Data commit

Task/Multi-dimensional-array/EchoLisp/multi-dimensional-array.l

@@ -0,0 +1,45 @@
+(require 'math) ;; dot-product
+
+;; dims = vector #(d1 d2 .....)
+;; allocates a new m-array
+(define (make-m-array dims (init 0))
+	;; allocate 2 + d1*d2*d3... consecutive cells
+	(define msize (apply * (vector->list dims)))
+	(define m-array (make-vector (+ 2 msize) init))
+	
+	;; compute displacements vector once for all
+	;; m-array[0] = [1 d1 d1*d2 d1*d2*d3 ...]
+	(define disps (vector-rotate! (vector-dup dims) 1))
+	(vector-set! disps 0 1)
+	(for [(i(in-range 1 (vector-length disps)) )]
+	      (vector-set! disps i (* [disps i] [disps (1- i)])))
+	(vector-set! m-array 0 disps)
+	
+	(vector-set! m-array 1 dims) ;; remember dims
+	m-array)
+
+;; from indices = #(i j k ...) to displacement
+(define-syntax-rule (m-array-index ma indices)
+	(+ 2 (dot-product (ma 0)  indices)))
+	
+;; check i < d1, j < d2, ...
+(define (m-array-check ma indices)
+	(for [(dim [ma 1]) (idx indices)]
+		#:break (>= idx dim) => (error 'm-array:bad-index (list idx  '>= dim))))
+
+;; --------------------
+;; A P I
+;; --------------------
+;; indices is a vector #[i j k ...]
+;; (make-m-array (dims) [init])
+
+(define (m-array-dims ma) [ma 1])
+
+; return ma[indices]
+(define (m-array-ref ma indices)
+	(m-array-check ma indices)
+	[ma (m-array-index ma indices)])
+; sets ma[indices]
+(define (m-array-set! ma indices value )
+	(m-array-check ma indices)
+	(vector-set! ma (m-array-index ma indices) value))