(define (half left right)
  "Get the half way point."
  (quotient (+ left right) 2))

(define (vector-empty? v)
  "Check if vector is empty."
  (= (vector-length v) 0))

(define (vector-search items target)
  "Search for TARGET in ITEMS."
  (when (vector-empty? items)
    #f)
  (let ((left 0)
	(right (- (vector-length items) 1)))
    (let loop ((left left)
	       (right right))
      (if (<= left right)
	  (let ((middle (half left right)))
	    (cond
	     ((= (vector-ref items middle) target)
	      middle)
	     ((< (vector-ref items middle) target)
	      (loop (1+ left) right))
	     (else
	      (loop left (1+ right)))))
	  #f))))

(vector-search #(1 2 3 4 35) 5)

(vector-search #() 5)