X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Flist.lisp;h=5f38f7126e26bace475fecfc625c22a0490b9c48;hb=fb76e3acd8b8a53cdadaa65bce1d090d99e004a0;hp=e21535c921071300e9cc4f8242f37da27479f1a0;hpb=4898ef32c639b1c7f4ee13a5ba566ce6debd03e6;p=sbcl.git

diff --git a/src/code/list.lisp b/src/code/list.lisp
index e21535c..5f38f71 100644
--- a/src/code/list.lisp
+++ b/src/code/list.lisp
@@ -18,8 +18,8 @@
 ;;;; -- WHN 20000127
 
 (declaim (maybe-inline
-          tree-equal nth %setnth nthcdr last make-list append
-          nconc member member-if member-if-not tailp adjoin union
+          tree-equal nth %setnth nthcdr last last1 make-list append
+          nconc nconc2 member member-if member-if-not tailp adjoin union
           nunion intersection nintersection set-difference nset-difference
           set-exclusive-or nset-exclusive-or subsetp acons assoc
           assoc-if assoc-if-not rassoc rassoc-if rassoc-if-not subst subst-if
@@ -230,18 +230,28 @@
               (fast-nthcdr (mod n i) r-i))
            (declare (type index i)))))))
 
+(defun last1 (list)
+  #!+sb-doc
+  "Return the last cons (not the last element) of a list"
+  (let ((rest list)
+        (list list))
+    (loop (unless (consp rest) (return list))
+          (shiftf list rest (cdr rest)))))
+
 (defun last (list &optional (n 1))
   #!+sb-doc
   "Return the last N conses (not the last element!) of a list."
-  (if (typep n 'index)
-      (do ((checked-list list (cdr checked-list))
-           (returned-list list)
-           (index 0 (1+ index)))
-          ((atom checked-list) returned-list)
-        (declare (type index index))
-        (if (>= index n)
-            (pop returned-list)))
-      list))
+  (if (eql n 1)
+      (last1 list)
+    (if (typep n 'index)
+        (do ((checked-list list (cdr checked-list))
+             (returned-list list)
+             (index 0 (1+ index)))
+            ((atom checked-list) returned-list)
+          (declare (type index index))
+          (if (>= index n)
+              (pop returned-list)))
+      list)))
 
 (defun list (&rest args)
   #!+sb-doc
@@ -266,7 +276,7 @@
   (declare (type index size))
   (do ((count size (1- count))
        (result '() (cons initial-element result)))
-      ((zerop count) result)
+      ((<= count 0) result)
     (declare (type index count))))
 
 (defun append (&rest lists)
@@ -400,6 +410,16 @@
                (return top-of-top)))
           (t (fail top-of-top)))))))
 
+(defun nconc2 (x y)
+  (if (null x) y
+    (let ((z x)
+          (rest (cdr x)))
+      (loop
+       (unless (consp rest)
+         (rplacd z y)
+         (return x))
+       (shiftf z rest (cdr rest))))))
+
 (defun nreconc (x y)
   #!+sb-doc
   "Return (NCONC (NREVERSE X) Y)."