1	import Base
2	
3	# Negative{n} denotes -(n+1), so zero has exactly one representation.
4	type Integer is Data:
5	  Positive{magnitude: Nat}
6	  Negative{predecessor: Nat}
7	
8	type Int64 is Data:
9	  I64{bits: Word(64n)}
10	
11	type Metrics is Data:
12	  Counts{inserts: Word(64n), evictions: Word(64n), removals: Word(64n), hits: Word(64n), misses: Word(64n)}
13	
14	type Entry<-K: Data, -V: Data> is Data:
15	  Item{key: K, value: V, deadline: Int64}
16	
17	type LruEvent<-K: Data, -V: Data> is Data:
18	  Evicted{key: K, value: V}
19	
20	def zero_metrics() -> Metrics:
21	  Counts{Word.zero(64n), Word.zero(64n), Word.zero(64n), Word.zero(64n), Word.zero(64n)}