[MLton-commit] r5024

[Vesa Karvonen]

Initial commit of a lib of misc utils to be refactored.
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A   mltonlib/trunk/com/ssh/misc-util/unstable/dummy.sml

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Added: mltonlib/trunk/com/ssh/misc-util/unstable/dummy.sml
===================================================================
--- mltonlib/trunk/com/ssh/misc-util/unstable/dummy.sml	2007-01-12 12:25:21 UTC (rev 5023)
+++ mltonlib/trunk/com/ssh/misc-util/unstable/dummy.sml	2007-01-12 12:25:32 UTC (rev 5024)
@@ -0,0 +1,106 @@
+(* Copyright (C) 2007 SSH Communications Security, Helsinki, Finland
+ *
+ * This code is released under the MLton license, a BSD-style license.
+ * See the LICENSE file or http://mlton.org/License for details.
+ *)
+
+(*
+ * An implementation of a type-indexed family of dummy values.  In Standard
+ * ML, dummy values are needed for things such as computing fixpoints and
+ * building cyclic values.
+ *
+ * This type-indexed function is unlikely to be directly useful in
+ * application programs and is more likely to be used internally in the
+ * implementation of some other type-indexed functions (e.g. pickling).
+ *)
+
+signature DUMMY = sig
+   type 'a dummy_t
+
+   exception Dummy
+   (**
+    * This is raised when trying to extract the dummy value in case of
+    * unfounded recursion or an abstract type that has not been given a
+    * dummy value.
+    *)
+
+   val dummy : 'a dummy_t -> 'a
+   (** Extracts the dummy value or raises {Dummy}. *)
+
+   val noDummy : 'a dummy_t UnOp.t
+   (**
+    * Removes the dummy value from the given type-index.  This can be used
+    * for encoding abstract types that can not be given dummy values.
+    *)
+end
+
+functor LiftDummy
+           (include DUMMY
+            type 'a t
+            val lift : ('a dummy_t, 'a t) Lift.t Thunk.t) : DUMMY = struct
+   type 'a dummy_t = 'a t
+   exception Dummy = Dummy
+   val dummy   = fn ? => Lift.get    lift dummy   ?
+   val noDummy = fn ? => Lift.update lift noDummy ?
+end
+
+structure Dummy :> sig
+   include STRUCTURAL_TYPE
+   include DUMMY where type 'a dummy_t = 'a t
+end = struct
+   type 'a t = 'a option
+   type 'a dummy_t = 'a t
+
+   exception Dummy
+
+   val dummy = fn SOME v => v
+                | NONE => raise Dummy
+
+   fun noDummy _ = NONE
+
+   fun iso b = flip Option.map b o Iso.from
+
+   fun a *` b = case a & b of
+                   SOME a & SOME b => SOME (a & b)
+                 | _ => NONE
+
+   fun a +` b = case a of
+                   SOME a => SOME (INL a)
+                 | NONE => Option.map INR b
+
+   val unit = SOME ()
+
+   fun Y ? = Tie.pure (const (NONE, id)) ?
+
+   local
+      val e = Fail "Dummy.-->"
+   in
+      fun _ --> _ = SOME (failing e)
+   end
+
+   val exn = SOME Empty
+   fun regExn _ _ = ()
+
+   fun array _ = SOME (Array.tabulate (0, undefined))
+   fun refc  ? = Option.map ref ?
+
+   fun vector _ = SOME (Vector.tabulate (0, undefined))
+
+   val largeInt  : LargeInt.int   t = SOME 0
+   val largeReal : LargeReal.real t = SOME 0.0
+   val largeWord : LargeWord.word t = SOME 0w0
+
+   fun list _ = SOME []
+
+   val bool   = SOME false
+   val char   = SOME #"\000"
+   val int    = SOME 0
+   val real   = SOME 0.0
+   val string = SOME ""
+   val word   = SOME 0w0
+
+   val word8  : Word8.word  t = SOME 0w0
+   val word16 : Word16.word t = SOME 0w0
+   val word32 : Word32.word t = SOME 0w0
+   val word64 : Word64.word t = SOME 0w0
+end


Property changes on: mltonlib/trunk/com/ssh/misc-util/unstable/dummy.sml
___________________________________________________________________
Name: svn:eol-style
   + native