Functions & Lambdas

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

// Default parameters
void greet(const string &name, const string &greeting = "Hello") {
    cout << greeting << ", " << name << "!" << endl;
}

// Function overloading (same name, different params)
int add(int a, int b) { return a + b; }
double add(double a, double b) { return a + b; }
string add(const string &a, const string &b) { return a + b; }

// Pass by const reference (efficient, no copy)
void printVector(const vector<int> &v) {
    for (int val : v) cout << val << " ";
    cout << endl;
}

// Pass by reference (modifies original)
void doubleAll(vector<int> &v) {
    for (int &val : v) val *= 2;
}

int main() {
    greet("Alice");            // "Hello, Alice!"
    greet("Bob", "Good morning"); // "Good morning, Bob!"

    cout << add(3, 4) << endl;        // int: 7
    cout << add(3.5, 2.1) << endl;    // double: 5.6
    cout << add("Hi", " there") << endl; // string: "Hi there"

    vector<int> nums = {5, 2, 8, 1, 9, 3};
    printVector(nums);  // 5 2 8 1 9 3

    // Lambda expressions
    auto square = [](int x) { return x * x; };
    cout << square(5) << endl;  // 25

    // Lambda with capture
    int multiplier = 3;
    auto multiply = [multiplier](int x) { return x * multiplier; };
    cout << multiply(7) << endl;  // 21

    // Lambda with algorithms
    sort(nums.begin(), nums.end());              // Ascending
    sort(nums.begin(), nums.end(), [](int a, int b) {
        return a > b;  // Descending
    });

    // for_each with lambda
    for_each(nums.begin(), nums.end(), [](int n) {
        cout << n << " ";
    });

    return 0;
}