Question

In a data-structure, how do you insert a function?

struct Student_info {
std::string name;
double midterm, final;
unsigned int& counter;
std::vector<double> homework;
double overall = grade(students[counter]);
};

always get this type of error:-

a. “variable” was not declared in this code.

b. “Student_info::counter” cannot appear in a constant-expression.

c. an array reference cannot appear in a constant-expression.

d. a function call cannot appear in a constant-expression

edit:-
oopps, i mean student_info contain in a vector, wait, why that’s info needed anyway… Dx

oh, and btw, this is from Accelerated C++, a book obviously, and I’m trying to answer one of its exercise, then I need to know this part, not found any on the book Dx

the question is 4-6. Rewrite the Student_info structure to calculate the grades immediately and store only the final grade.

Answer 1

You can NOT dynamically insert a function into a structure.

You can declare a structure that has a method()

struct Student_info
{
    void doDomethingToStudent()
    {
         // Manipulate the object here.
    }
    // STUFF
};

Also you can not initialize member like above.

double overall = grade(students[counter]);

Here you need to create constructor that will initialize members.

struct Student_info
{
    Student_info(std::string& studentName, unsigned int& externalCounter)
        : name(studentName)
        , midterm(0)
        , final(0)
        , counter(externalCounter)
        , homework()

        // It is not clear if overall is a normal memeber
        // Or a static member of the class
        , overall(grade(students[counter]))
    {}
    // STUFF
};
int main()
{
    unsigned int counter   = 0;
    Student_info bob("Bob", counter);
}