Alia 语法示例

本文档展示了 Alia 语言的各种语法示例。

1. 基础语法

1.1 变量声明

~ 声明变量
let x = 10
const y = 20

~ 带类型注解的变量声明
let name: String = 'Alice'
const age: Number = 30

1.2 数据类型

~ 字符串
const str1 = 'Hello'
const str2 = "World"

~ 数字
const num1 = 42
const num2 = 3.14

~ 布尔值
const bool1 = true
const bool2 = false

~ 数组
const arr = [1, 2, 3, 4, 5]

~ 对象
const obj = *[ name: 'Alice', age: 30 ]

~ 栈
const stack = *{
  let x = 1
  x + 1
}

1.3 运算符

~ 四则运算
const sum = 10 + 5
const difference = 10 - 5
const product = 10 * 5
const quotient = 10 / 5

~ 逻辑运算
const andResult = true & false
const orResult = true | false
const notResult = !true

~ 大小比较
const greater = 10 > 5
const less = 10 < 5
const equal = 10 == 5

~ 字符串连接
const greeting = 'Hello' .. ' ' .. 'World'

2. 控制流

2.1 if 语句

const age = 18

if age >= 18 {
  print '成年人'
} else {
  print '未成年人'
}

~ 嵌套 if 语句
const score = 85

if score >= 90 {
  print '优秀'
} else {
  if score >= 80 {
    print '良好'
  } else {
    if score >= 60 {
      print '及格'
    } else {
      print '不及格'
    }
  }
}

2.2 for 循环

~ 打印 1 到 10
for { let i = 0 } i < 10 { i ++ } {
  print i
}

~ 遍历数组
const arr = [1, 2, 3, 4, 5]
for { let i = 0 } i < arr.length { i ++ } {
  print '元素 ' .. i .. ': ' .. arr[i]
}

2.3 while 循环

~ 打印 1 到 5
let i = 1
while i <= 5 {
  print i
  i ++
}

~ 条件控制循环
let count = 0
while count < 3 {
  print '循环次数: ' .. count
  count ++
}

2.4 repeat 循环

~ 无限循环，以 throw 跳出
let i = 0
try {
  repeat {
    print i
    i ++
    if i >= 5 {
      throw 'done'
    }
  }
} catch e {
  print e
}

3. 函数

3.1 基本函数

~ 定义加法函数
const add = alias <Number a> and <Number b> -> Number { a + b }

~ 调用函数
const result = add 1 and 2
print result

3.2 带返回值的函数

const multiply = alias <Number a> and <Number b> -> Number { a * b }

const product = multiply 3 and 4
print product

3.3 匿名函数

const subtract = alias <Number a> and <Number b> -> Number { a - b }

const difference = subtract 10 and 5
print difference

3.4 高阶函数

const applyOperation = alias <Alias op> and <Number a> and <Number b> -> Number {
  call op [a, b]
}

const add = alias <Number x> and <Number y> -> Number { x + y }

const result = applyOperation add and 5 and 3
print result

3.5 递归函数

~ 计算阶乘
alias factorial <Number n> -> Number {
  if n <= 1 {
    return 1
  } else {
    return n * (factorial n - 1)
  }
}

print (factorial 5)

~ 斐波那契数列
alias fibonacci <Number n> -> Number {
  if n <= 1 {
    return n
  } else {
    return (fibonacci n - 1) + (fibonacci n - 2)
  }
}

print (fibonacci 10)

4. 类

4.1 基本类

class Person *[
  name: '',
  age: 0,
  new: alias <String name> and <Number age> -> {
    self.name = name
    self.age = age
    self
  }
]

const person = new Person *[name: 'Alice', age: 30]
print person.name .. ' is ' .. person.age .. ' years old'

4.2 带方法的类

class Person *[
  name: '',
  age: 0,
  greet: alias -> {
    'Hello, my name is ' .. self.name
  },
  celebrateBirthday: alias -> {
    self.age += 1
    'Happy birthday! You are now ' .. self.age .. ' years old'
  },
  new: alias <String name> and <Number age> -> {
    self.name = name
    self.age = age
    self
  }
]

const person = new Person *[name: 'Bob', age: 25]
print (call person.greet)
print (call person.celebrateBirthday)

4.3 类的继承

class Animal *[
  name: '',
  speak: alias -> {
    'Animal sound'
  },
  new: alias <String name> -> {
    self.name = name
    self
  }
]

class Dog extends Animal *[
  breed: '',
  speak: alias -> {
    'Woof! Woof!'
  }
]

const dog = new Dog *[name: 'Rex']
dog.breed = 'German Shepherd'
print dog.name .. ' says ' .. (call dog.speak)

5. 错误处理

5.1 try-catch

try {
  print '尝试执行'
  throw '发生错误'
  print '这行不会执行'
} catch e {
  print '捕获到错误: ' .. e
}

5.2 自定义错误

try {
  print '开始执行'
  throw new Error ['自定义错误', 'CustomError']
} catch e {
  print '错误信息: ' .. e.message
  print '错误名称: ' .. e.name
}

6. 标准库

6.1 文件系统

import 'fs' as fs

~ 写入文件
fs.write 'Hello World!' to 'example.txt'

~ 读取文件
const content = fs.read 'example.txt'
print content

~ 检查文件是否存在
const exists = fs.exist 'example.txt'
print '文件存在: ' .. exists

6.2 进程管理

import 'process' as process

~ 获取环境变量
const home = process.envGet 'HOME'

~ 执行命令
const result = process.exec 'echo Hello'
print result.stdout

6.3 内置对象

~ 数学运算
print 'PI: ' .. Math.PI
print 'E: ' .. Math.E
print '平方根: ' .. (Math.sqrt 16)
print '绝对值: ' .. (Math.abs -10)
print '最大值: ' .. (Math.max 1 and 2 and 3 and 4 and 5)
print '最小值: ' .. (Math.min 1 and 2 and 3 and 4 and 5)

~ 日期操作
const now = call Date.now
print '当前时间: ' .. now

const date = new Date [*[year: 2023, month: 11, day: 25]]
print '圣诞节: ' .. (date.toFormat 'YYYY-MM-DD')

7. 高级特性

7.1 Alias 高级用法

~ 自定义控制结构
alias repeatTimes <Number times> times <Stack stack> -> {
  for { let i = 0 } i < times { i ++ } {
    call stack.run
  }
}

~ 使用
repeatTimes 3 times {
  print 'Hello'
}

~ 链式调用
alias <Number num> squared -> Number {
  num * num
}

print (5 squared)

7.2 栈操作

~ 基本栈操作
const stack = *{
  let x = 10
  let y = 20
  x + y
}

const result = call stack.run
print result

~ 栈的语境
const stack2 = mut *{
  this.define 'name' 'Alice'
  print name
}

call stack2.run

7.3 可变栈

~ 可变栈（状态持久化）
const counter = mut *{
  if Has 'count' {
    count
  } else {
    let count = 1
    count
  }
}

print call counter.run  ~ 输出 1
counter.set 'count' 2
print call counter.run  ~ 输出 2
counter.set 'count' 3
print call counter.run  ~ 输出 3

~ 可变栈内的 this 操作
const stack = mut *{
  this.define 'name' 'Alice'
  this.set 'name' 'Bob'
  if this.has 'name' {
    this.resolve 'name'
  }
}
print call stack.run  ~ 输出 'Bob'

~ 栈递归执行
let sum = 0
const recursiveStack = {
  sum = sum + 1
  if sum > 5 {
    break
  }
  call this.run
}
call recursiveStack.run
print sum  ~ 输出 6

7.4 enter 关键字

~ 进入栈语境
const stack = mut *{
  let val = 100
  val
}
call stack.run

enter (stack) {
  if Has 'val' {
    print val  ~ 输出 100
  }
}

7.5 模块导入导出

~ math.alia：导出模块
const math = *[
  add: alias <Number a> and <Number b> -> Number { a + b },
  subtract: alias <Number a> and <Number b> -> Number { a - b }
]

export math

~ main.alia：导入模块
import 'math.alia' as math

print (math.add 1 and 2)
print (math.subtract 5 and 3)

8. 完整示例

8.1 猜数字游戏

~ 猜数字游戏
import 'io' as io

print '猜数字游戏'
print '我想了一个 1 到 100 之间的数字，你能猜出来吗？'

const raw = call Math.random
const scaled = raw * 100 + 1
const target = Math.floor scaled
let attempts = 0
let found = false

while !found {
  const task = io.readLine '请输入你的猜测: '
  const line = await task
  const guess = line as Number
  attempts ++
  if guess < target {
    print '太小了！'
  } else {
    if guess > target {
      print '太大了！'
    } else {
      print '恭喜你猜对了！'
      print '你用了 ' .. attempts .. ' 次尝试'
      found = true
    }
  }
}

8.2 待办事项列表

~ 待办事项列表
type Todo *[task: String, completed: Boolean]

let todos: [Todo, ...] = []

alias addTodo <String task> -> {
  const record: Todo = *[ task: task, completed: false ]
  todos.push record
  print '添加了任务: ' .. task
}

alias listTodos -> {
  print '待办事项:'
  for { let i = 0 } i < todos.length { i ++ } {
    const todo = todos[i]
    const status = todo.completed ? '✓' : '✗'
    print (i + 1) .. '. ' .. status .. ' ' .. todo.task
  }
}

alias completeTodo <Number index> -> {
  if index >= 0 & index < todos.length {
    todos[index].completed = true
    print '已完成任务: ' .. todos[index].task
  } else {
    print '无效的任务索引'
  }
}

~ 使用
addTodo '学习 Alia 语言'
addTodo '完成项目'
addTodo '锻炼身体'

call listTodos

completeTodo 0

call listTodos

下一步

• 常见问题