array-row-major-index

array-row-major-index Function

Syntax:

array-row-major-index array &rest subscripts → index

Arguments and Values:

array—an array.

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

index—a valid array row-major index for the array.

Description:

Computes the position according to the row-major ordering of array for the element that is specified by subscripts, and returns the offset of the element in the computed position from the beginning of array.

For a one-dimensional array, the result of array-row-major-index equals subscript. array-row-major-index ignores fill pointers.

Examples:

(setq a (make-array ’(4 7) :element-type ’(unsigned-byte 8))) 
(array-row-major-index a 1 2) → 9 
(array-row-major-index 
 (make-array ’(2 3 4) 
	      :element-type ’(unsigned-byte 8) 
	      :displaced-to a 
	      :displaced-index-offset 4) 
 0 2 1) → 9 

Notes:

A possible definition of array-row-major-index, with no error-checking, is

(defun array-row-major-index (a &rest subscripts)

(apply #’+ (maplist #’(lambda (x y)

(* (car x) (apply #’* (cdr y))))

subscripts

(array-dimensions a))))

Expanded Reference: array-row-major-index

tip

TODO: Please contribute to this page by adding explanations and examples

(array-row-major-index )