open System
open System.Drawing
open System.Drawing.Imaging
open System.Drawing.Drawing2D
open System.Windows.Forms

let r = 5.0
//let squareF = fun x -> Math.Sin(x)
let squareF = fun x -> Math.PI*r*r
let xArray = [|-3.0 .. 0.1..3.0|]
let yArray = Array.map squareF xArray
let W,H = 800,800
let scaleX = Array.map (fun x -> x*44.0+400.0) xArray
let scaleY = Array.map( fun x -> 400.0-44.0*x) yArray

let form =
     let b = new Bitmap(W,H)
     let g = Graphics.FromImage(b)
     let pen = new Pen(Color.Black)
     g.DrawLine(pen, W/2,0,W/2,H)
     g.DrawLine (pen, 0,H/2,W,H/2)
     let red = new Pen(Color.Red)

     let mutable i=1
     while i<scaleX.Length  do
        g.DrawLine(red, (float32)scaleX.[i-1], (float32)scaleY.[i-1], (float32)scaleX.[i], (float32)scaleY.[i])
        i<- i+1

     let temp = new Form()
     temp.Paint.Add(fun e -> e.Graphics.DrawImage(b, 0, 0))
     temp

[<STAThread>]
do Application.Run(form);;