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  • Compilers behave differently with a null parameter of a generic method

    - by Eyal Schneider
    The following code compiles perfectly with Eclipse, but fails to compile with javac: public class HowBizarre { public static <P extends Number, T extends P> void doIt(P value) { } public static void main(String[] args) { doIt(null); } } I simplified the code, so T is not used at all now. Still, I don't see a reason for the error. For some reason javac decides that T stands for Object, and then complains that Object does not conform to the bounds of T (which is true): HowBizarre.java:6: incompatible types; inferred type argument(s) java.lang.Number,java.lang.Object do not conform to bounds of type variable (s) P,T found : <P,T>void required: void doIt(null); ^ Note that if I replace the null parameter with a non-null value, it compiles fine. Which of the compilers behaves correctly and why? Is this a bug of one of them?

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  • Generic test suite for ASP.NET Membership/Role/Profile/Session Providers

    - by SztupY
    Hi! I've just created custom ASP.NET Membership, Role, Profile and Session State providers, and I was wondering whether there exists a test suite or something similar to test the implementation of the providers. I've checked some of the open source providers I could find (like the NauckIt.PostgreSQL provider), but neither of them contained unit tests, and all of the forum topics I've found mentioned only a few test cases (like checking whether creating a user works), but this is clearly not a complete test suite for a Membership provider. (And I couldn't find anything for the other three providers) Are there more or less complete test suites for the above mentioned providers, or are there custom providers out there that have at least some testing avaialable?

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  • Setting generic type at runtime

    - by destroyer of evil
    I have a class public class A<T> { public static string B(T obj) { return TransformThisObjectToAString(obj); } } I can call the static function like this just fine on a known/specified type: string s= A<KnownType>.B(objectOfKnownType); How do I make this call, if I don't know T beforehand, rather I have a variable of type Type that holds the type. If I do this: Type t= typeof(string); string s= A<t>.B(someStringObject); I get this compiler error: Cannot implicitly convert type 't' to 'object'

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  • Generic Rails Route Representation?

    - by Flemish Bee Cycle
    Given one or more instances of a model (AR or DM, whatever). Is it possible to generate the route in the requirement form, by which I mean "/foos/:id" Given the route: resource :foo do resource :bar end generate_route_method [@foo,@bar] - "/foos/:id/bars/:id" I'm not talking about #foos_path or #polymorphic_path, rather, literally generating the string containing the wildcard components (i.e ":id"), the same as it would appear as if you did "rake routes".

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  • Binding Generic List Array to GridView

    - by OliverS
    Hi I have a List which returns an array of "Question". My question is how can I bind this to a grid view? When I try to call Question.Ordinal I get that it does not exist in the data source. I am using the following code: GridView1.DataSource = myList.GetQ(); GrdiView1.DataBind(); myList.GetQ() returns a List which is an array of "Question". When I set the column DataField to "!" I get the object Question. My question is how can I get the objects property? I tried "!.Ordinal" does not work. I was reading this post for reference, here, any help is greatly appreciated, thanks.

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  • Generic WithEvents

    - by serhio
    Error: 'WithEvents' variables can only be typed as classes, interfaces or type parameters with class constraints Background: Public Class Tadpole(Of T As IVisibleChanged, P As IVisibleChanged) Private WithEvents _Tad As T ' ERROR ' Private WithEvents _Pole As P ' ERROR ' Public Property Tad() As T ... Public Property Pole() As P ... End Class ''' IVisibleChanged ''' Public Interface IVisibleChanged Property Visible() As Boolean Event VisibleChanged As EventHandler End Interface Workaround: a. Use AddHandler to handle events defined in a structure. EDIT b. use Private WithEvents _Tad AsIVisibleChanged (M.A. Hanin) c. ?

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  • Hot to get generic type from object type

    - by Murat
    My Classes are; class BaseClass { } class DerivedClass1 : BaseClass { } class GenericClass<T> { } class DerivedClass2 : BaseClass { GenericClass<DerivedClass1> subItem; } I want to access all fields of DerivedClass2 class. I use System.Reflection and FieldInfo.GetValue() method; Bu I cant get subItem field. FieldInfo.GetValue() method return type is "object". And I cant cast to GenericClass<DerivedClass1> or I cant get DerivedClass1 type. I try this with BaseClass BaseClass instance = FieldInfo.Getvalue(this) as GenericClass<BaseClass>; but instance is null. How to get instance with type or how to get only type?

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  • django app with a generic name

    - by zaharpopov
    Django tutorials everywhere use constant-set application name all around - in urls file, in HTML templates, in views. But if I want to distribute an application and let the user sets it name (i.e. its URL postfix on http://server.com/appname) - how can I do? I must have some common name setting then in configuration, but how to work it for template files, etc?

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  • Casting Generic Types

    - by David Rutten
    Public Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T) Return DirectCast(data, GenericType(Of T)) End Function The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T?

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  • Using Reflection Invoke static generic method passing a Lamba as parameter

    - by Nikos Baxevanis
    Is it possible to write the following code via Reflection? var fake = A.Fake<Foo>( o => o.WithArgumentsForConstructor(new[] { "Hello" })); Where o is: Action<IFakeOptionsBuilder<T>> Where WithArgumentsForConstructor is: IFakeOptionsBuilder<T> WithArgumentsForConstructor(IEnumerable<object> argumentsForConstructor); The Foo class is: class Foo { public Foo(string s) { } } What I did was: object fake = typeof(A) .GetMethod("Fake", new Type[] { }) .MakeGenericMethod(new[] { this.targetType }) .Invoke(null, /* Here I need to pass the lambda. */);

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  • How to implement generic callbacks in C++

    - by Kylotan
    Forgive my ignorance in asking this basic question but I've become so used to using Python where this sort of thing is trivial that I've completely forgotten how I would attempt this in C++. I want to be able to pass a callback to a function that performs a slow process in the background, and have it called later when the process is complete. This callback could be a free function, a static function, or a member function. I'd also like to be able to inject some arbitrary arguments in there for context. (ie. Implementing a very poor man's coroutine, in a way.) On top of that, this function will always take a std::string, which is the output of the process. I don't mind if the position of this argument in the final callback parameter list is fixed. I get the feeling that the answer will involve boost::bind and boost::function but I can't work out the precise invocations that would be necessary in order to create arbitrary callables (while currying them to just take a single string), store them in the background process, and invoke the callable correctly with the string parameter.

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  • Grouping a generic list via LINQ in VB.NET

    - by CD Smith
    I need to take a collection and group it via Linq but all the examples I've seen fail in some manner or other with some syntax difference that I can't quite lick. My collection: Dim a As New List(Of ProcessAlert) a.Add(New ProcessAlert("0000112367", "[email protected]", "Alert", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Document", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Note", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Alert", 1)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Document", 1)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Note", 1)) Return a I need to turn this collection into a simple way to give this final outcome: "[email protected]", "Alert, Document, Note" "[email protected]", "Alert, Document, Note" Here's the definition of the ProcessAlert class: Public Class ProcessAlert Public LoanNumber As String Public EmailAddress As String Public AlertType As String Public AlertMethodID As Byte End Class Thanks in advance, CD

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  • How to display a generic error page in Asp.Net MVC 2

    - by Picflight
    I have the following in my base controller: protected override void OnException(ExceptionContext filterContext) { if (filterContext == null) { throw new ArgumentNullException("filterContext"); } // If custom errors are disabled, we need to let the normal ASP.NET exception handler // execute so that the user can see useful debugging information. if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled) { return; } Exception exception = filterContext.Exception; // If this is not an HTTP 500 (for example, if somebody throws an HTTP 404 from an action method), // ignore it. if (new HttpException(null, exception).GetHttpCode() != 500) { return; } // TODO: What is the namespace for ExceptionType? //if (!ExceptionType.IsInstanceOfType(exception)) //{ // return; //} // Send Email MailException(exception); // TODO: What does this line do? base.OnException(filterContext); filterContext.Result = new ViewResult { ViewName = "Error" }; filterContext.ExceptionHandled = true; filterContext.HttpContext.Response.Clear(); filterContext.HttpContext.Response.StatusCode = 500; } In my Shared folder, I have an Error.aspx View. Web.config <customErrors mode="On" /> I am still seeing the yellow screen when an exception occurs. What am I doing incorrectly?

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  • Does ASP.net 1.1 support Generic HttpHandlers ?

    - by Campos
    I need to get an image from a SQL Server as a byte[], and load it to a WebControl.Image. The only seemingly good way to do it that I found is to implement IHttpHandler and handle the request accordingly. But I'm stuck to using asp.net 1.1. Does it support ashx files?

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  • Generic callbacks

    - by bobobobo
    Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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  • FileInputStream for a generic file System

    - by Akhil
    I have a file that contains java serialized objects like "Vector". I have stored this file over Hadoop Distributed File System(HDFS). Now I intend to read this file (using method readObject) in one of the map task. I suppose FileInputStream in = new FileInputStream("hdfs/path/to/file"); wont' work as the file is stored over HDFS. So I thought of using org.apache.hadoop.fs.FileSystem class. But Unfortunately it does not have any method that returns FileInputStream. All it has is a method that returns FSDataInputStream but I want a inputstream that can read serialized java objects like vector from a file rather than just primitive data types that FSDataInputStream would do. Please help!

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  • Use component id in Castle Windsor generic object configuration

    - by ChoccyButton
    2 questions in one, but very much related. Is it possible with Castle Windsor to resolve a configuration entry such as - Assembly.Namespace.Object1`2[[${ComponentId1}],[${ComponentId2}]], Assembly Where ComponentId1 and ComponentId2 are defined as components. Castle Windsor doesn't seem to be resolving the ComponentId, it is just looking for ComponentId1 in the Castle.Windsor assembly. The second question comes in to play if you can't do the first question. If you have to use a full assembly reference instead of a ComponentId, how can you pass any parameters to the object being created? eg to set ComponentId1.Field1 = "blah", or pass something to the constructor of ComponentId1 Hope that makes sense Update - Following the request for code I've knocked together the following - Objects public class Wrapper<T, T1> where T : ICollector where T1:IProcessor { private T _collector; private T1 _processor; public Wrapper(T collector, T1 processor) { _collector = collector; _processor = processor; } public void GetData() { _collector.CollectData(); _processor.ProcessData(); } } public class Collector1 : ICollector { public void CollectData() { Console.WriteLine("Collecting data from Collector1 ..."); } } public class Processor1 : IProcessor { public void ProcessData() { Console.WriteLine("Processing data from Processor1 ..."); } } repeated so 3 of each type of object in the example Config <components> <component id="Collector1" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector1, CastleWindsorPlay"/> <component id="Collector2" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector2, CastleWindsorPlay"/> <component id="Collector3" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector3, CastleWindsorPlay"/> <component id="Processor1" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor1, CastleWindsorPlay"/> <component id="Processor2" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor2, CastleWindsorPlay"/> <component id="Processor3" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor3, CastleWindsorPlay"/> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[[CastleWindsorPlay.Collector1, CastleWindsorPlay],[CastleWindsorPlay.Processor3, CastleWindsorPlay]], CastleWindsorPlay" /> </components> Instantiation var wrapper = (Wrapper<ICollector, IProcessor>) container.Resolve("Wrapper1"); wrapper.GetData(); This brief example errors with this error message though - Can't create component 'Wrapper1' as it has dependencies to be satisfied. Wrapper1 is waiting for the following dependencies: Services: - CastleWindsorPlay.Collector1 which was not registered. - CastleWindsorPlay.Processor3 which was not registered. The curious part about this is that I can get it to resolve Collector1 and Processor3 individually before the call to the wrapper, but the wrapper still can't see them. This is a basic example, the next thing I'd like to be able to do is when instantiating the Wrapper, set a property on the collector and/or processor. So it could be something like Collector.Id = 10, but set in the config where the wrapper is defined. Setting against the Collector component definition wouldn't work as I'd want to be able to instantiate multiple copies of each Collector, using different Id's Update 2 What I'm actually trying to do is have - <components> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=1)],[${Processor3}]], CastleWindsorPlay" /> <component id="Wrapper2" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=3)],[${Processor3}]], CastleWindsorPlay" /> </components> Then have another object defined as <component id="Manager" type="CastleWindsorPlay.Manager,CastleWindsorPlay"> <parameters> <wrappers> <array> <item>${Wrapper1}</item> <item>${Wrapper2}</item> </array> </wrappers> </parameters> Then finally in code just be able to call - var manager = (Manager)container.Resolve("Manager"); This should return the manager object, with an array of wrappers populated and the wrappers configured with the correct Collector and Convertor. I know there are errors in the Castle config here, that's why I'm asking the question, I don't know how to set the config up to do what I'm after, or even if it's possible to do it in Castle Windsor

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  • Generic transparent Qt widget that can catch clicks?

    - by Pieter
    I've figured out how to use QPainter to draw rectangles. Now I want to have a drawing area where if the user clicks, a 1x1 rectangle is drawn where the mouse pointer is. To accomplish this, I assume I need a transparent Qt widget that supports the clicked() signal. How do I make such a transparent widget? Or is there something else I can use? Perhaps I can only use the window's clicked() signal?

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  • I have a generic implementation of PHP mcrypt module and its not decrypting

    - by Ken Mitchner
    class Crypt_Data { protected $_mcrypt=null; protected $_iv=null; protected $_key=null; public function __construct() { $this->_mcrypt = mcrypt_module_open('rijndael_256', '', 'cbc', ''); $key_size = mcrypt_enc_get_key_size($this->_mcrypt); for($i=0;$i<$key_size;$i++) $test_key .= "0"; $this->_iv = $test_key; $this->_key = $test_key; mcrypt_generic_init($this->_mcrypt,$this->_key,$this->_iv); } public function dataEncrypt($data) { return base64_encode(mcrypt_generic($this->_mcrypt, $data)); } public function dataDecrypt($data) { return mdecrypt_generic($this->_mcrypt, base64_decode($data)); } } $crypt = new Crypt_Data(); $string = "encrypt me"; $encrypted = $crypt->dataEncrypt($string); echo $encrypted."<BR>"; $decrypted = $crypt->dataDecrypt($encrypted); echo $decrypted."<BR>"; output: JJKfKxZckkqwfZ5QWeyVR+3PkMQAsP0Gr1hWaygV20I= qÌÌi_ÖZí(®`iÜ¥wÝÿ ô0€Í6Ÿhf[%ër No idea why this isn't working, everything seems to be fine on my end.. i tried decrypting it with mcrypt_cbc(); and it decrypted it properly.. so it has something to do with my mdecrypt_generic.. any ideas?

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  • Cast Object to Generic List

    - by CrazyJoe
    I have 3 generict type list. List<Contact> = new List<Contact>(); List<Address> = new List<Address>(); List<Document> = new List<Document>(); And save it on a variable with type object. Now i nedd do Cast Back to List to perfom a foreach, some like this: List<Contact> = (List<Contact>)obj; But obj content change every time, and i have some like this: List<???> = (List<???>)obj; I have another variable holding current obj Type: Type t = typeof(obj); Can i do some thing like that??: List<t> = (List<t>)obj; Obs: I no the current type in the list but i need to cast , and i dont now another form instead: List<Contact> = new List<Contact>(); Help Plz!!!

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  • .NET generic class instance - passing a variable data type

    - by FerretallicA
    As the title suggests, I'm tyring to pass a variable data type to a template class. Something like this: frmExample = New LookupForm(Of Models.MyClass) 'Works fine Dim SelectedType As Type = InstanceOfMyClass.GetType() 'Works fine frmExample = New LookupForm(Of SelectedType) 'Ba-bow! frmExample = New LookupForm(Of InstanceOfMyClass.GetType()) 'Ba-bow! LookupForm<Models.MyClass> frmExample; Type SelectedType = InstanceOfMyClass.GetType(); frmExample = new LookupForm<SelectedType.GetType()>(); //Ba-bow frmExample = new LookupForm<(Type)SelectedType>(); //Ba-bow I'm assuming it's something to do with the template being processed at compile time but even if I'm off the mark there, it wouldn't solve my problem anyway. I can't find any relevant information on using Reflection to instance template classes either. (How) can I create an instance of a dynamically typed repository at runtime?

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  • Generic function to handle DataType Conversion

    - by Tommo1977
    I have the following function in C#, that I want to pass a MySQL DataReader value/object. If the value of the object passed is a DBNull I need to handle it and return a Null value of that data type e.g null int. Otherwise I want to convert the returned value like Convert.ToInt32(value) or similar. public static T ConvertFromDB<T>(object value) { return value == DBNull.Value ? default(T) : (T)value; } Can anyone offer any help on this ?

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  • Thread Safety of C# List<T> for readers

    - by ILIA BROUDNO
    I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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  • Generic InBetween Function.

    - by Luiscencio
    I am tired of writing x > min && x < max so i wawnt to write a simple function but I am not sure if I am doing it right... actually I am not cuz I get an error: bool inBetween<T>(T x, T min, T max) where T:IComparable { return (x > min && x < max); } errors: Operator '>' cannot be applied to operands of type 'T' and 'T' Operator '<' cannot be applied to operands of type 'T' and 'T' may I have a bad understanding of the where part in the function declaring note: for those who are going to tell me that I will be writing more code than before... think on readability =) any help will be appreciated EDIT deleted cuz it was resolved =) ANOTHER EDIT so after some headache I came out with this (ummm) thing following @Jay Idea of extreme readability: public static class test { public static comparision Between<T>(this T a,T b) where T : IComparable { var ttt = new comparision(); ttt.init(a); ttt.result = a.CompareTo(b) > 0; return ttt; } public static bool And<T>(this comparision state, T c) where T : IComparable { return state.a.CompareTo(c) < 0 && state.result; } public class comparision { public IComparable a; public bool result; public void init<T>(T ia) where T : IComparable { a = ia; } } } now you can compare anything with extreme readability =) what do you think.. I am no performance guru so any tweaks are welcome

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  • How to create a generic C free function .

    - by nomemory
    I have some C structures related to a 'list' data structure. They look like this. struct nmlist_element_s { void *data; struct nmlist_element_s *next; }; typedef struct nmlist_element_s nmlist_element; struct nmlist_s { void (*destructor)(void *data); int (*cmp)(const void *e1, const void *e2); unsigned int size; nmlist_element *head; nmlist_element *tail; }; typedef struct nmlist_s nmlist; This way I can have different data types being hold in "nmlist_element-data" . The "constructor" (in terms of OOP) has the following signature: nmlist *nmlist_alloc(void (*destructor)(void *data)); Where "destructor" is specific function that de-allocated "data" (being hold by the nmlist_element). If I want to have a list containing integers as data, my "destructor" would like this: void int_destructor(void *data) { free((int*)data); } Still i find it rather "unfriendly" for me to write a destructor functions for every simple primitive data type. So is there a trick to write something like this ? (for primitives): void "x"_destructor(void *data, "x") { free(("x" *)data); } PS: I am not a macro fan myself, and in my short experience regarding C, i don't use them, unless necessary.

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