Compound data type: Difference between revisions

<lang lisp>CL-USER> (defstruct point (x 0) (y 0)) ;If not provided, x or y default to 0

POINT</lang>

In addition to defining the ''point'' data type, the defstruct macro also created constructor and accessor functions:

<lang lisp>CL-USER> (setf a (make-point)) ;The default constructor using the default values for x and y

#S(POINT :X 0 :Y 0)

CL-USER> (setf b (make-point :x 5.5 :y #C(0 1))) ;Dynamic datatypes are the default

#S(POINT :X 5.5 :Y #C(0 1)) ;y has been set to the imaginary number i (using the Common Lisp complex number data type)

CL-USER> (point-x b) ;The default name for the accessor functions is structname-slotname

5.5

CL-USER> (point-y b)

#C(0 1)

CL-USER> (setf (point-y b) 3) ;The accessor is setfable

3

CL-USER> (point-y b)

3</lang>