X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=code%2Fmonads.ml;h=ae0ecc51690c82d0bb5316ec142c4cd8786d1518;hp=2ba851b3bb904b7a9784a56e65178d02056f5ed3;hb=1d3dba7d49400782f8d5529e4a3c850f4ab7f16c;hpb=595509c48871d2cf8f420dc6cbb3668d21e85a61

diff --git a/code/monads.ml b/code/monads.ml
index 2ba851b3..ae0ecc51 100644
--- a/code/monads.ml
+++ b/code/monads.ml
@@ -587,7 +587,7 @@ end) : sig
   (* declare additional operations, while still hiding implementation of type m *)
   type err = Err.err
   type 'a error = Error of err | Success of 'a
-  type 'a result = 'a
+  type 'a result = 'a error
   type 'a result_exn = 'a
   include Monad.S with type 'a result := 'a result and type 'a result_exn := 'a result_exn
   (* include Monad.PLUS with type 'a m := 'a m *)
@@ -595,37 +595,55 @@ end) : sig
   val catch : 'a m -> (err -> 'a m) -> 'a m
   (* ErrorT transformer *)
   module T : functor (Wrapped : Monad.S) -> sig
+    type 'a result = 'a error Wrapped.result
+    type 'a result_exn = 'a Wrapped.result_exn
+    include Monad.S with type 'a result := 'a result and type 'a result_exn := 'a result_exn
+    val elevate : 'a Wrapped.m -> 'a m
+    val throw : err -> 'a m
+    val catch : 'a m -> (err -> 'a m) -> 'a m
+  end
+  (* ErrorT transformer when wrapped monad has plus, zero *)
+  module TP : functor (Wrapped : Monad.P) -> sig
     type 'a result = 'a Wrapped.result
     type 'a result_exn = 'a Wrapped.result_exn
     include Monad.S with type 'a result := 'a result and type 'a result_exn := 'a result_exn
     val elevate : 'a Wrapped.m -> 'a m
     val throw : err -> 'a m
     val catch : 'a m -> (err -> 'a m) -> 'a m
+    include Monad.PLUS with type 'a m := 'a m
   end
   module T2 : functor (Wrapped : Monad.S2) -> sig
+    type ('x,'a) result = ('x,'a error) Wrapped.result
+    type ('x,'a) result_exn = ('x,'a) Wrapped.result_exn
+    include Monad.S2 with type ('x,'a) result := ('x,'a) result and type ('x,'a) result_exn := ('x,'a) result_exn
+    val elevate : ('x,'a) Wrapped.m -> ('x,'a) m
+    val throw : err -> ('x,'a) m
+    val catch : ('x,'a) m -> (err -> ('x,'a) m) -> ('x,'a) m
+  end
+  module TP2 : functor (Wrapped : Monad.P2) -> sig
     type ('x,'a) result = ('x,'a) Wrapped.result
     type ('x,'a) result_exn = ('x,'a) Wrapped.result_exn
     include Monad.S2 with type ('x,'a) result := ('x,'a) result and type ('x,'a) result_exn := ('x,'a) result_exn
     val elevate : ('x,'a) Wrapped.m -> ('x,'a) m
     val throw : err -> ('x,'a) m
     val catch : ('x,'a) m -> (err -> ('x,'a) m) -> ('x,'a) m
+    include Monad.PLUS2 with type ('x,'a) m := ('x,'a) m
   end
 end = struct
   type err = Err.err
   type 'a error = Error of err | Success of 'a
   module Base = struct
     type 'a m = 'a error
-    type 'a result = 'a
+    type 'a result = 'a error
     type 'a result_exn = 'a
     let unit a = Success a
     let bind u f = match u with
       | Success a -> f a
       | Error e -> Error e (* input and output may be of different 'a types *)
-    (* TODO: should run refrain from failing? *)
-    let run u = match u with
+    let run u = u
+    let run_exn u = match u with
       | Success a -> a
       | Error e -> raise (Err.Exc e)
-    let run_exn = run
     (*
     let zero () = Error Err.zero
     let plus u v = match (u, v) with
@@ -648,23 +666,16 @@ end = struct
     module Trans = struct
       module Wrapped = Wrapped
       type 'a m = 'a error Wrapped.m
-      type 'a result = 'a Wrapped.result
+      type 'a result = 'a error Wrapped.result
       type 'a result_exn = 'a Wrapped.result_exn
       let elevate w = Wrapped.bind w (fun a -> Wrapped.unit (Success a))
       let bind u f = Wrapped.bind u (fun t -> match t with
         | Success a -> f a
         | Error e -> Wrapped.unit (Error e))
-      (* TODO: should run refrain from failing? *)
-      let run u =
-        let w = Wrapped.bind u (fun t -> match t with
-          | Success a -> Wrapped.unit a
-          (* | _ -> Wrapped.fail () *)
-          | Error e -> raise (Err.Exc e))
-        in Wrapped.run w
+      let run u = Wrapped.run u
       let run_exn u =
         let w = Wrapped.bind u (fun t -> match t with
           | Success a -> Wrapped.unit a
-          (* | _ -> Wrapped.fail () *)
           | Error e -> raise (Err.Exc e))
         in Wrapped.run_exn w
     end
@@ -674,22 +685,51 @@ end = struct
       | Success _ -> Wrapped.unit t
       | Error e -> handler e)
   end
+  module TP(Wrapped : Monad.P) = struct
+    (* code repetition, ugh *)
+    module TransP = struct
+      include Monad.MakeT(struct
+        module Wrapped = Wrapped
+        type 'a m = 'a error Wrapped.m
+        type 'a result = 'a Wrapped.result
+        type 'a result_exn = 'a Wrapped.result_exn
+        let elevate w = Wrapped.bind w (fun a -> Wrapped.unit (Success a))
+        let bind u f = Wrapped.bind u (fun t -> match t with
+          | Success a -> f a
+          | Error e -> Wrapped.unit (Error e))
+        let run u =
+          let w = Wrapped.bind u (fun t -> match t with
+            | Success a -> Wrapped.unit a
+            | Error e -> Wrapped.zero ())
+          in Wrapped.run w
+        let run_exn u =
+          let w = Wrapped.bind u (fun t -> match t with
+            | Success a -> Wrapped.unit a
+            | Error e -> raise (Err.Exc e))
+          in Wrapped.run_exn w
+      end)
+      let throw e = Wrapped.unit (Error e)
+      let catch u handler = Wrapped.bind u (fun t -> match t with
+        | Success _ -> Wrapped.unit t
+        | Error e -> handler e)
+      let plus u v = Wrapped.plus u v
+      let zero () = elevate (Wrapped.zero ())
+    end
+    include TransP
+    include (Monad.MakeDistrib(TransP) : Monad.PLUS with type 'a m := 'a m)
+  end
   module T2(Wrapped : Monad.S2) = struct
     module Trans = struct
       module Wrapped = Wrapped
       type ('x,'a) m = ('x,'a error) Wrapped.m
-      type ('x,'a) result = ('x,'a) Wrapped.result
+      type ('x,'a) result = ('x,'a error) Wrapped.result
       type ('x,'a) result_exn = ('x,'a) Wrapped.result_exn
       (* code repetition, ugh *)
       let elevate w = Wrapped.bind w (fun a -> Wrapped.unit (Success a))
       let bind u f = Wrapped.bind u (fun t -> match t with
         | Success a -> f a
         | Error e -> Wrapped.unit (Error e))
-      let run u =
-        let w = Wrapped.bind u (fun t -> match t with
-          | Success a -> Wrapped.unit a
-          | Error e -> raise (Err.Exc e))
-        in Wrapped.run w
+      let run u = Wrapped.run u
       let run_exn u =
         let w = Wrapped.bind u (fun t -> match t with
           | Success a -> Wrapped.unit a
@@ -702,6 +742,39 @@ end = struct
       | Success _ -> Wrapped.unit t
       | Error e -> handler e)
   end
+  module TP2(Wrapped : Monad.P2) = struct
+    (* code repetition, ugh *)
+    module TransP = struct
+      include Monad.MakeT2(struct
+        module Wrapped = Wrapped
+        type ('x,'a) m = ('x,'a error) Wrapped.m
+        type ('x,'a) result = ('x,'a) Wrapped.result
+        type ('x,'a) result_exn = ('x,'a) Wrapped.result_exn
+        let elevate w = Wrapped.bind w (fun a -> Wrapped.unit (Success a))
+        let bind u f = Wrapped.bind u (fun t -> match t with
+          | Success a -> f a
+          | Error e -> Wrapped.unit (Error e))
+        let run u =
+          let w = Wrapped.bind u (fun t -> match t with
+            | Success a -> Wrapped.unit a
+            | Error e -> Wrapped.zero ())
+          in Wrapped.run w
+        let run_exn u =
+          let w = Wrapped.bind u (fun t -> match t with
+            | Success a -> Wrapped.unit a
+            | Error e -> raise (Err.Exc e))
+          in Wrapped.run_exn w
+      end)
+      let throw e = Wrapped.unit (Error e)
+      let catch u handler = Wrapped.bind u (fun t -> match t with
+        | Success _ -> Wrapped.unit t
+        | Error e -> handler e)
+      let plus u v = Wrapped.plus u v
+      let zero () = elevate (Wrapped.zero ())
+    end
+    include TransP
+    include (Monad.MakeDistrib2(TransP) : Monad.PLUS2 with type ('x,'a) m := ('x,'a) m)
+  end
 end
 
 (* pre-define common instance of Error_monad *)
@@ -714,6 +787,27 @@ module Failure = Error_monad(struct
   *)
 end)
 
+(*
+# EL.(run( plus (throw "bye") (unit 20) >>= fun i -> unit(i+10)));;
+- : int EL.result = [Failure.Error "bye"; Failure.Success 30]
+# LE.(run( plus (elevate (Failure.throw "bye")) (unit 20) >>= fun i -> unit(i+10)));;
+- : int LE.result = Failure.Error "bye"
+# EL.(run_exn( plus (throw "bye") (unit 20) >>= fun i -> unit(i+10)));;
+Exception: Failure "bye".
+# LE.(run_exn( plus (elevate (Failure.throw "bye")) (unit 20) >>= fun i -> unit(i+10)));;
+Exception: Failure "bye".
+
+# ES.(run( elevate (S.puts succ) >> throw "bye" >> elevate S.get >>= fun i -> unit(i+10) )) 0;;
+- : int Failure.error * S.store = (Failure.Error "bye", 1)
+# SE.(run( puts succ >> elevate (Failure.throw "bye") >> get >>= fun i -> unit(i+10) )) 0;;
+- : (int * S.store) Failure.result = Failure.Error "bye"
+# ES.(run_exn( elevate (S.puts succ) >> throw "bye" >> elevate S.get >>= fun i -> unit(i+10) )) 0;;
+Exception: Failure "bye".
+# SE.(run_exn( puts succ >> elevate (Failure.throw "bye") >> get >>= fun i -> unit(i+10) )) 0;;
+Exception: Failure "bye".
+ *)
+
+
 (* must be parameterized on (struct type env = ... end) *)
 module Reader_monad(Env : sig type env end) : sig
   (* declare additional operations, while still hiding implementation of type m *)
@@ -814,8 +908,8 @@ end = struct
   end
   module TP2(Wrapped : Monad.P2) = struct
     module TransP = struct
-      (* code repetition, ugh *)
       include T2(Wrapped)
+      (* code repetition, ugh *)
       let plus u v = fun s -> Wrapped.plus (u s) (v s)
       let zero () = elevate (Wrapped.zero ())
       let asks selector = ask >>= (fun e ->
@@ -943,6 +1037,7 @@ end = struct
   module TP2(Wrapped : Monad.P2) = struct
     module TransP = struct
       include T2(Wrapped)
+      (* code repetition, ugh *)
       let plus u v = fun s -> Wrapped.plus (u s) (v s)
       let zero () = elevate (Wrapped.zero ())
     end
@@ -1076,6 +1171,7 @@ end = struct
   module TP2(Wrapped : Monad.P2) = struct
     module TransP = struct
       include T2(Wrapped)
+      (* code repetition, ugh *)
       let plus u v = fun s -> Wrapped.plus (u s) (v s)
       let zero () = elevate (Wrapped.zero ())
     end