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ANSI Common Lisp  15 Arrays 15.2 Dictionary of Arrays
| 15.2.18 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))))
- Allegro CL Implementation Details:
-
None.
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