-- FC70B00.A -- -- Grant of Unlimited Rights -- -- Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687 and -- F08630-91-C-0015, the U.S. Government obtained unlimited rights in the -- software and documentation contained herein. Unlimited rights are -- defined in DFAR 252.227-7013(a)(19). By making this public release, -- the Government intends to confer upon all recipients unlimited rights -- equal to those held by the Government. These rights include rights to -- use, duplicate, release or disclose the released technical data and -- computer software in whole or in part, in any manner and for any purpose -- whatsoever, and to have or permit others to do so. -- -- DISCLAIMER -- -- ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR -- DISCLOSED ARE AS IS. THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED -- WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE -- SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE -- OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A -- PARTICULAR PURPOSE OF SAID MATERIAL. --* -- -- FOUNDATION DESCRIPTION: -- This foundation defines a generic list abstraction. List elements can -- be of any (nonlimited) type. Lists are implemented as singly linked -- lists. Access to list elements is sequential. For each list, pointers -- are maintained to the first and last elements in the list, as well as -- the next element to be accessed. -- -- CHANGE HISTORY: -- 06 Dec 94 SAIC ACVC 2.0 -- --! generic -- List abstraction. type Element_Type is private; -- List elems can be of any nonlimited type. package FC70B00 is type List_Type is limited private; -- Return true if current element is last in the list. function End_Of_List (L : List_Type) return Boolean; -- Read current element value; do NOT advance "current" pointer. procedure View_Element (L : in List_Type; E : out Element_Type); -- Read from current element and advance "current" pointer. procedure Read_Element (L : in out List_Type; E : out Element_Type); -- Write to current element and advance "current" pointer. procedure Write_Element (L : in out List_Type; E : in Element_Type); -- Add element to end of list. procedure Add_Element (L : in out List_Type; E : in Element_Type); -- Set "current" pointer to first list element. procedure Reset (L : in out List_Type); private type Node_Type; type Node_Pointer is access Node_Type; type Node_Type is record Item : Element_Type; Next : Node_Pointer; end record; type List_Type is record First : Node_Pointer; Current : Node_Pointer; Last : Node_Pointer; end record; end FC70B00; --==================================================================-- package body FC70B00 is function End_Of_List (L : List_Type) return Boolean is begin return (L.Current = null); end End_Of_List; procedure View_Element (L : in List_Type; E : out Element_Type) is begin -- ... Error-checking code omitted for brevity. E := L.Current.Item; -- Retrieve current element. end View_Element; procedure Read_Element (L : in out List_Type; E : out Element_Type) is begin -- ... Error-checking code omitted for brevity. E := L.Current.Item; -- Retrieve current element. L.Current := L.Current.Next; -- Advance "current" pointer. end Read_Element; procedure Write_Element (L : in out List_Type; E : in Element_Type) is begin -- ... Error-checking code omitted for brevity. L.Current.Item := E; -- Write to current element. L.Current := L.Current.Next; -- Advance "current" pointer. end Write_Element; procedure Add_Element (L : in out List_Type; E : in Element_Type) is New_Node : Node_Pointer := new Node_Type'(E, null); begin if L.First = null then -- No elements in list, so add new L.First := New_Node; -- element at beginning of list. else L.Last.Next := New_Node; -- Add new element at end of list. end if; L.Last := New_Node; -- Set last-in-list pointer. end Add_Element; procedure Reset (L : in out List_Type) is begin L.Current := L.First; -- Set "current" pointer to first end Reset; -- list element. end FC70B00;