Istari

Registry

The registry provides a mechanism for including Istari data structures in an Istari file. Most data types can be stored, but, significantly, nothing involving ML code, which includes functions and tactics.

A value of type t is stored using a key with type t key. Keys are constructed using a collection of combinators, one for each type operator.

To write a value x of type int * term into the registry using the name bar, one would say:

Registry.write 
   (Symbol.fromValue "bar") 
   (Registry.pair Registry.int Registry.term)
   x

With the customized parser, this can be rendered more conveniently:

Registry.write (parseIdent /bar/) (parseRegistryKey /int * term/) x

Using the pervasive function writeRegistry, one can write it even more briefly:

writeRegistry /bar/ /int * term/ x

If the current module is Foo when an entry is written to bar, it will appear in the registry under the name Foo.bar. It will use that name immediately, even before the Foo module is closed.

To read that same value, one would say:

Registry.read
   (map Symbol.fromValue ["Foo", "bar"])
   (Registry.pair Registry.int Registry.term)

or:

Registry.read (parseLongident /Foo.bar/) (parseRegistryKey /int * term/)

or just:

readRegistry /Foo.bar/ /int * term/

As a practical example, the notb_tru reduction (with type Reduction.reduction2) is obtained by:

val notb_tru = readRegistry /Bool.notb_tru/ /reduction2/

Here, Registry.reduction2 (the result of parsing /reduction2/) has the type Reduction.reduction2 Registry.key, so notb_tru will have the type Reduction.reduction2.

The key parser has a special syntax for keys for collapsed tuples. To construct the key for ((unit * bool) * int) * constant, one can write \[bool int constant]\.

The full interface for the registry is:

signature REGISTRY =
   sig

      type 'a key

      exception Registry of string

      val write  : Symbol.symbol -> 'a key -> 'a -> unit
      val read   : Symbol.symbol list -> 'a key -> 'a
      val delete : Symbol.symbol list -> unit

      val unit   : unit key
      val bool   : bool key
      val int    : int key
      val intInf : IntInf.int key
      val string : string key

      val symbol      : Symbol.symbol key
      val constant    : Constant.constant key
      val term        : Term.term key
      val reduction   : Reduction.reduction key
      val reduction1  : Reduction.reduction1 key
      val reduction2  : Reduction.reduction2 key

      val list    : 'a key -> 'a list key
      val option  : 'a key -> 'a option key
      val vector  : 'a key -> 'a Vector.vector key
      val seq     : 'a key -> 'a Seq.seq key

      val pair    : 'a key -> 'b key -> ('a * 'b) key
      val tuple2  : 'a key -> 'b key -> ('a * 'b) key  (* alias for pair *)
      val tuple3  : 'a key -> 'b key -> 'c key -> ('a * 'b * 'c) key
      val tuple4  : 'a key -> 'b key -> 'c key -> 'd key -> ('a * 'b * 'c * 'd) key
      val tuple5  : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> ('a * 'b * 'c * 'd * 'e) key
      val tuple6  : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> 'f key -> ('a * 'b * 'c * 'd * 'e * 'f) key
      val tuple7  : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> 'f key -> 'g key -> ('a * 'b * 'c * 'd * 'e * 'f * 'g) key
      val tuple8  : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> 'f key -> 'g key -> 'h key -> ('a * 'b * 'c * 'd * 'e * 'f * 'g * 'h) key
      val tuple9  : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> 'f key -> 'g key -> 'h key -> 'i key -> ('a * 'b * 'c * 'd * 'e * 'f * 'g * 'h * 'i) key
      val tuple10 : 'a key -> 'b key -> 'c key -> 'd key -> 'e key -> 'f key -> 'g key -> 'h key -> 'i key -> 'j key -> ('a * 'b * 'c * 'd * 'e * 'f * 'g * 'h * 'i * 'j) key

   end

The Registry exception is raised in various error conditions, including:

• Reading or deleting an entry that is not present.

• Reading an entry with the wrong key.

• Writing to a name that is already present.

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