As an example on non-list, literal data structure (atom), see: CL-USER> (ql:quickload :local-time) CL-USER> (in-package :local-time) LOCAL-TIME> (

As an example on non-list, literal data structure (atom), see: CL-USER> (ql:quickload :local-time) CL-USER> (in-package :local-time) LOCAL-TIME> (now) => @2016-08-05T17:41:54.492977+02:00 LOCAL-TIME> (enable-read-macros) LOCAL-TIME> (describe @2016-08-05T17:41:54.492977+02:00) @2016-08-05T17:41:54.492977+02:00 [standard-object] Slots with :INSTANCE allocation: DAY = 6001 SEC = 56514 NSEC = 492977000 LOCAL-TIME> (class-of @2016-08-05T17:41:54.492977+02:00) #<STANDARD-CLASS LOCAL-TIME:TIMESTAMP> And again, how your AST is encoded has nothing to do with the value you manipulate at execution: (make-hash-table) is a list with one symbol, but when evaluated, you obtain a good old hash-table.