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  • Type parameterization in Scala

    - by horatius83
    So I'm learning Scala at the moment, and I'm trying to create an abstract vector class with a vector-space of 3 (x,y,z coordinates). I'm trying to add two of these vectors together with the following code: package math class Vector3[T](ax:T,ay:T,az:T) { def x = ax def y = ay def z = az override def toString = "<"+x+", "+y+", "+z+">" def add(that: Vector3[T]) = new Vector3(x+that.x, y+that.y, z+that.z) } The problem is I keep getting this error: error: type mismatch; found : T required: String def add(that: Vector3[T]) = new Vector3(x+that.x, y+that.y, z+that.z) I've tried commenting out the "toString" method above, but that doesn't seem to have any effect. Can anyone tell me what I'm doing wrong?

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  • a completely decoupled OO system ?

    - by shrini1000
    To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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  • iphone screen - type of view to use

    - by Fiona
    Hi There everyone... looking for some advice on what type of view can be used to build a screen with the following elements: 2 labels followed by 2 buttons. Then a small table view with 3 rows. Should a UIView be used or a UITableView? I've attempted using a UITableView - however I couldn't add the labels or buttons. So I've now built the view using a UIView. I added the labels and buttons and then a UITableView from the library. However I have no idea how to populate the rows in the table? Any ideas? Regards, Fiona

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  • UITableView - iPad - Property '' Not Found on Object of type UITableViewCell

    - by user1797508
    I have added a UITableView prototype Cell into a UIView for an iPad application using StoryBoard in Xcode (targeting iOS6). The problem I'm having is that the labels are not being recognized in my viewController when I try to reference them. In my implementation, I have: - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"dashboardMessage"; UITableViewCell *cell = [_tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } int row = [indexPath row]; cell.messageSender.text = [_matches valueForKey:@"from"]; } The last line is causing an error: Property 'messageSender' Not Found on Object of type UITableViewCell In the cell's header file I have: @interface DashboardMessageCell : UITableViewCell @property (strong, nonatomic) IBOutlet UILabel *messageSender; @property (strong, nonatomic) IBOutlet UILabel *messageDescr; and the header file is imported into the viewController. I'm lost as to what can be causing the issue, any help would be greatly appreciated. Thanks.

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  • How to debug "The type initializer for 'my class' threw an exception"

    - by JFB
    I am getting the exception: The type initializer for 'my class' threw an exception. in my browser after running my web application. Since this seems to be an error message generated from the view (.aspx), there is no way I can see the stack trace or any log for the source of this error. I have read a bit around the net and one solution to debugging is to throw a TypeInitializationException and then looking at the inner exception to find out what was wrong. How can I do this when I don't know where to surround code with a try/catch ?

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  • Performance of: if (OBJECT_INSTANCE is TYPE)

    - by Axonn
    I am working both in C# and ActionScript 3. Both language are type-aware, so you can do verifications such as: if (some_object_instance is SomeClassName_ThatIs_SomeType) I'm doing these kind of verifications in a few places. Might be a dumb question, but I will ask it anyway, and I want answers from both camps, C# and ActionScript: What goes on behind the scenes? Is it Reflection? If is, isn't this a long verification which might degrade performance if done in thousands of loops? And by "degrade performance" I mean, is it more intensive than say if (Math.sqrt(8) > Math.sin(10))

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  • IntelliSense: expression must have integral or enum type

    - by user1743737
    Guys i need someone fix this problem ? when i compile that code i have this error: Error: IntelliSense: expression must have integral or enum type i have problem in this part: Console(0, V("seta sv_hostname " + servername + ";\n")); so how i can fix that if (strncmp(command, V("exec config_mp"), 14) == 0) { if (GAME_MODE == 'D') { CIniReader iniReader(V(".\\teknogods.ini")); char *servername = iniReader.ReadString(V("Settings"),V("Servername"),""); if (strcmp(servername,"") == 0) { info("Server name set to defult."); } else { //Console(0, V("seta scr_teambalance 1;\n")); Console(0, V("seta sv_hostname " + servername + ";\n")); info("server name set to: %s.", servername); } } }

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  • nullable type and a ReSharper warning

    - by Sarah Vessels
    I have the following code: private static LogLevel? _logLevel = null; public static LogLevel LogLevel { get { if (!_logLevel.HasValue) { _logLevel = readLogLevelFromFile(); } return _logLevel.Value; } } private static LogLevel readLogLevelFromFile() { ... } I get a ReSharper warning on the return statement about a possible System.InvalidOperationException and it suggests I check _logLevel to see if it is null first. However, readLogLevelFromFile returns LogLevel, not LogLevel?, so there is no way the return statement could be reached when _logLevel is null. Is this just an oversight by ReSharper, or am I missing something?

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  • How to use email adresses with special chars such as Ø

    - by Sir Code-A-Lot
    By writing this: var recipient = new MailAddress("name@abcø.dk"); Notice the "ø" in the domain part. I get an exception stating: System.FormatException: The specified string is not in the form required for an e-mail address. at System.Net.Mime.MailBnfHelper.ReadMailAddress(String data, Int32& offset, String& displayName) at System.Net.Mail.MailAddress.ParseValue(String address) at System.Net.Mail.MailAddress..ctor(String address, String displayName, Encoding displayNameEncoding) at System.Net.Mail.MailAddress..ctor(String address) The address used should be perfectly valid. So I'm guessing I have to encode the address somehow?

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  • java: ClassCastException - [Ljava.lang.Long; cannot be cast to java.lang.Long

    - by ufk
    Hello. well.. I use red5 and setting/getting attributes using the IConnection class but tha's really not relevant. 'L' means long in java. so 0L is 0 type Long instead of just '0' which is 0 type Integer. the following error message: stack trace: java.lang.ClassCastException: [Ljava.lang.Long; cannot be cast to java.lang.Long what's the difference between [Ljava.lang.Long and java.lang.Long ? thanks!

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  • Me As Child Type In General Function

    - by Steven
    I have a MustInherit Parent class with two Child classes which Inherit from the Parent. How can I use (or Cast) Me in a Parent function as the the child type of that instance? EDIT: My actual goal is to be able to serialize (BinaryFormatter.Serialize(Stream, Object)) either of my child classes. However, "repeating the code" in each child "seems" wrong. EDIT2: This is my Serialize function. Where should I implement this function? Copying and pasting to each child doesn't seem right, but casting the parent to a child doesn't seem right either. Public Function Serialize() As Byte() Dim bFmt As New BinaryFormatter() Dim mStr As New MemoryStream() bFmt.Serialize(mStr, Me) Return mStr.ToArray() End Function

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  • Unrecognized authentication type when doing an Auth to Exchange from Rails

    - by blakeage
    I'm getting this error when trying to authenticate with Exchange Server from Ruby on Rails: 504 5.7.4 Unrecognized authentication type config.action_mailer.raise_delivery_errors = true config.action_mailer.perform_deliveries = true config.action_mailer.delivery_method = :smtp config.action_mailer.smtp_settings = { :address => "x.x.x.x", :port => 25, :user_name => "xxdomain\xxuser", :password => "xxxxxx", :authentication => :login, :enable_starttls_auto => true } I've tried all sorts of combinations of configuration settings, including changing the settings to use "plain" authentication, adding the domain, setting enable_starttls_auto to true, false, and removing it entirely, removing the port. Nothing has worked. Any ideas?

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  • Returning new base class when the parent class shared pointer is the return type

    - by Ben Dol
    Can you have a parent class shared pointer return type of a function and then return a new child class without it being a shared pointer? I'm not sure how shared pointers work in these situations, do they act like a regular pointer? Here is my example: BaseEventPtr Actions::getEvent(const std::string& nodeName) { if(asLowerCaseString(nodeName) == "action") return new ActionEvent(&m_interface); return nullptr; } ActionEvent is the subclass of BaseEvent in this situation. Cheers!

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  • C++: Template functor cannot deduce reference type

    - by maciekp
    I've got a functor f, which takes a function func and a parameter t of the same type as func. I cannot pass g to f because of compilation error (no matching function for call to f(int&, void (&)(int&)) ). If g would take non-reference parameter g(int s), compilation finishes. Or if I manually specify template parameter f(i, g), compilation also finishes. template<typename T> void f(T t, void (*func)(T)) {} void g(int& s) {} int main(int, char*[]) { int i = 7; f(i, g); // compilation error here return 0; } How can I get deduction to work?

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  • How to build Linux system from kernel to UI layer

    - by mohit
    Hi, I have been looking into MeeGo, maemo, Android architecture. They all have Linux Kernel, build some libraries on it, then build middle layer libraries [e.g telephony, media etc...]. Suppose i wana build my own system, say Linux Kernel, with some binariers like glibc, Dbus,.... UI toolkit like GTK+ and its binaries. I want to compile every project from source to customize my own linux system for desktop, netbook and handheld devices. [starting from netbook first :)] How can i build my own customize system from kernel to UI.

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  • python dictionary with constant value-type

    - by s.kap
    hi there, I bumped into a case where I need a big (=huge) python dictionary, which turned to be quite memory-consuming. However, since all of the values are of a single type (long) - as well as the keys, I figured I can use python (or numpy, doesn't really matter) array for the values ; and wrap the needed interface (in: x ; out: d[x]) with an object which actually uses these arrays for the keys and values storage. I can use a index-conversion object (input -- index, of 1..n, where n is the different-values counter), and return array[index]. I can elaborate on some techniques of how to implement such an indexing-methods with reasonable memory requirement, it works and even pretty good. However, I wonder if there is such a data-structure-object already exists (in python, or wrapped to python from C/++), in any package (I checked collections, and some Google searches). Any comment will be welcome, thanks.

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  • Type casting Collections using Conversion Operators

    - by Vyas Bharghava
    The below code gives me User-defined conversion must convert to or from enclosing type, while snippet #2 doesn't... It seems that a user-defined conversion routine must convert to or from the class that contains the routine. What are my alternatives? Explicit operator as extension method? Anything else? public static explicit operator ObservableCollection<ViewModel>(ObservableCollection<Model> modelCollection) { var viewModelCollection = new ObservableCollection<ViewModel>(); foreach (var model in modelCollection) { viewModelCollection.Add(new ViewModel() { Model = model }); } return viewModelCollection; } Snippet #2 public static explicit operator ViewModel(Model model) { return new ViewModel() {Model = model}; } Thanks in advance!

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  • EXCEL import to sql returning NULL for decimals when in VARCHAR data type

    - by Daniel
    Hi, I am working on a peice of software which has expodentially grown over the last few years and the database needs to be regularly updated. Customers are providing us with data now on large spreadsheets which we format and will start importing into the database. I am using the Import and Export Data (32-bit) Wizard. One column in the database contains values like '1.1.1.2' etc and i am importing them in as a Varchar as that is the data type in the database. However, for values like '8.5', 'NULL' is getting imported insead. It only occurs when there is one decimal point. Is this a formatting error with excel or is it the wrong datatype?

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  • Missing System.Core.dll and others on Visual Studio 2010 Project targeting 3.5 Framework

    - by Mark Struzinski
    I just got Visual Studio 2010 installed and running on my development machine (alongside VS 2008). The first thing I did was make a copy of an existing project and convert it up to the VS 2010 project. I told the conversion wizard to leave the project targeting the 3.5 framework. The project compiles and runs just fine in VS 2008. When I go to build it, several of my references are marked as missing (System.Core, System.Xml.Linq, System.Data.DataSetExtensions). When I go to the Add Reference dialog, they are not present. Yet if I view the GAC at C:\Windows\Assembly, I can see the entries there. I have tried converting the projects to 4.0, then back down to 3.5, and also unloading/reloading the projects. Nothing works. Has anyone else ran across this problem?

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  • Sql Server XML-type column duplicate entry detection

    - by aaaa bbbb
    In Sql Server I am using an XML type column to store a message. I do not want to store duplicate messages. I only will have a few messages per user. I am currently querying the table for these messages, converting the XML to string in my C# code. I then compare the strings with what I am about to insert. Unfortunately, Sql Server pretty-prints the data in the XML typed fields. What you store into the database is not necessarily exactly the same string as what you get back out later. It is functionally equivalent, but may have white space removed, etc. Is there an efficient way to compare an XML string that I am considering inserting with those that are already in the database? As an aside, if I detect a duplicate I need to delete the older message then insert the replacement.

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  • inode_operations , warning: initialization from incompatible pointer type

    - by djTeller
    Hi everyone, I'm trying to compile a simple Kernel program that read and write from a proc file. I'm trying to set permission to that file by overriding the permission fp in inode_operations struct (.permission) static int module_permission(struct inode *inode, int op, struct nameidata *foo) { . . . } static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; For some reason, when I compile this i get - warning: initialization from incompatible pointer type on the following line: .permission = module_permission, /* check for permissions */ Any idea how to solve this? Thanks!

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  • Dynamically load a type from an external assembly

    - by Water Cooler v2
    From managed code, how do I load a managed type from another assembly at runtime, assuming the calling code does not have a static reference to the assembly? To clarify, let's say I have class Lib in Lib.cs compiled into Lib.dll. I want to write a class Foo in a separate assembly called Foo.dll, that does not have a reference to Lib.dll statically, but instead loads Lib.dll and then reflects on for the presence of the class Lib and then calls a method on it. Sorry for such an obvious question on Reflection. I figure it'll take much lesser time to get the answer on a forum that to read a few articles.

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  • xmlhttprequest responsetext coming for Accept header: text/xml , but server error for application/JS

    - by encryptor
    I have to get response text from a resourceindex page as JSON object. When I dont put a Accept header in the request, it shows me the xml response (i see it in an alert).. But I want the response as a JSON object.. What should I do. One solution would have been httpRequest.setRequestHeader('Accept', 'application/JSON'); but this gives me a server error :500 Also it says A message body writer for Java type, class ...., and MIME media type, application/octet-stream, was not found Can someone suggest on what to do to overcome this and get the response as JSON?

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  • Type-aware rendering (and editing) of tabular data in pyqt4

    - by pihentagy
    I would like to have a very short / minimal example of how to create some tabular widget with different types of item in it. In the first round let's say I'd like to render [["Hello", 12, True], ["World", 13, False]] (Hello as string, 12 as number (right-align), True as a checkbox for eg.), but it would be nice to have Dates, Colors, and other type of info. Next round: editing (integer with spinbox, maybe sometimes a combobox is handy, but that may not work out of the box). There must be a simple solution, but I couldn't find...

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  • The type{0} does not support direct content - WPF / XAML

    - by Levo
    Hi there: I defined in my code two classes: a "Person" class with public "Age" and "Name" property, and a "People" class that inherits from Generic.List(of T). The code for People class is as followed: Public Class People Inherits Collections.Generic.List(Of Person) ... End Class What I want to achieve is to directly initialize the People class, and add individual Person to it in XAML, i.e.: <local:People x:Key="Familty"> <local:Person Age="11" Name="John" /> <local:Person Age="12" Name="John2" /> ... </local:People> But I keep getting an error in XAML saying: The type 'People' does not support direct content. Any idea as for how to solve this problem? Thank you very much!

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