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• asp.net custom templated datalist - throws argument out of range (index) on button press

  - by MrTortoise

  I have a class BaseTemplate public abstract class BaseTemplate : ITemplate This adds the controls, and provides abstract methods to implement in the inheriting class. The inheriting class then adds its html according to its data source and manages the data binding. this all works fine - I get the control appearing with properly parsed html. the problem is that the base class adds controls into the template that have their own CommandName arguments ... the idea is that the class that implements the custom templated dataList will provide the logic of setting the Selected and Edit Indexes. This class also manages the data binding etc. It sets all of the templates ont he datalist in the Init method (which was another cause of this exception). the exception gets throw when i hit one of these buttons .. but after the ItemCommand event is being processed. The stack trace does not include any references to my methods or objects which is why i am so stuck. The Exception Details Exception Details: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: index The Stack Trace: [ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: index] System.Web.UI.ControlCollection.get_Item(Int32 index) +8665582 System.Web.UI.WebControls.DataList.GetItem(ListItemType itemType, Int32 repeatIndex) +8667655 System.Web.UI.WebControls.DataList.System.Web.UI.WebControls.IRepeatInfoUser.GetItemStyle(ListItemType itemType, Int32 repeatIndex) +11 System.Web.UI.WebControls.RepeatInfo.RenderVerticalRepeater(HtmlTextWriter writer, IRepeatInfoUser user, Style controlStyle, WebControl baseControl) +8640873 System.Web.UI.WebControls.RepeatInfo.RenderRepeater(HtmlTextWriter writer, IRepeatInfoUser user, Style controlStyle, WebControl baseControl) +27 System.Web.UI.WebControls.DataList.RenderContents(HtmlTextWriter writer) +208 System.Web.UI.WebControls.BaseDataList.Render(HtmlTextWriter writer) +30 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +163 System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +32 System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +51 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +40 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 System.Web.UI.Page.Render(HtmlTextWriter writer) +29 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266 This is driving me absolutley stark raving bonkers ... im talking cthulu style.

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• C++ Template const char array to int

  - by Levi Schuck

  So, I'm wishing to be able to have a static const compile time struct that holds some value based on a string by using templates. I only desire up to four characters. I know that the type of 'abcd' is int, and so is 'ab','abc', and although 'a' is of type char, it works out for a template<int v> struct What I wish to do is take sizes of 2,3,4,5 of some const char, "abcd" and have the same functionality as if they used 'abcd'. Note that I do not mean 1,2,3, or 4 because I expect the null terminator. cout << typeid("abcd").name() << endl; tells me that the type for this hard coded string is char const [5], which includes the null terminator on the end. I understand that I will need to twiddle the values as characters, so they are represented as an integer. I cannot use constexpr since VS10 does not support it (VS11 doesn't either..) So, for example with somewhere this template defined, and later the last line template <int v> struct something { static const int value = v; }; //Eventually in some method cout << typeid(something<'abcd'>::value).name() << endl; works just fine. I've tried template<char v[5]> struct something2 { static const int value = v[0]; } template<char const v[5]> struct something2 { static const int value = v[0]; } template<const char v[5]> struct something2 { static const int value = v[0]; } All of them build individually, though when I throw in my test, cout << typeid(something2<"abcd">::value).name() << endl; I get 'something2' : invalid expression as a template argument for 'v' 'something2' : use of class template requires template argument list Is this not feasible or am I misunderstanding something?

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• Custom HTTP Status Codes (a la Twitter 420: Enhance Your Calm) [migrated]

  - by Max Bucknell

  I'm currently implementing an HTTP API, my first ever. I've been spending a lot of time looking at the Wikipedia page for HTTP status codes, because I'm determined to implement the right codes for the right situations. Listed on that page is a code with number 420, which is a custom code that Twitter used to use for rate limiting. There is already a code for rate limiting, though. It's 429. This led me to wonder why they would set a custom one, when there is already a use case. Is that just being cute? And if so, then which circumstances would make it acceptable to return a different status code, and what, if any problems may clients have with it? I read somewhere that Mozilla doesn't implement the joke 418: I’m a teapot response, which makes me think that clients choose which status codes they implement. If that's true, then I can imagine Twitter's funny little enhance your calm code being problematic. Unless I'm mistaken, and we can appropriate any code number to mean whatever we like, and that only convention dictates that 404 means not found, and 429 means take it easy.

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• Policy-based template design: How to access certain policies of the class?

  - by dehmann

  I have a class that uses several policies that are templated. It is called Dish in the following example. I store many of these Dishes in a vector (using a pointer to simple base class), but then I'd like to extract and use them. But I don't know their exact types. Here is the code; it's a bit long, but really simple: #include <iostream> #include <vector> struct DishBase { int id; DishBase(int i) : id(i) {} }; std::ostream& operator<<(std::ostream& out, const DishBase& d) { out << d.id; return out; } // Policy-based class: template<class Appetizer, class Main, class Dessert> class Dish : public DishBase { Appetizer appetizer_; Main main_; Dessert dessert_; public: Dish(int id) : DishBase(id) {} const Appetizer& get_appetizer() { return appetizer_; } const Main& get_main() { return main_; } const Dessert& get_dessert() { return dessert_; } }; struct Storage { typedef DishBase* value_type; typedef std::vector<value_type> Container; typedef Container::const_iterator const_iterator; Container container; Storage() { container.push_back(new Dish<int,double,float>(0)); container.push_back(new Dish<double,int,double>(1)); container.push_back(new Dish<int,int,int>(2)); } ~Storage() { // delete objects } const_iterator begin() { return container.begin(); } const_iterator end() { return container.end(); } }; int main() { Storage s; for(Storage::const_iterator it = s.begin(); it != s.end(); ++it){ std::cout << **it << std::endl; std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? } return 0; } The tricky part is here, in the main() function: std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? How can I access the dessert? I don't even know the Dessert type (it is templated), let alone the complete type of the object that I'm getting from the storage. This is just a toy example, but I think my code reduces to this. I'd just like to pass those Dish classes around, and different parts of the code will access different parts of it (in the example: its appetizer, main dish, or dessert).

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• Partial specialization with reference template parameter fails to compile in VS2005

  - by Blair Holloway

  I have code that boils down to the following: template struct Foo {}; template & I struct FooBar {}; //////// template struct Baz {}; template & I struct Baz< FooBar { static void func(FooBar& value); }; //////// struct MyStruct { static const Foo s_floatFoo; }; // Elsewhere: const Foo MyStruct::s_floatFoo; void callBaz() { typedef FooBar FloatFooBar; FloatFooBar myFloatFooBar; Baz::func(myFloatFooBar); } This compiles successfully under GCC, however, under VS2005, I get: error C2039: 'func' : is not a member of 'Baz' with [ T=FloatFooBar ] error C3861: 'func': identifier not found However, if I change const Foo<T>& I to const Foo<T>* I (passing I by pointer rather than by reference), and defining FloatFooBar as: typedef FooBar FloatFooBar; Both GCC and VS2005 are happy. What's going on? Is this some kind of subtle template substitution failure that VS2005 is handling differently to GCC, or a compiler bug? (The strangest thing: I thought I had the above code working in VS2005 earlier this morning. But that was before my morning coffee. I'm now not entirely certain I wasn't under some sort of caffeine-craving-induced delirium...)

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• Why does this class declaration not work on Visual Studio

  - by Roel

  So I'm trying to get some code that is written for gcc to compile on Visual Studio 2008. I have a problem that I have narrowed down to this: class value_t { public: typedef std::deque<value_t> sequence_t; typedef sequence_t::iterator iterator; }; This code fails: 1>cpptest.cpp 1>c:\program files\microsoft visual studio 9.0\vc\include\deque(518) : error C2027: use of undefined type 'value_t' 1> c:\temp\cpptest\cpptest.cpp(10) : see declaration of 'value_t' 1> c:\temp\cpptest\cpptest.cpp(13) : see reference to class template instantiation 'std::deque<_Ty>' being compiled 1> with 1> [ 1> _Ty=value_t 1> ] 1>c:\program files\microsoft visual studio 9.0\vc\include\deque(518) : error C2027: use of undefined type 'value_t' 1> c:\temp\cpptest\cpptest.cpp(10) : see declaration of 'value_t' However when I try this with std::vector, it compiles fine: class value_t { public: typedef std::vector<value_t> sequence_t; typedef sequence_t::iterator iterator; }; What's wrong? I have tried adding 'typename' everywhere I can think of, but at this point in time I'm thinking it's just a bug in the Dinkumware STL. Can anyone explain what's happening, and/or offer a solution? Thanks.

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• "Undefined symbols" linker error with simple template class

  - by intregus

  Been away from C++ for a few years and am getting a linker error from the following code: Gene.h #ifndef GENE_H_INCLUDED #define GENE_H_INCLUDED template <typename T> class Gene { public: T getValue(); void setValue(T value); void setRange(T min, T max); private: T value; T minValue; T maxValue; }; #endif // GENE_H_INCLUDED Gene.cpp #include "Gene.h" template <typename T> T Gene<T>::getValue() { return this->value; } template <typename T> void Gene<T>::setValue(T value) { if(value >= this->minValue && value <= this->minValue) { this->value = value; } } template <typename T> void Gene<T>::setRange(T min, T max) { this->minValue = min; this->maxValue = max; } Using Code::Blocks and GCC if it matters to anyone. Also, clearly porting some GA stuff to C++ for fun and practice.

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• Convert templated parameter type to string

  - by wheaties

  I've got a small bit of DRY going on in code I and others have written that I'd like to reduce but I'm failing to figure out how to get it done. This is legacy COM code but it's interfering with the readability. I'd like to do the following: bool queryInterface<class T, class V>(T &_input, V &_output, Logger &_logger){ if( FAILED( _input->QueryInterface( &_output ) ) ){ _logger.error() << "Failed to Query Interface between " << MAGICHAPPENS<T>() << " and " << MAGICHAPPENS<V>(); return false; } if( _output == NULL ){ _logger.warn() << "Unable to Query Interface between " << MAGICHAPPENS<T>() << " and " << MAGICHAPPENS<V>(); return false; } } Wherein the "MAGICHAPPENS()" function would spit out the name of the variable type. Such that if "V" were a IQueryFilter I'd get back a string of "IQueryFilter." I can't think of any reasonable solution without having to write a bunch of template specializations totally defeating the point in the first place. Is there a way to write ANDMAGICHAPPENS?

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• operator<< cannot output std::endl -- Fix?

  - by dehmann

  The following code gives an error when it's supposed to output just std::endl: #include <iostream> #include <sstream> struct MyStream { std::ostream* out_; MyStream(std::ostream* out) : out_(out) {} std::ostream& operator<<(const std::string& s) { (*out_) << s; return *out_; } }; template<class OutputStream> struct Foo { OutputStream* out_; Foo(OutputStream* out) : out_(out) {} void test() { (*out_) << "OK" << std::endl; (*out_) << std::endl; // ERROR } }; int main(int argc, char** argv){ MyStream out(&std::cout); Foo<MyStream> foo(&out); foo.test(); return EXIT_SUCCESS; } The error is: stream1.cpp:19: error: no match for 'operator<<' in '*((Foo<MyStream>*)this)->Foo<MyStream>::out_ << std::endl' stream1.cpp:7: note: candidates are: std::ostream& MyStream::operator<<(const std::string&) So it can output a string (see line above the error), but not just the std::endl, presumably because std::endl is not a string, but the operator<< definition asks for a string. Templating the operator<< didn't help: template<class T> std::ostream& operator<<(const T& s) { ... } How can I make the code work? Thanks!

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• razor websites not working and all dlls are present

  - by Michael Tot Korsgaard

  I've uploaded a .cshtml website to a surftown server, and I got some problems running the code. But I have a problem with it running the Razor code. This is how the page renders:(Default.cshtml) I've already checked for internal communication problems. And this is my result: But then why isn't it working, and how can I fix it? I've heard that it can be a problem with views but how whould I fix this if that's the case? My websites folder tree: (And some files too) App_Code App_Data packages Microsoft.AspNet.Razor.2.0.20710.0 Microsoft.Asp.Net.WebPages.2.0.20710.0 Microsoft.Asp.Net.WebPages.Administration.2.0.20710.0 Microsoft.Asp.Net.WebPages.Data.2.0.20710.0 Microsoft.Asp.Net.WebPages.WebData.2.0.20710.0 Microsoft.Web.Infrastructure.1.0.0.0 NuGet.Core.1.6.2 bin packages jQuery.2.0.3 Content Scripts Tools Microsoft.AspNet.Mvc.4.0.30506.0 lib net40 Microsoft.AspNet.Razor.2.0.30506.0 lib net40 Microsoft.AspNet.WebPages.2.0.30506.0 lib net40 Pages Chapters Read.cshtml Edit Move Chapter.cshtml Entry.cshtml Entries EnterEntry.cshtml EnterNote.cshtml Login Login.cshtml Search Result.cshtml Scripts Addons TinyMCE Styles CSS Views _Layout.cshtml Default.cshtml My web.config file looks like this: <?xml version="1.0"?> <configuration> <system.web> <compilation debug="true" targetFramework="4.0"> <buildProviders> <add extension=".cshtml" type="System.Web.WebPages.Razor.RazorBuildProvider, System.Web.WebPages.Razor"/> </buildProviders> <assemblies> <add assembly="System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </assemblies> </compilation> </system.web> <connectionStrings> <add connectionString="database connection" providerName="System.Data.SqlClient"/> </connectionStrings> </configuration> EDIT: Is it a problem that all my files are .cshtml?

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• explicit template instantiations

  - by user323422

  see following code and please clear doubts1. as ABC is template why it not showing error when we put defination of ABC class member function in test.cpp 2.if i put test.cpp code in test.h and remve 2 , then it working fine. // test.h template <typename T> class ABC { public: void foo( T& ); void bar( T& ); }; // test.cpp template <typename T> void ABC<T>::foo( T& ) {} // definition template <typename T> void ABC<T>::bar( T& ) {} // definition template void ABC<char>::foo( char & ); // 1 template class ABC<char>; // 2 // main.cpp #include "test.h" int main() { ABC<char> a; a.foo(); // valid with 1 or 2 a.bar(); // link error if only 1, valid with 2 }

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• Template compiling errors on iPhone SDK 3.2

  - by Didier Malenfant

  I'm porting over some templated code from Windows and I'm hitting some compiler differences on the iPhone 3.2 SDK. Original code inside a class template's member function is: return BinarySearch<uint32, CSimpleKey<T> >(key); where BinarySearch is a method inherited from another template. This produces the following error: csimplekeytable.h:131: error: no matching function for call to 'BinarySearch(NEngine::uint32&)' The visual studio compiler seems to walk up the template hierarchy fine but gcc needs me to fully qualify where the function comes from (I have verified this by fixing the same issues with template member variables that way). So I now need to change this into: return CSimpleTable<CSimpleKey<T> >::BinarySearch<uint32, CSimpleKey<T> >(key); Which now produces the following error: csimplekeytable.h:132: error: expected primary-expression before ',' token csimplekeytable.h:132: error: expected primary-expression before '>' token After some head scratching, I believe what's going on here is that it's trying to resolve the '<' before BinarySearch as a 'Less Than' operator for some reason. So two questions: - Am I on the right path with my interpretation of the error? - How do I fix it? -D

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• C++ boost mpl vector

  - by Gokul

  I understand that the following code won't work, as i is a runtime parameter and not a compile time parameter. But i want to know, whether there is a way to achieve the same. i have a list of classes and i need to call a template function, with each of these classes. void GucTable::refreshSessionParams() { typedef boost::mpl::vector< SessionXactDetails, SessionSchemaInfo > SessionParams; for( int i = 0; i < boost::mpl::size<SessionParams>::value; ++i ) boost::mpl::at<SessionParams, i>::type* sparam = g_getSessionParam< boost::mpl::at<SessionParams, i>::type >(); sparam->updateFromGucTable(this); } } Can someone suggest me a easy and elegant way to perform the same? i need to iterate through the mpl::vector and use the type to call a global function and then use that parameter to do some run-time operations. Thanks in advance, Gokul. Working code typedef boost::mpl::vector< SessionXactDetails, SessionSchemaInfo > SessionParams; class GucSessionIterator { private: GucTable& m_table; public: GucSessionIterator(GucTable& table) :m_table(table) { } template< typename U > void operator()(const U& ) { g_getSessionParam<U>()->updateFromGucTable(m_table); } }; void GucTable::refreshSessionParams() { boost::mpl::for_each< SessionParams >( GucSessionIterator(*this) ); return; }

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• template style matrix implementation in c

  - by monkeyking

  From time to time I use the following code for generating a matrix style datastructure typedef double myType; typedef struct matrix_t{ |Compilation started at Mon Apr 5 02:24:15 myType **matrix; | size_t x; |gcc structreaderGeneral.c -std=gnu99 -lz size_t y; | }matrix; |Compilation finished at Mon Apr 5 02:24:15 | | matrix alloc_matrix(size_t x, size_t y){ | if(0) | fprintf(stderr,"\t-> Alloc matrix with dim (%lu,%lu) byteprline=%lu bytetotal:%l\| u\n",x,y,y*sizeof(myType),x*y*sizeof(myType)); | | myType **m = (myType **)malloc(x*sizeof(myType **)); | for(size_t i=0;i<x;i++) | m[i] =(myType *) malloc(y*sizeof(myType *)); | | matrix ret; | ret.x=x; | ret.y=y; | ret.matrix=m; | return ret; | } And then I would change my typedef accordingly if I needed a different kind of type for the entries in my matrix. Now I need 2 matrices with different types, an easy solution would be to copy/paste the code, but is there some way to do a template styled implementation. Thanks

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• Array of templated structs

  - by Jakub Mertlik

  I have structs templated by int derived from a Base struct. struct Base { int i; double d; }; template< int N > struct Derv : base { static const int mN = N; }; I need to make an array of Derv< N where N can vary for each struct in that array. I know C/C++ does not allow arrays of objects of different types, but is there a way around this? I was thinking of separating the type information somehow (hints like pointers to Base struct or usage of union spring to my mind, but with all of these I don't know how to store the type information of each array element for usage DURING COMPILE TIME). As you can see, the memory pattern of each Derv< N is the same. I need to access the type of each array element for template specialization later in my code. The general aim of this all is to have a compile-time dispatch mechanism without the need to do a runtime "type switch" somewhere in the code. Thank you.

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• How do i return a template class from a template function?

  - by LoudNPossiblyRight

  It looks logical but for some reason when i uncomment the last cout line, this code does not compile. How do i return a template class? What do i have to do to this code to make it work? #include<iostream> using namespace std; template <int x> class someclass{ public: int size; int intarr[x]; someclass():size(x){} }; template<int x, int y> int somefunc(someclass<x> A, someclass<y> B){ return ( A.size > B.size ? A.size : B.size); } template<int x, int y, int z> someclass<x> anotherfunc(someclass<y> A, someclass<z> B){ return ( A.size > B.size ? A : B); } int main(){ someclass<5> A; someclass<10> B; cout << "SIZE = " << somefunc(A,B) << endl; //cout << "SIZE = " << (anotherfunc(A,B)).size << endl; //THIS DOES NOT COMPILE return 0; }

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• Strange overloading rules in C++

  - by bucels

  I'm trying to compile this code with GCC 4.5.0: #include <algorithm> #include <vector> template <typename T> void sort(T, T) {} int main() { std::vector<int> v; sort(v.begin(), v.end()); } But it doesn't seem to work: $ g++ -c nm.cpp nm.cpp: In function ‘int main()’: nm.cpp:9:28: error: call of overloaded ‘sort(std::vector<int>::iterator, std::vector<int>::iterator)’ is ambiguous nm.cpp:4:28: note: candidates are: void sort(T, T) [with T = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] /usr/lib/gcc/i686-pc-linux-gnu/4.5.0/../../../../include/c++/4.5.0/bits/stl_algo.h:5199:69: note: void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] Comeau compiles this code without errors. (4.3.10.1 Beta2, strict C++03, no C++0x) Is this valid C++?

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• What is causing this template-related compile error? (c++)

  - by Setien

  When I try to compile this: #include <map> #include <string> template <class T> class ZUniquePool { typedef std::map< int, T* > ZObjectMap; ZObjectMap m_objects; public: T * Get( int id ) { ZObjectMap::const_iterator it = m_objects.find( id ); if( it == m_objects.end() ) { T * p = new T; m_objects[ id ] = p; return p; } return m_objects[ id ]; } }; int main( int argc, char * args ) { ZUniquePool< std::string > pool; return 0; } I get this: main.cpp: In member function ‘T* ZUniquePool<T>::Get(int)’: main.cpp:12: error: expected `;' before ‘it’ main.cpp:13: error: ‘it’ was not declared in this scope I'm using GCC 4.2.1 on Mac OS X. It works in VS2008. I'm wondering whether it might be a variation of this problem: http://stackoverflow.com/questions/1364837/why-doesnt-this-c-template-code-compile But as my error output is only partially similar, and my code works in VS2008, I am not sure. Can anyone shed some light on what I am doing wrong?

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• Usage of CRTP in a call chain

  - by fhw72

  In my widget library I'd like to implement some kind of call chain to initialize a user supplied VIEW class which might(!) be derived from another class which adds some additional functionality like this: #include <iostream> template<typename VIEW> struct App { VIEW view; void init() {view.initialize(); } }; template<typename DERIVED> struct SpecializedView { void initialize() { std::cout << "SpecializedView" << std::endl; static_cast<DERIVED*>(this)->initialize(); } }; struct UserView : SpecializedView<UserView> { void initialize() {std::cout << "UserView" << std::endl; } }; int _tmain(int argc, _TCHAR* argv[]) { // Cannot be altered to: App<SpecializedView<UserView> > app; App<UserView> app; app.init(); return 0; } Is it possible to achieve some kind of call chain (if the user supplied VIEW class is derived from "SpecializedView") such that the output will be: console output: SpecializedView UserView Of course it would be easy to instantiate variable app with the type derived from but this code is hidden in the library and should not be alterable. In other words: The library code should only get the user derived type as parameter.

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• Template function overloading with identical signatures, why does this work?

  - by user1843978

  Minimal program: #include <stdio.h> #include <type_traits> template<typename S, typename T> int foo(typename T::type s) { return 1; } template<typename S, typename T> int foo(S s) { return 2; } int main(int argc, char* argv[]) { int x = 3; printf("%d\n", foo<int, std::enable_if<true, int>>(x)); return 0; } output: 1 Why doesn't this give a compile error? When the template code is generated, wouldn't the functions int foo(typename T::type search) and int foo(S& search) have the same signature? If you change the template function signatures a little bit, it still works (as I would expect given the example above): template<typename S, typename T> void foo(typename T::type s) { printf("a\n"); } template<typename S, typename T> void foo(S s) { printf("b\n"); } Yet this doesn't and yet the only difference is that one has an int signature and the other is defined by the first template parameter. template<typename T> void foo(typename T::type s) { printf("a\n"); } template<typename T> void foo(int s) { printf("b\n"); } I'm using code similar to this for a project I'm working on and I'm afraid that there's a subtly to the language that I'm not understanding that will cause some undefined behavior in certain cases. I should also mention that it does compile on both Clang and in VS11 so I don't think it's just a compiler bug.

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• How do i return integers from a string ?

  - by kannan.ambadi

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Suppose you are passing a string(for e.g.: “My name has 1 K, 2 A and 3 N”)  which may contain integers, letters or special characters. I want to retrieve only numbers from the input string. We can implement it in many ways such as splitting the string into an array or by using TryParse method. I would like to share another idea, that’s by using Regular expressions. All you have to do is, create an instance of Regular Expression with a specified pattern for integer. Regular expression class defines a method called Split, which splits the specified input string based on the pattern provided during object initialization.     We can write the code as given below:   public static int[] SplitIdSeqenceValues(object combinedArgs)         {             var _argsSeperator = new Regex(@"\D+", RegexOptions.Compiled);               string[] splitedIntegers = _argsSeperator.Split(combinedArgs.ToString());               var args = new int[splitedIntegers.Length];               for (int i = 0; i < splitedIntegers.Length; i++)                 args[i] = MakeSafe.ToSafeInt32(splitedIntegers[i]);                           return args;         }    It would be better, if we set to RegexOptions.Compiled so that the regular expression will have performance boost by faster compilation.   Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Happy Programming  :))   

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• Guarding against CSRF Attacks in ASP.NET MVC2

  - by srkirkland

  Alongside XSS (Cross Site Scripting) and SQL Injection, Cross-site Request Forgery (CSRF) attacks represent the three most common and dangerous vulnerabilities to common web applications today. CSRF attacks are probably the least well known but they are relatively easy to exploit and extremely and increasingly dangerous. For more information on CSRF attacks, see these posts by Phil Haack and Steve Sanderson. The recognized solution for preventing CSRF attacks is to put a user-specific token as a hidden field inside your forms, then check that the right value was submitted. It's best to use a random value which you’ve stored in the visitor’s Session collection or into a Cookie (so an attacker can't guess the value). ASP.NET MVC to the rescue ASP.NET MVC provides an HTMLHelper called AntiForgeryToken(). When you call <%= Html.AntiForgeryToken() %> in a form on your page you will get a hidden input and a Cookie with a random string assigned. Next, on your target Action you need to include [ValidateAntiForgeryToken], which handles the verification that the correct token was supplied. Good, but we can do better Using the AntiForgeryToken is actually quite an elegant solution, but adding [ValidateAntiForgeryToken] on all of your POST methods is not very DRY, and worse can be easily forgotten. Let's see if we can make this easier on the program but moving from an "Opt-In" model of protection to an "Opt-Out" model. Using AntiForgeryToken by default In order to mandate the use of the AntiForgeryToken, we're going to create an ActionFilterAttribute which will do the anti-forgery validation on every POST request. First, we need to create a way to Opt-Out of this behavior, so let's create a quick action filter called BypassAntiForgeryToken: [AttributeUsage(AttributeTargets.Method, AllowMultiple=false)] public class BypassAntiForgeryTokenAttribute : ActionFilterAttribute { } Now we are ready to implement the main action filter which will force anti forgery validation on all post actions within any class it is defined on: [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)] public class UseAntiForgeryTokenOnPostByDefault : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { if (ShouldValidateAntiForgeryTokenManually(filterContext)) { var authorizationContext = new AuthorizationContext(filterContext.Controller.ControllerContext);   //Use the authorization of the anti forgery token, //which can't be inhereted from because it is sealed new ValidateAntiForgeryTokenAttribute().OnAuthorization(authorizationContext); }   base.OnActionExecuting(filterContext); }   /// <summary> /// We should validate the anti forgery token manually if the following criteria are met: /// 1. The http method must be POST /// 2. There is not an existing [ValidateAntiForgeryToken] attribute on the action /// 3. There is no [BypassAntiForgeryToken] attribute on the action /// </summary> private static bool ShouldValidateAntiForgeryTokenManually(ActionExecutingContext filterContext) { var httpMethod = filterContext.HttpContext.Request.HttpMethod;   //1. The http method must be POST if (httpMethod != "POST") return false;   // 2. There is not an existing anti forgery token attribute on the action var antiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(ValidateAntiForgeryTokenAttribute), false);   if (antiForgeryAttributes.Length > 0) return false;   // 3. There is no [BypassAntiForgeryToken] attribute on the action var ignoreAntiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(BypassAntiForgeryTokenAttribute), false);   if (ignoreAntiForgeryAttributes.Length > 0) return false;   return true; } } The code above is pretty straight forward -- first we check to make sure this is a POST request, then we make sure there aren't any overriding *AntiForgeryTokenAttributes on the action being executed. If we have a candidate then we call the ValidateAntiForgeryTokenAttribute class directly and execute OnAuthorization() on the current authorization context. Now on our base controller, you could use this new attribute to start protecting your site from CSRF vulnerabilities. [UseAntiForgeryTokenOnPostByDefault] public class ApplicationController : System.Web.Mvc.Controller { }   //Then for all of your controllers public class HomeController : ApplicationController {} What we accomplished If your base controller has the new default anti-forgery token attribute on it, when you don't use <%= Html.AntiForgeryToken() %> in a form (or of course when an attacker doesn't supply one), the POST action will throw the descriptive error message "A required anti-forgery token was not supplied or was invalid". Attack foiled! In summary, I think having an anti-CSRF policy by default is an effective way to protect your websites, and it turns out it is pretty easy to accomplish as well. Enjoy!

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• Figuring out the IIS Version for a given OS in .NET Code

  - by Rick Strahl

  Here's an odd requirement: I need to figure out what version of IIS is available on a given machine in order to take specific configuration actions when installing an IIS based application. I build several configuration tools for application configuration and installation and depending on which version of IIS is available on IIS different configuration paths are taken. For example, when dealing with XP machine you can't set up an Application Pool for an application because XP (IIS 5.1) didn't support Application pools. Configuring 32 and 64 bit settings are easy in IIS 7 but this didn't work in prior versions and so on. Along the same lines I saw a question on the AspInsiders list today, regarding a similar issue where somebody needed to know the IIS version as part of an ASP.NET application prior to when the Request object is available. So it's useful to know which version of IIS you can possibly expect. This should be easy right? But it turns there's no real easy way to detect IIS on a machine. There's no registry key that gives you the full version number - you can detect installation but not which version is installed. The easiest way: Request.ServerVariables["SERVER_SOFTWARE"] The easiest way to determine IIS version number is if you are already running inside of ASP.NET and you are inside of an ASP.NET request. You can look at Request.ServerVariables["SERVER_SOFTWARE"] to get a string like Microsoft-IIS/7.5 returned to you. It's a cinch to parse this to retrieve the version number. This works in the limited scenario where you need to know the version number inside of a running ASP.NET application. Unfortunately this is not a likely use case, since most times when you need to know a specific version of IIS when you are configuring or installing your application. The messy way: Match Windows OS Versions to IIS Versions Since Version 5.x of IIS versions of IIS have always been tied very closely to the Operating System. Meaning the only way to get a specific version of IIS was through the OS - you couldn't install another version of IIS on the given OS. Microsoft has a page that describes the OS version to IIS version relationship here: http://support.microsoft.com/kb/224609 In .NET you can then sniff the OS version and based on that return the IIS version. The following is a small utility function that accomplishes the task of returning an IIS version number for a given OS: /// <summary> /// Returns the IIS version for the given Operating System. /// Note this routine doesn't check to see if IIS is installed /// it just returns the version of IIS that should run on the OS. /// /// Returns the value from Request.ServerVariables["Server_Software"] /// if available. Otherwise uses OS sniffing to determine OS version /// and returns IIS version instead. /// </summary> /// <returns>version number or -1 </returns> public static decimal GetIisVersion() { // if running inside of IIS parse the SERVER_SOFTWARE key // This would be most reliable if (HttpContext.Current != null && HttpContext.Current.Request != null) { string os = HttpContext.Current.Request.ServerVariables["SERVER_SOFTWARE"]; if (!string.IsNullOrEmpty(os)) { //Microsoft-IIS/7.5 int dash = os.LastIndexOf("/"); if (dash > 0) { decimal iisVer = 0M; if (Decimal.TryParse(os.Substring(dash + 1), out iisVer)) return iisVer; } } } decimal osVer = (decimal) Environment.OSVersion.Version.Major + ((decimal) Environment.OSVersion.Version.MajorRevision / 10); // Windows 7 and Win2008 R2 if (osVer == 6.1M) return 7.5M; // Windows Vista and Windows 2008 else if (osVer == 6.0M) return 7.0M; // Windows 2003 and XP 64 bit else if (osVer == 5.2M) return 6.0M; // Windows XP else if (osVer == 5.1M) return 5.1M; // Windows 2000 else if (osVer == 5.0M) return 5.0M; // error result return -1M; } } Talk about a brute force apporach, but it works. This code goes only back to IIS 5 - anything before that is not something you possibly would want to have running. :-) Note that this is updated through Windows 7/Windows Server 2008 R2. Later versions will need to be added as needed. Anybody know what the Windows Version number of Windows 8 is?© Rick Strahl, West Wind Technologies, 2005-2011Posted in ASP.NET  IIS   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Code Structure / Level Design: Plants vs Zombies game level dissection

  - by lalan

  Hi Friends, I am interested in learning the class structure of Plants vs Zombies, particularly level design; for those who haven't played it - this video contains nice play-through: http://www.youtube.com/watch?v=89DfdOIJ4xw. How would I go ahead and design the code, mostly structure & classes, which allows for maximum flexibility & clean development? I am familiar with data driven design concepts, and would use events to handle most of dynamic behavior. Dissection at macro level: (Once every Level) Load tilemap, props, etc -- basically build the map (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) Show Enemies you'll face during present level (Once every Level) Unit Selection Window/Panel - selection of defensive plants (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) HUD Creation - based on unit selection (Level Loop) Enemy creation - based on types of zombies allowed (Level Loop) Sun/Resource generation (Level Loop) Show messages like 'huge wave of zombies coming', 'final wave' (Level Loop) Other unique events - Spawn gifts, money, tombstones, etc (Once every Level) Unlock new plant Potential game scripts: a) Level definitions: Level_1_1.xml, Level_1_2.xml, etc. Level_1_1.xml :: Sample script <map> <tilemap>tilemapFrontLawn</tilemap> <SpawnPoints> tiles where particular type of zombies (land vs water) may spawn</spawnPoints> <props> position, entity array -- lawnmower, </props> </map> <zombies> <... list of zombies who gonna attack by ids...> </zombies> <plants> <... list by plants which are available for defense by ids...> </plants> <progression> <ZombieWave name='first wave' spawnScript='zombieLightWave.lua' unlock='null'> <startMessages time=1.5>Ready</startMessages> <endMessages time=1.5>Huge wave of zombies incoming</endMessages> </ZombieWave> </progression> b) Entities definitions: .xmls containing zombies, plants, sun, lawnmower, coins, etc description. Potential classes: //LevelManager - Based on the level under play, it will load level script. Few of the // functions it may have: class LevelManager { public: bool load(string levelFileName); bool enter(); bool update(float deltatime); bool exit(); private: LevelData* mLevelData; } // LevelData - Contains the details of level loaded by LevelManager. class LevelData { private: string file; // array of camera,dialog,attackwaves, etc in active level LevelCutSceneCamera** mArrayCutSceneCamera; LevelCutSceneDialog** mArrayCutSceneDialog; LevelAttackWave** mArrayAttackWave; .... // which camera,dialog,attackwave is active in level uint mCursorCutSceneCamera; uint mCursorCutSceneDialog; uint mCursorAttackWave; public: // based on cursor, get the next camera,dialog,attackwave,etc in active level // return false/true based on failure/success bool nextCutSceneCamera(LevelCutSceneCamera**); bool nextCutSceneDialog(LevelCutSceneDialog**); } // LevelUnderPlay- LevelManager class LevelUnderPlay { private: LevelCutSceneCamera* mCutSceneCamera; LevelCutSceneDialog* mCutSceneDialog; LevelAttackWave* mAttackWave; Entities** mSelectedPlants; Entities** mAllowedZombies; bool isCutSceneCameraActive; public: bool enter(); bool update(float deltatime); bool exit(); } I am totally confused.. :( Does it make sense of using class composition (have flat class hierarchy) for managing levels. Is it a good idea to just add/remove/update sprites (or any drawable stuff) to current scene from LevelManager or LevelUnderPlay? If I want to make non-linear level design, how should I go ahead? Perhaps I would need a LevelProgression class, which would decide what to do based on decision tree. Any suggestions would be appreciated very much. Thank for your time, lalan

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• Any reliable polygon normal calculation code?

  - by Jenko

  Do you have any reliable face normal calculation code? I'm using this but it fails when faces are 90 degrees upright or similar. // the normal point var x:Number = 0; var y:Number = 0; var z:Number = 0; // if is a triangle with 3 points if (points.length == 3) { // read vertices of triangle var Ax:Number, Bx:Number, Cx:Number; var Ay:Number, By:Number, Cy:Number; var Az:Number, Bz:Number, Cz:Number; Ax = points[0].x; Bx = points[1].x; Cx = points[2].x; Ay = points[0].y; By = points[1].y; Cy = points[2].y; Az = points[0].z; Bz = points[1].z; Cz = points[2].z; // calculate normal of a triangle x = (By - Ay) * (Cz - Az) - (Bz - Az) * (Cy - Ay); y = (Bz - Az) * (Cx - Ax) - (Bx - Ax) * (Cz - Az); z = (Bx - Ax) * (Cy - Ay) - (By - Ay) * (Cx - Ax); // if is a polygon with 4+ points }else if (points.length > 3){ // calculate normal of a polygon using all points var n:int = points.length; x = 0; y = 0; z = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } if (minx > 0 || miny > 0 || minz > 0){ for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // if area is 0 if (length == 0) { return null; }else{ // turn large values into a unit vector x = x / length; y = y / length; z = z / length; }

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