请求从 C++ 转换为非标量类型

Question

我试图将 + 运算符重载为成员函数，以便我可以将两个多项式对象（它们是链表）加在一起，但我不断收到错误消息 conversion from 'Polynomial*' to non-scalar type 'std::shared_ptr<Polynomial>' requested 我不明白这是什么原因造成的？我已经为我的 Term 对象声明了两个共享指针，所以我不明白为什么我不能对多项式对象执行此操作？

Polynomial Polynomial::operator+( const Polynomial &other ) const
{
    shared_ptr<Polynomial> result = new Polynomial();
    shared_ptr<Polynomial::Term> a = this->head;
    shared_ptr<Polynomial::Term> b = other.head;
    double sum = 0;

    for(a; a != nullptr; a = a->next)
    {
        for(b; b != nullptr; b = b->next)
        {
            if(a->exponent == b->exponent)
            {
                sum = a->coeff + b->coeff;
                result->head = shared_ptr<Term>(new Term( sum, a->exponent, result->head ));
                cout << "function has found like terms" << endl;
            }
            else if(a->exponent != b->exponent)
            {
                result->head = shared_ptr<Term>(new Term( a->coeff, a->exponent, result->head ));
                cout << "function is working" << endl;

            }
        }
  }
  result;
}

main.cpp

void makePolynomials(shared_ptr [], int &x);

int main()
   {
   shared_ptr<Polynomial> poly[ 100 ];
   int nPolynomials = 0;

   makePolynomials( poly, nPolynomials );
   makePolynomials( poly, nPolynomials );

   for (int j=0; j < nPolynomials; j++)
      cout << *(poly[j]);


    //shows that the addition operator works
    Polynomial c;
    c = *(poly[0])+*(poly[1]);
    cout << c << endl;
}


void makePolynomials( shared_ptr<Polynomial> poly[], int &nPolynomials )
   {
   char filename[20];
   cout << "Enter the filename: ";
   cin >> filename;

   ifstream infile;
   infile.open( filename );
   if (! infile.is_open()) {
      cerr << "ERROR: could not open file " << filename << endl;
      exit(1);
      }

   string polynom;
   while (getline( infile, polynom ))
      {
      poly[ nPolynomials ] = shared_ptr<Polynomial>(new Polynomial( polynom ));
      nPolynomials++;
      }
   }

Answer 1

在这里，您请求从Polynomial* 到std::shared_ptr 的隐式转换：

shared_ptr<Polynomial> result = new Polynomial();

但由于std::shared_ptr 构造函数是explicit，因此无法进行转换。

您需要将Polynomial* 显式传递给std::shared_ptr 构造函数：

std::shared_ptr<Polynomial> result(new Polynomial);

或使用等效的新统一初始化语法：

std::shared_ptr<Polynomial> result{new Polynomial};