;; 4.1 Arrays

(deftest test-vector()
	(check
		(equal "hello" (svref (vector "hello" 'N 9) 0))))
		
;;; 4.2 Binary search
;; binary search function
;; 
(defun bin-search (obj vec)
	(let ((len (length vec)))
		(and (not (zerop len))
			(finder obj vec 0 ( - len 1)))))
			
(defun finder (obj vec start end)
	;(format t "~A%
	;	" (subseq vec start (+ end 1)))
	(let ((range (- end start)))
		(if (zerop range)
			(if (eql obj (aref vec start))
				obj
				nil)
		(let ((mid (+ start (round (/ range 2)))))
			(let ((obj2 (aref vec mid)))
				(if (< obj obj2)
					(finder obj vec start (- mid 1))
					(if (> obj obj2)
						(finder obj vec (+ mid 1) end)
						obj)))))))

(deftest test-bin-search()
	(check
		(eql 3 (bin-search 3 #(0 1 2 3 4 5 6 7 8)))
		(eql nil (bin-search 9 #(0 1 2 3 4 5 6 7 8)))))