blob: 57c4c87d38c0f87e5a94f8902ee090994820e96f (
plain)
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
|
/*
Carrol Morgan's calculator
7/2/2010 Kuat Dafny version
8/22/2010 translated into Chalice
*/
class Calc0 {
var vals: seq<int>;
method reset()
requires acc(vals);
ensures acc(vals);
{
vals := [];
}
method add(x: int)
requires acc(vals);
ensures acc(vals);
{
vals := [x] ++ vals;
}
method mean() returns (m: int)
requires acc(vals) && |vals| > 0;
ensures acc(vals);
{
m := total(vals)/|vals|;
}
unlimited function total(s: seq<int>): int
{
|s| == 0 ? 0 : s[0] + total(s[1..])
}
}
class Calc1 refines Calc0 {
var sum: int;
var num: int;
replaces vals by acc(sum) && acc(num) && sum == total(vals) && num == |vals|;
refines reset()
{
sum := 0;
num := 0;
}
refines add(x: int)
{
sum := sum + x;
num := num + 1;
}
refines mean() returns (m: int)
{
m := sum/num;
}
}
|
