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
|
datatype List<T> {
Nil;
Cons(T, List<T>);
}
class Node {
var data: int;
var next: Node;
function Repr(list: List<int>): bool
reads *;
decreases list;
{ match list
case Nil =>
next == null
case Cons(d,cdr) =>
data == d && next != null && next.Repr(cdr)
}
method Init()
modifies this;
ensures Repr(#List.Nil);
{
next := null;
}
method Add(d: int, L: List<int>) returns (r: Node)
requires Repr(L);
ensures r != null && r.Repr(#List.Cons(d, L));
{
r := new Node;
r.data := d;
r.next := this;
}
}
class AnotherNode {
var data: int;
var next: AnotherNode;
function Repr(n: AnotherNode, list: List<int>): bool
reads *;
decreases list;
{ match list
case Nil =>
n == null
case Cons(d,cdr) =>
n != null && n.data == d && Repr(n.next, cdr)
}
method Create() returns (n: AnotherNode)
ensures Repr(n, #List.Nil);
{
n := null;
}
method Add(n: AnotherNode, d: int, L: List<int>) returns (r: AnotherNode)
requires Repr(n, L);
ensures Repr(r, #List.Cons(d, L));
{
r := new AnotherNode;
r.data := d;
r.next := n;
}
}
|
