dotnet new console -lang="F#"

// Learn more about F# at http://docs.microsoft.com/dotnet/fsharp

open System

// Define a function to construct a message to print
let from whom = sprintf "from %s" whom

[<EntryPoint>]
let main argv =
    let message = from "F#" // Call the function
    printfn "Hello world %s" message
    0

dotnet add package FSharp.Scanf

open FSharp.Scanf

printfn "input a number"

try
    let ans = scanfn "%i"

    if ans = 42 then
        printfn "the ultimate answer"
    else
        printfn "recieved %i" ans
with _ -> printfn "not a number... :("

[ 1 .. 100 ] |> List.sum |> printfn "sum=%d"

type Person = { First: string; Last: string }

type Employee =
    | Worker of Person
    | Manager of Employee list

let asak = { Last = "Agoshi"; First = "Sakina" }
let schi = { Last = "Chiaki"; First = "Soen" }
let worker = Worker asak
let employee = Manager [ Worker schi; worker ]

let pChar char str =
  if System.String.IsNullOrEmpty(str) then
    let msg = "No more input"
    Error msg
  else
    let first = str.[0]

    if first = char then
      let remaining = str.[1..]
      Ok(char, remaining)
    else
      let msg = sprintf "Expected %c, got %c" char first
      Error msg

[<EntryPoint>]
let main _ =
  let pA = pChar 'A'
  printfn "%A" (pA "ABC")
  printfn "%A" (pA "ZBC")
  0

let either parser1 parser2 =
  let innerFn input =
    match run parser1 input with
    | Ok _ as r -> r
    | Error _ -> run parser2 input

  Parser innerFn

let (<|>) = either


[<EntryPoint>]
let main _ =
  let pA = pChar 'A'
  let pAOrB = pChar 'A' <|> pChar 'B'
  printfn "%A" (run pAOrB "ABC")
  printfn "%A" (run pAOrB "BBC")
  printfn "%A" (run pAOrB "ZBC")
  0

let choice parsers = List.reduce (<|>) parsers

[<EntryPoint>]
let main _ =
  let parseAOrBOrC =
    [ 'A'; 'B'; 'C' ]
    |> List.map pChar
    |> choice

  printfn "%A" (run parseAOrBOrC "ABC")
  printfn "%A" (run parseAOrBOrC "BBC")
  printfn "%A" (run parseAOrBOrC "CBC")
  printfn "%A" (run parseAOrBOrC "ZBC")
  0