Monte Carlo
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open System
type Point =
{ X : float
Y : float }
let isInsideUnitCircle point = point.X ** 2.0 + point.Y ** 2.0 <= 1.0
let randomPoints =
let random = Random()
Seq.initInfinite (fun _ ->
{ X = random.NextDouble()
Y = random.NextDouble() })
let pi batch =
let a =
(Seq.unfold (fun state ->
let (total, pointsInside, _) = state
let newPoinstsInside =
pointsInside + (Seq.take batch randomPoints
|> Seq.filter isInsideUnitCircle
|> Seq.length)
let ratio = (float) pointsInside / (float) total
let newState = (total + batch, newPoinstsInside, ratio * 4.0)
Some(state, newState))) (0, 0, 0.0)
seq {
for v in a do
let (_, _, pi) = v
yield pi
}
[<EntryPoint>]
let main argv =
let nDefault = 100
let n =
let argvLength = Array.length argv
match argvLength with
| _ when argvLength >= 1 ->
let first = Array.head argv
match Int32.TryParse first with
| true, n -> n
| false, _ -> nDefault
| _ -> nDefault
for estimate in Seq.take 1000 (pi n) do
printfn "%f" estimate
0 // return an integer exit code
Fsharp
INFO