aster/examples/practical.ast

// ============================================================================
// 实用脚本集合：文本统计、数组工具、排序、数据转换
// 运行: cargo run -- examples/practical.ast
// ============================================================================

// ============================================================================
// 1. 文本统计工具
// ============================================================================
fn count_chars(s) {
    return len(s)
}

fn count_words(s) {
    let count = 0
    let in_word = false
    for (c in s) {
        if (c == " " || c == "\n" || c == "\t") {
            in_word = false
        } else if (!in_word) {
            count = count + 1
            in_word = true
        }
    }
    return count
}

fn text_stats(text) {
    print("=== Text Stats ===")
    print("chars:", count_chars(text))
    print("words:", count_words(text))
}

let sample = "hello world from Aster scripting language"
text_stats(sample)


// ============================================================================
// 2. 数组工具函数 (map / filter / reduce)
// ============================================================================

fn map(arr, func) {
    let result = []
    for (x in arr) {
        push(result, func(x))
    }
    return result
}

fn filter(arr, pred) {
    let result = []
    for (x in arr) {
        if (pred(x)) {
            push(result, x)
        }
    }
    return result
}

fn reduce(arr, func, init) {
    let acc = init
    for (x in arr) {
        acc = func(acc, x)
    }
    return acc
}

let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

let doubled = map(nums, fn(x) { return x * 2 })
print("map (*2):", doubled)

let evens = filter(nums, fn(x) { return x % 2 == 0 })
print("filter (even):", evens)

let sum = reduce(nums, fn(a, b) { return a + b }, 0)
print("reduce (sum):", sum)

// 链式: 偶数平方和
let even_squares = map(
    filter(nums, fn(x) { return x % 2 == 0 }),
    fn(x) { return x * x }
)
let sum_squares = reduce(even_squares, fn(a, b) { return a + b }, 0)
print("sum of even squares:", sum_squares)


// ============================================================================
// 3. 冒泡排序
// ============================================================================

fn sort(arr) {
    let n = len(arr)
    let i = 0
    while (i < n - 1) {
        let j = 0
        while (j < n - i - 1) {
            if (arr[j] > arr[j + 1]) {
                let tmp = arr[j]
                arr[j] = arr[j + 1]
                arr[j + 1] = tmp
            }
            j = j + 1
        }
        i = i + 1
    }
    return arr
}

let unsorted = [42, 17, 8, 99, 3, 56]
print("unsorted:", unsorted)
print("sorted:", sort(unsorted))


// ============================================================================
// 4. 数据转换 (类 JSON 处理)
// ============================================================================

let users = [
    { name: "Alice", age: 28, active: true },
    { name: "Bob",   age: 35, active: false },
    { name: "Carol", age: 22, active: true },
    { name: "Dave",  age: 40, active: true },
]

// 找出活跃用户的名字，按年龄排序
let active = filter(users, fn(u) { return u["active"] })
print("active users:", len(active))

// 计算平均年龄
let total_age = reduce(users, fn(acc, u) { return acc + u["age"] }, 0)
print("avg age:", total_age / len(users))

// 生成名字列表
let names = map(users, fn(u) { return u["name"] })
print("names:", names)


// ============================================================================
// 5. 斐波那契 (递归 + 迭代 + 缓存对比)
// ============================================================================

fn fib_rec(n) {
    if (n <= 1) { return n }
    return fib_rec(n - 1) + fib_rec(n - 2)
}

fn fib_iter(n) {
    if (n <= 1) { return n }
    let a = 0
    let b = 1
    let i = 2
    while (i <= n) {
        let tmp = a + b
        a = b
        b = tmp
        i = i + 1
    }
    return b
}

print("fib_rec(20):", fib_rec(20))
print("fib_iter(20):", fib_iter(20))


// ============================================================================
// 6. 回文检测
// ============================================================================

fn is_palindrome(s) {
    let n = len(s)
    let i = 0
    while (i < n / 2) {
        if (s[i] != s[n - 1 - i]) {
            return false
        }
        i = i + 1
    }
    return true
}

print("is_palindrome('radar'):", is_palindrome("radar"))
print("is_palindrome('hello'):", is_palindrome("hello"))


// ============================================================================
// 7. 字符串工具（split / trim / substring / replace）
// ============================================================================

print("=== string utils ===")

let csv = "Alice,Bob,Carol,Dave"
let parts = split(csv, ",")
print("split CSV:", parts)
print("names count:", len(parts))

let padded = "  hello  "
print("trim:", "'" + trim(padded) + "'")

print("substring('hello', 1, 3):", substring("hello", 1, 3))

let template = "Hello, NAME!"
let greeting = replace(template, "NAME", "Aster")
print("replace:", greeting)

print("contains('hello', 'ell'):", contains("hello", "ell"))
print("upper:", upper("hello"))
print("lower:", lower("HELLO"))
print("starts_with('hello', 'he'):", starts_with("hello", "he"))
print("ends_with('hello', 'lo'):", ends_with("hello", "lo"))