22.1.3.20 Printing Structures

By default, a structure of type S is printed using #S syntax. This behavior can be customized by specifying a :print-function or :print-object option to the defstruct form that defines S, or by writing a print-object method that is specialized for objects of type S.

Different structures might print out in different ways; the default notation for structures is:

 #S(structure-name {slot-key slot-value}*)

where #S indicates structure syntax, structure-name is a structure name, each slot-key is an initialization argument name for a slot in the structure, and each corresponding slot-value is a representation of the object in that slot.

For information on how the Lisp reader parses structures, see Sharpsign S.