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(*
//
// Implementing the Hanoi Tower problem
//
// The code was first written by Hongwei Xi in the summer of 2004
// The code is ported to ATS2 by Hongwei Xi on the last day of May, 2012
//
*)
(* ****** ****** *)
//
#include
"share/atspre_staload.hats"
//
(* ****** ****** *)
//
abstype
post_type (n:int) = ptr // for posts
typedef post (n:int) = post_type (n)
//
(* ****** ****** *)
extern
fun post_make {sz:pos} (sz: int sz): post (sz)
extern
fun post_initize {sz:nat} (p: post (sz), sz: int sz): void
(* ****** ****** *)
extern
fun post_get_at
{sz:int} (p: post (sz), i: natLt sz): natLte (sz)
overload [] with post_get_at
extern
fun post_set_at
{sz:int} (p: post (sz), i: natLt sz, x: natLte (sz)): void
overload [] with post_set_at
(* ****** ****** *)
fun
showpiece
{sz:int}
(
sz: int sz, n: natLte sz
) : void = let
//
fun loop
{
i:nat | i <= 2*sz
} .<2*sz-i>.
(
i: int (i)
) :<cloref1> void = let
in
//
if i < (sz-n) then
(
print ' '; loop (i + 1)
) else if i < (sz+n-1) then
(
print 'O'; loop (i + 1)
) else if i < (sz + sz) then
(
print ' '; loop (i + 1)
) // end of [if]
//
end // end of [loop]
//
in
loop (0)
end // end of [showpiece]
(* ****** ****** *)
fun play
{sz:pos} .<>.
(sz: int sz): void = let
//
//
val lp = post_make (sz)
val mp = post_make (sz)
val rp = post_make (sz)
//
fun showposts
.<>. (
(*argumentless*)
) :<cloref1> void = let
//
fun loop
{i:nat | i <= sz} (
i: int i
) :<cloref1> void = let
in
if sz > i then begin
showpiece (sz, lp[i]);
showpiece (sz, mp[i]);
showpiece (sz, rp[i]);
print_newline ();
loop (i + 1)
end else begin
print_newline ()
end // end of [if]
end // end of [loop]
//
in
loop (0)
end // end of [showposts]
//
val () = post_initize (lp, sz)
//
viewtypedef post = post (sz)
//
fun move
{
n,s,p,p':nat
| p <= sz &&
p' <= sz &&
s + p + p' == sz + sz &&
n > 0 &&
s + n <= sz &&
n <= p &&
n <= p'
} .<n>. (
n: int n
, src: post, s: int s,
post: post, p: int p
, post': post, p': int p'
) :<cloref1> void = (
if n = 1 then (
post[p-1] := src[s]; src[s] := 0; showposts ()
) else (
move (
n-1, src, s, post', p', post, p
) ; // end of [move]
post[p-1] := src[s+n-1]; src[s+n-1] := 0; showposts ();
move (
n-1, post', p' - n + 1, post, p - 1, src, s + n
) ; // end of [move]
) (* end of [if] *)
) (* end of [move] *)
//
in
//
showposts ();
move (sz, lp, 0, rp, sz, mp, sz);
print ("This round of play has finished.");
print_newline ();
//
end // end of [play]
(* ****** ****** *)
implement
main (
argc, argv
) = let
val () = play (4) in 0(*normalexit*)
end // end of [main]
(* ****** ****** *)
local
typedef
T (n:int) = natLte n
assume
post_type (n:int) = arrayref (T(n), n)
in // in of [local]
implement
post_make {sz} (sz) =
arrayref_make_elt (g1int2uint(sz), 0)
// end of [post_make]
implement
post_initize
{sz} (p, sz) = let
//
fun loop {
i:nat | i <= sz
} .<sz-i>. (
i: int i
) :<cloref1> void =
if i < sz then let
val i1 = succ(i) in arrayref_set_at (p, i, i1) ; loop (i1)
end // end of [if]
//
in
loop (0)
end // end of [post_initize]
implement
post_get_at (p, i) = arrayref_get_at (p, i)
implement
post_set_at (p, i, x) = arrayref_set_at (p, i, x)
end // end of [local]
(* ****** ****** *)
(* end of [hanoi.dats] *)
|
