A tiny mandelbot fractal generator written in F#

mandelbrot.fs

open System.Numerics
open System.Drawing

let mandelbrotTest c z = Complex.Pow(z, 2.0) + c
let rec inSet c iterations z =
    let i = iterations - 1
    let newz = mandelbrotTest c z
    if newz.Magnitude > 2.0 then (c, false, i) else 
    if iterations > 0 then inSet c i newz else (c, true, i)

[<EntryPoint>]
let main argv =
     let p0 = new Complex(0.0, 0.0)
     let iterations = 50
     let plot =
      let stepSize = 0.01
      seq { for i in -2.0 .. stepSize .. 2.0 do 
             for j in -2.0 .. stepSize .. 2.0 do
              yield new Complex(i, j)}
     let resultsToPlot = Seq.map (fun x -> inSet x iterations p0) plot

     let imageResult = new Bitmap(401, 401)
     Seq.iter (fun (a : Complex, b, i) -> imageResult.SetPixel(System.Convert.ToInt32(((a.Real + 2.0) * 100.0)), System.Convert.ToInt32(((a.Imaginary + 2.0) * 100.0)), if b then Color.Black else Color.White)) resultsToPlot
     imageResult.Save("mandelbrot.bmp")
     printf "done"
     0

These 25-ish lines of code produce a very basic Mandlebrot plot. This can easily be extended to add color to the different iteration cycles, or tweaked to scale up the detail and resolution.