Hangman is a simple word-guessing game.
The program in this example chooses a word in some random fashion and then gives the player a fixed number of chances to guess the word. The player can guess one letter each time; if the letter does not appear in the word, then the player loses a chance; otherwise, each occurrence of the letter is displayed and the player does not lose a chance. The player loses if all of the given chances are used up, or the player wins after all of the letters in the word are correctly guessed.
The function GameLoop implements a standard loop for playing the game:
(* ****** ****** *)
//
extern
fun
GameLoop
(&state >> _, stream_vt(input)): int
and
GameLoop_solved
(&state >> _, stream_vt(input)): int
and
GameLoop_timeup
(&state >> _, stream_vt(input)): int
and
GameLoop_asking
(&state >> _, stream_vt(input)): int
//
(* ****** ****** *)
implement
GameLoop
(state, xs) = let
//
val
status = state_check(state)
//
in
case+ status of
| STATUSsolved() => GameLoop_solved(state, xs)
| STATUStimeup() => GameLoop_timeup(state, xs)
| STATUSasking() => GameLoop_asking(state, xs)
end // end of [GameLoop]Note that GameLoop takes two arguments: The first argument refers
to the current state of the game being played and the second one is a
linear stream representing inputs from the player. The state is passed
as a call-by-reference argument, and it is updated according to the
current input from the player:
implement
GameLoop_asking
(state, xs) = let
//
val () =
println!
("Chances: ", state.ntime)
val () =
println!
("Guessed: ", state.guess)
val () =
word_display
(state.word0, state.guess)
//
val () = println!((*void*))
//
in
//
case+ !xs of
| ~stream_vt_nil() => (~1) where
{
val () =
println!
("ERROR: no input from the player!!!")
}
| ~stream_vt_cons(x0, xs) =>
let
val err =
state_update(state, x0) in GameLoop(state, xs)
end
//
end // end of [GameLoop_asking]
Happy programming in ATS!!!