tweak monads-lib

[lambda.git] / code / monads.ml

diff --git a/code/monads.ml b/code/monads.ml
index 4dbd851..2ba851b 100644 (file)
--- a/code/monads.ml
+++ b/code/monads.ml
@@ -111,7 +111,7 @@ module Monad = struct
     val (>=>) : ('a -> 'b m) -> ('b -> 'c m) -> 'a -> 'c m
     val do_when :  bool -> unit m -> unit m
     val do_unless :  bool -> unit m -> unit m
-    val forever : 'a m -> 'b m
+    val forever : (unit -> 'a m) -> 'b m
     val sequence : 'a m list -> 'a list m
     val sequence_ : 'a m list -> unit m
   end
@@ -135,7 +135,9 @@ module Monad = struct
     let (>=>) f g = fun a -> f a >>= g
     let do_when test u = if test then u else unit ()
     let do_unless test u = if test then unit () else u
-    let rec forever u = u >> forever u
+    let forever uthunk =
+        let rec loop () = uthunk () >>= fun _ -> loop ()
+        in loop ()
     let sequence ms =
       let op u v = u >>= fun x -> v >>= fun xs -> unit (x :: xs) in
         Util.fold_right op ms (unit [])
@@ -247,7 +249,7 @@ module Monad = struct
     val (>=>) : ('a -> ('x,'b) m) -> ('b -> ('x,'c) m) -> 'a -> ('x,'c) m
     val do_when :  bool -> ('x,unit) m -> ('x,unit) m
     val do_unless :  bool -> ('x,unit) m -> ('x,unit) m
-    val forever : ('x,'a) m -> ('x,'b) m
+    val forever : (unit -> ('x,'a) m) -> ('x,'b) m
     val sequence : ('x,'a) m list -> ('x,'a list) m
     val sequence_ : ('x,'a) m list -> ('x,unit) m
   end
@@ -263,7 +265,9 @@ module Monad = struct
     let (>=>) f g = fun a -> f a >>= g
     let do_when test u = if test then u else unit ()
     let do_unless test u = if test then unit () else u
-    let rec forever u = u >> forever u
+    let forever uthunk =
+        let rec loop () = uthunk () >>= fun _ -> loop ()
+        in loop ()
     let sequence ms =
       let op u v = u >>= fun x -> v >>= fun xs -> unit (x :: xs) in
         Util.fold_right op ms (unit [])
@@ -1243,7 +1247,8 @@ module Continuation_monad : sig
   val callcc : (('a -> ('r,'b) m) -> ('r,'a) m) -> ('r,'a) m
   val reset : ('a,'a) m -> ('r,'a) m
   val shift : (('a -> ('q,'r) m) -> ('r,'r) m) -> ('r,'a) m
-  val abort : ('a,'a) m -> ('a,'b) m
+  (* val abort : ('a,'a) m -> ('a,'b) m *)
+  val abort : 'a -> ('a,'b) m
   val run0 : ('a,'a) m -> 'a
 end = struct
   let id = fun i -> i
@@ -1267,10 +1272,19 @@ end = struct
   let callcc f = fun k -> f k k
   let throw k a = fun _ -> k a
   *)
-  (* from http://www.haskell.org/haskellwiki/MonadCont_done_right *)
+
+  (* from http://www.haskell.org/haskellwiki/MonadCont_done_right
+   *
+   *  reset :: (Monad m) => ContT a m a -> ContT r m a
+   *  reset e = ContT $ \k -> runContT e return >>= k
+   *
+   *  shift :: (Monad m) => ((a -> ContT r m b) -> ContT b m b) -> ContT b m a
+   *  shift e = ContT $ \k ->
+   *              runContT (e $ \v -> ContT $ \c -> k v >>= c) return *)
   let reset u = unit ((u) id)
   let shift f = (fun k -> (f (fun a -> unit (k a))) id)
-  let abort a = shift (fun _ -> a)
+  (* let abort a = shift (fun _ -> a) *)
+  let abort a = shift (fun _ -> unit a)
   let run0 (u : ('a,'a) m) = (u) id
 end
 
@@ -1467,7 +1481,7 @@ module C = Continuation_monad
 module TC = T.T2(C);;
 
 
-print_endline "================================================";;
+print_endline "=== test Leaf(...).distribute ==================";;
 
 let t1 = Some (T.Node (T.Node (T.Leaf 2, T.Leaf 3), T.Node (T.Leaf 5, T.Node (T.Leaf 7, T.Leaf 11))));;
 
@@ -1537,6 +1551,7 @@ LS.run (LS.distribute (fun i -> if i = -1 then S.get else if i < 0 then S.(puts
 - : S.store list * S.store = ([10; 0; 0; 1; 20], 1)
 *)
 
+print_endline "=== test Leaf(Continuation).distribute ==================";;
 
 let id : 'z. 'z -> 'z = fun x -> x
 
@@ -1581,14 +1596,15 @@ let example3 () =
 (* (+ 100 (prompt (+ 10 (shift k (k (k 1)))))) ~~> 121 *)
 let example5 () : int =
   Continuation_monad.(let v = reset (
-      let u = shift (fun k -> k 1 >>= fun x -> k x)
+      let u = shift (fun k -> k 1 >>= k)
       in u >>= fun x -> unit (10 + x)
     ) in let w = v >>= fun x -> unit (100 + x)
     in run0 w)
 
-
 ;;
 
+print_endline "=== test bare Continuation ============";;
+
 (1011, 1111, 1111, 121);;
 (example1(), example2(), example3(), example5());;
 ((111,0), (0,0));;
@@ -1638,3 +1654,22 @@ TreeCont.monadize t1 (fun a k -> k [a; a*a]) initial_continuation;;
 
 testc C.(fun a -> shift (fun k -> k (a,a+1))) (fun t -> t);;
 
+print_endline "=== pa_monad's Continuation Tests ============";;
+
+(1, 5 = C.(run0 (unit 1 >>= fun x -> unit (x+4))) );;
+(2, 9 = C.(run0 (reset (unit 5 >>= fun x -> unit (x+4)))) );;
+(3, 9 = C.(run0 (reset (abort 5 >>= fun y -> unit (y+6)) >>= fun x -> unit (x+4))) );;
+(4, 9 = C.(run0 (reset (reset (abort 5 >>= fun y -> unit (y+6))) >>= fun x -> unit (x+4))) );;
+(5, 27 = C.(run0 (
+              let c = reset(abort 5 >>= fun y -> unit (y+6))
+              in reset(c >>= fun v1 -> abort 7 >>= fun v2 -> unit (v2+10) ) >>= fun x -> unit (x+20))) );;
+
+(7, 117 = C.(run0 (reset (shift (fun sk -> sk 3 >>= sk >>= fun v3 -> unit (v3+100) ) >>= fun v1 -> unit (v1+2)) >>= fun x -> unit (x+10))) );;
+
+(8, 115 = C.(run0 (reset (shift (fun sk -> sk 3 >>= fun v3 -> unit (v3+100)) >>= fun v1 -> unit (v1+2)) >>= fun x -> unit (x+10))) );;
+
+(12, ["a"] = C.(run0 (reset (shift (fun f -> f [] >>= fun t -> unit ("a"::t)  ) >>= fun xv -> shift (fun _ -> unit xv)))) );;
+
+
+(0, 15 = C.(run0 (let f k = k 10 >>= fun v-> unit (v+100) in reset (callcc f >>= fun v -> unit (v+5)))) );;
+