Digital Moose Tracks

I was watching Lingo and figured it would be good problem to experiment with F# on.  For the non game show watchers out there its basically the word game version of mastermind with letters instead of colored pegs.  F# pattern matching and discriminate unions made it elegant to write up.  For instance here is all the code to get possible solutions given the set of known clues.

type Clue =
    | FullMatch of int * char       //Correct letter at correct position
    | PartialMatch of int * char    //Correct letter at wrong position
    | Excluded of char * int        //No more than n instances of the letter

let GetPossibleSolutions clues =
    let IsValidWord (word : string) =
        clues |> Seq.forall (function
                                | FullMatch(i, c) -> word.[i] = c
                                | PartialMatch(i, c) -> word.[i] <> c && word |> Seq.exists ((=) c)
                                | Excluded(c, i) -> word |> count_of c = i
                              )

    Words.words |> Array.filter IsValidWord

With the discriminate union and pattern matching its pretty understandable even without a great deal of F# knowledge.  Basically it just filters out any words that doesn’t fit any of the clues.  Attached is the source code for a simple console app in F# that gives you guesses to try and refines them based off the resulting clues.

ConsoleLingo