f# - 在 F# 中非常简单的 RogueLike，使它更 "functional"

Question

我有一些现有的 C# 代码，用于一个非常非常简单的 RogueLike 引擎。故意天真，因为我试图尽可能简单地做最少的事情。它所做的只是使用箭头键和 System.Console 在硬编码 map 周围移动 @ 符号:

//define the map
var map = new List<string>{
  "                                        ",
  "                                        ",
  "                                        ",
  "                                        ",
  "    ###############################     ",
  "    #                             #     ",
  "    #         ######              #     ",
  "    #         #    #              #     ",
  "    #### #### #    #              #     ",
  "       # #  # #    #              #     ",
  "       # #  # #    #              #     ",
  "    #### #### ######              #     ",
  "    #              =              #     ",
  "    #              =              #     ",
  "    ###############################     ",
  "                                        ",
  "                                        ",
  "                                        ",
  "                                        ",
  "                                        "
};

//set initial player position on the map
var playerX = 8;
var playerY = 6;

//clear the console
Console.Clear();

//send each row of the map to the Console
map.ForEach( Console.WriteLine );

//create an empty ConsoleKeyInfo for storing the last key pressed
var keyInfo = new ConsoleKeyInfo( );

//keep processing key presses until the player wants to quit
while ( keyInfo.Key != ConsoleKey.Q ) {
  //store the player's current location
  var oldX = playerX;
  var oldY = playerY;

  //change the player's location if they pressed an arrow key
  switch ( keyInfo.Key ) {
    case ConsoleKey.UpArrow:
      playerY--;
      break;
    case ConsoleKey.DownArrow:
      playerY++;
      break;
    case ConsoleKey.LeftArrow:
      playerX--;
      break;
    case ConsoleKey.RightArrow:
      playerX++;
      break;
  }

  //check if the square that the player is trying to move to is empty
  if( map[ playerY ][ playerX ] == ' ' ) {
    //ok it was empty, clear the square they were standing on before
    Console.SetCursorPosition( oldX, oldY );
    Console.Write( ' ' );
    //now draw them at the new square
    Console.SetCursorPosition( playerX, playerY );
    Console.Write( '@' );
  } else {
    //they can't move there, change their location back to the old location
    playerX = oldX;
    playerY = oldY;
  }

  //wait for them to press a key and store it in keyInfo
  keyInfo = Console.ReadKey( true );
}

我在 F# 中尝试使用它，最初我尝试使用函数式概念来编写它，但结果我有点不知所措，所以我做了几乎直接的移植 - 它不是真正的 F# 程序(尽管它编译并运行)它是一个用 F# 语法编写的过程程序:

open System

//define the map
let map = [ "                                        ";
            "                                        ";
            "                                        ";
            "                                        ";
            "    ###############################     ";
            "    #                             #     ";
            "    #         ######              #     ";
            "    #         #    #              #     ";
            "    #### #### #    #              #     ";
            "       # #  # #    #              #     ";
            "       # #  # #    #              #     ";
            "    #### #### ######              #     ";
            "    #              =              #     ";
            "    #              =              #     ";
            "    ###############################     ";
            "                                        ";
            "                                        ";
            "                                        ";
            "                                        ";
            "                                        " ]

//set initial player position on the map
let mutable playerX = 8
let mutable playerY = 6

//clear the console
Console.Clear()

//send each row of the map to the Console
map |> Seq.iter (printfn "%s")

//create an empty ConsoleKeyInfo for storing the last key pressed
let mutable keyInfo = ConsoleKeyInfo()

//keep processing key presses until the player wants to quit
while not ( keyInfo.Key = ConsoleKey.Q ) do
    //store the player's current location
    let mutable oldX = playerX
    let mutable oldY = playerY

    //change the player's location if they pressed an arrow key
    if keyInfo.Key = ConsoleKey.UpArrow then
        playerY <- playerY - 1
    else if keyInfo.Key = ConsoleKey.DownArrow then
        playerY <- playerY + 1
    else if keyInfo.Key = ConsoleKey.LeftArrow then
        playerX <- playerX - 1
    else if keyInfo.Key = ConsoleKey.RightArrow then
        playerX <- playerX + 1

    //check if the square that the player is trying to move to is empty
    if map.Item( playerY ).Chars( playerX ) = ' ' then
        //ok it was empty, clear the square they were standing on
        Console.SetCursorPosition( oldX, oldY )
        Console.Write( ' ' )
        //now draw them at the new square 
        Console.SetCursorPosition( playerX, playerY )
        Console.Write( '@' )
    else
        //they can't move there, change their location back to the old location
        playerX <- oldX
        playerY <- oldY

    //wait for them to press a key and store it in keyInfo
    keyInfo <- Console.ReadKey( true )

所以我的问题是，我需要学习什么才能更有效地重写它，你能给我一些提示，一个模糊的概述，那种东西。

我更喜欢朝正确的方向推进，而不是只看一些代码，但如果这是你向我解释的最简单方法，那很好，但在这种情况下，你能不能解释一下“为什么”而不是“如何” ”的吗？

Answer 1

一般而言，游戏编程将测试您管理复杂性的能力。我发现函数式编程鼓励您将解决的问题分解成更小的部分。

您要做的第一件事是通过分离所有不同的关注点，将您的脚本变成一堆函数。我知道这听起来很愚蠢，但这样做的行为将使代码更具功能性(双关语)。您主要关注的是状态管理。我用一个记录来管理位置状态，用一个元组来管理运行状态。随着您的代码变得更高级，您将需要对象来干净地管理状态。

尝试在此游戏中添加更多内容，并随着功能的增长不断分解这些功能。最终，您将需要对象来管理所有功能。

在游戏编程笔记上，不要将状态更改为其他内容，如果未通过某些测试，则将其更改回来。你想要最小的状态变化。因此，例如下面我计算了 newPosition然后只更改 playerPosition如果这个 future 的职位过去了。

open System

// use a third party vector class for 2D and 3D positions
// or write your own for pratice
type Pos = {x: int; y: int} 
    with
    static member (+) (a, b) =
        {x = a.x + b.x; y = a.y + b.y}

let drawBoard map =
    //clear the console
    Console.Clear()
    //send each row of the map to the Console
    map |> List.iter (printfn "%s")

let movePlayer (keyInfo : ConsoleKeyInfo) =
    match keyInfo.Key with
    | ConsoleKey.UpArrow -> {x = 0; y = -1}
    | ConsoleKey.DownArrow -> {x = 0; y = 1}
    | ConsoleKey.LeftArrow -> {x = -1; y = 0}
    | ConsoleKey.RightArrow  -> {x = 1; y = 0}
    | _ -> {x = 0; y = 0}

let validPosition (map:string list) position =
    map.Item(position.y).Chars(position.x) = ' '

//clear the square player was standing on
let clearPlayer position =
    Console.SetCursorPosition(position.x, position.y)
    Console.Write( ' ' )

//draw the square player is standing on
let drawPlayer position =
    Console.SetCursorPosition(position.x, position.y)
    Console.Write( '@' )

let takeTurn map playerPosition =
    let keyInfo = Console.ReadKey true
    // check to see if player wants to keep playing
    let keepPlaying = keyInfo.Key <> ConsoleKey.Q
    // get player movement from user input
    let movement = movePlayer keyInfo
    // calculate the players new position
    let newPosition = playerPosition + movement
    // check for valid move
    let validMove = newPosition |> validPosition map
    // update drawing if move was valid
    if validMove then
        clearPlayer playerPosition
        drawPlayer newPosition
    // return state
    if validMove then
        keepPlaying, newPosition
    else
        keepPlaying, playerPosition

// main game loop
let rec gameRun map playerPosition =
    let keepPlaying, newPosition = playerPosition |> takeTurn map 
    if keepPlaying then
        gameRun map newPosition

// setup game
let startGame map playerPosition =
    drawBoard map
    drawPlayer playerPosition
    gameRun map playerPosition


//define the map
let map = [ "                                        ";
            "                                        ";
            "                                        ";
            "                                        ";
            "    ###############################     ";
            "    #                             #     ";
            "    #         ######              #     ";
            "    #         #    #              #     ";
            "    #### #### #    #              #     ";
            "       # #  # #    #              #     ";
            "       # #  # #    #              #     ";
            "    #### #### ######              #     ";
            "    #              =              #     ";
            "    #              =              #     ";
            "    ###############################     ";
            "                                        ";
            "                                        ";
            "                                        ";
            "                                        ";
            "                                        " ]

//initial player position on the map
let playerPosition = {x = 8; y = 6}

startGame map playerPosition