(setf (aref array &rest subscripts) new-element)
array—an array.
subscripts—a list of valid array indices for the array.
element, new-element—an object.
Accesses the array element specified by the subscripts.
If no subscripts are supplied and array is zero rank,
aref
accesses the sole element of array.
aref
ignores fill pointers.
It is permissible to use aref
to access any array element,
whether active or not.
If the variable foo
names a 3-by-5 array,
then the first index could be 0, 1, or 2, and then second index
could be 0, 1, 2, 3, or 4. The array elements can be referred to by using
the function aref
; for example, (aref foo 2 1)
refers to element (2, 1) of the array.
(aref (setq alpha (make-array 4)) 3) → implementation-dependent (setf (aref alpha 3) 'sirens) → SIRENS (aref alpha 3) → SIRENS (aref (setq beta (make-array '(2 4) :element-type '(unsigned-byte 2) :initial-contents '((0 1 2 3) (3 2 1 0)))) 1 2) → 1 (setq gamma '(0 2)) (apply #'aref beta gamma) → 2 (setf (apply #'aref beta gamma) 3) → 3 (apply #'aref beta gamma) → 3 (aref beta 0 2) → 3
bit, char, elt, row-major-aref, svref, Section 3.2.1 (Compiler Terminology)