operator-overloading

问题 What operators can not be overloaded in C++? 回答1: From Wikipedia: Operator Name Syntax Bind pointer to member by reference a.*b Member a.b Scope resolution a::b Size of sizeof(a) Ternary a ? b : c Type identification typeid(a) 回答2: I'm pretty sure the C++ FAQ Lite probably covers this. The ones I can think of right off are the ternary operator, the . operator and the scope resolution operator ( :: ). Thinking a moment, since the . operator can't be overloaded, .* probably can't be either.

问题 The assignment: Implement an Alien class using a provided Alien.h file. An alien, in this scenario is described in terms of his/her height, weight, and gender. To compare two aliens, you use the following equation to determine the alien’s statusPoints value: statusPoints = weight * height * genderValue where genderValue is 2 if the alien is male, and 3 if the alien is female. The status points should be calculated when needed, not kept as a data member. This avoids so-called stale data, in

问题 which operators of the comparison (<=, >, ==, etc.) do You usually implement as your basic operators, which You can after use to implement the rest comparison operators or to make all possible comparisons among the classes? 回答1: You can implement all six of the operators in terms of == and < using the following equivalencies: a != b => !(a == b) a > b => b < a a >= b => !(a < b) a <= b => !(b < a) 回答2: I normally implement operator== for objects and also operator!= . Many objects do not have

问题 While searching for methods for overloading Subscript('[]') operator for template class, I came across two different techniques. First Technique: Overloading the operator [] returning pointer to the container directly, which will allow both reading value and assigning value. A sample implementation of this technique: template <class T> class X { int _size; T *container; public: X(int sz) { _size=sz; container=new T[sz](); } ~X() { } T& operator [](int indx) { return container[indx]; } }; With

问题 In C++, must operator []() always be a member function? If yes, why? I read "An operator must be a member function" in book "The C++ Programming Language Special Edition" page 287. 回答1: From the C++ draft: 13.5.5 Subscripting [over.sub] operator[] shall be a non-static member function with exactly one parameter. It implements the subscripting syntax postfix-expression [ expression ] Thus, a subscripting expression x[y] is interpreted as x.operator for a class object x of type T if T::operator

问题 class Currency { public: explicit Currency(unsigned int value); // method form of operator+= Currency &operator +=(const Currency &other); // understood! ... }; The following code shows an equivalent API using a free function version of the operator: class Currency { public: explicit Currency(unsigned int value); ... }; // free function form of operator+= Currency &operator +=(Currency &lhs, const Currency &rhs); // ??? Question1 > Why should the free function return Currency& instead of

问题 Consider the following example: struct ConvertibleStruct {}; enum class ConvertibleEC {}; struct Target { // Implicit conversion constructors Target(ConvertibleStruct) {} Target(ConvertibleEC) {} }; Target operator~(const Target& t) { return t; } Target anotherFunction(const Target& t) { return t; } int main() { ConvertibleStruct t; ConvertibleEC ec; ~t; // 1. Works finding the operator overloaded above ~ec; // 2. Fails to compile on clang 3.4 and gcc 4.8.2 operator~(ec); // 3. Works finding

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . Why aren't the assignment operators (+=, -=, *=, /=) overloadable in VB.NET? 回答1: Perhaps this is their reasoning: Thanks for the

问题 I have a VB class which overloads the Not operator; this doesn't seem to be usable from C# applications. Public Shared Operator Not(item As MyClass) As Boolean Return False End Operator I can use this in VB.NET: If Not MyClassInstance Then ' Do something End If I am trying to us this in a C# application but it won't build. if (!MyClassInstance) { // do something } I get the error Operator '!' cannot be applied to operand of type 'MyClass' Can anyone tell me what I am missing? 回答1: The Not

问题 I have a VB class which overloads the Not operator; this doesn't seem to be usable from C# applications. Public Shared Operator Not(item As MyClass) As Boolean Return False End Operator I can use this in VB.NET: If Not MyClassInstance Then ' Do something End If I am trying to us this in a C# application but it won't build. if (!MyClassInstance) { // do something } I get the error Operator '!' cannot be applied to operand of type 'MyClass' Can anyone tell me what I am missing? 回答1: The Not