相关疑难解决方法(0)

我在F#中创建了一个函数来从Yahoo恢复历史数据(F#的经典异步示例):

let getCSV ticker dStart dEnd =
async   {
        let query = getFileUrl ticker dStart dEnd
        let req = WebRequest.Create(query)
        use! resp = req.AsyncGetResponse()
        use stream= resp.GetResponseStream()
        use reader = new StreamReader(stream)
        let content = reader.ReadToEnd()
        let ts = parseData content
        return ts
        }

现在,我可以通过执行以下操作异步运行此函数:

let test=
    ["MSFT";"YHOO"]
    |>List.map (fun x -> getCSV x (DateTime.Parse("01.01.2000")) (DateTime.Parse("01.01.2010")))
    |> Async.Parallel
    |> Async.RunSynchronously

好,这很酷.

现在,我想知道的是如何应用一些功能,这是价格的历史:

例如:

let getReturns (prices:(DateTime *float)list) =
    [for i in 1..(prices.Length-1) -> i]
    |> List.map (fun i ->(fst (List.nth …