Question

I have a simple program. The main is provided by my professor. We’re to write 3 functions called enter, simplify, display.

main

#include <iostream>
using namespace std;
// #include "fraction.h"

struct Fraction {
    int numerator;
    int denominator;
};

void enter(struct Fraction* fraction);
void simplify(struct Fraction* fraction);
void display(struct Fraction fraction);

int main() 
{
    struct Fraction fraction;
    cout << "Fraction Simplifier" << endl;
    cout << "===================" << endl;
    enter(&fraction);
    //simplify(&fraction);
    //display(fraction);
}

void enter(struct Fraction* fraction) {
    cout << "Numerator:     " << endl;
    cin >> *fraction.numerator; // the line that doesn't work, line 31
}

void simplify(struct Fraction* fraction) {}
void display(struct Fraction fraction) {}

error:

w2.cpp:31:19: error: request for member ânumeratorâ in âfractionâ, which is of non-class type âFraction*â

the line in question

void enter(struct Fraction* fraction) {
    cout << "Numerator:     " << endl;
    cin >> *fraction.numerator; // the line that doesn't work, line 31
}

Answer 1

You have an order of operations problem. You want:

cin >> (*fraction).numerator

Or more idiomatically:

cin >> fraction->numerator;