by on October 18, 2011
Today I made some effort to implement a very simple version of the game “Hangman” in F#. Even though I am already familiar with the general syntax of F# and do understand some basic functional programming styles I have to admit that it’s not that easy to get rid of usual iterative programming behaviors I am so used to.
Without further ado, this is what I came up with so far:
open System
open System.Text
open System.Text.RegularExpressions
/// Replace the non-guessed letters with an underscore
let replace (word : string) (letters : char list) =
let sb = StringBuilder(word.Length)
let contains c list = list |> List.exists (fun x -> x = c)
word.ToCharArray()
|> Array.iter (fun l -> sb.Append(if contains l letters then l else '_') |> ignore)
sb.ToString()
/// Determine whether the word was guessed
let solved (word : string) =
let rgx = Regex(@"^[^_]+$")
rgx.IsMatch(word)
/// Start the Hangman game with a maximum number of attempts
/// and a given word to guess
let hangman max (word : string) =
printfn "Hangman: %s" (replace word [])
let rec hangman' attempts (word : string) (letters : char list) =
if attempts = 0 then printfn "You lost the game"
else
printf "Attempts left %d: " attempts
let input = Console.ReadKey(true).KeyChar
let ls = input :: letters
let rep = replace word ls
if solved rep then
printfn "%s" word
else
printfn "%s" rep
hangman' (attempts-1) word ls
hangman' max word []I am pretty sure that there are much more elegant ways to implement this in F#. So if you have got any remarks or suggestions on how to improve this, I am very much interested in your opinion. So feel free to email me.
By the way, I did program on my linux machine at home using MonoDevelop with the great F# bindings 1 mainly written by Tomas Petricek. Go check that out if you are running linux or MacOS - it does work very well especially regarding that it’s completely open-source.