1	import Base
2	
3	# Neutral datatypes shared by src/binary_heap.bend and spec/binary_heap.bend.
4	
5	type Error is Data:
6	  EmptyHeap{}
7	
8	type Op<-A: Data> is Data:
9	  Length{}
10	  Push{value: A}
11	  Peek{}
12	  Pop{}
13	  FromList{items: List<&2, A>}
14	  ToSortedList{}
15	
16	type Obs<-A: Data> is Data:
17	  ONat{value: Nat}
18	  OItem{result: Result<&2, &2, Error, A>}
19	  OUnit{}
20	  OList{items: List<&2, A>}