can deserialize a Set, but can't serialize a Set about clj-yaml

[trevor]

This allows for Sets that contain numbers only, or strings only:

  clojure.lang.PersistentHashSet
  (encode [data]
    (java.util.HashSet. data))

  clojure.lang.PersistentTreeSet
  (encode [data]
    (java.util.TreeSet. data))

[trevor]

… but this is better:

clojure.lang.IPersistentSet
(encode [data]
  (into #{}
    (map encode data)))

example (with modified fn's):

=> (println (yaml-dump ["y" #{"d" 'b/c :a 2 [3 4 {5 6 :x [7 #{}]}]} "m" nil "n"]))
---
- y
- !!set
  a: null
  2: null
  ? - 3
    - 4
    - 5: 6
      x:
      - 7
      - !!set {}
  : null
  d: null
  ? !!clojure.lang.Symbol
    name: c
    namespace: b
  : null
- m
- null
- n
...