1	import Base
2	
3	# Treats only a missing-path errno as absence.
4	def missing_path_result(missing: Bool, +code: U32, message: String) -> Result<&1, &1, U32 & String, Bool>:
5	  match missing:
6	    case True{}:
7	      Done{False{}}
8	    case False{}:
9	      Fail{(code, message)}
10	
11	# Ignores absent optional levels and preserves other errors.
12	def optional_directory_result(
13	  optional: Bool,
14	  unavailable: Bool,
15	  +code: U32,
16	  message: String
17	) -> Result<&1, &1, U32 & String, Unit>:
18	  match optional:
19	    case False{}:
20	      Fail{(code, message)}
21	    case True{}:
22	      match unavailable:
23	        case True{}:
24	          Done{Unit{}}
25	        case False{}:
26	          Fail{(code, message)}