feat: publish Dever core with project scaffolding and versioned AI skills

examples/old/dever/async/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/async/data/.gitkeep

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+

examples/old/dever/async/module/main.dever

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+# Task、Group 和 Channel 都有明确所有者；示例不启动服务或访问网络。
+
+pause() () {
+  dever.time.sleep(1)
+}
+
+square(value: Int) (result: Int) pure {
+  result = value * value
+}
+
+send_after(channel: Channel<Int>, value: Int) () {
+  dever.task.sleep(1)
+  send(channel, value)
+}
+
+main() (task_value: Int?, grouped_value: Int?, computed: Int) {
+  messages = channel(Int, 1)
+  sender = run(send_after(messages, 7))
+  task_value = receive(messages)
+  wait(sender)
+  workers = group(1)
+  run(workers, send_after(messages, 21))
+  wait(workers)
+  grouped_value = receive(messages)
+  computed = parallel(square(12))
+  blocking(pause())
+  close(messages)
+}

examples/old/dever/async_tcp/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/async_tcp/data/.gitkeep

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+

examples/old/dever/async_tcp/module/main.dever

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+
+connection(event: dever.net.ConnectResult.Connected(socket)) () recover("监听错误是流的最后一项，记录后结束服务") {
+  dever.net.timeout(socket, 5000)
+  dever.net.write(socket, dever.bytes.from_text("Hello from Dever\n"))
+  dever.net.close(socket)
+}
+
+connection(event: dever.net.ConnectResult.Failed(message)) () recover("监听错误是流的最后一项，记录后结束服务") {
+  blocking(dever.io.println(message))
+}
+
+serve() () {
+  listener = dever.net.listen("127.0.0.1", 0)
+  # 随机分配本机端口；最多同时处理 32 条连接。
+  port = dever.net.port(listener)
+  blocking(dever.io.println(int.to_text(port)))
+  stream = dever.net.connections(listener)
+  parallel_each(connection, stream, 32)
+  dever.net.close_listener(listener)
+}
+
+main() () {
+  serve()
+}

examples/old/dever/backend/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/backend/data/.gitkeep

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+

examples/old/dever/backend/module/main.dever

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+# 自包含后端示例：随机回环端口，只请求一次，然后排空并关闭。
+
+type Context {
+  prefix: Text
+  requests: Channel<Int>
+}
+
+route(request: dever.http.Request, context: Context) (
+  response: dever.http.Response
+) {
+  send(context.requests, 1)
+  response = dever.http.Response {
+    status = 200
+    headers = [dever.http.header("Content-Type", "text/plain; charset=utf-8")]
+    body = dever.bytes.from_text(context.prefix + request.target)
+  }
+}
+
+serve(listener: dever.system.Listener, context: Context) () {
+  dever.system.http_serve(route, listener, dever.http.default_limits(), context)
+}
+
+expired() () {
+  blocking(dever.io.println("服务排空超时，剩余任务已停止"))
+}
+
+count(value: Int) (text: Text) {
+  text = "requests = " + int.to_text(value)
+}
+
+count(value: null) (text: Text) {
+  text = "request channel ended"
+}
+
+main() () {
+  listener = dever.net.listen("127.0.0.1", 0)
+  port = dever.net.port(listener)
+  requests = channel(Int, 1)
+  server = run(
+    serve(
+      listener,
+      Context {
+        prefix = "Hello "
+        requests = requests
+      }
+    )
+  )
+  client = dever.http.client(
+    "http://127.0.0.1:" + int.to_text(port),
+    dever.tls.system(),
+    dever.http.default_limits(),
+    dever.http.default_pool_limits()
+  )
+  response = dever.http.request(
+    client,
+    dever.http.Request {
+      method = "GET"
+      target = "/Dever"
+      headers = []
+      body = dever.bytes.from_text("")
+    }
+  )
+  blocking(dever.io.println(dever.bytes.to_text(response.body)))
+  dever.net.close_listener(listener)
+  timeout(server, 2000, expired)
+  dever.http.close_client(client)
+  close(requests)
+  blocking(dever.io.println(count(receive(requests))))
+}

examples/old/dever/contracts/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/contracts/data/.gitkeep

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+

examples/old/dever/contracts/dever.api

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+dever-api 4
+function domain.port(Int) (port: domain.Port []) pure=true recover=None effects=[] errors=[domain.PortResult.Failed] recoveries={}
+type domain.Port record construct=public {value: Int [1..65535]}
+type domain.PortResult Ready(port: domain.Port []) | error Failed(message: Text [])

examples/old/dever/contracts/module/domain.dever

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+
+public type Port {
+  value: Int >= 1 and <= 65535
+}
+
+public type PortResult {
+  Ready(port: Port)
+  error Failed(message: Text)
+}
+
+public port(value: Int >= 1 and <= 65535) (port: Port) pure {
+  port = Port {
+    value = value
+  }
+}
+
+public port(value: other) (port: Port) pure {
+  fail(PortResult.Failed("port must be between 1 and 65535"))
+}

examples/old/dever/contracts/module/main.dever

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+
+main() (configured: domain.Port, invalid: domain.PortResult, fallback: domain.Port) pure {
+  configured = domain.Port {
+    value = 8080
+  }
+  invalid = result(domain.port(0))
+  fallback = configured_or_default(result(domain.port(-1)))
+}
+
+configured_or_default(result: domain.PortResult.Ready(port)) (value: domain.Port) pure recover("optional local configuration uses port 8080") {
+  value = port
+}
+
+configured_or_default(result: domain.PortResult.Failed(message)) (value: domain.Port) pure recover("optional local configuration uses port 8080") {
+  value = domain.Port {
+    value = 8080
+  }
+}

examples/old/dever/core/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/core/data/.gitkeep

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+

examples/old/dever/core/module/main.dever

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+
+type Pair {
+  left: Int
+  right: Int
+}
+
+type Number {
+  Present(value: Int)
+  Missing
+}
+
+type Key {
+  First
+  Second
+}
+
+number(value: Number.Present(payload)) (answer: Int) {
+  answer = payload
+}
+
+number(value: other) (answer: Int) {
+  answer = 0
+}
+
+grade(value: Int < 0) (answer: Text) {
+  answer = "negative"
+}
+
+grade(value: Int >= 0 and < 10) (answer: Text) {
+  answer = "small"
+}
+
+grade(value: Int >= 10) (answer: Text) {
+  answer = "large"
+}
+
+scale(value: Int, factor: Int) (answer: Int) {
+  answer = value * factor
+}
+
+positive(value: Int) (answer: Bool) {
+  answer = value > 0
+}
+
+target(value: Int, expected: Int) (answer: Bool) {
+  answer = value == expected
+}
+
+parts(value: Text) (first: Text, last: Text) {
+  first = text.trim(value)
+  last = text.lower(first)
+}
+
+change(pair: Pair) (answer: Pair) {
+  pair.left = 99
+  answer = pair
+}
+
+map_key(entry: MapEntry<Text, Int>) (key: Text) {
+  key = entry.key
+}
+
+optional(value: Int?) (answer: Int?) {
+  answer = value
+}
+
+main() (
+  original: Int,
+  changed: Int,
+  choice: Int,
+  category: Text,
+  exact: Bool,
+  quotient: Decimal,
+  third: Decimal,
+  rounded: Decimal,
+  integer_division: Int,
+  remainder: Int,
+  selected: List<Int>,
+  found: Int?,
+  total: Int,
+  empty_total: Decimal,
+  names: Text,
+  ordered_keys: List<Text>,
+  maps_equal: Bool,
+  nan_equal: Bool,
+  finite: Bool,
+  optionals: List<Int?>,
+  key_value: Int?,
+  identity: Bool
+) {
+  pair = Pair {
+    right = 2
+    left = 1
+  }
+  saved = pair
+  pair = change(pair)
+  original = saved.left
+  changed = pair.left
+  choice = number(Number.Present(7)) + number(Number.Missing)
+  category = grade(12)
+  exact = 0.1 + 0.2 == 0.3
+  quotient = 5 / 2
+  third = 1 / 3
+  rounded = decimal.round(2.345, 2)
+  integer_division = -5 // 2
+  remainder = -5 % 2
+  values = each(scale, [-1, 0, 1, 2], 3)
+  selected = filter(positive, values)
+  found = find(target, values, 3)
+  total = sum(scale, selected, 2)
+  empty_total = sum([])
+  split = parts(" ABC ")
+  names = split.first + split.last
+  labels = {
+    "first" = 1
+    "second" = 2
+  }
+  original_labels = labels
+  labels = put(labels, "first", 3)
+  labels = remove(labels, "first")
+  labels = put(labels, "first", 1)
+  ordered_keys = each(map_key, entries(labels))
+  maps_equal = labels == original_labels
+  nan = 0.0e0 / 0.0e0
+  nan_equal = [nan] == [nan]
+  finite = math.is_finite(float.from_int(4))
+  optionals = each(optional, [null, 1, null])
+  keys = {
+    Key.First = 1
+    Key.Second = 2
+  }
+  key_value = get(keys, Key.Second)
+  identity = dever.id.from_text("stable") == dever.id.from_text("stable")
+}

examples/old/dever/hello/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/hello/data/.gitkeep

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+

examples/old/dever/hello/module/app/user.dever

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+public greet() () {
+  dever.io.println("hello")
+}

examples/old/dever/hello/module/main.dever

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+main() () {
+  app.user.greet()
+}

examples/old/dever/http/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/http/data/.gitkeep

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+

examples/old/dever/http/module/main.dever

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+
+route(request: dever.http.Request) (response: dever.http.Response) {
+  response = dever.http.Response {
+    status = 200
+    headers = [dever.http.header("Content-Type", "text/plain; charset=utf-8")]
+    body = dever.bytes.from_text("Hello Dever: " + request.target)
+  }
+}
+
+serve() () {
+  listener = dever.net.listen("127.0.0.1", 0)
+  port = dever.net.port(listener)
+  blocking(dever.io.println("HTTP listening on 127.0.0.1:" + int.to_text(port)))
+  dever.http.serve(route, listener, dever.http.default_limits())
+}
+
+main() () {
+  serve()
+}

examples/old/dever/library/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/library/data/.gitkeep

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+

examples/old/dever/library/module/main.dever

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+
+main() (json: Text) {
+  total = reduce(add, [1, 2, 3], 0)
+  json = dever.json.stringify(
+    dever.json.parse("{\"message\":\"你好 Dever\",\"total\":" + int.to_text(total) + "}")
+  )
+}
+
+add(value: Int, total: Int) (next: Int) {
+  next = total + value
+}

examples/old/dever/live_http/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/live_http/data/.gitkeep

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+

examples/old/dever/live_http/module/main.dever

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+
+route(request: dever.http.Request, reply: dever.system.HttpReply) () {
+  path(request.target, reply)
+}
+
+path(target: "/events", reply: dever.system.HttpReply) () {
+  dever.sse.start(reply, [])
+  tick(1, reply)
+  tick(2, reply)
+  tick(3, reply)
+}
+
+path(target: "/stream", reply: dever.system.HttpReply) () {
+  dever.http.start(reply, 200, [dever.http.header("Content-Type", "text/plain")])
+  dever.http.write(reply, dever.bytes.from_text("first\n"))
+  dever.task.sleep(100)
+  dever.http.write(reply, dever.bytes.from_text("second\n"))
+  dever.http.finish(reply)
+}
+
+path(target: "/ws", reply: dever.system.HttpReply) () {
+  upgraded(result(dever.websocket.accept(reply, dever.websocket.default_limits())), reply)
+}
+
+path(target: other, reply: dever.system.HttpReply) () {
+  dever.http.respond(
+    reply,
+    dever.http.Response {
+      status = 200
+      headers = [dever.http.header("Content-Type", "text/plain; charset=utf-8")]
+      body = dever.bytes.from_text("Dever: /stream, /events, /ws")
+    }
+  )
+}
+
+tick(index: Int, reply: dever.system.HttpReply) () {
+  dever.task.sleep(100)
+  dever.sse.send(
+    reply,
+    dever.sse.Event {
+      event = "tick"
+      data = int.to_text(index)
+      id = int.to_text(index)
+      retry_ms = 1000
+    }
+  )
+}
+
+upgraded(
+  result: dever.websocket.ConnectResult.Connected(socket),
+  reply: dever.system.HttpReply
+) () recover("WebSocket handshake errors are returned as HTTP 400") {
+  each(message, dever.websocket.messages(socket), socket)
+}
+
+upgraded(
+  result: dever.websocket.ConnectResult.Failed(message),
+  reply: dever.system.HttpReply
+) () recover("WebSocket handshake errors are returned as HTTP 400") {
+  dever.http.respond(
+    reply,
+    dever.http.Response {
+      status = 400
+      headers = []
+      body = dever.bytes.from_text(message)
+    }
+  )
+}
+
+message(
+  event: dever.websocket.MessageEvent.Read(value),
+  socket: dever.system.WebSocket
+) () {
+  echo(value, socket)
+}
+
+message(
+  event: dever.websocket.MessageEvent.Failed(message),
+  socket: dever.system.WebSocket
+) () {
+  fail(dever.websocket.MessageEvent.Failed(message))
+}
+
+echo(value: dever.websocket.Message.Text(text), socket: dever.system.WebSocket) () {
+  dever.websocket.send(socket, dever.websocket.Message.Text(text))
+}
+
+echo(value: dever.websocket.Message.Binary(bytes), socket: dever.system.WebSocket) () {
+  dever.websocket.send(socket, dever.websocket.Message.Binary(bytes))
+}
+
+# Ping/Pong 已由协议引擎处理，应用只消费控制帧。
+echo(value: other, socket: dever.system.WebSocket) () {}
+
+main() () {
+  listener = dever.net.listen("127.0.0.1", 0)
+  port = dever.net.port(listener)
+  blocking(
+    dever.io.println("HTTP / SSE / WebSocket on 127.0.0.1:" + int.to_text(port))
+  )
+  dever.http.serve_live(
+    route,
+    listener,
+    dever.http.default_limits(),
+    dever.http.default_live_limits()
+  )
+}

examples/old/dever/parallel/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/parallel/data/.gitkeep

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+

examples/old/dever/parallel/module/main.dever

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+# 最多两个工作线程；输出顺序不保证，parallel_each 返回时任务都已完成。
+
+show(name: Text) () {
+  dever.io.println(name)
+}
+
+main() () {
+  parallel_each(show, ["alpha", "beta", "gamma"], 2)
+  dever.io.println("done")
+}

examples/old/dever/privacy/config/setting.json

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+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/privacy/data/.gitkeep

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+

examples/old/dever/privacy/module/counter.dever

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+# private 隐藏表示，调用方通过操作使用 Counter；普通数据无需强行套这层封装。
+
+public type Counter {
+  private value: Int
+}
+
+public start() (counter: Counter) pure {
+  counter = Counter {
+    value = 0
+  }
+}
+
+public increment(counter: Counter) (next: Counter) pure {
+  next = counter
+  next.value = counter.value + 1
+}
+
+public read(counter: Counter) (value: Int) pure {
+  value = counter.value
+}

examples/old/dever/privacy/module/main.dever

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+
+main() (before: Int, after: Int) pure {
+  original = counter.start()
+  changed = counter.increment(original)
+  before = counter.read(original)
+  after = counter.read(changed)
+}

examples/old/dever/rejected/coverage/module/main.dever

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+# 预期 C009：缺少 false 分句。补齐后才能覆盖全部 Bool 输入。
+
+label(enabled: true) (text: Text) {
+  text = "enabled"
+}
+
+main() (text: Text) {
+  text = label(true)
+}

examples/old/dever/rejected/failure/module/main.dever

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+# 预期 C012：赋值后丢弃失败。把失败作为命名输出返回可通过。
+
+type Result {
+  error Failed(message: Text)
+}
+
+main(value: Result) () {
+  discarded = value
+}

examples/old/dever/rejected/private/module/main.dever

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+# 预期 C006：另一个 package 不能读取私有字段。
+
+public read(box: secret.Box) (value: Int) {
+  value = box.value
+}

examples/old/dever/rejected/private/module/secret.dever

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+
+public type Box {
+  private value: Int
+}

examples/old/dever/rejected/pure/module/main.dever

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+# 预期 C013：输出属于副作用。需要输出时应移除 pure。
+
+main() () pure {
+  dever.io.println("hello")
+}

examples/old/dever/rejected/range/module/main.dever

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+# 预期 C011：0 不能构造合法端口。改为 8080 可通过。
+
+type Port {
+  value: Int >= 1 and <= 65535
+}
+
+main() (port: Port) {
+  port = Port {
+    value = 0
+  }
+}

examples/old/dever/sequences/config/setting.json

@@ -0,0 +1,10 @@
+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/sequences/data/.gitkeep

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+

examples/old/dever/sequences/module/main.dever

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+# handler 是具名函数；reduce_until 处理当前元素后停止，不处理后面的 100。
+
+type Summary {
+  total: Int
+  count: Int
+}
+
+double(value: Int) (result: Int) pure {
+  result = value * 2
+}
+
+map_values(transform: handler(value: Int) (result: Int), values: List<Int>) (
+  results: List<Int>
+) {
+  results = each(transform, values)
+}
+
+add(value: Int, total: Int) (next: Int) pure {
+  next = total + value
+}
+
+collect(value: Int, summary: Summary) (next: Summary, stop: Bool) pure {
+  next = Summary {
+    total = summary.total + value
+    count = summary.count + 1
+  }
+  stop = next.total >= 6
+}
+
+main() (
+  mapped: List<Int>,
+  total: Int,
+  stopped: Summary,
+  empty_total: Int,
+  bytes_total: Int,
+  first_value: Int?,
+  missing: Int?
+) pure {
+  mapped = map_values(double, [1, 2, 3])
+  total = reduce(add, [1, 2, 3], 0)
+  stopped = reduce_until(
+    collect,
+    [1, 2, 3, 100],
+    Summary {
+      total = 0
+      count = 0
+    }
+  )
+  empty_total = reduce(add, [], 0)
+  bytes_total = reduce(add, dever.bytes.from_text("AB"), 0)
+  first_value = first(mapped)
+  missing = get(
+    {
+      "count" = 3
+    },
+    "unknown"
+  )
+}

examples/old/dever/stream/config/setting.json

@@ -0,0 +1,10 @@
+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/stream/data/.gitkeep

@@ -0,0 +1 @@
+

examples/old/dever/stream/input.txt

@@ -0,0 +1 @@
+ABC

examples/old/dever/stream/module/main.dever

@@ -0,0 +1,21 @@
+
+sum_byte(value: Int, total: Int) (next: Int) {
+  next = total + value
+}
+
+consume(event: dever.io.ReadEvent.Chunk(bytes), total: Int) (next: Int) {
+  next = total + reduce(sum_byte, bytes, 0)
+}
+
+consume(event: dever.io.ReadEvent.Failed(message), total: Int) (
+  next: Int
+) {
+  fail(dever.io.ReadEvent.Failed(message))
+}
+
+main() (total: Int) {
+  file = dever.io.open("examples/old/dever/stream/input.txt")
+  stream = dever.io.chunks(file, 2)
+  total = reduce(consume, stream, 0)
+  close(stream)
+}

examples/old/dever/system/config/setting.json

@@ -0,0 +1,10 @@
+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/system/data/.gitkeep

@@ -0,0 +1 @@
+

examples/old/dever/system/module/main.dever

@@ -0,0 +1,11 @@
+# 结果随启动参数及当前时间变化；失败以结果返回。
+
+main() (
+  arguments: List<Text>,
+  clock: Int,
+  invalid_sleep: dever.time.SleepResult
+) {
+  arguments = dever.process.arguments()
+  clock = dever.time.unix_millis()
+  invalid_sleep = result(dever.time.sleep(-1))
+}

examples/old/dever/text/config/setting.json

@@ -0,0 +1,10 @@
+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/dever/text/data/.gitkeep

@@ -0,0 +1 @@
+

examples/old/dever/text/module/main.dever

@@ -0,0 +1,29 @@
+# 文本下标按 Unicode 标量；解析失败和越界保留 null，不自动改成零或空字符串。
+
+main() (
+  cleaned: Text,
+  character: Text?,
+  slice: Text?,
+  pieces: List<Text>,
+  joined: Text,
+  parsed: Int?,
+  invalid: Int?,
+  exact: Decimal?,
+  rounded: Decimal,
+  utf8: Text,
+  invalid_utf8: dever.bytes.DecodeResult,
+  invalid_byte: dever.bytes.BufferResult
+) pure {
+  cleaned = text.lower(text.trim(" Dever "))
+  character = text.at("a中😀", 2)
+  slice = text.slice("a中😀", 1, 3)
+  pieces = text.split("a,,b", ",")
+  joined = text.join(pieces, "|")
+  parsed = int.parse("42")
+  invalid = int.parse("forty-two")
+  exact = decimal.parse("1.25")
+  rounded = decimal.round(2.345, 2)
+  utf8 = dever.bytes.to_text(dever.bytes.from_text("你好"))
+  invalid_utf8 = result(dever.bytes.to_text(dever.bytes.from_ints([255])))
+  invalid_byte = result(dever.bytes.from_ints([256]))
+}

examples/old/markdown/config/setting.json

@@ -0,0 +1,10 @@
+{
+  "database": {
+    "default": {
+      "type": "sqlite",
+      "path": "data/db/app.db",
+      "max_connections": 1,
+      "max_page_size": 100
+    }
+  }
+}

examples/old/markdown/data/.gitkeep

@@ -0,0 +1 @@
+

examples/old/markdown/module/main.dever.md

@@ -0,0 +1,150 @@
+# 购物车结算
+
+计算购物车中所有商品的合计金额、优惠金额和最终应付金额。
+
+- 包：`main`
+- 公开类型：
+  - `Product`
+  - `OrderSummary`
+- 公开方法：无
+- 使用：无
+
+## 商品
+
+保存商品名称、单价和购买数量。
+
+- 类型：`Product`
+- 字段：
+  - `name: Text`：商品名称
+  - `price: Decimal`：商品单价
+  - `quantity: Int >= 1`：购买数量，最少为 1
+
+```typescript dever
+public type Product {
+  name: Text
+  price: Decimal
+  quantity: Int >= 1
+}
+```
+
+## 订单结算结果
+
+保存参与结算的商品以及各项金额。
+
+- 类型：`OrderSummary`
+- 字段：
+  - `items: List<Product>`：参与结算的商品
+  - `subtotal: Decimal`：优惠前的商品合计
+  - `discount: Decimal`：优惠金额
+  - `payable: Decimal`：最终应付金额
+
+```typescript dever
+public type OrderSummary {
+  items: List<Product>
+  subtotal: Decimal
+  discount: Decimal
+  payable: Decimal
+}
+```
+
+## 计算单项商品金额
+
+使用商品单价乘以购买数量。
+
+- 函数：`line_total`
+- 输入：
+  - `product: Product`：需要计算金额的商品
+- 输出：
+  - `total: Decimal`：该商品的总金额
+
+```typescript dever
+line_total(product: Product) (total: Decimal) {
+  total = product.price * product.quantity
+}
+```
+
+## 汇总商品金额
+
+计算商品列表中所有商品的金额总和。
+
+- 函数：`sum_products`
+- 输入：
+  - `products: List<Product>`：需要汇总的商品列表
+- 输出：
+  - `subtotal: Decimal`：所有商品的合计金额
+
+```typescript dever
+sum_products(products: List<Product>) (subtotal: Decimal) {
+  subtotal = sum(line_total, products)
+}
+```
+
+## 结算订单
+
+根据商品列表和会员应付比例计算订单结果。
+
+- 函数：`checkout`
+- 输入：
+  - `products: List<Product>`：需要结算的商品列表
+  - `member_rate: Decimal`：会员实际应付比例，例如 0.90
+- 输出：
+  - `summary: OrderSummary`：订单结算结果
+
+```typescript dever
+checkout(products: List<Product>, member_rate: Decimal) (summary: OrderSummary) {
+  subtotal = sum_products(products)
+  payable = decimal.round(subtotal * member_rate, 2)
+  discount = subtotal - payable
+  summary = OrderSummary {
+    items = products
+    subtotal = subtotal
+    discount = discount
+    payable = payable
+  }
+}
+```
+
+## 运行购物车示例
+
+创建商品列表，并以九折会员价格完成结算。
+
+- 函数：`main`
+- 输入：无
+- 输出：
+  - `customer: Text`：客户名称
+  - `summary: OrderSummary`：客户的订单结算结果
+
+```typescript dever
+main() (customer: Text, summary: OrderSummary) {
+  customer = "小明"
+  products = [
+    Product {
+      name = "笔记本"
+      price = 12.50
+      quantity = 3
+    },
+    Product {
+      name = "签字笔"
+      price = 5.00
+      quantity = 2
+    }
+  ]
+  summary = checkout(products, 0.90)
+}
+```
+
+### 执行
+
+```bash
+deverc check examples/old/markdown --entry app.main
+deverc fmt examples/old/markdown --check
+deverc run examples/old/markdown app.main
+```
+
+结算结果：
+
+| 项目 | 金额 |
+| --- | ---: |
+| 商品合计 | 47.50 |
+| 优惠金额 | 4.75 |
+| 应付金额 | 42.75 |