(*****************************************************************************
 * su4sml --- a SML repository for managing (Secure)UML/OCL models
 *             http://projects.brucker.ch/su4sml/
 *                                                                            
 * datatab.sml  --- a very simplistic datatab implementation
 * This file is part of su4sml.
 *
 * Copyright (c) 2008-2009 Achim D. Brucker, Germany
 *
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(* $Id: wfcpog.sml 7256 2008-02-10 19:31:53Z brucker $ *)


(** 
   A simple Object Type (similar to the one used in Isabelle) for 
   fooling the type system of SML.
*)
structure Object = struct type T = exn end;

(**
  A very simplistic table using integers as key. The signature is a 
  subset of the TableFun provided by Isabelle, i.e., when using a 
  Isabelle based setup, 'a Datatab can be implemented/replaced
  by 

  structure Datatab = TableFun(type key = int val ord = int_ord);

*)
signature DATATAB =
sig
  type 'a table 
  type key
  exception DUP of key
  exception SAME of key
  exception UNDEF of key
  val empty : 'a table
  val keys : 'a table -> key list
  val lookup : 'a table -> key -> 'a option 
  val update : key * 'a -> 'a table -> 'a table
end

structure Datatab:DATATAB = 
struct
type key = int
type 'a table = (key * 'a) list
	       
exception DUP of key
exception SAME of key
exception UNDEF of key
val empty=[]

(* 'a option *)
fun lookup t k = case (List.filter (fn (k',v) => (k'=k))  t) of
		   []    => NONE
		 | t' => SOME ((#2 o hd) t')

(* 'a table *)
fun update (k,v) [] = [(k,v)] 
  | update (k,v) (x::xs) = if (#1 x) = k 
			   then raise DUP k         (* (k,v)::xs *)
			   else x::(update (k,v) xs)
(* key list *)
fun keys (t:'a table) = map (#1) t
end
