小编Da *_*est的帖子

所以我有这4个例子,其中3个是我从这个youtube视频中得到的.

我刚刚参加了关于函数式编程的课程(在Racket中),如果我对F#的基本理解是对的,我就是这样.

let data = [1.;2.;3.;4.]

let sqr x = x * x

// Bad, very bad   
let sumOfSquareI nums =
    let mutable acc = 0.0
    for x in nums do
        acc <- acc + sqr x
    acc

// Better than above, but may cause stack overflow with very long list    
let rec sumOfSquareF1 nums = 
    match nums with 
    | [] -> 0.0
    | h::t -> sqr h + sumOfSquareF1 t

// much much better, uses tail-recursion, no …

我有一个表,其中列有数据,如($23,324.09).如果是$23,324.09,那么我可以将其转换为money,然后是float.但是( )当我尝试时会导致错误.我是否必须将UDF应用于该列,或者是否有另一种方法来转换此类值.

注意:我无法控制数据如何到达该表.

添加更改事件的正确方法是什么？

    public static void WatchFileForChange()
        {
            FileSystemWatcher fsw = new FileSystemWatcher();

            fsw.Path = Path.Join(System.Configuration.ConfigurationManager.AppSettings["AccessDBFolder"]);
            fsw.Changed += new FileSystemEventHandler(UpdateMDBChange);
            fsw.Filter = "*.mdb";
            fsw.NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite;
            fsw.EnableRaisingEvents = true;
            fsw.IncludeSubdirectories = true;
        }

        private static void UpdateMDBChange(object sender, FileSystemEventArgs e)
        {
            ///sf/answers/213007441/
            DateTime lastWriteTime = File.GetLastWriteTime(e.FullPath);
            if (lastWriteTime.Ticks - lastRead.Ticks > 100000)
            {
                TestClient().Wait();
                lastRead = lastWriteTime;
            }
        }

是fsw.Changed += new FileSystemEventHandler(UpdateMDBChange);还是fsw.Changed += UpdateMDBChange;

两种方式似乎都很好。但我不知道是否会出现技术问题。或者如果某种方式不受欢迎。