1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
-- FC70B00.A
--
-- Grant of Unlimited Rights
--
-- Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
-- F08630-91-C-0015, and DCA100-97-D-0025, 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;
|
