out xyzzy was never inside the unless form at all: (defun test () (unless (foo bar (qux quux) (or corge (grault warg) (fred))) xyzzy)) I auto-indent habitually and use parenthesis highlighting to avoid counting parentheses. For the most part it works like a breeze, but occasionally, I discover my syntax mistakes only by debugging. What can I do?

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• Usage Rails 3.0 beta 3 without ActiveRecoord ORM

  - by Anton

  Hi everybody! Just installed Rails 3.0 beta 3 in Windows 7. And started playing with some easy examples class SignupController < ApplicationController def index @user = User.new(params[:user]) if method.post? and @user.save redirect_to :root end end end class User def initialize(params = {}) @email = params[:email] @passw = params[:passw] end def save end end <div align="center"> <% form_for :user do |form| %> <%= form.label :email %> <%= form.text_field :email %><br /> <%= form.label :password %> <%= form.text_field :password %><br /> <%= form.submit :Register! %> <% end %> </div> When I go to /signup I'm getting this error NoMethodError in SignupController#index You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.[] Is there a problem with constructor or what's wrong?Please, need your help!

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• Session scoped bean as class attribute of Spring MVC Controller

  - by Sotirios Delimanolis

  I have a User class: @Component @Scope("session") public class User { private String username; } And a Controller class: @Controller public class UserManager { @Autowired private User user; @ModelAttribute("user") private User createUser() { return user; } @RequestMapping(value = "/user") public String getUser(HttpServletRequest request) { Random r = new Random(); user.setUsername(new Double(r.nextDouble()).toString()); request.getSession().invalidate(); request.getSession(true); return "user"; } } I invalidate the session so that the next time i got to /users, I get another user. I'm expecting a different user because of user's session scope, but I get the same user. I checked in debug mode and it is the same object id in memory. My bean is declared as so: <bean id="user" class="org.synchronica.domain.User"> <aop:scoped-proxy/> </bean> I'm new to spring, so I'm obviously doing something wrong. I want one instance of User for each session. How?

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• How to lazy load a data structure (python)

  - by Anton Geraschenko

  I have some way of building a data structure (out of some file contents, say): def loadfile(FILE): return # some data structure created from the contents of FILE So I can do things like puppies = loadfile("puppies.csv") # wait for loadfile to work kitties = loadfile("kitties.csv") # wait some more print len(puppies) print puppies[32] In the above example, I wasted a bunch of time actually reading kitties.csv and creating a data structure that I never used. I'd like to avoid that waste without constantly checking if not kitties whenever I want to do something. I'd like to be able to do puppies = lazyload("puppies.csv") # instant kitties = lazyload("kitties.csv") # instant print len(puppies) # wait for loadfile print puppies[32] So if I don't ever try to do anything with kitties, loadfile("kitties.csv") never gets called. Is there some standard way to do this? After playing around with it for a bit, I produced the following solution, which appears to work correctly and is quite brief. Are there some alternatives? Are there drawbacks to using this approach that I should keep in mind? class lazyload: def __init__(self,FILE): self.FILE = FILE self.F = None def __getattr__(self,name): if not self.F: print "loading %s" % self.FILE self.F = loadfile(self.FILE) return object.__getattribute__(self.F, name) What might be even better is if something like this worked: class lazyload: def __init__(self,FILE): self.FILE = FILE def __getattr__(self,name): self = loadfile(self.FILE) # this never gets called again # since self is no longer a # lazyload instance return object.__getattribute__(self, name) But this doesn't work because self is local. It actually ends up calling loadfile every time you do anything.

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