Fix (CONCATENATE 'null ...) for generic sequences

[sbcl.git] / src / pcl / sequence.lisp

diff --git a/src/pcl/sequence.lisp b/src/pcl/sequence.lisp
index 7dc5904..89912ad 100644 (file)
--- a/src/pcl/sequence.lisp
+++ b/src/pcl/sequence.lisp
@@ -17,6 +17,11 @@
   (error 'sequence::protocol-unimplemented
          :datum sequence :expected-type '(or list vector)))
 
+(defgeneric sequence:emptyp (sequence)
+  (:method ((s list)) (null s))
+  (:method ((s vector)) (zerop (length s)))
+  (:method ((s sequence)) (zerop (length s))))
+
 (defgeneric sequence:length (sequence)
   (:method ((s list)) (length s))
   (:method ((s vector)) (length s))