request for a member in which is of non class type c++ - c++

Question

I am striving to test every function in this class and I cannot test the function that will assign a numerator and denominator to the constructor that takes no arguments here is my code. I get this error request for a member 'numerator' in 'first' which is of non class type 'Rational'
#include "Rational.h"
#include <iostream>
#include <string>
#include "GCD.h"
#include <assert.h>
using namespace std;
Rational:: Rational()
{
myNumerator = 1;
myDenominator = 1;
}
Rational:: Rational(int numerator, int denominator)
{
assert(denominator != 0);
myNumerator = numerator;
myDenominator = denominator;
reduce();
}
Rational:: Rational(const Rational &r)
{
myNumerator = r.myNumerator;
myDenominator = r.myDenominator;
}
const Rational& Rational :: operator = (const Rational &rhs)
{
if (this != &rhs)
{
myNumerator = rhs.myNumerator;
myDenominator = rhs.myDenominator;
return rhs;
}
}
int Rational:: numerator(int a) const
{
myNumerator = a;
return myNumerator;
}
int Rational:: denominator(int b) const
{
myNumerator = b;
return myDenominator;
}
void Rational:: reduce()
{
int commonDivisor = GCD(myNumerator, myDenominator);
myNumerator = myNumerator / commonDivisor;
myDenominator = myDenominator / commonDivisor;
}
Rational operator + (const Rational &lhs, const Rational &rhs)
{
int numerator = lhs.numerator() * rhs.denominator() + rhs.numerator() * lhs.denominator();
int denominator = lhs.denominator() * rhs.denominator();
Rational sum(numerator, denominator);
return sum;
}
Rational operator - (const Rational &lhs, const Rational &rhs)
{
int numerator = lhs.numerator() * rhs.denominator() + rhs.numerator() * lhs.denominator();
int denominator = lhs.denominator() * rhs.denominator();
Rational difference(numerator, denominator);
return difference;
}
Rational operator * (const Rational &lhs, const Rational &rhs)
{
int numerator = lhs.numerator() * rhs.numerator();
int denominator = lhs.denominator() * rhs.denominator();
Rational product(numerator, denominator);
return product;
}
Rational operator / (const Rational &lhs, const Rational &rhs)
{
int numerator = lhs.numerator() * rhs.denominator();
int denominator = lhs.denominator() * rhs.numerator();
Rational product(numerator, denominator);
return product;
}
ostream& operator << (ostream & os, const Rational &r)
{
os << r.numerator() << "/" << r.denominator();
return os;
}
istream& operator >> (istream &is, Rational &r)
{
char divisionSymbol;
int numerator = 0, denominator = 0;
is >> numerator >> divisionSymbol >> denominator;
assert(divisionSymbol == '/');
assert(denominator != 0);
Rational number(numerator, denominator);
r = number;
return is;
}
#include <iostream>
#include "Rational.h"
using namespace std;
int main()
{
Rational first(), second(75, 350), third(13, 55);
Rational fourth(second);
cout << first << endl << second << endl << third << endl << fourth <<endl;
first.numerator(3)const;
first.denominator(5)const;
cout << first;
}

Answer 1

Rational first(); is parsed as a function declaration. it is known as Most vexing parse.
You may use Rational first;
And in C++11, you may also use Rational first{};

Answer 2

There is no reason to mark your functions as const if you're going to modify your member variables. It's a promise that you won't modify *this and you do so anyway. So simply remove it. You also provide const "getters" anyway.
int numerator(int a);
int numerator() const {return myNumerator;}
int denominator(int b);
int denominator() const {return myDenominator;}
int Rational:: numerator(int a)
{
// ..
}
int Rational:: denominator(int b)
{
// ..
}
Your copy assignment operator also doesn't make sense. I suggest changing it:
if (this == &rhs)
{
return *this;
}
myNumerator = rhs.numerator();
myDenominator = rhs.denominator();
return *this;
Now for the error others pointed out, your compiler happily warns that empty parentheses interpreted as a function declaration. Simply remove the parentheses or replace them with brackets {} in C++11 mode. Also, you don't need the const keyword when calling a const member function.
Rational first, second(75, 350), third(13, 55);
first.numerator(3);
first.denominator(5);