C++ 使用运算符重载累加（）

我有一个关于accumulate（）和运算符重载的问题

我有一个包含

private:
Customer cust;
std::vector<Purchase> vP;

我想使用accumulate（）将订单向量中所有采购的价格（即单价*计数）相加。我的解决方案是重载顺序的+运算符，但它不起作用。这就是它的样子：

double Order::operator+(Order& p) {

    double gesamt{};
    gesamt=(gesamtpreisEinerPerson()+p.gesamtpreisEinerPerson());

    return gesamt;
}

double Order::gesamtpreisEinerPerson(){
    double kosten=0.0;

    for (int i=0; i<vP.size(); ++i){
    kosten+=(vP.at(i).getPrice()*vP.at(i).getCount());        
    }   
    return kosten;
} 

double Order:：operator+（Order&p）{
双gesamt{}；
gesamt=（gesamtpreisenerperson（）+p.gesamtpreisenerperson（））；
返回gesamt；
}
双顺序：：gesamtpreisenerperson（）{
双kosten=0.0；
对于（int i=0；i累加器谓词应具有签名
double（double，const Order&）
：

进行积累的简单方法是：

double d = accumulate(vectOrd.begin(),
                      vectOrd.end(),
                      0.0,
                      [](double acc, const Order& order) {
                          return acc + order.gesamtpreisEinerPerson();
                      });

如果确实要使用运算符重载，则必须实现（free函数）：

可能相关，也可能不相关，但是通过采取
顺序&
并且不使函数
常量
，你是说不允许任何人调用它，除非LHS是一个非常量对象，RHS不是临时的，也不是常量。对于一个不应该修改任何操作数的操作符来说，这些都是非常不正常的要求。这不管用吗k是什么意思？哦，是的，谢谢，我把它改成了双运算符+（常数顺序和p）。谢谢！代码没有编译，我收到以下错误消息：复制并粘贴错误消息。谢谢你的回答！对不起，我还是个编程高手。累加器谓词到底是什么？有没有办法解决运算符重载问题？累加器谓词是
std:：acculate。我使用运算符+（）作为成员函数，它不允许我接受3个参数。我说的是作为自由函数（非成员函数）…左操作数应该是
double
。如果使用成员函数，第一个参数是
Order
。
double totalPrice(vector<Order> vectOrd) {

    double d = accumulate(vectOrd.begin(), vectOrd.end(), 0.0);

    return d;
    }

In file included from main.cpp:5:
In file included from ./global.hpp:16:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/numeric:81:25: error: invalid operands to binary expression ('double' and 'Order')
        __init = __init + *__first;
                 ~~~~~~ ^ ~~~~~~~~
./global.hpp:272:16: note: in instantiation of function template specialization 'std::__1::accumulate<std::__1::__wrap_iter<Order *>, double>' requested here
    double d = accumulate(vectOrd.begin(), vectOrd.end(), 0.0);
               ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iterator:743:1: note: candidate template ignored: could not match 'reverse_iterator<type-parameter-0-0>' against 'Order'
operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iterator:1163:1: note: candidate template ignored: could not match 'move_iterator<type-parameter-0-0>' against 'Order'
operator+(typename move_iterator<_Iter>::difference_type __n, const move_iterator<_Iter>& __x)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iterator:1576:1: note: candidate template ignored: could not match '__wrap_iter<type-parameter-0-0>' against 'Order'
operator+(typename __wrap_iter<_Iter>::difference_type __n,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3698:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3711:1: note: candidate template ignored: could not match 'const _CharT *' against 'double'
operator+(const _CharT* __lhs , const basic_string<_CharT,_Traits,_Allocator>& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3723:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'Order'
operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Allocator>& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3734:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, const _CharT* __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3746:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, _CharT __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3760:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const basic_string<_CharT, _Traits, _Allocator>& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3768:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3776:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3784:1: note: candidate template ignored: could not match 'const _CharT *' against 'double'
operator+(const _CharT* __lhs , basic_string<_CharT,_Traits,_Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3792:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'Order'
operator+(_CharT __lhs, basic_string<_CharT,_Traits,_Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3801:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const _CharT* __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:3809:1: note: candidate template ignored: could not match 'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>' against 'double'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, _CharT __rhs)
^
1 error generated.
make[2]: *** [build/Debug/GNU-MacOSX/main.o] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2

double d = accumulate(vectOrd.begin(),
                      vectOrd.end(),
                      0.0,
                      [](double acc, const Order& order) {
                          return acc + order.gesamtpreisEinerPerson();
                      });

double operator+ (double d, const Order& order)
{
    return d + order.gesamtpreisEinerPerson();
}