DiceRoller.fs

open System

// Attempts to read a string and parse it into an integer
// If the string was not an integer, return "None", otherwise return "Some (integer)"
// I absolutely stole this code from the internet. Don't worry about it too much, it's just a shortcut.
// I don't really get the syntax either, but shit works
let (|Int|_|) str =
   match System.Int32.TryParse(str) with
   | (true,int) -> Some(int)
   | _ -> None

// Given a random number generator and a number, roll a number between 1 and the number
let getRandomRoll (randomGenerator:Random) maxNumber =
    randomGenerator.Next(1, maxNumber)

// Use this program like "roller.exe 20 10 4 5" to roll dice with each number as the max
// This code runs when the program actually starts. We call the other two functions above in it
[<EntryPoint>]
let main argv = 
    let randomGenerator = new Random()
    // "argv" is a list of arguments when you run the program, so we work with one at a time
    argv |> Seq.iter(fun inputString ->
    // This match statement will run different code if it is or isn't a number
    match inputString with
    // This code only runs if it's actually a number
    | Int number -> 
        // Ok, it was a number so first do a random roll from 1 to number
        let diceRoll = getRandomRoll randomGenerator number
        // Now print out the result of the roll
        printfn "Rolled a %i" diceRoll
    // This code runs if it wasn't a number
    | _ -> 
        // Politely inform the user that they are a dumbass
        printfn "%s is not a number!" inputString)

    0 // return an integer exit code (this is for Windows, doesn't matter for our code)