ob-ref.el

(defun org-babel-ref-index-list (index lis)
  "Return the subset of LIS indexed by INDEX.

Indices are 0 based and negative indices count from the end of
LIS, so 0 references the first element of LIS and -1 references
the last.  If INDEX is separated by \",\"s then each \"portion\"
is assumed to index into the next deepest nesting or dimension.

A valid \"portion\" can consist of either an integer index, two
integers separated by a \":\" in which case the entire range is
returned, or an empty string or \"*\" both of which are
interpreted to mean the entire range and as such are equivalent
to \"0:-1\"."
  (if (and (> (length index) 0) (string-match "^\\([^,]*\\),?" index))
      (let ((ind-re "\\(\\([-[:digit:]]+\\):\\([-[:digit:]]+\\)\\|\*\\)")
	    (length (length lis))
            (portion (match-string 1 index))
            (remainder (substring index (match-end 0))))
        (flet ((wrap (num) (if (< num 0) (+ length num) num))
               (open (ls) (if (and (listp ls) (= (length ls) 1)) (car ls) ls)))
          (open
           (mapcar
            (lambda (sub-lis) (org-babel-ref-index-list remainder sub-lis))
            (if (or (= 0 (length portion)) (string-match ind-re portion))
                (mapcar
		 (lambda (n) (nth n lis))
		 (apply 'number-sequence
			(if (and (> (length portion) 0) (match-string 2 portion))
			    (list
			     (wrap (string-to-number (match-string 2 portion)))
			     (wrap (string-to-number (match-string 3 portion))))
			  (list (wrap 0) (wrap -1)))))
              (list (nth (wrap (string-to-number portion)) lis)))))))
    lis))