diff options
Diffstat (limited to 'lisp/emacs-lisp/seq.el')
| -rw-r--r-- | lisp/emacs-lisp/seq.el | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el index 9eed36eb68c..038b20e3b5e 100644 --- a/lisp/emacs-lisp/seq.el +++ b/lisp/emacs-lisp/seq.el @@ -221,12 +221,17 @@ TESTFN is used to compare elements, or `equal' if TESTFN is nil." (defun seq-subseq (seq start &optional end) "Return the subsequence of SEQ from START to END. If END is omitted, it defaults to the length of the sequence. -If START or END is negative, it counts from the end." +If START or END is negative, it counts from the end. + +Signal an error if START or END are outside of the sequence (i.e +too large if positive or too small if negative)" (cond ((or (stringp seq) (vectorp seq)) (substring seq start end)) ((listp seq) (let (len (errtext (format "Bad bounding indices: %s, %s" start end))) (and end (< end 0) (setq end (+ end (setq len (seq-length seq))))) (if (< start 0) (setq start (+ start (or len (setq len (seq-length seq)))))) + (unless (>= start 0) + (error "%s" errtext)) (when (> start 0) (setq seq (nthcdr (1- start) seq)) (or seq (error "%s" errtext)) |