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  • std::string insert method has ambiguous overloads?

    - by sdg
    Environment: VS2005 C++ using STLPort 5.1.4. Compiling the following code snippet: std::string copied = "asdf"; char ch = 's'; copied.insert(0,1,ch); I receive an error: Error 1 error C2668: 'stlpx_std::basic_string<_CharT,_Traits,_Alloc>::insert' : ambiguous call to overloaded function It appears that the problem is the insert method call on the string object. The two defined overloads are void insert ( iterator p, size_t n, char c ); string& insert ( size_t pos1, size_t n, char c ); But given that STLPort uses a simple char* as its iterator, the literal zero in the insert method in my code is ambiguous. So while I can easily overcome the problem by hinting such as copied.insert(size_t(0),1,ch); My question is: is this overloading and possible ambiguity intentional in the specification? Or more likely an unintended side-effect of the specific STLPort implementation? (Note that the Microsoft-supplied STL does not have this problem as it has a class for the iterator, instead of a naked pointer)

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  • C++0x rvalue references and temporaries

    - by Doug
    (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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  • hadoop implementing a generic list writable

    - by Guruprasad Venkatesh
    I am working on building a map reduce pipeline of jobs(with one MR job's output feeding to another as input). The values being passed around are fairly complex, in that there are lists of different types and hash maps with values as lists. Hadoop api does not seem to have a ListWritable. Am trying to write a generic one, but it seems i can't instantiate a generic type in my readFields implementation, unless i pass in the class type itself: public class ListWritable<T extends Writable> implements Writable { private List<T> list; private Class<T> clazz; public ListWritable(Class<T> clazz) { this.clazz = clazz; list = new ArrayList<T>(); } @Override public void write(DataOutput out) throws IOException { out.writeInt(list.size()); for (T element : list) { element.write(out); } } @Override public void readFields(DataInput in) throws IOException{ int count = in.readInt(); this.list = new ArrayList<T>(); for (int i = 0; i < count; i++) { try { T obj = clazz.newInstance(); obj.readFields(in); list.add(obj); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } } } } But hadoop requires all writables to have a no argument constructor to read the values back. Has anybody tried to do the same and solved this problem? TIA.

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  • PHP Object References in Frameworks

    - by bigstylee
    Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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  • Are document-oriented databases any more suitable than relational ones for persisting objects?

    - by Owen Fraser-Green
    In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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  • Safe and polymorphic toEnum

    - by jetxee
    I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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  • WCF REST adding data using POST or PUT 400 Bad Request

    - by user55474
    HI How do i add data using wcf rest architecture. I dont want to use the channelfactory to call my method. Something similar to the webrequest and webresponse used for GET. Something similar to the ajax WebServiceProxy restInvoke Or do i always have to use the Webchannelfactory implementation I am getting a 400 BAD request by using the following Dim url As String = "http://localhost:4475/Service.svc/Entity/Add" Dim req As WebRequest = WebRequest.Create(url) req.Method = "POST" req.ContentType = "application/xml; charset=utf-8" req.Timeout = 30000 req.Headers.Add("SOAPAction", url) Dim xEle As XElement xEle = <Entity xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <Name>Entity1</Name> </Entity> Dim sXML As String = xEle .Value req.ContentLength = sXML.Length Dim sw As New System.IO.StreamWriter(req.GetRequestStream()) sw.Write(sXML) sw.Close() Dim res as HttpWebResponse = req.GetResponse() Sercice Contract is as follows <OperationContract()> _ <WebInvoke(Method:="PUT", UriTemplate:="Entity/Add")> _ Function AddEntity(ByVal e1 As Entity) DataContract is as follows <Serializable()> _ <DataContract()> _ Public Class Entity private m_Name as String <DataMember()> _ Public Property Name() As String Get Return m_Name End Get Set(ByVal value As String) m_Name = value End Set End Property End Class thanks

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  • java 6 web services share domain specific classes between server and client

    - by user173446
    Hi all, Context: Considering below defined Engine class being parameter of some webservice method. As we have both server and client in java we may have some benefits (???) in sharing Engine class between server and client ( i.e we may put in a common jar file to be added to both client and server classpath ) Some benefits would be : we keep specific operations like 'brushEngine' in same place build is faster as we do not need in our case to generate java code for client classes but to use them from the server build) if we later change server implementation for 'brushEngine' this is reflected automatically in client . Questions: How to share below detailed Engine class using java 6 tools ( i.e wsimport , wsgen etc )? Is there other tools for java that can achieve this sharing ? Is sharing a case that java 6 web services support is missing ? Can this case be reduced to other web service usage patterns? Thanks. Code: public class Engine { private String engineData; public String getData(){ return data; } public setData(String value){ this.data = value; } public void brushEngine(){ engineData = "BrushedEngine"+engineData; } }

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  • forward invocation, by hand vs magically?

    - by John Smith
    I have the following two class: //file FruitTree.h @interface FruitTree : NSObject { Fruit * f; Leaf * l; } @end //file FruitTree.m @implementation FruitTree //here I get the number of seeds from the object f @end //file Fruit @interface Fruit : NSObject { int seeds; } -(int) countfruitseeds; @end My question is at the point of how I request the number of seeds from f. I have two choices. Either: Since I know f I can explicitly call it, i.e. I implement the method -(int) countfruitseeds { return [f countfruitseeds]; } Or: I can just use forwardInvocation: - (NSMethodSignature *)methodSignatureForSelector:(SEL)selector { // does the delegate respond to this selector? if ([f respondsToSelector:selector]) return [f methodSignatureForSelector:selector]; else if ([l respondsToSelector:selector]) return [l methodSignatureForSelector:selector]; else return [super methodSignatureForSelector: selector]; } - (void)forwardInvocation:(NSInvocation *)invocation { [invocation invokeWithTarget:f]; } (Note this is only a toy example to ask my question. My real classes have lots of methods, which is why I am asking.) Which is the better/faster method?

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  • sigleton EXC_BAD_ACCESS

    - by lclaud
    Hi, so I have a class that I decleare as a singleton and in that class I have a NSMutableArray that contains some NSDictionaries with some key/value pairs in them. The trouble is it doesn't work and I dont't know why... I mean it crashes with EXC_BAD_ACCESS but i don't know where. I followed the code and it did create a new array on first add, made it to the end of the funtion ..and crashed ... @interface dataBase : NSObject { NSMutableArray *inregistrari; } @property (nonatomic,retain) NSMutableArray *inregistrari; -(void)adaugaInregistrareCuData:(NSDate *)data siValoare:(NSNumber *)suma caVenit:(BOOL)venit cuDetaliu:(NSString *)detaliu; -(NSDictionary *)raportIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)luniDisponibileIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)aniDisponibiliIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)vectorDateIntreData:(NSDate *)dataI siData:(NSDate *)dataF; -(void)salveazaInFisier; -(void)incarcaDinFisier; + (dataBase *)shareddataBase; @end And here is the .m file #import "dataBase.h" #import "SynthesizeSingleton.h" @implementation dataBase @synthesize inregistrari; SYNTHESIZE_SINGLETON_FOR_CLASS(dataBase); -(void)adaugaInregistrareCuData:(NSDate *)data siValoare:(NSNumber *)suma caVenit:(BOOL)venit cuDetaliu:(NSString *)detaliu{ NSNumber *v=[NSNumber numberWithBool:venit]; NSArray *input=[NSArray arrayWithObjects:data,suma,v,detaliu,nil]; NSArray *keys=[NSArray arrayWithObjects:@"data",@"suma",@"venit",@"detaliu",nil]; NSDictionary *inreg=[NSDictionary dictionaryWithObjects:input forKeys:keys]; if(inregistrari == nil) { inregistrari=[[NSMutableArray alloc ] initWithObjects:inreg,nil]; }else { [inregistrari addObject:inreg]; } [inreg release]; [input release]; [keys release]; } It made it to the end of that adaugaInregistrareCuData ... ok . said the array had one object ... and then crashed

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  • What's wrong with my HtmlHelper?

    - by Dejan.S
    I done a htmlhelper but I can not get it to work tho. I did like I seen on different tutorials. my MenuItemHelper static Class public static string MenuItem(this HtmlHelper helper, string linkText, string actionName, string controllerName) { var currentControllerName = (string)helper.ViewContext.RouteData.Values["controller"]; var currentActionName = (string)helper.ViewContext.RouteData.Values["action"]; var sb = new StringBuilder(); if (currentControllerName.Equals(controllerName, StringComparison.CurrentCultureIgnoreCase) && currentActionName.Equals(actionName, StringComparison.CurrentCultureIgnoreCase)) sb.Append("<li class=\"selected\">"); else sb.Append("<li>"); sb.Append(helper.ActionLink(linkText, actionName, controllerName)); sb.Append("</li>"); return sb.ToString(); } import namespace <%@ Import Namespace="MYAPP.Web.App.Helpers" %> Implementation on my master.page <%= Html.MenuItem("TEST LINK", "About", "Site") %> Errormessage I get Method not found: 'System.String System.Web.Mvc.Html.LinkExtensions.ActionLink(System.Web.Mvc.HtmlHelper, System.String, System.String, System.String)

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  • WCF code generation for large/complex schema (HR-XML/OAGIS) - is there an alternative?

    - by Sasha Borodin
    Hello, and thank you for reading. I am implementing a WCF Service based on a predefined specification (HR-XML 3.0). As such, I am starting with the schema, and working my way back to code. There are a number of large Schema documents (which import yet more Schema documents) related to my implementation, provided by this specification. I am able to generate code using xsd.exe, by supplying the "main" and "supporting" xsd files as arguments. But there are several issues, and I am wondering if this is the right approach. there are litterally hundreds of classes - the code file is half a meg in size duplicate classes (ex. Type, Type1 - which both represent the same type) there are classes declared as inheriting from a base class, but that base class is not generated/defined I understand that there are limitations to the types of Schema supported by svcutil.exe/xsd.exe when targeting the DataContractSerializer and even XmlSerializer. My question is two-fold: Are code generation "issues" fairly common when dealing with larger, modular xsd files? Has anyone had success with generating data contracts from OAGIS or HR-XML schema? Given the above issues, are there better approaches to this task, avoiding generating code and working with concrete objects? Does it make better sence to read and compose a SOAP message directly, while still taking advantage of the rest of the WCF framework? I understand that I am loosing the convenience of working with .NET objects, and the framekwork-provided (de)serialization; given these losses, would it still be advantageous to base my Service on WCF? Is there some "middle ground" between working with .NET types and pure XML? Thank you very much! -Sasha Borodin DFWHC.org

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  • Animation is slow on iPhone

    - by Anthony Chan
    I'm developing an app that would display images and change them according to the user's action. I've created a subclass of UIView to contain an image, an index number and an array of image names. The code is like this: @interface CustomPic : UIView { UIImageView *pic; NSInteger index; NSMutableArray *picNames; //<-- an array of NSString } And in the implementation part, it has a method to change the image using a dissolve effect. - (void)nextPic { index++; if (index >= [picNames count]) { index = 0; } UIImageView *temp = pic; pic.image = [UIImage imageNamed:[picNames objectAtIndex:index]]; temp.alpha = 0; [UIView beginAnimations:nil context:nil]; [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; [UIView setAnimationDuration:0.25]; pic.alpha = 0; temp.alpha = 1; [UIView commitAnimations]; } In the viewController, there are several CustomPic which would change the images depends on users' choice. The images would change as expected with the fade in/out effect, but the animation performance is really bad. I've tested it on an iPhone 3G, the Instruments shows that the animation is only 2-3FPS! I tried many methods to simplify and modify the codes but with no hope. Is there something wrong in my code or in my concept? Thanks for any help. P.S. all the images are 320*480 PNGs with a max size of 15KB.

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  • Using StructureMap to create classes by a name?

    - by Bevan
    How can I use StructureMap to resolve to an appropriate implementation of an interface based on a name stored in an attribute? In my project, I have many different kinds of widgets, each descending from IWidget, and each decorated with an attribute specifying the kind of associated element. To illustrate: [Configuration("header")] public class HeaderWidget : IWidget { } [Configuration("linegraph")] public class LineGraphWidget : IWidget { } When processing my (XML) configuration file, I want to obtain an instance of the appropriate concrete class based on the name of the element I'm processing. public IWidget CreateWidget(XElement definition) { var kind = definition.Name.LocalName; var widget = // What goes here? widget.Configure(definition); return widget; } Each definition should result in a different widget being created - I don't need or want the instances to be shared. In the past I've written plenty of code to do this kind of thing manually, including writing a custom "roll-your-own" IoC container for one project. However, one of my goals with this project is to become proficient with StructureMap instead of reinventing the wheel. I think I've already managed to set up automatic scanning of assemblies so that StructureMap knows about all my IWidget implementations: public class WidgetRegistration : Registry { public WidgetRegistration() { Scan( scanner => { scanner.AssembliesFromApplicationBaseDirectory(); scanner.AddAllTypesOf<IWidget>(); }); } } However, this isn't registering the names of my widgets with StructureMap. What do I need to add to make my scenario work? (While I am trying to use StructureMap in this project, an answer showing me how to solve this problem with a different DI/IoC tool would still be valuable.)

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  • (nested) user controls within a mvp pattern causing sporadic problems

    - by LLEA
    hi everyone, I have a serious problem with nested user controls (UCs) in WinForms while trying to implement the mvp pattern (passive view). The project consists of one model (designed as a singleton) and a set of different presenters with corresponding view interfaces. To avoid one huge view interface and therefore an overloaded main UI, I decided to make use of a set of different UCs. Each UC has one view interface and one presenter that can access the model. But there are nested UCs: meaning that one specialised UC implements sort of a basic UC. The main UI just represents a container for all those UCs. So far, so good (if not, please ask)?! There are two problems that I am facing now (but I guess both are of the same origin): From time to time it is not possible anymore to load the UCs and test them within the Visual Studio 2008 User Control Test Container. The error message just says that a project with an output type of class library cannot be started directly etc. I can "handle" that by unloading all UC projects and reloading them afterwards. (I guess the references to all mvp components and other UCs are then updated). Assuming that the implementation of my mvp pattern is okay and all those UCs are testable within the VS Test Container at a certain time - there is the biggest problem still left: I am not able to add any UC (even the basic and unnested ones) to a simple Form (UI). The error message: error message.jpg Could it be that my basic UC causes all these Problems?! It consists of two simple ComboBoxes and implements a basic presenter and basic view interface. Whenever I add this UC to a different UC the VS designer adds two references to the public getter methods of the UC as resources. I then manually remove those resources from the resx-file and commend the corresponding lines in the designer file. thx in advance

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  • In Python, how can I find the index of the first item in a list that is NOT some value?

    - by Ryan B. Lynch
    Python's list type has an index(x) method. It takes a single parameter x, and returns the (integer) index of the first item in the list that has the value x. Basically, I need to invert the index(x) method. I need to get the index of the first value in a list that does NOT have the value x. I would probably be able to even just use a function that returns the index of the first item with a value != None. I can think of a 'for' loop implementation with an incrementing counter variable, but I feel like I'm missing something. Is there an existing method, or a one-line Python construction that can handle this? In my program, the situation comes up when I'm handling lists returned from complex regex matches. All but one item in each list have a value of None. If I just needed the matched string, I could use a list comprehension like '[x for x in [my_list] if x is not None]', but I need the index in order to figure out which capture group in my regex actually caused the match.

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  • wcf class implementing multiple service contracts

    - by Archie
    Hello, I have a class TestService which implements two service contracts called IService1 and IService2. But I'm facing a difficulty in implementation. My Code looks as follows: Uri baseAddress = new Uri("http://localhost:8000/ServiceModel/Service"); Uri baseAddress1 = new Uri("http://localhost:8080/ServiceModel/Service1"); ServiceHost selfHost = new ServiceHost(typeof(TestService)); selfHost.AddServiceEndpoint(typeof(IService1), new WSHttpBinding(), baseAddress); selfHost.AddServiceEndpoint(typeof(IService2), new WSHttpBinding(), baseAddress1); ServiceMetadataBehavior smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; selfHost.Description.Behaviors.Add(smb); selfHost.Open(); Console.WriteLine("The service is ready."); Console.WriteLine("Press <ENTER> to terminate service."); Console.WriteLine(); Console.ReadLine(); selfHost.Close(); I'm getting a run time error as: The HttpGetEnabled property of ServiceMetadataBehavior is set to true and the HttpGetUrl property is a relative address, but there is no http base address. Either supply an http base address or set HttpGetUrl to an absolute address. What shall i do about it? Do I realy need two separate endpoints? Thanks.

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  • How can I optimize retrieving lowest edit distance from a large table in SQL?

    - by Matt
    Hey, I'm having troubles optimizing this Levenshtein Distance calculation I'm doing. I need to do the following: Get the record with the minimum distance for the source string as well as a trimmed version of the source string Pick the record with the minimum distance If the min distances are equal (original vs trimmed), choose the trimmed one with the lowest distance If there are still multiple records that fall under the above two categories, pick the one with the highest frequency Here's my working version: DECLARE @Results TABLE ( ID int, [Name] nvarchar(200), Distance int, Frequency int, Trimmed bit ) INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@Source, [Name])) As Distance, Frequency, 'False' As Trimmed FROM MyTable INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@SourceTrimmed, [Name])) As Distance, Frequency, 'True' As Trimmed FROM MyTable SET @ResultID = (SELECT TOP 1 ID FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @Result = (SELECT TOP 1 [Name] FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultDist = (SELECT TOP 1 Distance FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultTrimmed = (SELECT TOP 1 Trimmed FROM @Results ORDER BY Distance, Trimmed, Frequency) I believe what I need to do here is to.. Not dumb the results to a temporary table Do only 1 select from `MyTable` Setting the results right in the select from the initial select statement. (Since select will set variables and you can set multiple variables in one select statement) I know there has to be a good implementation to this but I can't figure it out... this is as far as I got: SELECT top 1 @ResultID = ID, @Result = [Name], (dbo.Levenshtein(@Source, [Name])) As distOrig, (dbo.Levenshtein(@SourceTrimmed, [Name])) As distTrimmed, Frequency FROM MyTable WHERE /* ... yeah I'm lost */ ORDER BY distOrig, distTrimmed, Frequency Any ideas?

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  • Is there a standard pattern for scanning a job table executing some actions?

    - by Howiecamp
    (I realize that my title is poor. If after reading the question you have an improvement in mind, please either edit it or tell me and I'll change it.) I have the relatively common scenario of a job table which has 1 row for some thing that needs to be done. For example, it could be a list of emails to be sent. The table looks something like this: ID Completed TimeCompleted anything else... ---- --------- ------------- ---------------- 1 No blabla 2 No blabla 3 Yes 01:04:22 ... I'm looking either for a standard practice/pattern (or code - C#/SQL Server preferred) for periodically "scanning" (I use the term "scanning" very loosely) this table, finding the not-completed items, doing the action and then marking them completed once done successfully. In addition to the basic process for accomplishing the above, I'm considering the following requirements: I'd like some means of "scaling linearly", e.g. running multiple "worker processes" simultaneously or threading or whatever. (Just a specific technical thought - I'm assuming that as a result of this requirement, I need some method of marking an item as "in progress" to avoid attempting the action multiple times.) Each item in the table should only be executed once. Some other thoughts: I'm not particularly concerned with the implementation being done in the database (e.g. in T-SQL or PL/SQL code) vs. some external program code (e.g. a standalone executable or some action triggered by a web page) which is executed against the database Whether the "doing the action" part is done synchronously or asynchronously is not something I'm considering as part of this question.

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  • NSOperations or NSThread for bursts of smaller tasks that continuously cancel each other?

    - by RickiG
    Hi I would like to see if I can make a "search as you type" implementation, against a web service, that is optimized enough for it to run on an iPhone. The idea is that the user starts typing a word; "Foo", after each new letter I wait XXX ms. to see if they type another letter, if they don't, I call the web service using the word as a parameter. The web service call and the subsequent parsing of the result I would like to move to a different thread. I have written a simple SearchWebService class, it has only one public method: - (void) searchFor:(NSString*) str; This method tests if a search is already in progress (the user has had a XXX ms. delay in their typing) and subsequently stops that search and starts a new one. When a result is ready a delegate method is called: - (NSArray*) resultsReady; I can't figure out how to get this functionality 'threaded'. If I keep spawning new threads each time a user has a XXX ms. delay in the typing I end up in a bad spot with many threads, especially because I don't need any other search, but the last one. Instead of spawning threads continuously, I have tried keeping one thread running in the background all the time by: - (void) keepRunning { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; SearchWebService *searchObj = [[SearchWebService alloc] init]; [[NSRunLoop currentRunLoop] run]; //keeps it alive [searchObj release]; [pool release]; } But I can't figure out how to access the "searchFor" method in the "searchObj" object, so the above code works and keeps running. I just can't message the searchObj or retrieve the resultReady objects? Hope someone could point me in the right direction, threading is giving me grief:) Thank you.

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  • What should I do if i have a factory method which requires different parameters for different implem

    - by Sam Holder
    I have an interface, IMessage and a class which have several methods for creating different types of message like so: class MessageService { IMessage TypeAMessage(param 1, param 2) IMessage TypeBMessage(param 1, param 2, param 3, param 4) IMessage TypeCMessage(param 1, param 2, param 3) IMessage TypeDMessage(param 1) } I don't want this class to do all the work for creating these messages so it simply delegates to a MessageCreatorFactory which produces an IMessageCreator depending on the type given (an enumeration based on the type of the message TypeA, TypeB, TypeC etc) interface IMessageCreator { IMessage Create(MessageParams params); } So I have 4 implementations of IMessageCreator: TypeAMessageCreator, TypeBMessageCreator, TypeCMessageCreator, TypeDMessageCreator I ok with this except for the fact that because each type requires different parameters I have had to create a MessageParams object which contains 4 properties for the 4 different params, but only some of them are used in each IMessageCreator. Is there an alternative to this? One other thought I had was to have a param array as the parameter in the Create emthod, but this seems even worse as you don't have any idea what the params are. Or to create several overloads of Create in the interface and have some of them throw an exception if they are not suitable for that particular implementation (ie you called a method which needs more params, so you should have called one of the other overloads.) Does this seem ok? Is there a better solution?

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  • Concise C# code for gathering several properties with a non-null value into a collection?

    - by stakx
    A fairly basic problem for a change. Given a class such as this: public class X { public T A; public T B; public T C; ... // (other fields, properties, and methods are not of interest here) } I am looking for a concise way to code a method that will return all A, B, C, ... that are not null in an enumerable collection. (Assume that declaring these fields as an array is not an option.) public IEnumerable<T> GetAllNonNullAs(this X x) { // ? } The obvious implementation of this method would be: public IEnumerable<T> GetAllNonNullAs(this X x) { var resultSet = new List<T>(); if (x.A != null) resultSet.Add(x.A); if (x.B != null) resultSet.Add(x.B); if (x.C != null) resultSet.Add(x.C); ... return resultSet; } What's bothering me here in particular is that the code looks verbose and repetitive, and that I don't know the initial List capacity in advance. It's my hope that there is a more clever way, probably something involving the ?? operator? Any ideas?

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  • Solr/Lucene Scorer

    - by TFor
    We are currently working on a proof-of-concept for a client using Solr and have been able to configure all the features they want except the scoring. Problem is that they want scores that make results fall in buckets: Bucket 1: exact match on category (score = 4) Bucket 2: exact match on name (score = 3) Bucket 3: partial match on category (score = 2) Bucket 4: partial match on name (score = 1) First thing we did was develop a custom similarity class that would return the correct score depending on the field and an exact or partial match. The only problem now is that when a document matches on both the category and name the scores are added together. Example: searching for "restaurant" returns documents in the category restaurant that also have the word restaurant in their name and thus get a score of 5 (4+1) but they should only get 4. I assume for this to work we would need to develop a custom Scorer class but we have no clue on how to incorporate this in Solr. Another option is to create a custom SortField implementation similar to the RandomSortField already present in Solr. Maybe there is even a simpler solution that we don't know about. All suggestions welcome!

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  • iPhone: Using dispatch_after to mimick NSTimer

    - by Joseph Tura
    Don't know a whole lot about blocks. How would you go about mimicking a repeating NSTimer with dispatch_after? My problem is that I want to "pause" a timer when the app moves to the background, but subclassing NSTimer does not seem to work. I tried something which seems to work. I cannot judge its performance implications or whether it could be greatly optimized. Any input is welcome. #import "TimerWithPause.h" @implementation TimerWithPause @synthesize timeInterval; @synthesize userInfo; @synthesize invalid; @synthesize invocation; + (TimerWithPause *)scheduledTimerWithTimeInterval:(NSTimeInterval)aTimeInterval target:(id)aTarget selector:(SEL)aSelector userInfo:(id)aUserInfo repeats:(BOOL)aTimerRepeats { TimerWithPause *timer = [[[TimerWithPause alloc] init] autorelease]; timer.timeInterval = aTimeInterval; NSMethodSignature *signature = [[aTarget class] instanceMethodSignatureForSelector:aSelector]; NSInvocation *aInvocation = [NSInvocation invocationWithMethodSignature:signature]; [aInvocation setSelector:aSelector]; [aInvocation setTarget:aTarget]; [aInvocation setArgument:&timer atIndex:2]; timer.invocation = aInvocation; timer.userInfo = aUserInfo; if (!aTimerRepeats) { timer.invalid = YES; } [timer fireAfterDelay]; return timer; } - (void)fireAfterDelay { dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, self.timeInterval * NSEC_PER_SEC); dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_after(delay, queue, ^{ [invocation performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:NO]; if (!invalid) { [self fireAfterDelay]; } }); } - (void)invalidate { invalid = YES; [invocation release]; invocation = nil; [userInfo release]; userInfo = nil; } - (void)dealloc { [self invalidate]; [super dealloc]; } @end

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  • Insert data in an object to a database.

    - by paul
    I am facing the following design/implementation dilemma. I have a class Customer which is below with getters and setters. I would like to insert the value of the Customer into a "Customer" table of a database. But Customer has an address which is of type "Address". How do I go about inserting this field into the database?(I am using sqlite3). I thought of writing a separate table "Address(customerId,doorNo,city,state,country,pinCode)". But I am having second thoughts about generating the primary key(customerId) which should be same for both the "customer" and "Address" table. Sqlite3 faq states that I can do "Integer Primary Key" to use the field to generate an auto number. But if I do that in customer table, I would have to retrieve the same Id to be used in Address table. This kinda looks wrong to me :-?. There should be an elegant method to solve this. Any ideas would be much appreciated. Thanks in advance. import java.io.*; import java.sql.*; class Customer { private String id; private String name; private Address address; private Connection connection; private ResultSet resultSet; private PreparedStatement preparedStatement; public void insertToDatabase(){ } } class Address{ private String doorNumber; private String streetName; private String cityName; private String districtName; private String stateName; private String countryName; private long pinCode; }

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