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• Best way to handle input from a keyboard "wedge"

  - by Mykroft

  I'm writing a C# POS (point of sale) system that takes input from a keyboard wedge magcard reader. This means that any data it reads off of a mag stripe is entered as if it were typed on the keyboard very quickly. Currently I'm handling this by attaching to the KeyPress event and looking for a series of very fast key presses that contain the card swipe sentinel characters. Is there a better way to deal with this sort of input? Edit: The device does simply present the data as keystrokes and doesn't interface through some other driver. Also We use a wide range of these types of devices so ideally a method should work independent of the specific model of wedge being used. However if there is no other option I'll have to make do.

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• Why is Read-Modify-Write necessary for registers on embedded systems?

  - by Adam Shiemke

  I was reading http://embeddedgurus.com/embedded-bridge/2010/03/different-bit-types-in-different-registers/, which said: With read/write bits, firmware sets and clears bits when needed. It typically first reads the register, modifies the desired bit, then writes the modified value back out and I have run into that consrtuct while maintaining some production code coded by old salt embedded guys here. I don't understand why this is necessary. When I want to set/clear a bit, I always just or/nand with a bitmask. To my mind, this solves any threadsafe problems, since I assume setting (either by assignment or oring with a mask) a register only takes one cycle. On the other hand, if you first read the register, then modify, then write, an interrupt happening between the read and write may result in writing an old value to the register. So why read-modify-write? Is it still necessary?

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• Google app engine and paging

  - by klausbyskov

  How would one go about writing a query that selects items 2000-2010 out of a collection of 10000 objects in the data store. I know that it can be done like this in GQL: select * from MyObject limit 10 offset 2000 According to the documentation, when using an offset the engine will still fetch all the rows, only not return them, thus making the query perform in a way that corresponds linearly with the value of offset. Is there any better way? Such as using a pseudo ROWNUM column like one could do in other types of data stores.

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• What permissions are required to create a new work item type in TFS

  - by harsha

  I am new to creating work item types in TFS and want to create a new Work Item type. I looked at work item template option, but that is not sufficient for me. I need to add few new fields and have a customized form. From search I got information about Work Item Type definition but I am looking for some detailed example. Also I would like to know the permissions needed to add a new work item type. I got administrator privileges for my project, but not on TFS as a whole. With that can I add a new template for my project. Please provide me direction.

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• Does DataType DataAnnotation Check the Expression?

  - by Jason

  I am currently using DataAnnotations within my ASP.NET MVC website to ensure data is properly validated. One question I wanted to verify (I think I know the answer, but I can't find verification online) - does the DataType DataAnnotation perform regular expression checks to ensure that you have received a valid e-mail/phone/currency/etc? [Required(ErrorMessage = "Price required")] [DataType(DataType.Currency, ErrorMessage = "Not a valid price")] [Range(0, double.MaxValue, ErrorMessage = "Price must be greater than 0.")] public decimal Price { get; set; } I believe the answer is no (meaning I have to provide my own, custom, RegularExpressionAttribute), but I wanted to double check before I do that for various field types.

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• SqlParameter contructor compiler overload choice

  - by Ash

  When creating a SqlParameter (.NET3.5) or OdbcParameter I often use the SqlParameter(string parameterName, Object value) constructor overload to set the value in one statement. When I tried passing a literal 0 as the value paramter I was initially caught by the C# compiler choosing the (string, OdbcType) overload instead of (string, Object). MSDN actually warns about this gotcha in the remarks section, but the explanation confuses me. Why does the C# compiler decide that a literal 0 parameter should be converted to OdbcType rather than Object? The warning also says to use Convert.ToInt32(0) to force the Object overload to be used. It confusingly says that this converts the 0 to an "Object type". But isn't 0 already an "Object type"? The Types of Literal Values section of this page seems to say literals are always typed and so inherit from System.Object. This behavior doesn't seem very intuitive given my current understanding? Is this something to do with Contra-variance or Co-variance maybe?

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• MongoDB - how to join parent and child products by reference

  - by Jaro

  my mongo collection stores products. There are two product types: child and parent. Parent product holds array of its child as reference. Use case: use mydb; child1 = { _id: 1, name: "Child 1", is_child: true, is_parent: false, children : [] } child2 = { _id: 2, name: "Child 2", is_child: true, is_parent: false, children : [] } parent = { _id: 3, name: "Parent product", is_child: false, is_parent: true, children : [1, 2] } db.product.insert( [child1, child2, parent] ); And I'm looking for any query returning { _id: 3, name: "Parent product", is_child: false, is_parent: true, children: [ { _id: 1, name: "Child 1", is_child: true, is_parent: false, children : [] }, { _id: 2, name: "Child 2", is_child: true, is_parent: false, children : [] } ] } I'm newbie to mongodb, but I guess an usage of map-reduce could solve the problem. Can anyone advice? Thx

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• Undo/Redo Support for Table Changes in WPF RichTextBox

  - by Jeff

  As part of an editor project, I need to add functionality to the WPF RichTextBox control to allow the user to perform operations on a table. One of those operations is to apply a new width value to one or more columns of the table. I have a function that is applying a new Width value to the TableColumn objects in question, and the table is resizing itself nicely. However, I've noticed that the column-width change operation does not seem to be added to the undo stack. In other words, if a user types something, then changes a column width, then selects undo, the RichTextBox control undoes the user's typing. Undo and redo don't seem to be picking up the property change on the TableColumn object. Is there some way to make this operation occur in a way that it actually is undoable/redoable?

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• How can I get Dashcode to open JSP files?

  - by user332000

  A simple tools question but it's driving me nuts. I have some .jsp files on my computer that I associated with Dashcode, figuring it would be a suitable editor. But when I try to open the files, all I get is a dialog box that says, "Dashcode cannot open files of this type". I thought there'd be an easy way to fix this but I can't find it. Nowhere in Dashcode's preferences can I find any list of valid file extensions. I poked around its resources folder for a while and couldn't find it there either. The Dashcode menubar is visible when the error is up, so I'm guessing that this is Dashcode itself complaining that it cannot open this file rather than the OS preventing it from trying. How exactly does this work? Is Dashcode really just hard-coded to recognize only files of certain types by their file extension? Isn't there a way to change it? Thanks, Frank

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• I like to learn computer science and programming, but i have no understanding.

  - by Josiah

  Hi all, I like to learn computer science and programming, but i don't know where and how to start. For the past two months, i have been researching on types of programming, i found my interest in desktop programming, and also found this subjects (discrete maths, logic, algorithms, data structures, artificial intelligence, simulation) said to be a most known (subjects). Well as a beginner, i have no understanding on what type of language or books that can cover all these subjects, or even how to write any code. Secondly, am as young as you can guess and i need a language to start with that will be easy for me to understand, and books to read. Thank you.

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• Polymorphic Behavior in VB6

  - by Tom Tresansky

  I recently noticed the CallByName keyword in VB6. Since this takes a object, procedure name, "call type" and arguments array, can this be used to "fake" some types of polymorphic behavior? I can make 2 classes, class A and B, each with the same method Foo, and do: Dim list As New Collection Dim instanceA As New ClassA Dim instanceB As New ClassB Dim current As Object Call list.Add(instanceA) Call list.Add(instanceB) For Each current in list Call CallByName(current, "methodName", vbMethod) Next Anyone done this before? Problems? Horrible idea or genius idea? Implications? Unintended consequences?

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• How to get visual studio 10 to open .mk files in the same instance?

  - by Russ Schultz

  I've recently been migrated to windows 7, and upon re-installing VS2010, it seems to want to treat .mk files differently than it used to. For whatever reason, it insists on opening a new instance of visual studio to edit these files. It doesn't for .c, .h, etc. I've tried using types, a freeware association manager, to change how it is associated. I've deleted the association, recreated, etc. but it still seems to want to treat these separately. Anybody know how to beat this thing into submission?

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• xsd:datetime and XmlGregorianCalendar causes NullPointerException

  - by Draemon

  The following works: public Date getDate() { return date; } and produces something like: <date>2010-03-23T17:43:50.879Z</date> And I can use an XmlGregorianCalendar to return xsd:date or xsd:time types fine: @XmlSchemaType(name="date") public XmlGregorianCalendar getDate() { return date; } which produces something like: <date>2010-03-23</date> But trying to return xsd:datetime like so: @XmlSchemaType(name="datetime") public XmlGregorianCalendar getDate() { return date; } Causes this stack trace: java.lang.NullPointerException at com.sun.xml.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl.checkXmlGregorianCalendarFieldRef(RuntimeBuiltinLeafInfoImpl.java:864) at com.sun.xml.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl.access$200(RuntimeBuiltinLeafInfoImpl.java:111) at com.sun.xml.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$13.print(RuntimeBuiltinLeafInfoImpl.java:536) ...snip... at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) Which doesn't mention my code at all. I'm using tomcat 6.0.24, java 1.6.0_16-b01

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• Use of enums in C?

  - by maddy

  Hi all, Is there anyway by which we can copy one enum to another one?For eg: enum Element4_Range{a4=1,b4,c4,d4}; enum Element3_Range{a3=1,b3,c3}; enum Element3_Range Myarr3[10]; enum Element4_Range Myarr4[10]; enum Element3_Range MyFunc(Element4_Range); main() { MyFunc(Myarr4); } enum Element3_Range MyFunc(Element4_Range Target) { enum Element3_Range Source; Source = Target;-----------Is this possible? } If not can anyone please show me the way to copy the values of enum from one to another? I was getting an error while executing this like a) incompatible types in assignment of `Element3_Range*' to `Element3_Range[10]' b)cannot convert `Element4_Range' to `Element3_Range' in assignment Thanks and regards Maddy

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• InvalidOperationException When XML Serializing Inherited Class

  - by Nick

  I am having an issue serializing a c# class to an XML file that has a base class... here is a simple example: namespace Domain { [Serializable] public class ClassA { public virtual int MyProperty { get; set; } } } namespace Derived { public class ClassA : Domain.ClassA { public override int MyProperty { get { return 1; } set { /* Do Nothing */ } } } } When I attempt to serialize an instance of Derived.ClassA, I receive the following exception: InvalidOperationException(Types 'Domain.ClassA' and 'Derived.ClassA' both use the XML type name 'ClassA', from the namespace ". Use XML attributes to specify a unique XML name and/or namespace for the type.) The problem is that I want to create a single base class that simply defines the structure of the XML file, and then allow anyone else to derive from that class to insert business rules, but that the formatting will come through from the base. Is this possible, and if so, how do I attribute the base class to allow this?

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• Unable to use 'class' as a key in NSDictionary with Xcode 4.5

  - by Vivin Paliath

  I'm trying to use a class as a key in an NSDictionary. I looked at the answer to this question and what I have is pretty much the same; I'm using setObject: forKey:. However, XCode complains, saying Incompatible pointer types sending 'Class' to parameter of type 'id<NSCopying>'. The call I have is: [_bugTypeToSerializerDictionary setObject: bugToStringSerializer forKey: [bugToStringSerializer serializedObjectType]]; bugToStringSerializer is an instance of BugToStringSerializer whose concrete implementations implement serializedObjectType. An example of a concrete implementation looks like this: - (Class) serializedObjectType { return [InfectableBug class]; } What am I doing wrong here?

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• Is there a way to log when a particular memory location gets written and by which function?

  - by rusbi

  I'm having a bug in my c++ program which happens very rarely but crashes my program. It's seems I have some buffer overflow problem or something similar. I find that these types of bug are most difficult to find. My program always crashes because of the same corrupted memory location. I'm wondering if there is some debugging tool which could detect when a particular memory location get written to and logs the function which does it. I'm using VLD (visual leak detector) for my memory leak hunting and it works great. It substitutes the original mallocs which its own and logs every allocation. I was wondering if there is something similar for memory? I know that something like that would cripple a program, but it could be really helpful.

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• SQL Complicated Group / Join by Category

  - by Mike Silvis

  I currently have a database structure with two important tables. 1) Food Types (Fruit, Vegetables, Meat) 2) Specific Foods (Apple, Oranges, Carrots, Lettuce, Steak, Pork) I am currently trying to build a SQL statement such that I can have the following. Fruit < Apple, Orange Vegetables < Carrots, Lettuce Meat < Steak, Port I have tried using a statement like the following Select * From Food_Type join (Select * From Foods) as Foods on Food_Type.Type_ID = Foods.Type_ID but this returns every Specific Food, while I only want the first 2 per category. So I basically need my subquery to have a limit statement in it so that it finds only the first 2 per category. However if I simply do the following Select * From Food_Type join (Select * From Foods LIMIT 2) as Foods on Food_Type.Type_ID = Foods.Type_ID My statement only returns 2 results total.

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• ruby c extensions: character values over 127

  - by Adrian

  I am trying to make a C extension for Ruby that includes a method returning a string, which will sometimes have character values that need to be in an unsigned char. In http://github.com/shyouhei/ruby/blob/trunk/README.EXT, all of the functions listed for turning C strings into Ruby strings take signed chars. So I couldn't do this: unsigned char bytes[] = {0xf0, 0xf1, 0xf2}; return rb_str_new(bytes, 3); How could I make a method that returns these types of strings? In other words, how would I make a C extension with a method returning "\xff"?

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• .NET Decimal = what in SQL?

  - by dmose

  What's the best data type in SQL to represent Decimal in .NET? We want to store decimal numbers with up to 9 decimal place precision and want to avoid rounding errors etc on the front end. Reading about data types, it appears using Decimal in .NET is the best option because you will not get rounding errors, although it is a bit slower than a Double. We want to carry this through down to the DB and want minimum conversion issues when moving data through the layers. Any suggestions?

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• New to programming

  - by Shaun

  I have a form (Quote) with an auto-number ID, on the form at the moment are two subforms that show different items (sub 1 shows partition modules sub 2 shows partition abutments) both forms use the same parts tables to build them. Both forms are linked to the quote form using the ID. All works well until the forms is refreshed or re-loaded, subform 1 shows the module names and quantities and blank spaces for the abutment names but shows the quantiews for the abutments, the reverse of this is shown in the abutments subform 2. When the lists for the variuos types and the detailed parts lists are printed they are correct. This seems to be only a visual problem. All based on Access 2003. Subform 1 SELECT Quote_Modules.ModuleID, Quote_Modules.QuoteID, Quote_Modules.ModuleDescription, Quote_Modules.ModuleQty, Quote.Style, Quote.Trim FROM Quote INNER JOIN Quote_Modules ON Quote.QuoteID=Quote_Modules.QuoteID ORDER BY Quote_Modules.ModuleID; Subform 2 SELECT Quote_Modules.ModuleID, Quote_Modules.QuoteID, Quote_Modules.ModuleDescription, Quote_Modules.ModuleQty, Quote.Style, Quote.Trim FROM Quote INNER JOIN Quote_Modules ON Quote.QuoteID=Quote_Modules.QuoteID ORDER BY Quote_Modules.ModuleID;

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• Visual Studio 2008. MFC event wizard broken

  - by G Forty

  OK, so it's almost a programming question - The VS2008 dialog event wizard has stopped working. Double-clicking on a button in an MFC dialog project does not fire the wizard as usual and a right-click to get to the 'Add Event Handler...' shows a dialog with no message types. Further to this the MFC message mapping and virtual class listing that generally appears in the properties window (Alt + Enter) is now empty. Has anyone elese seen this and if so, how'd they fix it? I have 'repaired' my VS08 installation ... Thx++ Jerry

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• Obtain stored procedure metadata for a procedure within an Oracle package using ADO.NET

  - by alwayslearning

  Hi, I am trying to obtain the stored procedure metadata (procedure name,parameter types,parameter names etc) for a procedure declared within an Oracle package, using the standard ADO.NET API - DbConnection.GetSchema call. I am using the ODP driver. I see that the Package is listed in the 'Packages' and 'PackageBodies' metadata collections. The procedure parameter appears in the 'Arguments' and 'ProcedureParameters' collections. I do not see a way to get to the procedure information via the package metadata. Even if the procedure does not have any parameters there is a row in the 'ProcedureParameters' collection for this procedure. My question: To obtain the procedure metadata do I have to query the 'ProcedureParameters' collection and search for an entry with the required package name? I can then construct the procedure metadata based on the parameter information. Is there a shorter or quicker way to obtain the same information?

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• uWSGI loggin format unification

  - by Mediocre Gopher

  I'm attempting to unify the log format of my uwsgi instance. Currently there's three different types of log items: Sun Sep 2 17:31:00 2012 - spawned uWSGI worker 10 (pid: 2958, cores: 8) (DEBUG) 2012-09-02 17:31:01,526 - getFileKeys_rpc called Traceback (most recent call last): File "src/dispatch.py", line 13, in application obj = discovery(env) File "src/dispatch.py", line 23, in discovery ret_obj = {"return":dispatch(method,env)} File "src/dispatch.py", line 32, in dispatch raise Exception("test") Exception: test The first is an error spawned by uWSGI internally (I have the --log-date option set). The second is from the logging module, which has logging.basicConfig(format='(%(levelname)s) %(asctime)s - %(message)s') set. The final one is an uncaught exception. I understand that the uncaught exception probably can't be formatted, but is there some way of having uwsgi use the logging module for its internal logs? Or the other way around?

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• Drupal - editing tab options for a content type not showing up

  - by easement

  I'm working on a D5 site and a lot of the content types have the menus at the top of the edit page. Examples: Overview | Grants | Dev load | Dev render | Edit | Revisions | Track | Workflow Overview | Dev load | Dev render | Edit | Revisions | Track | Workflow | Node queue | RelatedContent I'm not sure where these tabs come from, but I need to enable the menu for a content type that doesn't have them visible. I checked the workflow setting and the content type in question was specified to use workflow. So there should be at least another tab in addition to edit. The end goal is to have revisions show up in the menu, but I need to get the menu showing first. Any ideas where to start looking?

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