FSharp Lesson

Lesson.fsx

open System

(*Version 1
let rec handle (command:string) =
 match command.ToLower() with
 | "quit" -> printfn "Bye Bye!"//exit condition first!
 | _ ->
  printfn "I don't understand %s" command
  Console.ReadLine() |> handle

Console.ReadLine() |> handle
*)

(*Version 2
let quitMessage() = printfn "Bye Bye!"

let processCommand command = printfn "Can't do %s" command

let rec handle (command:string) =
 match command.ToLower() with
 | "quit" -> quitMessage()
 | _ -> 
  processCommand command
  Console.ReadLine() |> handle

Console.ReadLine() |> handle
*)

(*Version 3
let processCommand command = printfn "Can't do %s" command

let rec handle (command:string) =
 let quit() = printfn "Bye Bye!"
 let evaluate() = 
  processCommand command
  Console.ReadLine() |> handle
 match command.ToLower() with
 | "quit" -> quit()
 | _ -> evaluate()

Console.ReadLine() |> handle
*)

(*Version 4

type Result =
| Quit
| Continue

let isQuit (command:string) = command.ToLower() = "quit"
let execute command = printfn "Can't do %s" command

let evaluate command =
 if command |> isQuit then Quit
 else execute command; Continue

let rec handle (command:string) =
 match evaluate command with
 | Quit -> printfn "Bye Bye!"
 | Continue -> Console.ReadLine() |> handle

Console.ReadLine() |> handle
*)

(*Version 5

type Result =
| Quit
| Continue

let isQuit (command:string) = command.ToLower() = "quit"
let execute command = printfn "Can't do %s" command

let evaluate command =
 if command |> isQuit then Quit
 else execute command; Continue

let next fn = 
 Console.Write("> ")
 Console.ReadLine() |> fn

let rec handle (command:string) =
 match evaluate command with
 | Quit -> printfn "Bye Bye!"
 | Continue -> handle |> next

handle |> next
*)

(*Version 6*)

type Result =
| Quit
| Continue

type ColouredConsole(colour) =
 do Console.ForegroundColor <- colour
 member this.Write message = Console.Write(message:string)
 interface IDisposable with
  member this.Dispose() = Console.ResetColor()

let execute command = printfn "Can't do %s" command
let isQuit (command:string) = command.ToLower() = "quit"

let evaluate command =
 if command |> isQuit then Quit
 else execute command; Continue

let writeIn colour message =
 use cc = new ColouredConsole(colour)
 cc.Write message

let next fn = 
 writeIn ConsoleColor.DarkGray "> "
 Console.ReadLine() |> fn

let rec handle (command:string) =
 match evaluate command with
 | Quit -> printfn "Bye Bye!"
 | Continue -> handle |> next

writeIn ConsoleColor.Cyan "Welcome! (type 'quit' to exit)\n"
handle |> next