Understanding friend functions

#include <bits/stdc++.h>
using namespace std;

struct mint {
private:
    int val;
    static int const mod = 7;
public:

    mint(int x) : val(x) {
        cout << "Int constructor called with " << x << '\n';
    }
    mint() {val = 0;}
    mint(mint &other) {
        val = other.val;
        cout << "Copy constructor called " << val << '\n';
    }

    // 13 + ins means 13 ko construct krega mint me and then call this
    friend mint operator+(mint a, mint const b) {
        a.val += b.val;
        cout << "+ operator called " << b.val << '\n';
        return a;
    }
    // https://softwareengineering.stackexchange.com/a/68888
    friend mint operator+(int x, mint other) {
        mint tmp(x);
        tmp.val += other.val;
        cout << "+ operator called " << other.val << '\n';
        return tmp;
    }
};

// or
// mint operator+(int x, mint other) {
//     mint tmp(x);
//     tmp.val += other.val;
//     cout << "+ operator called " << other.val << '\n';
//     return tmp;
// }

int main() {
    mint ins(10);
    ins = 23 - 13 + ins + 13;

    return 0;
}#include <bits/stdc++.h>
using namespace std;

struct mint {
private:
    int val;
    static int const mod = 7;
public:

    mint(int x) : val(x) {
        cout << "Int constructor called with " << x << '\n';
    }
    mint() {val = 0;}
    mint(mint &other) {
        val = other.val;
        cout << "Copy constructor called " << val << '\n';
    }

    // 13 + ins means 13 ko construct krega mint me and then call this
    friend mint operator+(mint a, mint const b) {
        a.val += b.val;
        cout << "+ operator called " << b.val << '\n';
        return a;
    }
    // https://softwareengineering.stackexchange.com/a/68888
    friend mint operator+(int x, mint other) {
        mint tmp(x);
        tmp.val += other.val;
        cout << "+ operator called " << other.val << '\n';
        return tmp;
    }
};

// or
// mint operator+(int x, mint other) {
//     mint tmp(x);
//     tmp.val += other.val;
//     cout << "+ operator called " << other.val << '\n';
//     return tmp;
// }

int main() {
    mint ins(10);
    ins = 23 - 13 + ins + 13;

    return 0;
}#include <bits/stdc++.h>
using namespace std;

struct mint {
private:
    int val;
    static int const mod = 7;
public:

    mint(int x) : val(x) {
        cout << "Int constructor called with " << x << '\n';
    }
    mint() {val = 0;}
    mint(mint &other) {
        val = other.val;
        cout << "Copy constructor called " << val << '\n';
    }

    // 13 + ins means 13 ko construct krega mint me and then call this
    friend mint operator+(mint a, mint const b) {
        a.val += b.val;
        cout << "+ operator called " << b.val << '\n';
        return a;
    }
    // https://softwareengineering.stackexchange.com/a/68888
    friend mint operator+(int x, mint other) {
        mint tmp(x);
        tmp.val += other.val;
        cout << "+ operator called " << other.val << '\n';
        return tmp;
    }
};

// or
// mint operator+(int x, mint other) {
//     mint tmp(x);
//     tmp.val += other.val;
//     cout << "+ operator called " << other.val << '\n';
//     return tmp;
// }

int main() {
    mint ins(10);
    ins = 23 - 13 + ins + 13;

    return 0;
}