aref

aref Accessor

Syntax:

aref array &rest subscripts → element

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

Arguments and Values:

array—an array.

subscripts—a list of valid array indices for the array.

element, new-element—an 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, elt, row-major-aref, svref, Section 3.2.1 (Compiler Terminology)

Expanded Reference: aref

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(aref )