MIXIN: nested-sequence
INSTANCE: nested-sequence sequence

TUPLE: wrapped-array { underlying array read-only } ;
CONSULT: sequence-protocol wrapped-array underlying>> ;

TUPLE: nested-array < wrapped-array ;
INSTANCE: nested-array nested-sequence

ERROR: not-all-sequences ;

: >nested-array ( seq -- nested-array )
  dup [ sequence? ] all? [ not-all-sequences ] unless
  >array nested-array boa ;

DEFER: }} ( -- * ) delimiter
SYNTAX: {{ \ }} [ >nested-array ] parse-literal ;