operator-overloading

问题 I would like to be able to write statements like a = b.c; where b and c are std::vector and a is their scalar dot product (double). For doing this, I should associate the dot product operation with '.' symbol. Is this possible? 回答1: You cannot override the dot-operator ( . ). Moreover, even if you could you never should for this purpose. When overriding operators, you should follow these three rules : If the meaning of an operator is ambigious, it should not be overloaded. Always conform to

问题 In stock trading, quantities are usually integers (e.g. 5x shares, 10x options, etc). With cryptocurrencies, quantities are fractions (e.g. 0.01 bitcoin). In both scenarios, there is typically a minimum unit (e.g. multiples of 100x shares). I would like to wrap this logic in a Quantity class. However: Java native types (e.g. double ) are final , so I cannot extend them Java does not support operator overloading, so arithmetic will be ugly Java does not support typedefs, so I cannot wrap a

问题 I need help with both of my operator overloading functions presented below. I'm unsure of how I can implement this without actually using the assignment in the function definitions. Code for operator + in my .cpp file: MyString& MyString::operator +(const MyString& rhs) { delete [] String; String = new char[rhs.Size]; Size = rhs.Size; // needs to be a loop for cascading + // so that String1=String2+String3+String4 will work for(int i = 0; i < rhs.Size+1 ; i++) { // String[i] + rhs.String[i];

问题 Consider a struct (as in: stupid aggergation of several members) with members that all implement a certain relation R (e.g. < ): struct X { A a; B b; }; For most operators there exists a canonical definition for X R X . For instance: bool operator<(X const& x1, X const& x2) { if ((x1.a < x2.a) || (x2.a < x1.a)) // I intentionally did not use != here return x1.a < x2.a; if ((x1.b < x2.b) || (x2.b < x1.b)) return x1.b < x2.b; return false; } This is pretty boring to do for all operators,

问题 How do I define an operator where one operand is a defined type and the other is an int? I have a class Damage and defined as such in Damage.h : #pragma once class Damage { public: Damage(int, int = 0, int = 0); int operator-= (int& num) { return num - this->GetDamage(); } private: int damage; int dotDamage; int dotDamageLength; }; And I am trying to use the operator like this in Monster.cpp : #include "Monster.h" #include "Damage.h" int Monster::TakeDamage(Damage& damage) { this->health -=

问题 This question has a detailed answer here: Overloading operator<<: cannot bind lvalue to ‘std::basic_ostream<char>&&’ I am trying to overload a nested subclass, and spent an hour trying to overload operator<< . Researched a little here, but still couldn't resolve it. Any help? :) Whenever I try compiling it using g++ -std=c++11 -lm -ggdb -g -O0 -Wall p_7_1.cpp -o p_7_1 , it gives me an error: Undefined symbols for architecture x86_64: "operator<<(std::__1::basic_ostream<char, std::__1::char

问题 I frequently see people only overriding operator<, not > or ==. Does it mean that by default, operator> and operator== are implemented using operator< ? I also frequently see people writing (see here) bool operator() (Node const& n1, Node const& n2) const { // TODO: your condition return n1.a < n2.a; } What does operator() mean here then? it seems very counter-intuitive. 回答1: The reason they're only overriding < is because by default that's what ordered containers use to compare values, so

问题 What would be the best (most elegant or performing) way of overloading the equality operator on a class containing only string attributes? Example: class MagicClass { public string FirstAttribute { get; set; } public string SecondAttribute { get; set; } public string ThirdAttribute { get; set; } public string FourthAttribute { get; set; } public string FifthAttribute { get; set; } } I know how to overload the operator itself, however, I am wondering about the following points: Is there a way

问题 I was watching a boostcon talk on youtube titled "Introduction to Modern C++ Techniques (Part I)". Around minute 22 the speaker shows a class which overloads the dereference operator. template<typename T, typename CheckingPolicy = NoChecking, typename BadPointerPolicy = BadPointerDoNothing> class pointer_wrapper { public: pointer_wrapper() : value_(0) {} explicit pointer_wrapper(T* p) : value_(p) {} operator T*() { if ( ! CheckingPolicy::check_pointer(value_) ) { return BadPointerPolicy:

问题 I was wondering how can you use operators along with 'this'. To put an example: class grd : clm { inline int &operator()(int x, int y) { return g[x][y]; } /* blah blah blah */ }; grd grd::crop(int cx1, int cy1, int cx2, int cy2) { grd ngrd(abs(cx1-cx2), abs(cy1-cy2)); int i, j; // for (i = cx1; i < cx2; i++) { for (j = cy1; j < cy2; j++) { if (i >= 0 && i < x && j >= 0 && j < y) ngrd(i-cx1,j-cy2) = ?? // this->(i,j); **** } } return ngrd; } Thanks! 回答1: Either: this->operator()(i,j) or (*this