分数重载运算符+（使用lcm）

Question

I want to compute the sum of two fraction using lcm of numerator and denominator. That means as a result I want to get a fraction in the reduced form. I have the following cpp file.

#include <iostream> //need it for cin and cout
#include "fraction.h"
Fraction::Fraction()
{
   num = 1;
   den = 1;
}

Fraction::Fraction(int n, int d)
{
   int tmp_gcd = gcd(n, d);

   num = n / tmp_gcd;
   den = d / tmp_gcd;
}

int Fraction::gcd(int a, int b)
{
   int tmp_gcd = 1;

// Implement GCD of two numbers;

   return tmp_gcd;
 }

 int Fraction::lcm(int a, int b)
 {
return a * b / gcd(a, b);

 }
 Fraction operator+(const Fraction&a,const Fraction &b)
 {
    int c=(lcm(b.den,a.den)/b.den)*a.num+b.num*(lcm(b.den,a.den)/a.den);
    int d=lcm(b.den,a.den);
    Fraction result(c,d);
    return result;
 }

However this code does not work because lcm is not defined in this scope.

What is the key that allows lcm work in this scope? If you please could explain more, I would be very thankful.

Answer 1

lcm is a member of Fraction . You can refer to it just as lcm within members of Fraction ; but operator+ isn't a member, so you'll have to use the qualified name Fraction::lcm .

It will also need to be static . (Hopefully it already is, but I can't see the declaration to be sure).