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adjustable-array-p Arrays Dictionary array-dimension
Accessor

aref

aref array &rest subscripts ⇒ element

(setf ( aref array &rest subscripts) new-element)

Arguments and Values

arrayan array.
subscriptsa list of valid array indices for the array.
element, new-elementan object.

Description

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.

Examples

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

See Also

bit, char; schar, elt, row-major-aref, svref,

Compiler Terminology

Backlinks

APPLY Forms as Places, array, Arrays Dictionary, bit, sbit, char, schar, elt, Function Call Forms as Places, make-array, row-major-aref, Specialized Arrays, substitute, substitute-if, substitute-if-not, nsubstitute, nsubstitute-if, nsubstitute-if-not, svref, Symbols in the COMMON-LISP Package