1	# Set helpers. Base's Set.has gives the set back beside its answer; these give the answer alone.
2	import Base
3	
4	def has(set: Set(), key: String) -> Bool:
5	  Pair.snd(Set(), Bool, Set.has(set, key))
6	
7	# Whether one of `keys` is in `set`, or `found`.
8	def has_any(keys: List<&2, String>, +set: Set(), found: Bool) -> Bool:
9	  match keys found:
10	    case _ True{}:
11	      True{}
12	    case Nil{} False{}:
13	      False{}
14	    case Con{key, rest} False{}:
15	      has_any(rest, set, has(set, key))