什么是“！” []” Todomvc中的Elm代码语法的含义 [英] What does "! []" Elm code syntax in Todomvc mean

问题描述

从反应开始，我正在学习理解榆木。

Coming from react, I am learning to understand Elm.

在 Todomvc示例代码，其中包含以下代码段：

In the Todomvc example code, there is the following code snippet:

-- How we update our Model on a given Msg?
update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
  case msg of
    NoOp ->
      model ! []        <-- What is this?

我（我想）理解的是，更新函数接受类型为 Msg 的 msg 和模型 Model 的c $ c>，并返回一个包含 Model 和的元组Cmd Msg 。

What I (think I) understand, is that the update function takes in a msg of type Msg and a model of type Model, and returns a tuple of containing a Model and a Cmd Msg.

但是我应该如何阅读返回语句？

But how should I read the return statement?

model ! []

此语句是什么意思？返回模型[某物]空列表？

我在文档中错过了某些解释过的内容吗？ （谷歌搜索 elm！并没有帮助我：）

What does this statement mean? return a "model [something] empty list"?
Did I miss something in the docs where this is explained? (Googling "elm !" did not get me far :)

推荐答案

更新为Elm 0.19

Elm 0.19已删除感叹号运算符。现在，您必须手动构造元组，如（模型，Cmd.none）。

Elm 0.19 has removed the exclamation point operator. You must now construct the tuple manually, as in (model, Cmd.none).

原始回答Elm 0.18

模型中的感叹号！ [] 只是（模型，Cmd.batch []）的简写函数，这是从典型的<$ c返回的类型。 $ c> update 语句。 在此处定义

The exclamation point in model ! [] is just a short-hand function for (model, Cmd.batch []), which is the type returned from typical update statements. It is defined here

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