// Variables: let = immutable, var = mutable
let name = "Yen";
var count = 0;
count++;

// Functions with default parameters
func greet(name, greeting = "Hello") {
    print greeting + ", " + name + "!";
}

// Pattern matching with guards
match (score) {
    90..=100        => "A";
    n when n >= 80 => "B";
    n when n >= 70 => "C";
    _              => "F";
}

// Lambdas and closures
let square = |x| x * x;
let add = |a, b = 10| a + b;

// Pipe operator
let result = 5 |> square |> add;

// Lists with negative indexing & slicing
let nums = [1, 2, 3, 4, 5];
print nums[-1];     // 5
print nums[1:3];    // [2, 3]

// Higher-order functions
let evens = filter(nums, |x| x % 2 == 0);
let doubled = map(nums, |x| x * 2);
let total = reduce(nums, 0, |a, b| a + b);

// Maps and destructuring
let user = {"name": "Alice", "age": 30};

for [key, val] in map_entries(user) {
    print key + ": " + str(val);
}

// Spread operator
let a = [1, 2];
let b = [3, 4];
let merged = [...a, ...b]; // [1,2,3,4]

// Ternary & null coalescing
let label = total > 10 ? "big" : "small";
let val = find(nums, |x| x > 99) ?? 0;

// Structs
struct Point { x; y; }
let p = Point { x: 10, y: 20 };

// Classes with methods
class Person {
    let name;
    let age;

    func init(name, age) {
        this.name = name;
        this.age = age;
    }

    func greet() {
        print "Hi, I'm " + this.name;
    }
}

// Enums
enum Color { Red, Green, Blue }

let person = Person { name: "Yen", age: 1 };
person.greet();

import 'async';
import 'net.http';
import 'os';

// Goroutines with channels
let ch = chan(10);

func producer(channel) {
    for i in 0..5 {
        send(channel, i * 10);
    }
    close_chan(channel);
}

go producer(ch);

// Error handling with defer
func safe_read(path) {
    defer log_info("Done reading");
    try {
        return io_read_file(path);
    } catch (e) {
        log_error("Failed: " + e);
        return None;
    }
}