Dining philosophers (Joinads)

A simple and declarative solution based on Joinads.

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open System
open FSharp.Extensions.Joinads

// Init
let n = 5
let chopsticks = [| for i = 1 to n do yield new Channel<unit>() |]
let hungry = [| for i = 1 to n do yield new Channel<unit>() |]
let philosophers = [| "Plato"; "Konfuzius"; "Socrates"; "Voltaire"; "Descartes" |]

let randomDelay (r : Random) = System.Threading.Thread.Sleep(r.Next(1, 10) * 1000)

// Fork 
for i = 0 to n - 1 do
    let left = chopsticks.[i]
    let right = chopsticks.[(i+1) % n]
    let random = new Random()
    join {
        match! hungry.[i], left, right with
        | _, _, _ ->
            printfn "%s is eating" philosophers.[i] 
            randomDelay random
            left.Call(); right.Call()
            printfn "%s is thinking" philosophers.[i] 
    }
    
// Run
for chopstick in chopsticks do
    chopstick.Call()

let random = new Random()    
while true do
    hungry.[random.Next(0, n)].Call()
    randomDelay random

namespace System

namespace Microsoft.FSharp

val n : int

Full name: Script.n

val chopsticks : obj []

Full name: Script.chopsticks

val i : int

type unit = Unit

Full name: Microsoft.FSharp.Core.unit

val hungry : obj []

Full name: Script.hungry

val philosophers : string []

Full name: Script.philosophers

val randomDelay : r:Random -> unit

Full name: Script.randomDelay

val r : Random

Multiple items
type Random =
  new : unit -> Random + 1 overload
  member Next : unit -> int + 2 overloads
  member NextBytes : buffer:byte[] -> unit
  member NextDouble : unit -> float

Full name: System.Random

--------------------
Random() : unit
Random(Seed: int) : unit

namespace System.Threading

Multiple items
type Thread =
  inherit CriticalFinalizerObject
  new : start:ThreadStart -> Thread + 3 overloads
  member Abort : unit -> unit + 1 overload
  member ApartmentState : ApartmentState with get, set
  member CurrentCulture : CultureInfo with get, set
  member CurrentUICulture : CultureInfo with get, set
  member DisableComObjectEagerCleanup : unit -> unit
  member ExecutionContext : ExecutionContext
  member GetApartmentState : unit -> ApartmentState
  member GetCompressedStack : unit -> CompressedStack
  member GetHashCode : unit -> int
  ...

Full name: System.Threading.Thread

--------------------
Threading.Thread(start: Threading.ThreadStart) : unit
Threading.Thread(start: Threading.ParameterizedThreadStart) : unit
Threading.Thread(start: Threading.ThreadStart, maxStackSize: int) : unit
Threading.Thread(start: Threading.ParameterizedThreadStart, maxStackSize: int) : unit

Threading.Thread.Sleep(timeout: TimeSpan) : unit
Threading.Thread.Sleep(millisecondsTimeout: int) : unit

Random.Next() : int
Random.Next(maxValue: int) : int
Random.Next(minValue: int, maxValue: int) : int

val left : obj

val right : obj

val random : Random

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

Raw view Test code New version

More information

Link:	http://fssnip.net/aL
Posted:	12 years ago
Author:	Nick Palladinos
Tags:	joinads