-
Notifications
You must be signed in to change notification settings - Fork 10
/
Rule6.dfy
199 lines (181 loc) · 5.74 KB
/
Rule6.dfy
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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
include "Rule3.dfy"
method InternalAdd(xs: seq<NeIntRange>, a: IntRange) returns (rs: seq<NeIntRange>)
requires ValidSeq(xs)
ensures ValidSeq(rs)
ensures SeqToSet(rs) == SeqToSet(xs) + RangeToSet(a)
{
if IsEmpty(a)
{
rs := xs;
}
else
{
var notTouching, merged := PartitionAndMerge(xs, a);
var indexAfter := NoTouchIndexAfter(notTouching, merged);
rs := InsertAt(notTouching, [merged], indexAfter);
}
}
ghost function RangeToSet(pair: IntRange): set<int>
{
set i {:autotriggers false} | pair.0 <= i <= pair.1 :: i
}
ghost function SeqToSet(sequence: seq<NeIntRange>): set<int>
decreases |sequence|
requires ValidSeq(sequence)
{
if |sequence| == 0 then {}
else if |sequence| == 1 then RangeToSet(sequence[0])
else RangeToSet(sequence[0]) + SeqToSet(sequence[1..])
}
method PartitionAndMerge(xs: seq<NeIntRange>, a: NeIntRange) returns (notTouching: seq<NeIntRange>, merged: NeIntRange)
requires ValidSeq(xs)
ensures ValidSeq(notTouching)
ensures RangeToSet(merged) >= RangeToSet(a)
ensures forall range | range in notTouching :: !Touch(range, merged)
ensures SeqToSet(xs) + RangeToSet(a) == SeqToSet(notTouching) + RangeToSet(merged)
{
// Split into touching and not touching seqs
var touching: seq<NeIntRange>;
touching, notTouching := Partition(a, xs);
// Merge the touching seq into one range with our original range
merged := UnionSeq(a, touching);
}
method Partition(a: NeIntRange, xs: seq<NeIntRange>) returns (touching: seq<NeIntRange>, notTouching: seq<NeIntRange>)
requires ValidSeq(xs)
ensures ValidSeq(touching) && ValidSeq(notTouching)
ensures forall range | range in xs :: (range in touching) != (range in notTouching)
ensures forall i:nat | i < |touching| :: touching[i] in xs
ensures forall i:nat | i < |notTouching| :: notTouching[i] in xs
ensures forall i:nat | i < |xs| && Touch(xs[i], a) :: xs[i] in touching
ensures forall i:nat | i < |xs| && !Touch(xs[i], a) :: xs[i] in notTouching
ensures SeqToSet(touching) + SeqToSet(notTouching) == SeqToSet(xs)
{
var touchA := (b: NeIntRange) => Touch(a,b);
if |xs| == 0
{
touching, notTouching := [], [];
}
else
{
if Touch(xs[0],a)
{
var t1, nt1 := Partition(a, xs[1..]);
touching := [xs[0]] + t1;
notTouching := nt1;
}
else
{
var t1, nt1 := Partition(a, xs[1..]);
touching := t1;
notTouching := [xs[0]] + nt1;
}
}
}
method NoTouchIndexAfter(xs: seq<NeIntRange>, a: NeIntRange) returns (i: nat)
requires ValidSeq(xs)
requires forall j: nat | j < |xs| :: !Touch(xs[j], a)
ensures i <= |xs|
ensures forall p | p in xs[..i] :: p.1+1 < a.0
ensures forall p | p in xs[i..] :: a.1+1 < p.0
{
i := 0;
while i < |xs| && xs[i].1+1 < a.0
invariant i <= |xs|
invariant forall j:nat | j < i :: xs[j].0 < a.0
{
i := i + 1;
}
}
method InsertAt(xs: seq<NeIntRange>, ys: seq<NeIntRange>, i: nat) returns (r: seq<NeIntRange>)
requires ValidSeq(xs)
requires ValidSeq(ys)
requires i <= |xs|
requires forall p | p in xs[..i] :: forall q | q in ys :: p.1+1 < q.0
requires forall p | p in ys :: forall q | q in xs[i..] :: p.1+1 < q.0
ensures ValidSeq(r)
ensures SeqToSet(r) == SeqToSet(xs) + SeqToSet(ys)
ensures r == xs[..i] + ys + xs[i..]
{
var left, right := SplitAt(xs, i);
var left2 := Concat(left,ys);
r := Concat(left2, right);
}
method SplitAt(xs: seq<NeIntRange>, i: nat) returns (left: seq<NeIntRange>, right: seq<NeIntRange>)
requires ValidSeq(xs)
requires i <= |xs|
ensures ValidSeq(left)
ensures ValidSeq(right)
ensures forall p | p in left :: forall q | q in right :: p.1+1 < q.0
ensures forall i: nat | i < |left| :: forall j: nat | j < |right| :: left[i].1+1 < right[j].0
ensures SeqToSet(xs) == SeqToSet(left) + SeqToSet(right)
ensures SeqToSet(left) !! SeqToSet(right)
ensures xs == left + right
ensures |left| == i
{
left := xs[..i];
ElementsBelowAndBelowLemma(xs[..i]);
right := xs[i..];
ElementsBelowAndBelowLemma(xs[i..]);
ghost var c := Concat(left,right);
assert xs == c;
}
method Concat(xs: seq<NeIntRange>, ys: seq<NeIntRange>) returns (r: seq<NeIntRange>)
requires ValidSeq(xs)
requires ValidSeq(ys)
requires forall p | p in xs :: forall q | q in ys :: p.1+1 < q.0
ensures ValidSeq(r)
ensures SeqToSet(r) == SeqToSet(xs) + SeqToSet(ys)
ensures r == xs + ys
{
if xs == [] {
r := ys;
}
else {
var t := Concat(xs[1..], ys);
r := [xs[0]] + t;
}
}
method UnionSeq(a: NeIntRange, touching: seq<NeIntRange>) returns (merged: NeIntRange)
requires ValidSeq(touching)
requires forall i:nat | i < |touching| :: Touch(a, touching[i])
ensures forall el | Contains(merged,el) :: Contains(a, el) || exists i:nat :: i < |touching| && Contains(touching[i], el)
ensures forall i:nat | i < |touching| :: forall el :: Contains(touching[i], el) ==> Contains(merged, el)
ensures forall el | Contains(a, el) :: Contains(merged, el)
ensures RangeToSet(merged) == RangeToSet(a) + SeqToSet(touching)
{
if |touching| == 0 {
merged := a;
}
else
{
var rest_set := UnionSeq(a, touching[1..]);
merged := UnionRange(touching[0], rest_set);
}
}
lemma ElementsBelowAndBelowLemma(xs: seq<NeIntRange>)
requires ValidSeq(xs)
ensures forall e | e in SeqToSet(xs) :: e <= xs[|xs|-1].1
ensures forall e | e in SeqToSet(xs) :: xs[0].0 <= e
{
}
function UnionRange(x: IntRange, y: IntRange): IntRange
requires IsEmpty(x) || IsEmpty(y) || Touch(x, y)
ensures RangeToSet(x) + RangeToSet(y) == RangeToSet(UnionRange(x,y))
{
if IsEmpty(x) then y
else if IsEmpty(y) then x
else (Min(x.0, y.0), Max(x.1, y.1))
}
function Min(a: int, b: int): int
{
if a < b
then a
else b
}
method Main()
{
var xs := [(101,102), (400,402), (404,404), (500,500)];
var a := (401,403);
var rs := InternalAdd(xs, a);
print rs;
}