| Allegro CL version 8.2 Minimal update since 8.2 release. 8.1 version |
Arguments: (array simple-vector-var &optional displacement-var length-var explicit-end allow-nil) &body body
This macro returns the last values of the implict progn of the body of the macro.
Within the body of this macro, the simple-vector-var, which must be a symbol, and it is lexically or specially bound to the array's most primitive data vector, which will always be a simple-array of 1 dimension and the same element type as the array.
The array must be an array of any kind; it may itself be a simple-array, and it can be of any dimensionality.
If displacement-var is supplied, it must be a symbol, and it is lexically or specially bound to the total displacement of the array onto its underlying data. If an array is displaced to another array which is also displaced, then the displacements are added together; the displacement-var will contain the sum of the displacements.
If length-var is supplied it must be a symbol, and it is lexically or specially bound to the sum of the total displacement of the array onto its underlying data and one of the following values:
nil
, the value
of explicit-end, or
explicit-end supplies one of the values used in the computation of length-var, which overrides the macro's concept of the upper boundary of the array. This value is not checked against any real storage; care must be given when providing explicit-end that it does not overreach the bounds of the simple-vector-var.
If array is a vector, displacement-var, length-var, and explicit-end can be summarized as follows:
displacement-var and length-var are the real bounding index designators of simple-vector-var which correspond to the virtual bounding index designators 0 and explicit-end (which defaults to the length of array) of array.
If allow-nil is supplied and non-nil
, and if the array is
nil
then no initialization is done for the
displacememt-var, if supplied, and the
length-var, if supplied, gets the value most-positive-fixnum
.
The body code is still responsible for testing the
simple-vector-var value for nil, but at least the
with-underlying-simple-vector macro will not
complain about a supplied array value of nil
,
if allow-nil is true.
Declarations for the variables can be made immediately following the argument list, and will be transferred to the final expanded form.
The following code: (deftype adim () '(mod #.array-dimension-limit)) (defun simple-write-string (string stream &optional (start 0) end) (declare (type adim start) (optimize speed)) (excl::with-underlying-simple-vector (string str disp len end t) (declare (type adim disp) (type (simple-array character 1) str)) (when string (do* ((i (+ start disp) (1+ i))) ((>= i len)) (declare (type adim i)) (write-char (aref str i) stream)))) string) Results in the following output: cl-user(2): (setq sstring "hello") "hello" cl-user(3): (setq string (make-array 3 :element-type 'character :displaced-to sstring :displaced-index-offset 2)) "llo" cl-user(4): (simple-write-string nil *standard-output*) nil cl-user(5): (simple-write-string sstring *standard-output*) hello "hello" cl-user(6): (simple-write-string string *standard-output*) llo "llo" cl-user(7):
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Minimal update since 8.2 release. 8.1 version |