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  • Type casting in C++ by detecting the current 'this' object type

    - by Elroy
    My question is related to RTTI in C++ where I'm trying to check if an object belongs to the type hierarchy of another object. The BelongsTo() method checks this. I tried using typeid, but it throws an error and I'm not sure about any other way how I can find the target type to convert to at runtime. #include <iostream> #include <typeinfo> class X { public: // Checks if the input type belongs to the type heirarchy of input object type bool BelongsTo(X* p_a) { // I'm trying to check if the current (this) type belongs to the same type // hierarchy as the input type return dynamic_cast<typeid(*p_a)*>(this) != NULL; // error C2059: syntax error 'typeid' } }; class A : public X { }; class B : public A { }; class C : public A { }; int main() { X* a = new A(); X* b = new B(); X* c = new C(); bool test1 = b->BelongsTo(a); // should return true bool test2 = b->BelongsTo(c); // should return false bool test3 = c->BelongsTo(a); // should return true } Making the method virtual and letting derived classes do it seems like a bad idea as I have a lot of classes in the same type hierarchy. Or does anybody know of any other/better way to the do the same thing? Please suggest.

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  • Getting the type of an array of T, without specifying T - Type.GetType("T[]")

    - by Merlyn Morgan-Graham
    I am trying to create a type that refers to an array of a generic type, without specifying the generic type. That is, I would like to do the equivalent of Type.GetType("T[]"). I already know how to do this with a non-array type. E.g. Type.GetType("System.Collections.Generic.IEnumerable`1") // or typeof(IEnumerable<>) Here's some sample code that reproduces the problem. using System; using System.Collections.Generic; public class Program { public static void SomeFunc<T>(IEnumerable<T> collection) { } public static void SomeArrayFunc<T>(T[] collection) { } static void Main(string[] args) { Action<Type> printType = t => Console.WriteLine(t != null ? t.ToString() : "(null)"); Action<string> printFirstParameterType = methodName => printType( typeof(Program).GetMethod(methodName).GetParameters()[0].ParameterType ); printFirstParameterType("SomeFunc"); printFirstParameterType("SomeArrayFunc"); var iEnumerableT = Type.GetType("System.Collections.Generic.IEnumerable`1"); printType(iEnumerableT); var iEnumerableTFromTypeof = typeof(IEnumerable<>); printType(iEnumerableTFromTypeof); var arrayOfT = Type.GetType("T[]"); printType(arrayOfT); // Prints "(null)" // ... not even sure where to start for typeof(T[]) } } The output is: System.Collections.Generic.IEnumerable`1[T] T[] System.Collections.Generic.IEnumerable`1[T] System.Collections.Generic.IEnumerable`1[T] (null) I'd like to correct that last "(null)". This will be used to get an overload of a function via reflections by specifying the method signature: var someMethod = someType.GetMethod("MethodName", new[] { typeOfArrayOfT }); // ... call someMethod.MakeGenericMethod some time later I've already gotten my code mostly working by filtering the result of GetMethods(), so this is more of an exercise in knowledge and understanding.

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  • Rename parameter in a WCF client interface

    - by user295479
    Hello everyone, I was wondering if there is a way to rename a parameter in a WCF client interface method ,just the same way I can rename methods or enumerations: Renaming methods: [System.Runtime.Serialization.DataMemberAttribute(Name = "intError")] public int ErrorCode {...} Renaming enumerations: public enum MyEnumeration: int { [System.Runtime.Serialization.EnumMemberAttribute()] None = 0, [System.Runtime.Serialization.EnumMemberAttribute(Value = "FirstOption")] First= 1, [System.Runtime.Serialization.EnumMemberAttribute()] SecondOption= 2, } Renaming parameters?? I want to rename an interface parameter named "error" which FxCop doesn't like. Any help will be appreciated. Thank you.

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  • Verify method with Delegate parameter in Moq

    - by Hans Løken
    I have a case where I want to verify that a method that takes a Delegate parameter is called. I don't care about the particular Delegate parameter supplied I just want to make sure that the method is in fact called. The method looks like this: public interface IInvokerProxy{ void Invoke(Delegate method); ... } I would like to do something like this: invokerProxyMock.Verify( proxy => proxy.Invoke( It.IsAny<Delegate>)); Currently it gives me an error Argument '1': cannot convert from 'method group' to 'System.Delegate'. Does anyone know if this is possible?

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  • transfer parameter to next request

    - by user234194
    I have a situation where clicking a link in one column on the datatable opens A update FORM in the same page. The problem is when I hit the submit button for update, the render is set to false again of that update panel which was previously set true by parameter passed clicking the link. I tried htmlhiddenInput and did setValue and getvalue but the value is lost. Is there any way I can save that parameter send from link, when clicked, even after submitting the form. I achieved it doing session but I dont wanna use session. Any help is appreciated, thanks.

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  • What can Haskell's type system do that Java's can't?

    - by Matt Fenwick
    I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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  • What can Haskell's type system do that Java's can't and vice versa?

    - by Matt Fenwick
    I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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  • What are some reasonable stylistic limits on type inference?

    - by Jon Purdy
    C++0x adds pretty darn comprehensive type inference support. I'm sorely tempted to use it everywhere possible to avoid undue repetition, but I'm wondering if removing explicit type information all over the place is such a good idea. Consider this rather contrived example: Foo.h: #include <set> class Foo { private: static std::set<Foo*> instances; public: Foo(); ~Foo(); // What does it return? Who cares! Just forward it! static decltype(instances.begin()) begin() { return instances.begin(); } static decltype(instances.end()) end() { return instances.end(); } }; Foo.cpp: #include <Foo.h> #include <Bar.h> // The type need only be specified in one location! // But I do have to open the header to find out what it actually is. decltype(Foo::instances) Foo::instances; Foo() { // What is the type of x? auto x = Bar::get_something(); // What does do_something() return? auto y = x.do_something(*this); // Well, it's convertible to bool somehow... if (!y) throw "a constant, old school"; instances.insert(this); } ~Foo() { instances.erase(this); } Would you say this is reasonable, or is it completely ridiculous? After all, especially if you're used to developing in a dynamic language, you don't really need to care all that much about the types of things, and can trust that the compiler will catch any egregious abuses of the type system. But for those of you that rely on editor support for method signatures, you're out of luck, so using this style in a library interface is probably really bad practice. I find that writing things with all possible types implicit actually makes my code a lot easier for me to follow, because it removes nearly all of the usual clutter of C++. Your mileage may, of course, vary, and that's what I'm interested in hearing about. What are the specific advantages and disadvantages to radical use of type inference?

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  • Event receiver on Content Type not triggered on WikiPageLibrary

    - by Ciprian Grosu
    Hello all, I created a new content type for a wiki page library. I added this content type to library by code (the interface did not allow this). Next, I added an event receiver to this content type (on ItemAdded and ItemAdding). My problem is that no event is trrigered. If I add this events directly to the wiki page library all works fine. Is there a limitation/bug/trick ? I looked at the content type attached to the library with SharePoint Manager and in his schema the part for event receiver is missing...I know that there should be something like: <XmlDocuments> <XmlDocument NamespaceURI="http://schemas.microsoft.com/sharepoint/events"> <spe:Receivers xmlns:spe="http://schemas.microsoft.com/sharepoint/events"> <Receiver> <Name> </Name> <Type>1</Type> <SequenceNumber>10000</SequenceNumber> <Assembly>RssFeedWP, Version=1.0.0.0, Culture=neutral, PublicKeyToken=f6722cbeba696def</Assembly> <Class>RssFeedWP.ItemEventReceiver</Class> <Data> </Data> <Filter> </Filter> </Receiver> <Receiver> <Name> </Name> <Type>10001</Type> <SequenceNumber>10000</SequenceNumber> <Assembly>RssFeedWP, Version=1.0.0.0, Culture=neutral, PublicKeyToken=f6722cbeba696def</Assembly> <Class>RssFeedWP.ItemEventReceiver</Class> <Data> </Data> <Filter> </Filter> </Receiver> </spe:Receivers> </XmlDocument> If I look with SPM to the content type added to site I see this part into schema. Here is my code: public override void FeatureActivated(SPFeatureReceiverProperties properties) { using (SPWeb web = (SPWeb)properties.Feature.Parent) { // create RssWiki content type SPContentType rssFeedContentType = new SPContentType(web.AvailableContentTypes["Wiki Page"], web.ContentTypes, "RssFeed Wiki Page"); // add rssfeed url field to the new content type AddFieldToContentType(web, rssFeedContentType, "RssFeed Url", SPFieldType.Note); // add use xslt check box field to the new content type AddFieldToContentType(web, rssFeedContentType, "Use Xslt", SPFieldType.Boolean); // add xslt url field to the new content type AddFieldToContentType(web, rssFeedContentType, "Xslt Url", SPFieldType.Note); web.ContentTypes.Add(rssFeedContentType); rssFeedContentType.Update(); web.Update(); AddContentTypeToList(web, rssFeedContentType); AddEventReceiversToCT(rssFeedContentType); //AddEventReceiverToList(web); } } private void AddFieldToContentType(SPWeb web, SPContentType ct, string fieldName, SPFieldType fieldType) { SPField rssUrlField = null; try { rssUrlField = web.Fields.GetField(fieldName); } catch (Exception ex) { if (rssUrlField == null) { web.Fields.Add(fieldName, fieldType, false); } } SPFieldLink rssUrlFieldLink = new SPFieldLink(web.Fields[fieldName]); ct.FieldLinks.Add(rssUrlFieldLink); } private static void AddContentTypeToList(SPWeb web, SPContentType ct) { SPList wikiList = web.Lists[listName]; wikiList.ContentTypesEnabled = true; wikiList.ContentTypes.Add(ct); wikiList.Update(); } private static void AddEventReceiversToCT(SPContentType ct) { //add event receivers string assemblyName = System.Reflection.Assembly.GetExecutingAssembly().FullName; string ctReceiverName = "RssFeedWP.ItemEventReceiver"; ct.EventReceivers.Add(SPEventReceiverType.ItemAdding, assemblyName, ctReceiverName); ct.EventReceivers.Add(SPEventReceiverType.ItemAdded, assemblyName, ctReceiverName); ct.Update(); } Thx !

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  • [Haskell] Problem when mixing type classes and type families

    - by Giuseppe Maggiore
    Hi! This code compiles fine: {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances, FlexibleContexts, EmptyDataDecls, ScopedTypeVariables, TypeOperators, TypeSynonymInstances, TypeFamilies #-} class Sel a s b where type Res a s b :: * instance Sel a s b where type Res a s b = (s -> (b,s)) instance Sel a s (b->(c,a)) where type Res a s (b->(c,a)) = (b -> s -> (c,s)) but as soon as I add the R predicate ghc fails: {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances, FlexibleContexts, EmptyDataDecls, ScopedTypeVariables, TypeOperators, TypeSynonymInstances, TypeFamilies #-} class Sel a s b where type Res a s b :: * instance Sel a s b where type Res a s b = (s -> (b,s)) class R a where type Rec a :: * cons :: a -> Rec a elim :: Rec a -> a instance Sel a s (b->(c,Rec a)) where type Res a s (b->(c,Rec a)) = (b -> s -> (c,s)) complaining that: Illegal type synonym family application in instance: b -> (c, Rec a) In the instance declaration for `Sel a s (b -> (c, Rec a))' what does it mean and (most importantly) how do I fix it? Thanks

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  • How to deal with multiple sub-type of one super-type in Django admin

    - by Henri
    What would be the best solution for adding/editing multiple sub-types. E.g a super-type class Contact with sub-type class Client and sub-type class Supplier. The way shown here works, but when you edit a Contact you get both inlines i.e. sub-type Client AND sub-type Supplier. So even if you only want to add a Client you also get the fields for Supplier of vice versa. If you add a third sub-type , you get three sub-type field groups, while you actually only want one sub-type group, in the mentioned example: Client. E.g.: class Contact(models.Model): contact_name = models.CharField(max_length=128) class Client(models.Model): contact = models.OneToOneField(Contact, primary_key=True) user_name = models.CharField(max_length=128) class Supplier(models.Model): contact.OneToOneField(Contact, primary_key=True) company_name = models.CharField(max_length=128) and in admin.py class ClientInline(admin.StackedInline): model = Client class SupplierInline(admin.StackedInline): model = Supplier class ContactAdmin(admin.ModelAdmin): inlines = (ClientInline, SupplierInline,) class ClientAdmin(admin.ModelAdmin): ... class SupplierAdmin(admin.ModelAdmin): ... Now when I want to add a Client, i.e. only a Client I edit Contact and I get the inlines for both Client and Supplier. And of course the same for Supplier. Is there a way to avoid this? When I want to add/edit a Client that I only see the Inline for Client and when I want to add/edit a Supplier that I only see the Inline for Supplier, when adding/editing a Contact? Or perhaps there is a different approach. Any help or suggestion will be greatly appreciated.

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  • With PascalMock how do I mock a method with an untyped out parameter and an open array parameter?

    - by Oliver Giesen
    I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all?

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  • OdbcCommand on Stored Procedure - "Parameter not supplied" error on Output parameter

    - by Aaron
    I'm trying to execute a stored procedure (against SQL Server 2005 through the ODBC driver) and I recieve the following error: Procedure or Function 'GetNodeID' expects parameter '@ID', which was not supplied. @ID is the OUTPUT parameter for my procedure, there is an input @machine which is specified and is set to null in the stored procedure: ALTER PROCEDURE [dbo].[GetNodeID] @machine nvarchar(32) = null, @ID int OUTPUT AS BEGIN SET NOCOUNT ON; IF EXISTS(SELECT * FROM Nodes WHERE NodeName=@machine) BEGIN SELECT @ID = (SELECT NodeID FROM Nodes WHERE NodeName=@machine) END ELSE BEGIN INSERT INTO Nodes (NodeName) VALUES (@machine) SELECT @ID = (SELECT NodeID FROM Nodes WHERE NodeName=@machine) END END The following is the code I'm using to set the parameters and call the procedure: OdbcCommand Cmd = new OdbcCommand("GetNodeID", _Connection); Cmd.CommandType = CommandType.StoredProcedure; Cmd.Parameters.Add("@machine", OdbcType.NVarChar); Cmd.Parameters["@machine"].Value = Environment.MachineName.ToLower(); Cmd.Parameters.Add("@ID", OdbcType.Int); Cmd.Parameters["@ID"].Direction = ParameterDirection.Output; Cmd.ExecuteNonQuery(); _NodeID = (int)Cmd.Parameters["@Count"].Value; I've also tried using Cmd.ExecuteScalar with no success. If I break before I execute the command, I can see that @machine has a value. If I execute the procedure directly from Management Studio, it works correctly. Any thoughts? Thanks

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  • form_form and custom parameter in path_prefix

    - by fguillen
    Hi people, I have this route: # config/routes.rb map.namespace :backshop, :path_prefix => '/:shop_id/admin' do |backshop| backshop.resources :items end And I want to use the form_for magic to reuse the same form on both: new and edit views: <% form_for [:backshop, @item] do |f| %> This used to works, and used to build a create url for the item or update url for the item depending on the status of the @item object. But this is not working on this case because the routes don't exists without the shop_id parameter, and I don't know how to say to the form_for something like this: <% form_for [:backshop, @item], :shop_id => @shop do |f| %> Because it tries to use the @item like the :shop_id parameter. Or like this <% form_for [:backshop, @shop, @item] do |f| %> Because it tries to build this url: backshop_shop_order_path I Know I can just to extract the form_for declaration from the partial and do different calls on depending if new or edit: <% form_for( @item, :url => backshop_items_path( @shop ) ) do |f| %> and <% form_for( @item, :url => backshop_item_path( @shop, @item ) ) do |f| %> But I just wanted don't do this because I have a bunch of models and is a few boring :) Thanks for any suggestion f.

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  • objective-c determine if parameter is an object

    - by Broch Pirate
    in Objective-c I have this function prototype: -(NSString*)formatSQL:(NSString*) sql, ... I may pass to this function any type of parameters: NSString, NSNumber, integer, float How can I determine in the function if a parameter is an object (NSString..) or a primitive (integer...)? thanks BrochPirate

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  • Describe the Damas-Milner type inference in a way that a CS101 student can understand

    - by user128807
    Hindley-Milner is a type system that is the basis of the type systems of many well known functional programming languages. Damas-Milner is an algorithm that infers (deduces?) types in a Hindley-Milner type system. Wikipedia gives a description of the algorithm which, as far as I can tell, amounts to a single word: "unification." Is that all there is to it? If so, that means that the interesting part is the type system itself not the type inference system. If Damas-Milner is more than unification, I would like a description of Damas-Milner that includes a simple example and, ideally, some code. Also, this algorithm is often said to do type inference. Is it really an inference system? I thought it was only deducing the types. Related questions: What is Hindley Miller? Type inference to unification problem

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  • Enum as a Parameter in Dynamics AX

    - by Lauren
    My report has a parameter which uses a base enum. The enum has 4 different options to choose when running the report. How do I insert an option which uses all 4 at once? For example, I have an enum named Phone and it has 4 types: 1 = None, 2 = Home, 3 = Mobile, 4 = Work. In a drop down, how do I add option 5 = None+Home+Mobile+Work? Thank you!

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  • ASP.NET MVC Controller parameter processing

    - by Leonardo
    In my application I have a string parameter called "shop" that is required in all controllers, but it needs to be transformed using code like this: shop = shop.Replace("-", " ").ToLower(); How can I do this globally for all controllers without repeating this line in over and over? Thanks, Leo

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  • Custom field not showing in Custom Content Type

    - by BeraCim
    Hi all: I created a custom column in a custom content type in a Sharepoint Web manually (e.g. /MySite/MyWeb). I now want to programmatically copy this content type across to another web (e.g. /MySite/MyWeb2). However, upon looping through the custom content type in code, I could only find 2 fields: Content Type and Title (expected: Title and custom column). The custom column was missing. I'm very sure that the content type and field are added at the web level. The custom content type is inherited from Item. When I loop through the web's fields, I can see the custom column, and that was copied to the new web. It is only within the content type that the custom column is not showing up. Any ideas why this is happening? Thanks.

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  • Passing parameter as final in C#

    - by Ravisha
    This might be a duplicate question.But could not find it in search In java to mark a method parameter as constant we declare it as final whats the equivalent C# keyword? Like: public void doSomeThing(final object myObject) { //print myobject }

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  • Haskell type classes and type families (cont'd)

    - by Giuseppe Maggiore
    I need some help in figuring a compiler error which is really driving me nuts... I have the following type class: infixl 7 --> class Selectable a s b where type Res a s b :: * (-->) :: (CNum n) => (Reference s a) -> (n,(a->b),(a->b->a)) -> Res a s b which I instance twice. First time goes like a charm: instance Selectable a s b where type Res a s b = Reference s b (-->) (Reference get set) (_,read,write) = (Reference (\s -> let (v,s') = get s in (read v,s')) (\s -> \x -> let (v,s') = get s v' = write v x (_,s'') = set s' v' in (x,s''))) since the type checker infers (-->) :: Reference s a -> (n,a->b,a->b->a) -> Reference s b and this signature matches with the class signature for (--) since Res a s b = Reference s b Now I add a second instance and everything breaks: instance (Recursive a, Rec a ~ reca) => Selectable a s (Method reca b c) where type Res a s (Method reca b c) = b -> Reference s c (-->) (Reference get set) (_,read,write) = \(x :: b) -> from_constant( Constant(\(s :: s)-> let (v,s') = get s :: (a,s) m = read v ry = m x :: Reference (reca) c (y,v') = getter ry (cons v) :: (c,reca) v'' = elim v' (_,s'') = set s' v'' in (y,s''))) :: Reference s c the compiler complains that Couldn't match expected type `Res a s (Method reca b c)' against inferred type `b -> Reference s c' The lambda expression `\ (x :: b) -> ...' has one argument, which does not match its type In the expression: \ (x :: b) -> from_constant (Constant (\ (s :: s) -> let ... in ...)) :: Reference s c In the definition of `-->': --> (Reference get set) (_, read, write) = \ (x :: b) -> from_constant (Constant (\ (s :: s) -> ...)) :: Reference s c reading carefully the compiler is telling me that it has inferred the type of (--) thusly: (-->) :: Reference s a -> (n,a->(Method reca b c),a->(Method reca b c)->a) -> (b -> Reference s c) which is correct since Res a s (Method reca b c) = b -> Reference s c but why can't it match the two definitions? Sorry for not offering a more succint and standalone example, but in this case I cannot figure how to do it...

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  • Output Parameter in java

    - by soclose
    Hi, could u give me a sample code of using output parameter in function? I tried to google it but just found it in function. I'd like to use this output value in another function. I will use this code in Android.

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  • C++ template nontype parameter arithmetic

    - by aaa
    hello I am trying to specialize template the following way: 132 template<size_t _1,size_t _2> 131 struct integral_index_ {}; ... 141 template<size_t _1> 142 struct integral_index_<_1, _1 + 1> { ... 148 }; however I get compiler message error the template argument list of the partial specialization includes a non -type argument whose type depends on a template parameter. what do my doing wrong? thanks

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