(*
This file is simply the “tangled” F# code of ruby-f#-demo.org;
it is the “raw” source code, provided for your convenience.
*)

let x, y = 5, 10

printfn "%b" (x > y)
printfn "%b" (x < y)
printfn "%b" (x = y)

let x, y = 5, 10
let printbool = (printfn "%b")

printbool (x < y)
printbool (x = y)

let x = printfn "Hello world"

printfn "%O" x

printfn "hello"

if 2 = 5 then printfn "What reality am I in?"

if   2 = 7 then printfn "Now I'm even more concerned..."
elif 2 = 4 then printfn "This doesn't help either..."
else            printfn "Okay, maybe everything's okay."

let r =
  match 5 with
  | 0 -> "Factorial is 1."
  | 1 -> "Factorial is 1."
  | 2 -> "Factorial is 2."
  | 3 -> "Factorial is 6."
  | 4 -> "Factorial is 24."
  | _ -> "I'm tired, go away."

printfn "%s" r

let r =
  match 5 with
  | 5 when false -> "It might match, but it can't satisfy this guard!"
  | 5 when true  -> "This guard's easily pleased."
  | _ -> "Uh... hello?"

printfn "%s" r

let rec fact n =
  match n with
  | 0 -> 1
  | n when n > 0 -> n * fact (n - 1)
  | _ -> printfn "Can't calculate factorial of a negative!"
         -1

printfn "Factorial 5 is %d" (fact 5)

let rec forever (x : int) : int =
  printfn "All work and no play makes F# a dull language..."
  forever x

let rec forever' (_ : unit) : Lazy<unit> =
  printfn "I can do it, I can do it ∞ times!"
  forever'()

let forever : Lazy<unit> =
  lazy while true do
    printfn "Much better..."

for x in [1;2;3] do
  printfn "Iterating through a list %d" x

for x = 1 to 3 do
  printfn "Counting up %d" x

for x = 3 downto 1 do
  printfn "Counting down %d" x

let value = System.Console.ReadLine()

System.Console.WriteLine("Is there an echo in here?");
System.Console.WriteLine(value)

let rec forever : Lazy<sbyte> =
  let rec forever_helper (so_far : sbyte) : sbyte =
    match so_far with
    | 0y -> printfn "Starting out..."
            forever_helper 1y
    | n when n % 100y = 0y -> printfn "Took a hundred steps..."
                              forever_helper (n + 1y)
    | n when n = -1y -> printfn "Sorry, fell asleep and overflowed a bit!"
                        forever_helper (n + 1y)
    | n -> forever_helper (n + 1y)
  in lazy forever_helper 0y