Accessor aref

Syntax:

Arguments and Values:

array—an array.

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

element, new-element—an object.

Description:

17.2.0 3Accesses the array element specified by the subscripts. If no subscripts are supplied and array is zero rank, aref accesses the sole element of array.

17.2.0 4aref ignores fill pointers. It is permissible to use aref to access any array element, whether active or not.

This is implied by the use of "access" above. 17.2.0 5 \macref{setf} can be used with \funref{aref} to destructively replace an \term{array} element with a new value.

Examples:

2.5.0 6If 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

Affected By:

None.

Exceptional Situations:

None.

See Also:

bit, char, elt, row-major-aref, svref, Section 3.2.1 (Compiler Terminology)

Notes:

None.