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;;;;"array.scm" Arrays for Scheme
; Copyright (C) 2001 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1. Any copy made of this software must include this copyright notice
;in full.
;
;2. I have made no warrantee or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3. In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.
;;@code{(require 'array)}
;;@ftindex array
(require 'record)
(define array:rtd
(make-record-type "array"
'(shape
scales ;list of dimension scales
offset ;exact integer
store ;data
)))
(define array:shape (record-accessor array:rtd 'shape))
(define array:scales
(let ((scales (record-accessor array:rtd 'scales)))
(lambda (obj)
(cond ((string? obj) '(1))
((vector? obj) '(1))
(else (scales obj))))))
(define array:store
(let ((store (record-accessor array:rtd 'store)))
(lambda (obj)
(cond ((string? obj) obj)
((vector? obj) obj)
(else (store obj))))))
(define array:offset
(let ((offset (record-accessor array:rtd 'offset)))
(lambda (obj)
(cond ((string? obj) 0)
((vector? obj) 0)
(else (offset obj))))))
(define array:construct
(record-constructor array:rtd '(shape scales offset store)))
;;@args obj
;;Returns @code{#t} if the @1 is an array, and @code{#f} if not.
(define array?
(let ((array:array? (record-predicate array:rtd)))
(lambda (obj) (or (string? obj) (vector? obj) (array:array? obj)))))
;;@noindent
;;@emph{Note:} Arrays are not disjoint from other Scheme types. Strings
;;and vectors also satisfy @code{array?}. A disjoint array predicate can
;;be written:
;;
;;@example
;;(define (strict-array? obj)
;; (and (array? obj) (not (string? obj)) (not (vector? obj))))
;;@end example
;;@body
;;Returns @code{#t} if @1 and @2 have the same rank and shape and the
;;corresponding elements of @1 and @2 are @code{equal?}.
;;
;;@example
;;(array=? (make-array 'foo 3 3) (make-array 'foo '(0 2) '(1 2)))
;; @result{} #t
;;@end example
(define (array=? array1 array2)
(and (equal? (array:shape array1) (array:shape array2))
(equal? (array:store array1) (array:store array2))))
(define (array:dimensions->shape dims)
(map (lambda (dim) (if (list? dim) dim (list 0 (+ -1 dim)))) dims))
;;@args initial-value bound1 bound2 @dots{}
;;Creates and returns an array with dimensions @var{bound1},
;;@var{bound2}, @dots{} and filled with @1.
(define (make-array initial-value . dimensions)
(let* ((shape (array:dimensions->shape dimensions))
(dims (map (lambda (bnd) (- 1 (apply - bnd))) shape))
(scales (reverse (cons 1 (cdr (reverse dims))))))
(array:construct shape
scales
(- (apply + (map * (map car shape) scales)))
(make-vector (apply * dims) initial-value))))
;;@noindent
;;When constructing an array, @var{bound} is either an inclusive range of
;;indices expressed as a two element list, or an upper bound expressed as
;;a single integer. So
;;
;;@example
;;(make-array 'foo 3 3) @equiv{} (make-array 'foo '(0 2) '(0 2))
;;@end example
;;@args array mapper bound1 bound2 @dots{}
;;@code{make-shared-array} can be used to create shared subarrays of other
;;arrays. The @var{mapper} is a function that translates coordinates in
;;the new array into coordinates in the old array. A @var{mapper} must be
;;linear, and its range must stay within the bounds of the old array, but
;;it can be otherwise arbitrary. A simple example:
;;
;;@example
;;(define fred (make-array #f 8 8))
;;(define freds-diagonal
;; (make-shared-array fred (lambda (i) (list i i)) 8))
;;(array-set! freds-diagonal 'foo 3)
;;(array-ref fred 3 3)
;; @result{} FOO
;;(define freds-center
;; (make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j)))
;; 2 2))
;;(array-ref freds-center 0 0)
;; @result{} FOO
;;@end example
(define (make-shared-array array mapper . dimensions)
(define odl (array:scales array))
(define rank (length dimensions))
(define shape (array:dimensions->shape dimensions))
(do ((idx (+ -1 rank) (+ -1 idx))
(uvt (append (cdr (vector->list (make-vector rank 0))) '(1))
(append (cdr uvt) '(0)))
(uvts '() (cons uvt uvts)))
((negative? idx)
(let* ((ker0 (apply + (map * odl (apply mapper uvt))))
(scales (map (lambda (uvt)
(- (apply + (map * odl (apply mapper uvt))) ker0))
uvts)))
(array:construct
shape
scales
(- (apply + (array:offset array)
(map * odl (apply mapper (map car shape))))
(apply + (map * (map car shape) scales)))
(array:store array))))))
;;@body
;;Returns the number of dimensions of @1. If @1 is not an array, 0 is
;;returned.
(define (array-rank obj)
(if (array? obj) (length (array-shape obj)) 0))
;;@body
;;Returns a list of inclusive bounds.
;;
;;@example
;;(array-shape (make-array 'foo 3 5))
;; @result{} ((0 2) (0 4))
;;@end example
(define array-shape
(lambda (array)
(cond ((vector? array) (list (list 0 (+ -1 (vector-length array)))))
((string? array) (list (list 0 (+ -1 (string-length array)))))
(else (array:shape array)))))
;;@body
;;@code{array-dimensions} is similar to @code{array-shape} but replaces
;;elements with a 0 minimum with one greater than the maximum.
;;
;;@example
;;(array-dimensions (make-array 'foo 3 5))
;; @result{} (3 5)
;;@end example
(define (array-dimensions array)
(map (lambda (bnd) (if (zero? (car bnd)) (+ 1 (cadr bnd)) bnd))
(array-shape array)))
(define (array:in-bounds? array indices)
(do ((bnds (array:shape array) (cdr bnds))
(idxs indices (cdr idxs)))
((or (null? bnds)
(null? idxs)
(not (integer? (car idxs)))
(not (<= (caar bnds) (car idxs) (cadar bnds))))
(and (null? bnds) (null? idxs)))))
;;@args array index1 index2 @dots{}
;;Returns @code{#t} if its arguments would be acceptable to
;;@code{array-ref}.
(define (array-in-bounds? array . indices)
(array:in-bounds? array indices))
;;@args array index1 index2 @dots{}
;;Returns the (@2, @3, @dots{}) element of @1.
(define (array-ref array . indices)
(define store (array:store array))
(or (array:in-bounds? array indices)
(slib:error 'array-ref 'bad-indices indices))
((if (string? store) string-ref vector-ref)
store (apply + (array:offset array) (map * (array:scales array) indices))))
;;@args array obj index1 index2 @dots{}
;;Stores @2 in the (@3, @4, @dots{}) element of @1. The value returned
;;by @0 is unspecified.
(define (array-set! array obj . indices)
(define store (array:store array))
(or (array:in-bounds? array indices)
(slib:error 'array-set! 'bad-indices indices))
((if (string? store) string-set! vector-set!)
store (apply + (array:offset array) (map * (array:scales array) indices))
obj))
;;; Legacy functions
;; These procedures are fast versions of @code{array-ref} and
;; @code{array-set!} for non-string arrays; they take a fixed number of
;; arguments and perform no bounds checking.
(define array-1d-ref array-ref)
(define array-2d-ref array-ref)
(define array-3d-ref array-ref)
(define array-1d-set! array-set!)
(define array-2d-set! array-set!)
(define array-3d-set! array-set!)
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