1.2 define-struct

(define-struct structid (fieldid ...))

Define a new type of structure. The structure’s fields are named by the fieldids in parentheses. After evaluation of a define-struct form, a set of new primitives is available for creation, extraction, and type-like queries:

• make-structid : takes a number of arguments equal to the number of fields in the structure type, and creates a new instance of the structure type.

• structid-fieldid : takes an instance of the structure and returns the field named by structid.

• structid? : takes any value, and returns true if the value is an instance of the structure type.

• structid : an identifier representing the structure type, but never used directly.

The created names must not be the same as a primitive or another defined name.