C++程序编译报错C3867：非标准语法问题求助

错误信息 #

Error   C3867   'budget::check_mort': non-standard syntax; use '&' to create a pointer to member
Error   C3867   'budget::check_car': non-standard syntax; use '&' to create a pointer to member
Error   C3867   'budget::check_groc': non-standard syntax; use '&' to create a pointer to member
Error   C3867   'budget::check_util': non-standard syntax; use '&' to create a pointer to member

问题根源 #

错误出在budget类的display()成员函数中。你直接使用check_mort、check_car等标识符，这在C++中会被解释为成员函数指针，而非调用该成员函数。编译器提示你用&取指针，但这不是你想要的——你需要的是执行这些函数并获取返回的布尔值。

修复方案 #

在display()函数中，所有调用check_*系列函数的地方，都需要加上括号()来明确是函数调用，而不是取指针。

修改前的错误代码片段： #

void budget::display() const{
    float x = mortgage + utilities + groceries + car_payment + misc;
    cout << "The sum of all of your expenses is " << x << endl;
    cout << "Based on your inputs: ";
    if (check_mort) {
        cout << "Your mortgage is higher than the national average./n Consider taking steps to reduce this such as refinancing or relocating./n ";
    }
    if (check_car) {
        cout << "Your car payments are higher than the average. Consider finding alternate transportation and downgrading/n";
    }
    if (check_groc) {
        cout << "Your grocieries are higher than the average. Consider finding cheaper alternatives and not eating out./n";
    }
    if (check_util) {
        cout << "Your utilities cost is higher than the average. Consider finding ways to reduce usage, such as raising or lowering the thermometer./n";
    }
}

修改后的正确代码片段： #

void budget::display() const{
    float x = mortgage + utilities + groceries + car_payment + misc;
    cout << "The sum of all of your expenses is " << x << endl;
    cout << "Based on your inputs: ";
    if (check_mort()) {
        cout << "Your mortgage is higher than the national average.\n Consider taking steps to reduce this such as refinancing or relocating.\n ";
    }
    if (check_car()) {
        cout << "Your car payments are higher than the average. Consider finding alternate transportation and downgrading\n";
    }
    if (check_groc()) {
        cout << "Your groceries are higher than the average. Consider finding cheaper alternatives and not eating out.\n";
    }
    if (check_util()) {
        cout << "Your utilities cost is higher than the average. Consider finding ways to reduce usage, such as raising or lowering the thermometer.\n";
    }
}

同时顺便修正了两处小问题：

• 将错误的换行符/n改为标准的\n
• 修正了拼写错误grocieries为groceries

额外说明 #

你之前推测需要将函数设为static或const是不必要的——这些check_*函数已经被声明为const（符合类成员函数访问const对象的要求），且它们需要访问类的私有成员变量，因此不能设为static。

内容的提问来源于stack exchange，提问作者Sir Davahoy