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interface List[T] {
var list: seq[T]
constructor Empty()
ensures list = []
constructor Singleton(t: T)
ensures list = [t]
constructor Double(p: T, q: T)
ensures list = [p q]
}
datamodel List[T] {
var root: Node[T]
frame
root
invariant
root = null ==> |list| = 0
root != null ==> list = root.list
}
interface Node[T] {
var list: seq[T]
invariant
|list| > 0
constructor Init(t: T)
ensures list = [t]
constructor Double(p: T, q: T)
ensures list = [p q]
method List() returns (ret: seq[T])
ensures ret = list
method Tail() returns (tail: Node[T])
ensures |list| = 1 ==> tail = null
ensures |list| > 1 ==> tail != null && tail.list = list[1..]
method Size() returns (ret: int)
ensures ret = |list|
method SkipFew(num: int) returns (ret: Node[T])
requires num >= 0
ensures num >= |list| ==> ret = null
ensures num < |list| ==> ret != null && ret.list = list[num..]
method Get(idx: int) returns (ret: T)
requires idx >= 0 && idx < |list|
ensures ret = list[idx]
method Index(n: T) returns (ret: int)
ensures n !in list ==> ret = -1
ensures n in list ==> ret >= 0 && ret < |list| && list[ret] = n
method Find(n: T) returns (ret: bool)
ensures ret = (n in list)
method Insert(n: T)
ensures list = old(list) + [n]
}
datamodel Node[T] {
var data: T
var next: Node[T]
frame
next
invariant
next = null ==> list = [data]
next != null ==> list = [data] + next.list
}
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