0.9.3.11:

[sbcl.git] / src / code / late-extensions.lisp

diff --git a/src/code/late-extensions.lisp b/src/code/late-extensions.lisp
index 4f1ffd0..a841f90 100644 (file)
--- a/src/code/late-extensions.lisp
+++ b/src/code/late-extensions.lisp
@@ -19,3 +19,19 @@
 ;;; not improper and which is not circular?
 (defun list-with-length-p (x)
   (values (ignore-errors (list-length x))))
+
+;;; not used in 0.7.8, but possibly useful for defensive programming
+;;; in e.g. (COERCE ... 'VECTOR)
+;;;(defun list-length-or-die (x)
+;;;  (or (list-length x)
+;;;      ;; not clear how to do this best:
+;;;      ;;   * Should this be a TYPE-ERROR? Colloquially that'd make
+;;;      ;;     lots of sense, but since I'm not sure how to express
+;;;      ;;     "noncircular list" as a Lisp type expression, coding
+;;;      ;;     it seems awkward.
+;;;      ;;   * Should the ERROR object include the offending value?
+;;;      ;;     Ordinarily that's helpful, but if the user doesn't have
+;;;      ;;     his printer set up to deal with cyclicity, we might not
+;;;      ;;     be doing him a favor by printing the object here.
+;;;      ;; -- WHN 2002-10-19
+;;;      (error "can't calculate length of cyclic list")))