open System
open System.Drawing
open System.Windows.Forms

let mutable num1 = "NULL"
let mutable num2 = "NULL"
let mutable oper = "NULL"
let mutable flag="-"

let Math(op:string, box:TextBox) =
 flag<-"+"
 if (num1="NULL") then num1<-box.Text
 else num2<-box.Text
 if (oper="NULL") then oper<-op else do
 match oper with
 | "+" when (num1<>"NULL" && num2<>"NULL") -> num1 <- (Double.Parse(num1)+Double.Parse(num2)).ToString()
 | "-" when (num1<>"NULL" && num2<>"NULL") -> num1 <- (Double.Parse(num1)-Double.Parse(num2)).ToString()
 | "*" when (num1<>"NULL" && num2<>"NULL") -> num1 <- (Double.Parse(num1)*Double.Parse(num2)).ToString()
 | "/" when (num1<>"NULL" && num2<>"NULL") -> if (num2<>"0") then do
   num1 <- (Double.Parse(num1) / Double.Parse(num2)).ToString() else num1<-"ERROR"
 | "=" -> num2 <-"NULL"
 box.Text<-num1
 oper<-op
0

//Создание кнопки с нужными параметрами, обработка событий
let createButton (text:string,form:Form, box:TextBox, pos1, pos2) =
 let btn = new Button()
 btn.Text <- text
 btn.Size <- new Size(40,40)
 btn.Location <- new System.Drawing.Point(pos1, pos2)
 btn.Click.Add(fun _ -> if (flag="+") then do
                           flag<-"-"
                           box.Text<-""
                           box.AppendText(text)
                         else if (box.Text="0") then do
                         box.Text<-""
                         box.AppendText(text)
                        else if (box.Text.Length<18)
                         then
                         box.AppendText(text))

 form.Controls.Add(btn)
 btn

//Cоздаёv кнопки с цифрами и операциями
let Buttons (form:Form, box:TextBox) =
 let mutable multiplier = 2
 for x=7 to 9 do
      if (x<>7) then
       createButton(x.ToString(),form, box, 20+20*multiplier, 50)
       multiplier<-multiplier*2
      else do createButton(x.ToString(),form, box, 20, 50)
 multiplier <- 2
 for x=4 to 6 do
     if (x<>4) then
       createButton(x.ToString(),form, box, 20+20*multiplier, 100)
       multiplier<-multiplier*2
     else do createButton(x.ToString(),form, box, 20, 100)
 multiplier <- 2
 for x=1 to 3 do
    if (x<>1) then
      createButton(x.ToString(),form, box, 20+20*multiplier, 150)
      multiplier<-multiplier*2
    else do createButton(x.ToString(),form, box, 20, 150)

 let zeroBtn = new Button(Text="0", Size = new Size (40,45), Location = new Point(20,190))
 zeroBtn.Click.Add(fun _ -> if (flag="+") then do
                                          flag="-"
                                          box.Text <- "0" else
  if (box.Text<>"0" && box.Text.Length<18) then box.AppendText("0"))
 form.Controls.Add(zeroBtn)

 let eqBtn = new Button(Text="=", Size = new Size (40,45), Location = new Point (100, 190))
 eqBtn.Click.Add(fun _ -> Math("=", box))
 form.Controls.Add(eqBtn)

 let clearBtn = new Button(Text="CE", Size = new Size (40,45), Location = new Point(170,230))
 clearBtn.Click.Add(fun _ ->
 num1 <- "NULL"
 num2 <- "NULL"
 oper <- "NULL"
 box.Text <-"0"
 flag<-"+"
  )
 form.Controls.Add(clearBtn)

 let dotBtn = new Button(Text=",", Size = new Size(40,45), Location = new Point (60,190))
 dotBtn.Click.Add(fun _ -> box.AppendText(","))
 form.Controls.Add(dotBtn)

 let sinBtn = new Button(Text="Sin", Size = new Size(40, 45), Location = new Point (210, 50))
 sinBtn.Click.Add(fun _ ->
 box.Text <- System.Math.Sin(Double.Parse(box.Text)).ToString()
 )
 form.Controls.Add(sinBtn)

 let cosBtn = new Button(Text="Cos", Size = new Size(40, 45), Location = new Point (210, 95))
 cosBtn.Click.Add(fun _ ->
 box.Text <- System.Math.Cos(Double.Parse(box.Text)).ToString()
 )
 form.Controls.Add(cosBtn)

 let tgBtn = new Button(Text="Tg", Size = new Size(40, 45), Location = new Point (210, 140))
 tgBtn.Click.Add(fun _ ->
 box.Text <- System.Math.Tan(Double.Parse(box.Text)).ToString()
 )
 form.Controls.Add(tgBtn)

 let divideBtn = new Button(Text="/", Size = new Size (40,45), Location = new Point (170,185))
 divideBtn.Click.Add(fun _ -> Math("/", box))
 form.Controls.Add(divideBtn)
 let plusBtn = new Button(Text="+", Size = new Size (40,45), Location = new Point (170,50))
 plusBtn.Click.Add(fun _ -> Math("+", box))
 form.Controls.Add(plusBtn)
 let minusBtn = new Button(Text="-", Size = new Size (40,45), Location = new Point (170,95))
 minusBtn.Click.Add(fun _ -> Math("-", box))
 form.Controls.Add(minusBtn)
 let multiBtn = new Button(Text="*", Size = new Size (40,45), Location = new Point (170,140))
 multiBtn.Click.Add(fun _ -> Math("*", box))
 form.Controls.Add(multiBtn)
 0

let Main =
    let form = new Form()
    form.Height <- 320
    form.Width <-280
    form.FormBorderStyle <- FormBorderStyle.FixedDialog
    let box = new TextBox(Size=new Size(210,50))
    box.Location = new System.Drawing.Point(100,80)
    box.AppendText("0")
    form.Controls.Add(box)
    Buttons(form, box)


    Application.Run(form)