在c ++中出现“表达式必须具有（指针到）函数类型”的错误

Question

Hi i have the below code

# include <iostream>
# include <limits>
# include <cmath>

using namespace std;

class fahrenheit
{
    float f,c,x;
public:
    void getdata();
    void display();
}

void fahrenheit::getdata()
{
    cout << "Enter the value of f : ";
    cin >> f;
    x=f-32;
    c=5/9(x);   //Here i am getting error as Expression must have (pointer-to-)function type //
}

void fahrenheit::display()
{
    cout << "c=" << c;
    std::cin.ignore();
    std::cin.get();

}

int main()
{
    fahrenheit f;
    f.getdata();
    f.display();
}

i have given the datatype as float for the input variables , but i am not sure what should be done to rectify the error .

Answer 1

5/9(x) doesn't remotely look like C++. You likely meant c = 5.0 / 9.0 * x;

Answer 2

first of all, you forgot about a semicolon right after the class definition. Second, I presume you wanted to multiply x by 9. Write c=5/9*(x)

otherwise the compiler tries to find a function called 9(int x) (which is an incorrect name for a function anyway) and realizes that 9 is in no sense any function pointer but just an int .. that's what the error means.

By the way.. if you write 5/9 compiler understands it as int values being divided. It will divide int(5) by 9 using an int / operator, which after dividing will return floor(5/9) = 0 . If you want to have a float or double division you have to inform the compiler that your values are floats(doubles).

For doubles: 5.0/9.0*x For floats: 5.0f/9.0f * x

Answer 3

您应该使用乘法运算符* 。

c=5/9*(x);