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  • Cannot use ternary operator in LINQ query

    - by Nissan Fan
    I can't figure out why I get a Object reference not set to an instance of an object. error if I use a ternary operator in my LINQ query. var courses = from d in somesource orderby d.SourceName, d.SourceType select new { ID = d.InternalCode, Name = string.Format("{0} - {1}{2}", d.InternalCode, d.SourceName, (d.SourceType.Length > 0 ? ", " + d.SourceType : string.Empty)) }; Any thoughts?

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  • new operator overwriting an existing object

    - by dvpdiner2
    I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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  • How to use the IN operator in linq

    - by Hallaghan
    I'm querying a view and filtering the results with a column named status. I'd like to query it so I can search for rows with different status, by using the IN operator as I'd do in SQL. As so: SELECT * FROM VIEW WHERE Status in ('....', '.....') How can I achieve this?

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  • How to user IN operator in Linq?

    - by Umapathy
    Query: Select * from pu_Products where Part_Number in ('031832','027861', '028020', '033378') and User_Id = 50 and Is_Deleted = 0 The above mentioned query is in SQL and i need the query might be converted into Linq. Is there any option using the "IN" operator in Linq?. can you convert above mentioned query into Linq?

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  • any stl/boost functors to call operator()

    - by Voivoid
    template <typename T> struct Foo { void operator()(T& t) { t(); } }; Is there any standart or boost functor with the similar implementation? I need it to iterate over container of functors: std::for_each(beginIter, endIter, Foo<Bar>()); Or maybe there are other way to do it?

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  • Regarding address operator C/C++

    - by iSight
    Hi, What does address operator mean. say in the method below. what should be passed in the method as parameter value of integer or the address of an integer variable. void func1(int&)// method declaration void func1(int& inNumber)//method definition { //some code }

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  • C++ operator ','

    - by user286215
    what is result of operator ',' by standard? Last argument? in code like this, for example: int a = 0; int b = 1; while(a,b); or using it like this is not allowed? MSVS thiks that result is b, is it true?

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  • % operator for time calculation

    - by Chris
    I am trying to display minutes and seconds based on a number of seconds. I have: float seconds = 200; float mins = seconds / 60.0; float sec = mins % 60.0; [timeIndexLabel setText:[NSString stringWithFormat:@"%.2f , %.2f", mins,seconds]]; But I get an error: invalid operands of types 'float' and 'double' to binary 'operator%' And I don't understand why... Can someone throw me a bone!?

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  • Templated << friend not working when in interrelationship with other templated union types

    - by Dwight
    While working on my basic vector library, I've been trying to use a nice syntax for swizzle-based printing. The problem occurs when attempting to print a swizzle of a different dimension than the vector in question. In GCC 4.0, I originally had the friend << overloaded functions (with a body, even though it duplicated code) for every dimension in each vector, which caused the code to work, even if the non-native dimension code never actually was called. This failed in GCC 4.2. I recently realized (silly me) that only the function declaration was needed, not the body of the code, so I did that. Now I get the same warning on both GCC 4.0 and 4.2: LINE 50 warning: friend declaration 'std::ostream& operator<<(std::ostream&, const VECTOR3<TYPE>&)' declares a non-template function Plus the five identical warnings more for the other function declarations. The below example code shows off exactly what's going on and has all code necessary to reproduce the problem. #include <iostream> // cout, endl #include <sstream> // ostream, ostringstream, string using std::cout; using std::endl; using std::string; using std::ostream; // Predefines template <typename TYPE> union VECTOR2; template <typename TYPE> union VECTOR3; template <typename TYPE> union VECTOR4; typedef VECTOR2<float> vec2; typedef VECTOR3<float> vec3; typedef VECTOR4<float> vec4; template <typename TYPE> union VECTOR2 { private: struct { TYPE x, y; } v; struct s1 { protected: TYPE x, y; }; struct s2 { protected: TYPE x, y; }; struct s3 { protected: TYPE x, y; }; struct s4 { protected: TYPE x, y; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR2() {} VECTOR2(const TYPE& x, const TYPE& y) { v.x = x; v.y = y; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); }; template <typename TYPE> union VECTOR3 { private: struct { TYPE x, y, z; } v; struct s1 { protected: TYPE x, y, z; }; struct s2 { protected: TYPE x, y, z; }; struct s3 { protected: TYPE x, y, z; }; struct s4 { protected: TYPE x, y, z; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR3() {} VECTOR3(const TYPE& x, const TYPE& y, const TYPE& z) { v.x = x; v.y = y; v.z = z; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ", " << toString.v.z << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); }; template <typename TYPE> union VECTOR4 { private: struct { TYPE x, y, z, w; } v; struct s1 { protected: TYPE x, y, z, w; }; struct s2 { protected: TYPE x, y, z, w; }; struct s3 { protected: TYPE x, y, z, w; }; struct s4 { protected: TYPE x, y, z, w; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR4() {} VECTOR4(const TYPE& x, const TYPE& y, const TYPE& z, const TYPE& w) { v.x = x; v.y = y; v.z = z; v.w = w; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR4& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ", " << toString.v.z << ", " << toString.v.w << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); }; // Test code int main (int argc, char * const argv[]) { vec2 my2dVector(1, 2); cout << my2dVector.x << endl; cout << my2dVector.xx << endl; cout << my2dVector.xxx << endl; cout << my2dVector.xxxx << endl; vec3 my3dVector(3, 4, 5); cout << my3dVector.x << endl; cout << my3dVector.xx << endl; cout << my3dVector.xxx << endl; cout << my3dVector.xxxx << endl; vec4 my4dVector(6, 7, 8, 9); cout << my4dVector.x << endl; cout << my4dVector.xx << endl; cout << my4dVector.xxx << endl; cout << my4dVector.xxxx << endl; return 0; } The code WORKS and produces the correct output, but I prefer warning free code whenever possible. I followed the advice the compiler gave me (summarized here and described by forums and StackOverflow as the answer to this warning) and added the two things that supposedly tells the compiler what's going on. That is, I added the function definitions as non-friends after the predefinitions of the templated unions: template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); And, to each friend function that causes the issue, I added the <> after the function name, such as for VECTOR2's case: friend ostream& operator<< <> (ostream& os, const VECTOR3<TYPE>& toString); friend ostream& operator<< <> (ostream& os, const VECTOR4<TYPE>& toString); However, doing so leads to errors, such as: LINE 139: error: no match for 'operator<<' in 'std::cout << my2dVector.VECTOR2<float>::xxx' What's going on? Is it something related to how these templated union class-like structures are interrelated, or is it due to the unions themselves? Update After rethinking the issues involved and listening to the various suggestions of Potatoswatter, I found the final solution. Unlike just about every single cout overload example on the internet, I don't need access to the private member information, but can use the public interface to do what I wish. So, I make a non-friend overload functions that are inline for the swizzle parts that call the real friend overload functions. This bypasses the issues the compiler has with templated friend functions. I've added to the latest version of my project. It now works on both versions of GCC I tried with no warnings. The code in question looks like this: template <typename SWIZZLE> inline typename EnableIf< Is2D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; } template <typename SWIZZLE> inline typename EnableIf< Is3D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; } template <typename SWIZZLE> inline typename EnableIf< Is4D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; }

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  • += Overloading in C++ problem.

    - by user69514
    I am trying to overload the += operator for my rational number class, but I don't believe that it's working because I always end up with the same result: RationalNumber RationalNumber::operator+=(const RationalNumber &rhs){ int den = denominator * rhs.denominator; int a = numerator * rhs.denominator; int b = rhs.numerator * denominator; int num = a+b; RationalNumber ratNum(num, den); return ratNum; } Inside main //create two rational numbers RationalNumber a(1, 3); a.print(); RationalNumber b(6, 7); b.print(); //test += operator a+=(b); a.print(); After calling a+=(b), a is still 1/3, it should be 25/21. Any ideas what I am doing wrong?

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  • Type casting Collections using Conversion Operators

    - by Vyas Bharghava
    The below code gives me User-defined conversion must convert to or from enclosing type, while snippet #2 doesn't... It seems that a user-defined conversion routine must convert to or from the class that contains the routine. What are my alternatives? Explicit operator as extension method? Anything else? public static explicit operator ObservableCollection<ViewModel>(ObservableCollection<Model> modelCollection) { var viewModelCollection = new ObservableCollection<ViewModel>(); foreach (var model in modelCollection) { viewModelCollection.Add(new ViewModel() { Model = model }); } return viewModelCollection; } Snippet #2 public static explicit operator ViewModel(Model model) { return new ViewModel() {Model = model}; } Thanks in advance!

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  • A Linker Resolution Problem in a C++ Program

    - by Vlad
    We have two source files, a.cpp and b.cpp and a header file named constructions.h. We define a simple C++ class with the same name (class M, for instance) in each source file, respectively. The file a.cpp looks like this: #include "iostream" #include "constructions.h" class M { int i; public: M(): i( -1 ) { cout << "M() from a.cpp" << endl; } M( int a ) : i( a ) { cout << "M(int) from a.cpp, i: " << i << endl; } M( const M& b ) { i = b.i; cout << "M(M&) from a.cpp, i: " << i << endl; } M& operator = ( M& b ) { i = b.i; cout << "M::operator =(), i: " << i << endl; return *this; } virtual ~M(){ cout << "M::~M() from a.cpp" << endl; } operator int() { cout << "M::operator int() from a.cpp" << endl; return i; } }; void test1() { cout << endl << "Example 1" << endl; M b1; cout << "b1: " << b1 << endl; cout << endl << "Example 2" << endl; M b2 = 5; cout << "b2: " << b2 << endl; cout << endl << "Example 3" << endl; M b3(6); cout << "b3: " << b3 << endl; cout << endl << "Example 4" << endl; M b4 = b1; cout << "b4: " << b4 << endl; cout << endl << "Example 5" << endl; M b5; b5 = b2; cout << "b5: " << b5 << endl; } int main(int argc, char* argv[]) { test1(); test2(); cin.get(); return 0; } The file b.cpp looks like this: #include "iostream" #include "constructions.h" class M { public: M() { cout << "M() from b.cpp" << endl; } ~M() { cout << "M::~M() from b.cpp" << endl; } }; void test2() { M m; } Finally, the file constructions.h contains only the declaration of the function "test2()" (which is defined in "b.cpp"), so that it can be used in "a.cpp": using namespace std; void test2(); We compiled and linked these three files using either VS2005 or the GNU 4.1.0 compiler and the 2.16.91 ld linker under Suse. The results are surprising and different between the two build environments. But in both cases it looks like the linker gets confused about which definition of the class M it should use. If we comment out the definition of test2() from b.cpp and its invocation from a.cpp, then all the C++ objects created in test1() are of the type M defined in a.cpp and the program executes normally under Windows and Suse. Here is the run output under Windows: Example 1 M() from a.cpp M::operator int() from a.cpp b1: -1 Example 2 M(int) from a.cpp, i: 5 M::operator int() from a.cpp b2: 5 Example 3 M(int) from a.cpp, i: 6 M::operator int() from a.cpp b3: 6 Example 4 M(M&) from a.cpp, i: -1 M::operator int() from a.cpp b4: -1 Example 5 M() from a.cpp M::operator =(), i: 5 M::operator int() from a.cpp b5: 5 M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp If we enable the definition of test2() in "b.cpp" but comment out its invocation from main(), then the results are different. Under Suse, the C++ objects created in test1() are still of the type M defined in a.cpp and the program still seems to execute normally. The VS2005 versions behave differently in Debug or Release mode: in Debug mode, the program still seems to execute normally, but in Release mode, b1 and b5 are of the type M defined in b.cpp (as the constructor invocation proves), although the other member functions called (including the destructor), belong to M defined in a.cpp. Here is the run output for the executable built in Release mode: Example 1 M() from b.cpp M::operator int() from a.cpp b1: 4206872 Example 2 M(int) from a.cpp, i: 5 M::operator int() from a.cpp b2: 5 Example 3 M(int) from a.cpp, i: 6 M::operator int() from a.cpp b3: 6 Example 4 M(M&) from a.cpp, i: 4206872 M::operator int() from a.cpp b4: 4206872 Example 5 M() from b.cpp M::operator =(), i: 5 M::operator int() from a.cpp b5: 5 M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp Finally, if we allow the call to test2() from main, the program misbehaves in all circumstances (that is under Suse and under Windows in both Debug and Release modes). The Windows-Debug version finds a memory corruption around the variable m, defined in test2(). Here is the Windows output in Release mode (test2() seems to have created an instance of M defined in b.cpp): Example 1 M() from b.cpp M::operator int() from a.cpp b1: 4206872 Example 2 M(int) from a.cpp, i: 5 M::operator int() from a.cpp b2: 5 Example 3 M(int) from a.cpp, i: 6 M::operator int() from a.cpp b3: 6 Example 4 M(M&) from a.cpp, i: 4206872 M::operator int() from a.cpp b4: 4206872 Example 5 M() from b.cpp M::operator =(), i: 5 M::operator int() from a.cpp b5: 5 M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M() from b.cpp M::~M() from b.cpp And here is the Suse output. The objects created in test1() are of the type M defined in a.cpp but the object created in test2() is also of the type M defined in a.cpp, unlike the object created under Windows which is of the type M defined in b.cpp. The program crashed in the end: Example 1 M() from a.cpp M::operator int() from a.cpp b1: -1 Example 2 M(int) from a.cpp, i: 5 M::operator int() from a.cpp b2: 5 Example 3 M(int) from a.cpp, i: 6 M::operator int() from a.cpp b3: 6 Example 4 M(M&) from a.cpp, i: -1 M::operator int() from a.cpp b4: -1 Example 5 M() from a.cpp M::operator =(), i: 5 M::operator int() from a.cpp b5: 5 M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M::~M() from a.cpp M() from a.cpp M::~M() from a.cpp Segmentation fault (core dumped) I couldn't make the angle brackets appear using Markdown, so I used quotes around the header file name iostream. Otherwise, the code could be copied verbatim and tried. It is purely scholastic. The statement cin.get() at the end of main() was included just to facilitate running the program directly from VS2005 (cause it to display the output window until we could analyze the output). We are looking for a software engineer in Sunnyvale, CA and may offer that position to the programmer capable of providing an intelligent and comprehensive explanation of these anomalies. I can be contacted at [email protected].

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  • Generated SQL with PredicateBuilder, LINQPad and operator ANY

    - by Sig. Tolleranza
    I previously asked a question about chaining conditions in Linq To Entities. Now I use LinqKit and everything works fine. I want to see the generated SQL and after reading this answer, I use LinqPad. This is my statement: var predProduct = PredicateBuilder.True<Product>(); var predColorLanguage = PredicateBuilder.True<ColorLanguage>(); predProduct = predProduct.And(p => p.IsComplete); predColorLanguage = predColorLanguage.And(c => c.IdColorEntity.Products.AsQueryable().Any(expr)); ColorLanguages.Where(predColorLanguage).Dump(); The code works in VS2008, compile and produce the correct result set, but in LinqPad, I've the following error: NotSupportedException: The overload query operator 'Any' used is not Supported. How can I see the generated SQL if LINQPad fails?

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  • operator not defined for System.Data.SqlClient.SqlConnection and System.Data.SqlClient.SqlConnection

    - by Beta033
    i hope i'm just doing something wrong here. Ideally i'm trying to open the connection, open a transaction execute a ton of prebuilt sqlstatements (with parameters) against this connection then close the connection. ideally all in the same batch. It's easy enough to wrap this all in a for loop, however i'd like to use the forEach function of the list generic to set the connection as it'll probably be faster than my implementation of calling List.Item(i) in the loop but i get some strange errors. Dim sqlStatements As List(Of SqlCommand) = New List(Of SqlCommand) Dim conn As SqlClient.SqlConnection = New SqlConnection("...") sqlStatements.Item(0).Connection = conn 'Works sqlStatements.ForEach(Function(ByRef cmd As SqlCommand) cmd.Connection = conn) 'ERROR: Operator '=' is not defined for types 'System.Data.SqlClient.SqlConnection' 'and 'System.Data.SqlClient.SqlConnection What does this error really mean?

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  • C# LINQ to SQL Except Operator

    - by kb
    Hi i have a list of event Ids that i want to be excluded from my select statement, but no sure how to implement this: this is what stores my list of event Ids List<int> ExcludedEvents; and this is my select statement (from an XML feed) var allEvents = from eventsList in xmlDoc.Elements("shows").Elements("Show") select new EventFeed() { EventName = eventsList.Attribute("Name").Value, EventSummary = eventsList.Attribute("ShortDesc").Value, EventDetails = eventsList.Attribute("LongDesc").Value, EventShowCode = eventsList.Attribute("Code").Value }; i want to select all events except for the events that have their eventId matching the EventShowCode value i have looked at the except operator, but not sure how to implement it thanks

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