(表示一個二元運算符)，a ? b 的操作會被解釋為下面2種形式之一 

? b
a.(b);    
(a, b);  

2、應用舉例(對象 ? 對象)

#include <iostream>
 （Default constructor）
    ComplexA(){cout<<<<(The constructor with parameters)
    ComplexA( re,  im):real(re),image(im){cout<<<<（Copy constructor）
    ComplexA( ComplexA& ){real = .real; image = .image; cout<<<<(destructor)
    ~ComplexA(){cout<<<<
    ComplexA +(ComplexA&  ComplexA(real + .real, image + 
    ComplexA -(ComplexA&  ComplexA(real - .real, image - 
    ComplexA *(ComplexA&  ComplexA(real * .real, image * 
    ComplexA /(ComplexA&  ComplexA(real / .real, image / 
     display(){cout<<real<<<<image<<<< real;    
     image;   
（Default constructor）
    ComplexB(){cout<<<<(The constructor with parameters)
    ComplexB( re,  im):real(re),image(im){cout<<<<（Copy constructor）
    ComplexB( ComplexB& ){real = .real; image = .image; cout<<<<(destructor)
    ~ComplexB(){cout<<<<
    friend ComplexB +(ComplexB& ref1, ComplexB& ComplexB(ref1.real + ref2.real, ref1.image +
    friend ComplexB -(ComplexB& ref1, ComplexB& ComplexB(ref1.real - ref2.real, ref1.image -
    friend ComplexB *(ComplexB& ref1, ComplexB& ComplexB(ref1.real * ref2.real, ref1.image *
    friend ComplexB /(ComplexB& ref1, ComplexB& ComplexB(ref1.real / ref2.real, ref1.image /
     display(){cout<<real<<<<image<<<< real;    
     image;   
（Default constructor）
    ComplexC(){cout<<<<(The constructor with parameters)
    ComplexC( re,  im):real(re),image(im){cout<<<<（Copy constructor）
    ComplexC( ComplexC& ){real = .real; image = .image; cout<<<<(destructor)
    ~ComplexC(){cout<<<<
     GetReal(){ GetImage(){
 display(){cout<<real<<<<image<<<< real;    
     image;   

ComplexC +(ComplexC& ref1, ComplexC& ComplexC(ref1.GetReal() + ref2.GetReal(), ref1.GetImage() +
ComplexC -(ComplexC& ref1, ComplexC& ComplexC(ref1.GetReal() - ref2.GetReal(), ref1.GetImage() -
ComplexC *(ComplexC& ref1, ComplexC& ComplexC(ref1.GetReal() * ref2.GetReal(), ref1.GetImage() *
ComplexC /(ComplexC& ref1, ComplexC& ComplexC(ref1.GetReal() / ref2.GetReal(), ref1.GetImage() / main(,), C2(, = C1 += C1 -= C1 *= C1 /<<<<,), C5(, = C4 += C4 -= C4 *= C4 /<<<<,), C8(, = C7 += C7 -= C7 *= C7 / 

，或者反過來 ，這時上面的程序的重載方式就不適用了。

#include <iostream>
  re = ,  im = +(ComplexD& ){ ComplexD(real+.real, image++( a){cout<<; ComplexD(real++( d){cout<<; ComplexD(real++( f){cout<<; ComplexD(real+ display(){cout<<real<<<<image<<<< GetReal(){ GetImage(){+( a, ComplexD& ){cout<<; ComplexD(.GetReal()+a, +( d, ComplexD& ){cout<<; ComplexD(.GetReal()+d, +( f, ComplexD& ){cout<<; ComplexD(.GetReal()+f,  main(,= D1 + = D1 + = D1 + =  +=  +=  +