消除我通过like，monads和stuff传递的显式状态
我正在研究F＃中的Land of Lisp一书（是的，我很奇怪）。对于他们的第一个示例文本冒险，他们使用全局变量变异，我想避免它。我的monad-fu很弱，所以现在我正在做这样丑陋的状态：
let pickUp player thing (objects: Map<Location, Thing list>) =
let objs = objects.[player.Location]
let attempt = objs |> List.partition (fun o -> o.Name = thing)
match attempt with
| [], _ -> "You cannot get that.", player, objs
| thing :: _, things ->
let player' = { player with Objects = thing :: player.Objects }
let msg = sprintf "You are now carrying %s %s" thing.Article thing.Name
msg, player', things
let player = { Location = Room; Objects = [] }
let objects =
[Room, [{ Name = "whiskey"; Article = "some" }; { Name = "bucket"; Article = "a" }];
Garden, [{ Name = "chain"; Article = "a length of" }]]
|> Map.ofList
let msg, p', o' = pickUp player "bucket" objects
// etc.
没有找到相关结果
已邀请:
2 个回复
究补闯
函数来线程化玩家的库存和世界状态，这里有一种方法：type State<'s,'a> = State of ('s -> 'a * 's) type StateBuilder<'s>() = member x.Return v : State<'s,_> = State(fun s -> v,s) member x.Bind(State v, f) : State<'s,_> = State(fun s -> let (a,s) = v s let (State v') = f a v' s) let withState<'s> = StateBuilder<'s>() let getState = State(fun s -> s,s) let putState v = State(fun _ -> (),v) let runState (State f) init = f init type Location = Room | Garden type Thing = { Name : string; Article : string } type Player = { Location : Location; Objects : Thing list } let pickUp thing = withState { let! (player, objects:Map<_,_>) = getState let objs = objects.[player.Location] let attempt = objs |> List.partition (fun o -> o.Name = thing) match attempt with | [], _ -> return "You cannot get that." | thing :: _, things -> let player' = { player with Objects = thing :: player.Objects } let objects' = objects.Add(player.Location, things) let msg = sprintf "You are now carrying %s %s" thing.Article thing.Name do! putState (player', objects') return msg } let player = { Location = Room; Objects = [] } let objects = [Room, [{ Name = "whiskey"; Article = "some" }; { Name = "bucket"; Article = "a" }] Garden, [{ Name = "chain"; Article = "a length of" }]] |> Map.ofList let (msg, (player', objects')) = (player, objects) |> runState (pickUp "bucket")傻零凰死授
类型：type Player(initial:Location, objects:ResizeArray<Thing>) = let mutable location = initial member x.AddThing(obj) = objects.Add(obj) member x.Location with get() = location and set(v) = location <- v函数可以返回表示选择项目的请求的某个对象，而不是选择项目（并修改播放器）。然后世界将有一些引擎来评估这些请求（从所有玩家收集）并计算世界的新状态。