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• Installation stuck on "Installation Type" screen

  - by Andrew Latham

  I am trying to install Ubuntu 11.10 with Windows 7 from a CD. I am using an HP Pavilion dm4. I've never used Ubuntu (or any Linux) before. Everything goes alright until I get to the "Installation Type" screen. Instead of giving me options, it just has a blank menu, and all the buttons are disabled. When I click "Continue", it gives me an error saying that it can't find the root or something like that. The trial version works fine, but I can't actually install it. Everything on the trial version is really slow, presumably because everything is on the CD or the Windows partition. I did some research, but the only post I could find was http://ubuntuforums.org/showthread.php?t=1870478 Where the only advice is to format the entire drive, which I'm not willing to do. Any suggestions? I'm downloading 10.04 right now and I'm going to try with that instead. EDIT: 10.04 didn't work either. I got to the partitioning screen and got the same problem. I read some more forums, loaded up 11.10 trial from the disk, opened the Terminal and typed sudo apt-get remove dmraid and then y. Then I was actually able to see something on the "Installation type" page: "Erase disk and install Ubuntu" or "Something else". Which is weird, since Windows 7 should be installed. When I click Something Else, I get: /dev/sda /dev/sdb /dev/sdb1 (ntfs) (208 MB) (69 MB used) /dev/sdb2 (ntfs) (477542 MB) (unknown used) /dev/sdb3 (ntfs) (18085 MB) (16094 MB used) /dev/sdb4 (fat32) (4265 MB) (3084 MB used) I have no idea what any of this means. Also, my device for boot loader installation changed from /dev/sda to /dev/sda ATA SAMSUNG MZMPA032 (32.0 GB)

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• Abstract exception super type

  - by marcof

  If throwing System.Exception is considered so bad, why wasn't Exception made abstract in the first place? That way, it would not be possible to call: throw new Exception("Error occurred."); This would enforce using derived exceptions to provide more details about the error that occurred. For example, when I want to provide a custom exception hierarchy for a library, I usually declare an abstract base class for my exceptions: public abstract class CustomExceptionBase : Exception { /* some stuff here */ } And then some derived exception with a more specific purpose: public class DerivedCustomException : CustomExceptionBase { /* some more specific stuff here */ } Then when calling any library method, one could have this generic try/catch block to directly catch any error coming from the library: try { /* library calls here */ } catch (CustomExceptionBase ex) { /* exception handling */ } Is this a good practice? Would it be good if Exception was made abstract? EDIT : My point here is that even if an exception class is abstract, you can still catch it in a catch-all block. Making it abstract is only a way to forbid programmers to throw a "super-wide" exception. Usually, when you voluntarily throw an exception, you should know what type it is and why it happened. Thus enforcing to throw a more specific exception type.

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• "wrong fs type, bad option, bad superblock" error while mounting FAT Drives

  - by cshubhamrao

  I am unable to mount any fat32 or fat16 formatted usb disks under Ubuntu 13.10. The thing here to note is that it is happening only with fat formatted Disks. ntfs, ext formatted external usb disks work well (I tried formatting the same with ext4 and it worked) While mounting via nautilus: Error while mounting from terminal: root@shubham-pc:~# mount -t vfat /dev/sdc1 /media/shubham/n mount: wrong fs type, bad option, bad superblock on /dev/sdc1, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so As suggested by the error: Output from dmesg | tail root@shubham-pc:~# dmesg | tail [ 3545.482598] scsi8 : usb-storage 1-1:1.0 [ 3546.481530] scsi 8:0:0:0: Direct-Access SanDisk Cruzer 1.26 PQ: 0 ANSI: 5 [ 3546.482373] sd 8:0:0:0: Attached scsi generic sg3 type 0 [ 3546.483758] sd 8:0:0:0: [sdc] 15633408 512-byte logical blocks: (8.00 GB/7.45 GiB) [ 3546.485254] sd 8:0:0:0: [sdc] Write Protect is off [ 3546.485262] sd 8:0:0:0: [sdc] Mode Sense: 43 00 00 00 [ 3546.488314] sd 8:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA [ 3546.499820] sdc: sdc1 [ 3546.503388] sd 8:0:0:0: [sdc] Attached SCSI removable disk [ 3547.273396] FAT-fs (sdc1): IO charset iso8859-1 not found Output from fsck.vfat: root@shubham-pc:~# fsck.vfat /dev/sdc1 dosfsck 3.0.16, 01 Mar 2013, FAT32, LFN /dev/sdc1: 1 files, 1/1949978 clusters All normal Tried re-creating the whole partition table and then formatting as fat32 but to no avail so the possibility of corrupted drive is ruled out. Tried the same with around 4 Disks or so and all have the same things

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• changing body type without change of center of mass

  - by philipp

  I have an box2d project with some bodies in it, which move around without any user interaction. But if the user selects one of the bodies, he should be able to move it around just like he wants to. To keep it short, I want to change the type of the body to "kinematic" while the user controls it and back to "dynamic" afterwards. If I do so the rotation center of the body changes with the change of the type. How can I reset this? The body's fixture is created of a single b2PolygonShape, with its vertices set via SetAsArray(). Greetings philipp EDIT:: So I looked around about setting the local center of bodies. what brought me to this solution: var md = new b2MassData(); this.body.GetMassData( md ); this.body.SetType( b2body.b2_kinematicBody ); this.body.SetMassData( md ); that did not work, so I had a look at the source and found that SetMassData() always returns if the body is not "dynamic". So I tried this: var md = new b2MassData(); this._body.GetMassData( md ); this._body.SetType( b2Body.b2_kinematicBody ); this._body.m_sweep.localCenter.Set( md.center.x, md.center.y ); what actually is modifying the private data of the body. But it works and no errors appear, but can I really do this without the risk of breaking the application, or in other words, under which circumstances could this solution might cause errors? n.b.: I am using box2dweb of the latest release. Greetings philipp

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• Calculating the "power" of a player in a "Defend Your Castle" type game

  - by Jesse Emond

  I'm a making a "Defend Your Castle" type game, where each player has a castle and must send units to destroy the opponent's castle. It looks like this (and yeah, this is the actual game, not a quick paint drawing..): Now, I'm trying to implement the AI of the opponent, and I'd like to create 4 different AI levels: Easy, Normal, Hard and Hardcore. I've never made any "serious" AI before and I'd like to create a quite complete one this time. My idea is to calculate a player's "power" score, based on the current health of its castle and the individual "power" score of its units. Then, the AI would just try to keep a score close to the player's one(Easy would stay below it, Normal would stay near it and Hard would try to get above it). But I just don't know how to calculate a player's power score. There are just too many variables to take into account and I don't know how to properly use them to create one significant number(the power level). Could anyone help me out on this one? Here are the variables that should influence a player's power score: Current castle health, the unit's total health, damage, speed and attack range. Also, the player can have increased Income(the money bag), damage(the + Damage) and speed(the + speed)... How could I include them in the score? I'm really stuck here... Or is there an other way that I could implement AI for this type of game? Thanks for your precious time.

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• Generated Methods with Type Hints

  - by Ondrej Brejla

  Hi all! Today we would like to introduce you just another feature from upcoming NetBeans 7.3. It's about generating setters, constructors and type hints of their parameters. For years, you can use Insert Code action to generate setters, getters, constructors and such. Nothing new. But from NetBeans 7.3 you can generate Fluent Setters! What does it mean? Simply that $this is returned from a generated setter. This is how it looks like: But that's not everything :) As you know, before a method is generated, you have to choose a field, which will be associated with that method (in case of constructors, you choose fileds which should be initialized by that constructor). And from NetBeans 7.3, type hints are generated automatically for these parameters! But only if a proper PHPDoc is used in a corresponding field declaration, of course. Here is how it looks like. And that's all for today and as usual, please test it and if you find something strange, don't hesitate to file a new issue (product php, component Editor). Thanks a lot!

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• Choosing the correct network protocol for my type of game (its Wc3 Warlock style)

  - by Moritz

  I need to code a little game for a school project. The type of the game is like the Warcraft 3 map "Warlock", if anyone doesnt know it, here is a short description: up to ten players spawn into an arena filled with lava, the goal of each player is to push the other players into the lava with spells (basically variations of missiles, aoe nukes, moba spells etc) http://www.youtube.com/watch?v=c3PoO-gcJik&feature=related we need to provide multiplayer-support over the internet, for that reason I am looking for the best network protocol for this type of game (udp, tcp, lock step, client-server...) what the requirements are: - same/stable simulation on all clients - up to ten players - up to ~100 missiles on the field - very low latency since its reaction based (i dont know the method wc3 used, but it was playable with the old servers) what would be nice (if even possible, since the traffic might be too big): - support for soft bodies over the network (with bullet physics), but this is no real requirement I read several articles about the lock step method used for RTS games, this seems to be great, but does it fit for real-time action games too (ping-related)? If anyone has run into the same problems/questions like me, I would be very happy about any help

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• SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28

  - by pinaldave

  CXPACKET has to be most popular one of all wait stats. I have commonly seen this wait stat as one of the top 5 wait stats in most of the systems with more than one CPU. Books On-Line: Occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if contention on this wait type becomes a problem. CXPACKET Explanation: When a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. There is an organizer/coordinator thread (thread 0), which takes waits for all the threads to complete and gathers result together to present on the client’s side. The organizer thread has to wait for the all the threads to finish before it can move ahead. The Wait by this organizer thread for slow threads to complete is called CXPACKET wait. Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query. Reducing CXPACKET wait: We cannot discuss about reducing the CXPACKET wait without talking about the server workload type. OLTP: On Pure OLTP system, where the transactions are smaller and queries are not long but very quick usually, set the “Maximum Degree of Parallelism” to 1 (one). This way it makes sure that the query never goes for parallelism and does not incur more engine overhead. EXEC sys.sp_configure N'cost threshold for parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Data-warehousing / Reporting server: As queries will be running for long time, it is advised to set the “Maximum Degree of Parallelism” to 0 (zero). This way most of the queries will utilize the parallel processor, and long running queries get a boost in their performance due to multiple processors. EXEC sys.sp_configure N'cost threshold for parallelism', N'0' GO RECONFIGURE WITH OVERRIDE GO Mixed System (OLTP & OLAP): Here is the challenge. The right balance has to be found. I have taken a very simple approach. I set the “Maximum Degree of Parallelism” to 2, which means the query still uses parallelism but only on 2 CPUs. However, I keep the “Cost Threshold for Parallelism” very high. This way, not all the queries will qualify for parallelism but only the query with higher cost will go for parallelism. I have found this to work best for a system that has OLTP queries and also where the reporting server is set up. Here, I am setting ‘Cost Threshold for Parallelism’ to 25 values (which is just for illustration); you can choose any value, and you can find it out by experimenting with the system only. In the following script, I am setting the ‘Max Degree of Parallelism’ to 2, which indicates that the query that will have a higher cost (here, more than 25) will qualify for parallel query to run on 2 CPUs. This implies that regardless of the number of CPUs, the query will select any two CPUs to execute itself. EXEC sys.sp_configure N'cost threshold for parallelism', N'25' GO EXEC sys.sp_configure N'max degree of parallelism', N'2' GO RECONFIGURE WITH OVERRIDE GO Read all the post in the Wait Types and Queue series. Additionally a must read comment of Jonathan Kehayias. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest you all to read the online book for further clarification. All the discussion of Wait Stats over here is generic and it varies from system to system. It is recommended that you test this on the development server before implementing on the production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• How could I pass the type using Variables to the generic method???

  - by Sam Zhou

  Hi All, I have a generic method in c#: public IList<T> getList<T>(); When I call it as the way below? ... Type T1=metadata.ModelType; getList<T1>(); ... I got error in compiling. How could I do for it? I really need to pass the type as Variables to the generic method!

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• Is there a way to make `enum` type to be unsigned?

  - by Kirill V. Lyadvinsky

  Is there a way to make enum type to be unsigned? The following code gives me a warning about signed/unsigned comparison. enum EEE { X1 = 1 }; int main() { size_t x = 2; EEE t = X1; if ( t < x ) std::cout << "ok" << std::endl; return 0; } I've tried to force compiler to use unsigned underlying type for enum with the following: enum EEE { X1 = 1, XN = 18446744073709551615LL }; But that still gives the warning.

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• convert video file to .ogg

  - by Levan

  I've been having trouble with this because I'm new to Linux: I would like to convert different video formats to ogv. I found some terminal commands like this: ffmpeg -i input.avi -acodec libvorbis -ac 1 -b 768k output.ogg The problem with these type of commands is that they are intended to change bit rate, fps, or even resolution. I would like to just change the file format without changing anything else about the video. I looked at the man pages for ffmpeg and found some useful info but I don't know how to space command-line options. Are there any easy ways to do this? In addition, is there a command to change the bit rate so that it doesn't go over a certain rate?

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• Any way to access the type of a Scala Option declaration at runtime using reflection?

  - by Graham Lea

  So, I have a Scala class that looks like this: class TestClass { var value: Option[Int] = None } and I'm tackling a problem where I have a String value and I want to coerce it into that Option[Int] at runtime using reflection. To do so, I need to know that the field is an Option and that the type parameter of the Option is Int. What are my options for figuring out that the type of 'value' is Option[Int] at runtime (i.e. using reflection)? I have seen similar problems solved by annotating the field, e.g. @OptionType(Int.class). I'd prefer a solution that didn't require annotations on the reflection target if possible.

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• Resource interpreted as other but transferred with MIME type text/html.

  - by Zhami

  I'm transferring fragments of HTML via Ajax. Safari (4.0.5) reports: "Resource interpreted as other but transferred with MIME type text/html." The file name of the file I get has a .html extension. The server does set the header for this: Content-Type:text/html As I said, the content is a fragment of HTML, which is injected into the page (with jQuery). The contents of the file look like: <html> ... some valid html ... </html> What else might Safari need to see to make it interpret the received content as HTML? TIA.

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• How to coerce type of ActiveRecord attribute returned by :select phrase on joined table?

  - by tribalvibes

  Having trouble with AR 2.3.5, e.g.: users = User.all( :select => "u.id, c.user_id", :from => "users u, connections c", :conditions => ... ) Returns, e.g.: => [#<User id: 1000>] >> users.first.attributes => {"id"=>1000, "user_id"=>"1000"} Note that AR returns the id of the model searched as numeric but the selected user_id of the joined model as a String, although both are int(11) in the database schema. How could I better form this type of query to select columns of tables backing multiple models and retrieving their natural type rather than String ? Seems like AR is punting on this somewhere. How could I coerce the returned types at AR load time and not have to tack .to_i (etc.) onto every post-hoc access?

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• In C#: How to declare a generic Dictionary whose key and value types have a common constraint type?

  - by Marcel

  Hi all, I want to declare a dictionary that stores typed IEnumerable's of a specific type, with that exact type as key, like so: private IDictionary<T, IEnumerable<T>> _dataOfType where T: BaseClass; //does not compile! The concrete classes I want to store, all derive from BaseClass, therefore the idea to use it as constraint. The compiler complains that it expects a semicolon after the member name. If it would work, I would expect this would make the later retrieval from the dictionary simple like: IEnumerable<ConcreteData> concreteData; _sitesOfType.TryGetValue(typeof(ConcreteType), out concreteData); How to define such a dictionary?

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• How do I restrict accepting only one type in my generic method?

  - by kunjaan

  I have a generic function foo, which accepts any type and prints them out. public static <T> T foo(T... arg) { List<T> foo = Arrays.asList(arg); for (T t : foo) { System.out.println(t); } return null; } How do I make sure that the arguments received are of only 1 type. For example, {1,'a',3} should be invalid. It should either be all numbers or all characters.

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• Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

  - by Alex Kravets

  //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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• Moving windows-2003 hdd into virtual machine - with HDD shrink

  - by jm666

  Before you vote to close as exact duplicate, please read the full question. I was already read: Can I make a virtual machine out of a Windows XP physical machine? Disk2vhd,convert my PC to Hyper-V Virtual Machine Creating a Windows Virtual PC image from a Physical machine physical machine to virtual machine and place into VirtualBox BSOD trying to migrate Windows XP from a physical to a virtual machine http://en.wikipedia.org/wiki/Physical-to-Virtual and all other similiar questions here and several external sites too Unfortunately, don't find answer for my problem. I have an physical machine with 500GB HDD, on what is installed old Windows-2003 server with one server application. The application is like the windows itself, too old, no support for it today, haven't installation media and so on.. ;( On the HDD it is used only approx. 100MB (maybe less when will delete all unnecessary files). Want convert the the machine into the VirtualBox, and the VirtualBox should run on the same machine. Is possible to do this with the next steps? I can attach another HDD (via USB or internally) Boot an live Linux from CD, mount HDDs Run "something" on the Linux (the above wikipedia article have many pointer for the SW) for the conversion and store the image on the USB HDD - unfortunately, many of tools uses some specialty what exists in Windows-XP and above. No informations about Windows-2003 server, so what is an working solution for Windows-2003? try boot the virtual image with VirtualBox when it will run ok, remove the old installation, install Linux on the old 500GB hdd, copy the image and run.. The above should works (i hope), but the problems: i currently have only 320GB external USB hdd. (ofc, i can remove it from a box and enter it as internal HDD too) so, for the conversion I looking for the on the fly HDD shrink, so while moving the physical 500GB HDD need shrink it into smaller HDD - as i told above, only 100MB is used Exists something for this? (free) - or the only way is buying and larger 1TB hdd and using it for the conversion? Another question are: is anybody have real experience with windows-2003 conversion into VirtualBox? Looking for an answer from someone who really doing it and can figure out real pitfalls. (googling can do myself). exists here better approach for the solution?

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• How to convert djvu file to pdf or other more common file format?

  - by Zeta2

  I have downloaded file which is in djvu format. I want to convert it to pdf or some other more common format, so I can read the document from other devices (e.g. my phone etc). I found a conversion utility at Lizardtech, but when I converted the doc using the lizardtech software, every page had a watermark - which rendered the converted doc virtually useless. Does anyone know where I can get a free conversion utility that does not watermark the converted doc?

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• Problem with conversion of existing project to Silverlight 4

  - by derklaus

  We have a working Silverlight 3 project. After changing the target framework to Silverlight 4 the application won't start anymore. It throws an exception in the following line in the generated InitializeComponent() method: System.Windows.Application.LoadComponent(this, new System.Uri("/SLAppMain;component/App.xaml", System.UriKind.Relative)); Here is the exception (note the inner exception): System.Windows.Markup.XamlParseException occurred Message= [Line: 0 Position: 0] LineNumber=0 LinePosition=0 StackTrace: bei System.Windows.Application.LoadComponent(Object component, Uri resourceLocator) InnerException: System.TypeLoadException Message=Der Typ 'System.Security.AllowPartiallyTrustedCallersAttribute' konnte nicht aus der mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e -Assembly geladen werden. StackTrace: bei System.ModuleHandle.ResolveType(RuntimeModule module, Int32 typeToken, IntPtr* typeInstArgs, Int32 typeInstCount, IntPtr* methodInstArgs, Int32 methodInstCount, ObjectHandleOnStack type) bei System.ModuleHandle.ResolveTypeHandleInternal(RuntimeModule module, Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext) bei System.Reflection.RuntimeModule.ResolveType(Int32 metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) bei System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly, RuntimeModule decoratedModule, MetadataToken decoratedToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[] attributes, IList derivedAttributes, RuntimeType& attributeType, IRuntimeMethodInfo& ctor, Boolean& ctorHasParameters, Boolean& isVarArg) bei System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeModule decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean mustBeInheritable, IList derivedAttributes, Boolean isDecoratedTargetSecurityTransparent) bei System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeModule decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean isDecoratedTargetSecurityTransparent) bei System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeAssembly assembly, RuntimeType caType) bei System.Reflection.RuntimeAssembly.GetCustomAttributes(Type attributeType, Boolean inherit) bei System.Attribute.GetCustomAttributes(Assembly element, Type attributeType, Boolean inherit) bei MS.Internal.XamlSchemaContext.ProcessXmlnsDefinitions(Assembly assembly, String assemblyName) bei MS.Internal.XamlSchemaContext.EnsureManagedAssemblyAttributesLoaded() InnerException: The problem is that the type System.Security.AllowPartiallyTrustedCallersAttribute is not contained in the Silverlight version of mscorlib.dll. I have no idea how to fix this nor where to look for causes. Has anyone encountered this problem? What could possibly cause this error?

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• Why this Either-monad code does not type check?

  - by pf_miles

  instance Monad (Either a) where return = Left fail = Right Left x >>= f = f x Right x >>= _ = Right x this code frag in 'baby.hs' caused the horrible compilation error: Prelude> :l baby [1 of 1] Compiling Main ( baby.hs, interpreted ) baby.hs:2:18: Couldn't match expected type `a1' against inferred type `a' `a1' is a rigid type variable bound by the type signature for `return' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the expression: Left In the definition of `return': return = Left In the instance declaration for `Monad (Either a)' baby.hs:3:16: Couldn't match expected type `[Char]' against inferred type `a1' `a1' is a rigid type variable bound by the type signature for `fail' at <no location info> Expected type: String Inferred type: a1 In the expression: Right In the definition of `fail': fail = Right baby.hs:4:26: Couldn't match expected type `a1' against inferred type `a' `a1' is a rigid type variable bound by the type signature for `>>=' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the first argument of `f', namely `x' In the expression: f x In the definition of `>>=': Left x >>= f = f x baby.hs:5:31: Couldn't match expected type `b' against inferred type `a' `b' is a rigid type variable bound by the type signature for `>>=' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the first argument of `Right', namely `x' In the expression: Right x In the definition of `>>=': Right x >>= _ = Right x Failed, modules loaded: none. why this happen? and how could I make this code compile ? thanks for any help~

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• Generic property- specify the type at runtime

  - by Lirik

  I was reading a question on making a generic property, but I'm a little confused at by the last example from the first answer (I've included the relevant code below): You have to know the type at compile time. If you don't know the type at compile time then you must be storing it in an object, in which case you can add the following property to the Foo class: public object ConvertedValue { get { return Convert.ChangeType(Value, Type); } } That's seems strange: it's converting the value to the specified type, but it's returning it as an object when the value was stored as an object. Doesn't the returned object still require un-boxing? If it does, then why bother with the conversion of the type? I'm also trying to make a generic property whose type will be determined at run time: public class Foo { object Value {get;set;} Type ValType{get;set;} Foo(object value, Type type) { Value = value; ValType = type; } // I need a property that is actually // returned as the specified value type... public object ConvertedValue { get { return Convert.ChangeType(Value, ValType); } } } Is it possible to make a generic property? Does the return property still require unboxing after it's accessed?

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• Conversion failed when converting the varchar value to int

  - by onedaywhen

  Microsoft SQL Server 2008 (SP1), getting an unexpected 'Conversion failed' error. Not quite sure how to describe this problem, so below is a simple example. The CTE extracts the numeric portion of certain IDs using a search condition to ensure a numeric portion actually exists. The CTE is then used to find the lowest unused sequence number (kind of): CREATE TABLE IDs (ID CHAR(3) NOT NULL UNIQUE); INSERT INTO IDs (ID) VALUES ('A01'), ('A02'), ('A04'), ('ERR'); WITH ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); The error is, 'Conversion failed when converting the varchar value 'RR' to data type int.' I can't understand why the value ID = 'ERR' should be being considered for conversion because the predicate ID LIKE 'A[0-9][0-9]' should have removed the invalid row from the resultset. When the base table is substituted with an equivalent CTE the problem goes away i.e. WITH IDs (ID) AS ( SELECT 'A01' UNION ALL SELECT 'A02' UNION ALL SELECT 'A04' UNION ALL SELECT 'ERR' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); Why would a base table cause this error? Is this a known issue? UPDATE @sgmoore: no, doing the filtering in one CTE and the casting in another CTE still results in the same error e.g. WITH FilteredIDs (ID) AS ( SELECT ID FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM FilteredIDs ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 );

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• Event type property lost in IE-8

  - by Channel72

  I've noticed a strange Javascript error which only seems to happen on Internet Explorer 8. Basically, on IE-8 if you have an event handler function which captures the event object in a closure, the event "type" property seems to become invalidated from within the closure. Here's a simple code snippet which reproduces the error: <html> <head> <script type = "text/javascript"> function handleClickEvent(ev) { ev = (ev || window.event); alert(ev.type); window.setTimeout(function() { alert(ev.type); // Causes error on IE-8 }, 20); } function foo() { var query = document.getElementById("query"); query.onclick = handleClickEvent; } </script> </head> <body> <input id = "query" type = "submit"> <script type = "text/javascript"> foo(); </script> </body> </html> So basically, what happens here is that within the handleClickEvent function, we have the event object ev. We call alert(ev.type) and we see the event type is "click". So far, so good. But then when we capture the event object in a closure, and then call alert(ev.type) again from within the closure, now all of a sudden Internet Explorer 8 errors, saying "Member not found" because of the expression ev.type. It seems as though the type property of the event object is mysteriously gone after we capture the event object in a closure. I tested this code snippet on Firefox, Safari and Chrome, and none of them report an error condition. But in IE-8, the event object seems to become somehow invalidated after it's captured in the closure. Question: Why is this happening in IE-8, and is there any workaround?

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• Make conversion to a native type explicit in C++

  - by Tal Pressman

  I'm trying to write a class that implements 64-bit ints for a compiler that doesn't support long long, to be used in existing code. Basically, I should be able to have a typedef somewhere that selects whether I want to use long long or my class, and everything else should compile and work. So, I obviously need conversion constructors from int, long, etc., and the respective conversion operators (casts) to those types. This seems to cause errors with arithmetic operators. With native types, the compiler "knows" that when operator*(int, char) is called, it should promote the char to int and call operator*(int, int) (rather than casting the int to char, for example). In my case it gets confused between the various built-in operators and the ones I created. It seems to me like if I could flag the conversion operators as explicit somehow, that it would solve the issue, but as far as I can tell the explicit keyword is only for constructors (and I can't make constructors for built-in types). So is there any way of marking the casts as explicit? Or am I barking up the wrong tree here and there's another way of solving this? Or maybe I'm just doing something else wrong...

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