How do Lisp developers deal with XML and JSON? Convert it to s-expressions.

As a common lisp developer, that is only very vaguely true for me.

The mapping I prefer for json<->Lisp is:

  true:  t
  false: nil
  null:  :null
  []     #()
  {}     (make-hash-table :test #'equal)

This falls out of my desire for the mapping to be bijective:

- The only built-in type that is unambiguously a mapping type is hash-tabe.

- nil is the only value that is falsy in CL

- () is the same as nil, so we can't use it as an empty list; vectors are the obvious alternative

- Not really any obvious values left to use for "null" so punt to a keyword.