Solution for problem of Edx F# Module 4

fsharp-module-4.fs

open System
open System.IO

type Shot =
    { X  : float
      Y  : float
      Speed    : float
      ExpectedDistance : float
      Name     : string }

type ShotStatus = Hit|Miss|TooFar

type ShotResult =
    { Status  : ShotStatus
      Angle    : float
      Name     : string }

let gravity = 9.81

let fire shot =
    let { X = x; Y = y; Speed = speed; ExpectedDistance = expectedDistance; Name = name } = shot
    let speed2 = Math.Pow(speed,2.0);
    let maxDistance = speed2 / gravity
    let theta = Math.Atan(y / x)
    let angleOfReach = 0.5 * Math.Asin((gravity * expectedDistance) / speed2)
    let distanceTravelled = (speed2 * Math.Sin(2.0 * theta)) /  gravity

    let status =
        if (expectedDistance > maxDistance) then ShotStatus.TooFar
        elif (distanceTravelled = expectedDistance) then ShotStatus.Hit
        else ShotStatus.Miss

    let result = { Status = status; Angle = angleOfReach; Name = name }
    result
   
let result shot =
    match fire shot with
        | { ShotResult.Status = status; ShotResult.Angle = angle; ShotResult.Name = name } 
            when status = ShotStatus.TooFar      -> sprintf "%s has missed. Distance out of reach." name
        | { ShotResult.Status = status; ShotResult.Angle = angle; ShotResult.Name = name } 
            when status = ShotStatus.Hit      -> sprintf "%s is a hit!" name
        | { ShotResult.Status = status; ShotResult.Angle = angle; ShotResult.Name = name } 
            when status = ShotStatus.Miss  -> sprintf "%s has missed. Angle of reach needed was %f." name angle
        | _ -> ""

let GetFile =
    let mutable filepath = ""
    while filepath = "" do
        Console.Write("Enter the full path to the name of the input file: ")
        filepath <- Console.ReadLine()
    filepath
        
[<EntryPoint>]    
let main argv =
    try
        use input =
            new StreamReader(match argv.Length with
                             | 0 -> GetFile
                             | _ -> argv.[0])

        let shots =
            [ while not input.EndOfStream do
                  let raw = input.ReadLine()
                  let values = raw.Split(',')
                  yield { X  = float values.[0]
                          Y  = float values.[1]
                          Speed    = float values.[2]
                          ExpectedDistance = float values.[3]
                          Name  = values.[4] } ]

        Console.WriteLine("The shots fired were: ")
        for e in shots do
            Console.WriteLine(result e)

        let c = Console.ReadKey()
        0 // return an integer exit code
    with
    | :? System.IO.FileNotFoundException ->
        -1
    | _ ->
        -1