Hello. I am a senior computer science student that has worked almost exclusively with c/c++/c# imperative style programming. With microsoft's release of F# I have taken it upon myself to try and learn functional programming. My very first program with F# or a functional language is below...a blackjack game!

Currently it's not complete, but I've ran into a problem, therefore i had a few questions. Whenever I call DealCard I always get the same results. I realize I'm calling from Random here, and so I added a sleep for 1 second to try and ensure different results for testing, unfortunately it seems like the Sleep only gets called once. It's almost as if F# is caching my previous function call return value from the parameters given? Also if you have any way that I can improve the design of the program to be more "functional" please let me know. I'm probably doing it all wrong in a c++ style.

#light

open System

type Suit = Hearts | Spades | Clubs | Diamonds
type CardType = ValueCard | Jack | Queen | King | Ace
type Card = {Suit:Suit; CardType:CardType; CardValue:int}

let CreateCardFromNumber cardNumberFromDeck =
match cardNumberFromDeck with
(* Hearts Suit [1 - 13] *)
| value when cardNumberFromDeck >= 1 && cardNumberFromDeck <= 13 -> {Suit = Hearts; CardType = ValueCard; CardValue = cardNumberFromDeck}
(* Spades Suit [14 - 26] *)
| value when cardNumberFromDeck >= 14 && cardNumberFromDeck <= 26 -> {Suit = Spades; CardType = ValueCard; CardValue = cardNumberFromDeck - 13}
(* Clubs Suit [27 - 39] *)
| value when cardNumberFromDeck >= 27 && cardNumberFromDeck <= 39 -> {Suit = Clubs; CardType = ValueCard; CardValue = cardNumberFromDeck - 26}
(* Diamonds Suit [40 - 52] *)
| value when cardNumberFromDeck >= 40 && cardNumberFromDeck <= 52 -> {Suit = Diamonds; CardType = ValueCard; CardValue = cardNumberFromDeck - 39}

let DealCard =
let randomCardGenerator = new System.Random()
let randomCard = randomCardGenerator.Next(1, 52)

let newCard = (CreateCardFromNumber randomCard)

match newCard.CardValue with
(* Initially assume all aces are valued at 11 *)
| 1 -> {newCard with CardType = Ace; CardValue = 11}
| 11 -> {newCard with CardType = Jack; CardValue = 10}
| 12 -> {newCard with CardType = Queen; CardValue = 10}
| 13 -> {newCard with CardType = King; CardValue = 10}
| value when newCard.CardValue > 1 && newCard.CardValue < 11 -> newCard

let CalculateHandValue hand =
let totalValue = List.fold (fun acc item -> acc + item.CardValue) 0 hand
if totalValue > 21 then
List.fold (fun acc item -> if item.CardType = Ace && acc > 21 then acc - 10 else acc) totalValue hand
else
totalValue
let CardTypeToString item =
match item.CardType with
| ValueCard -> item.CardValue.ToString()
| Jack -> "Jack"
| Queen -> "Queen"
| King -> "King"
| Ace -> "Ace"

let SuitToString item =
match item.Suit with
| Hearts -> "Hearts"
| Spades -> "Spades"
| Clubs -> "Clubs"
| Diamonds -> "Diamonds"

let DisplayHand hand =
List.iter (fun item -> printfn "%s of %s" (CardTypeToString item) (SuitToString item)) hand

let mutable playerCards = []
let dealerCards = []

let mutable playerTotal = 0

playerCards <- (DealCard) :: (DealCard) :: playerCards
DisplayHand playerCards
playerTotal <- (CalculateHandValue playerCards)

printfn "%d" playerTotal

while playerTotal < 21 do
printfn "(H)it (S)tand ?"
let input = Console.ReadLine()
match input with
| "H" | "h" ->
playerCards <- (DealCard) :: playerCards
playerTotal <- (CalculateHandValue playerCards)
DisplayHand playerCards
printfn "%d" playerTotal
| "S" | "s" ->
printfn "%d" playerTotal