F #: Leverage the. NET Framework

F # acts as a language running on the. NET Framework, and it is natural to use the. NET Framework.

This time we'll try to write code by calling the. NET framework.

The code that ignores the return value first is written as follows:

Ignore (System.Windows.Forms.MessageBox.Show ("Hello World")

This will show the MessageBox. In addition, if you want to omit the namespace, you can rewrite it as:

open　System.Windows.Forms
ignore　(MessageBox.Show("Hello　world"))

Of these, the using used in C # becomes open.

The code to use the thread is as follows:

open　System.Threading
Thread.Sleep(4000)

Next try using datetime and Console.WriteLine:

open　System
let　dt　=　new　DateTime(1984,1,24)
Console.WriteLine("{0}　{1}　{2}",dt.Year,　dt.Month,　dt.Day)
let　today　=　DateTime.Today　
Console.WriteLine("{0}　{1}　{2}",today.Year,　today.Month,　today.Day)
let　diff　=　today　-　dt;
Console.WriteLine("{0}",　diff.TotalDays)

Also, the variables for F # functions do not need ():

Thread.Sleep 4000

It is also possible to pass the pipeline:

4000 |> Thread.Sleep

What happens when you have multiple parameters? Try the following code:

Console.WriteLine　"{0}"　dt.Year
Console.WriteLine　"{0}",　dt.Year

Not at all. It is only when you feel that you have one parameter. The code is as follows:

Console.WriteLine (dt. ToString ())

However, the following code will cause a compilation error:

Console.WriteLine (123.ToString ())

The feeling is that numeric constants cannot use method.

Try writing some other code.

open　System　
open　System.Collections.Generic
let　n　=　123　
Console.WriteLine("{0}",n.ToString())
Console.WriteLine("{0}",Int32.MaxValue)
let　rnd　=　new　Random()
let　list　=　new　List<int>()
for　x　in　1..10　do
　　　　　　　　 list.Add(rnd.Next(1,10))
for　x　in　list　do
　　　　　　　　 printfn　"%A"　x

If you have used C #, you can use the. NET framework quite naturally. F # is a worthy. NET language Ah!