operator-overloading

问题 Say that I want to make up a special operator !+ in C++ between two objects. I would like to use !+, on example, because I think it is much more meaningful than any other operator. One basic thing I could do is to find a free, unused operator and make the replacement work with a #define: #define !+ % class myclass { public: int operator %(myclass &c) { return 3; } } So that if I later write something like a!+b with a and b instances of myclass, it would work. Now, is there any way to define

问题 I'm trying to create more useful debug messages for my class where store data. My code is looking something like this #include <QAbstractTableModel> #include <QDebug> /** * Model for storing data. */ class DataModel : public QAbstractTableModel { // for debugging purposes friend QDebug operator<< (QDebug d, const DataModel &model); //other stuff }; /** * Overloading operator for debugging purposes */ QDebug operator<< (QDebug d, const DataModel &model) { d << "Hello world!"; return d; } I

问题 I am trying to overload == operator to compare objects like below. class A { int a; public: A(int x) { a = x; } bool operator==(const A& obRight) { if(a == obRight.a) { return true; } return false; } }; int main() { A ob(10), ob2(10), ob3(10); if(ob == ob2) // This equality comparison compiles fine. cout<<"Equal"<<endl; if(ob == ob2 == ob3) //This line doesn't compile as overloaded // == operator doesn't return object (returns bool) cout<<"Equal"<<endl; } As i described above, i am unable to

问题 Related: what can I use as std::map keys? I needed to create a mapping where specific key locations in space map to lists of objects. std::map seemed the way to do it. So I'm keying a std::map on an xyz Vector class Vector { float x,y,z } ; , and I'm making a std::map<Vector, std::vector<Object*> > . So note the key here is not a std::vector , its an object of class Vector which is just a math xyz vector of my own making. To produce a "strictly weak ordering" I've written the following

问题 So, after reading some SO questions and answers, i still doesn't understand why use friend bool operator==( BaseClass const &left, BaseClass const &right ) instead of bool operator==( BaseClass const &right ) right now I have something like this http://pastebin.com/pKsTabC0 (Fixed) - and it seems to work fine. But maybe I'm missing something? Any Suggestions? Update 1 Ok i changed the source to make it work right http://ideone.com/fIAmB. Removed unnecessary virtual and added const. Still i

问题 I`d like to print enum values as text and use for it overloading. Suppose I have the following code: #include <iostream> #include <map> #include <string> #include <vector> #include <unordered_set> enum enm{ One, Two }; class Complex{ public: friend std::ostream& operator<<(std::ostream& out, std::unordered_multiset<int>::const_iterator i){ switch (*i){ case One:{ return out<<"One"; } case Two:{ return out << "Two"; } } } void func(std::unordered_multiset<int> _v); }; void Complex:: func(std:

问题 Let say I have something like this: var x: Int = 6 var y: Float = 11.5 so, the result has to be written like this var result = Float(x) * y or var result = x * Int(y) This makes sense, right ? However, I think that a little clumsy, so I'm trying to make some custom operators for this: infix operator *~ { associativity left precedence 150 } //floating func *~ (lhs: Float, rhs: Int) -> Float { return lhs * Float(rhs) } func *~ (lhs: Int, rhs: Float) -> Float { return rhs * Float(lhs) } infix

问题 There have been a lot of similar questions asked but all involve operands of same type or same generic type. This one in particular (How can I use a generic type parameter with an operator overload?) is close to what I am looking for but no answer or work-around. Is it possible to do something like this for the ‘*’ operator overload: public class MyNumericClass<T> { public double Value { get; set; } //OK but works only for same type operands public static double operator *(MyNumericClass<T>

问题 I want to overload the operator += in the way that when i will use it a+=b; it will add b to the vector a having this in the header: public: ... void Book::operator+=(std::string a, std::vector<std::string>>b); private: ... std::string b; stf::vector<std::string> a; this is the implementation in cpp void Book::operator+=(std::string a, std::vector<std::string>>b) { b.push_back(a); } What can be my error? It is not clear for me the use of overload operators yet 回答1: You can overload the +=

问题 I need to create an operator that accepts a double 'parameter'. myClass myobject(); double mydouble = 10000; mydouble += myobject; My operator: double operator+=(double value, const myclass& object) { value += object.value; return value; } The parameter value is being passed to the operator += as zero, even though mydouble is initialized to 10000. How do you create an operator that can accept the left operand as a parameter? 回答1: The correct prototype is the following: double& operator+=