Question

fn main() {
    let data = &[1..3];
    println!("Data is {:?}", data);
}

将&[1..3]作为此声明的指定值是什么意思？

Answer 1

首先：

//MainForm.cs
namespace WindowsFormsApplication
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            this.Load += new EventHandler(MainForm_Load);
            this.IsMdiContainer = true;

            this.Size = new System.Drawing.Size(900, 600);
        }

        public void MainForm_Load(object sender, EventArgs e)
        {

            UserForm userForm1 = new UserForm();
            userForm1.Text = "User Form 1";
            userForm1.MdiParent = this;
            userForm1.Size = new System.Drawing.Size(820, 465);
            userForm1.WindowState = System.Windows.Forms.FormWindowState.Normal;
            userForm1.Show();

            UserForm userForm2 = new UserForm();
            userForm2.TopLevel = false;
            userForm2.Location = new System.Drawing.Point(200, 100);
            userForm2.Size = new System.Drawing.Size(820, 465);
            userForm2.Text = "User Form 2";
            userForm2.Show();
            userForm2.Parent = userForm1;
        }
    }
}

//UserForm.cs
namespace WindowsFormsApplication
{
    public partial class UserForm : Form
    {
        public TextBox m_txtEdit;

        public UserForm()
        {
            InitializeComponent();
        }
    }
}

//UserForm.Designer.cs
namespace WindowsFormsApplication
{
    partial class UserForm
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.components = new System.ComponentModel.Container();
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.Text = "Form1";
            this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
            this.m_txtEdit = new System.Windows.Forms.TextBox();
            this.m_txtEdit.Location = new System.Drawing.Point(5, 100);
            this.m_txtEdit.Name = "m_txtEdit";
            this.m_txtEdit.Size = new System.Drawing.Size(149, 20);
            this.m_txtEdit.Visible = true;
            this.Controls.Add(this.m_txtEdit);
        }

        #endregion
    }
}

创建一个与let foo = &[1,2,3];绑定具有相同生命周期的临时数组，并在foo中存储对该数组的引用。

但是，这并不是您的计划正在做的事情。正如另一个答案所说，运行它是有用的，你得到：

foo

这看起来不像Data is [1..3]！我们可以通过使用它的错误消息欺骗编译器告诉我们它到底是什么。我们知道它绝对不是[1,2,3]，所以让我们先尝试一下：

()

这给我们带来了错误，其中包括：

fn main() {
    let data = &[1..3];
    let () = data;
}

这告诉我们答案 - error: mismatched types [--explain E0308] --> <anon>:3:17 |> 3 |> let () = data; |> ^^ expected &-ptr, found () note: expected type `&[std::ops::Range<_>; 1]` note: found type `()`是一个项目（data）的数组的引用（&），它是一个std::ops::Range<_>对象。< / p>

Answer 2

我猜您希望data属于&[i32; 2]类型;它不是。在这些时候，如果您不确定，可以通过尝试编写来验证它：

let data: &[i32; 2] = &[1..3];

不会起作用。错误消息将类似于：

main.rs:11:26: 11:30 error: mismatched types [E0308]
main.rs:11:26: 11:30 note: expected type `i32`
main.rs:11:26: 11:30 note:    found type `std::ops::Range<_>`

你实际拥有的是：

let data: &[std::ops::Range<_>] = &[1..3];

以下代码段中的变量有什么价值？

2 个答案: