array-displacement

array-displacement Function

Syntax:

array-displacement array → displaced-to, displaced-index-offset

Arguments and Values:

array—an array.

displaced-to—an array or nil.

displaced-index-offset—a non-negative fixnum.

Description:

If the array is a displaced array, returns the values of the :displaced-to and :displaced-index-offset options for the array (see the functions make-array and adjust-array). If the array is not a displaced array, nil and 0 are returned.

If array-displacement is called on an array for which a non-nil object was provided as the :displaced-to argument to make-array or adjust-array, it must return that object as its first value. It is implementation-dependent whether array-displacement returns a non-nil primary value for any other array.

Examples:

(setq a1 (make-array 5)) → #<ARRAY 5 simple 46115576> 
(setq a2 (make-array 4 :displaced-to a1 
		     :displaced-index-offset 1)) 
→ #<ARRAY 4 indirect 46117134> 
(array-displacement a2) 
→ #<ARRAY 5 simple 46115576>, 1 
(setq a3 (make-array 2 :displaced-to a2 
		     :displaced-index-offset 2)) 
→ #<ARRAY 2 indirect 46122527> 

(array-displacement a3) 
→ #<ARRAY 4 indirect 46117134>, 2 

Exceptional Situations:

Should signal an error of type type-error if array is not an array.

See Also:

make-array

Expanded Reference: array-displacement

tip

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(array-displacement )