-- Match: exhaustive pattern matching. Arms separated by ;. First match wins.
-- _ is the wildcard arm (required for exhaustiveness on open types like n).
-- Describe a small number
desc n:n>t;?n{0:"zero";1:"one";2:"two";_:"many"}
-- Map HTTP status to a label
status c:n>t;?c{200:"ok";404:"not found";500:"server error";_:"unknown"}
-- run: desc 0
-- out: zero
-- run: desc 2
-- out: two
-- run: desc 99
-- out: many
-- run: status 200
-- out: ok
-- run: status 404
-- out: not found
-- run: status 418
-- out: unknown