list-builder: remove wasteful slot accesses.

* share/txr/stdlib/build.tl (list-builder add,
list-builder pend, list-builder pend): Refer to previously
cached variable holding self.head or self.tail, instead of
re-accessing the slot.

1 files changed, 11 insertions, 11 deletions

diff --git a/share/txr/stdlib/build.tl b/share/txr/stdlib/build.tl
index 76be9f55..91a39223 100644
--- a/share/txr/stdlib/build.tl
+++ b/share/txr/stdlib/build.tl
@@ -33,10 +33,10 @@
 
   (:method add (self . items)
     (let ((st self.tail))
-      (rplacd st (append (cdr st) nil)))
-    (let ((tl (last self.tail)))
-      (usr:rplacd tl (append (cdr tl) items))
-      (set self.tail tl))
+      (rplacd st (append (cdr st) nil))
+      (let ((tl (last st)))
+        (usr:rplacd tl (append (cdr tl) items))
+        (set self.tail tl)))
     nil)
 
   (:method add* (self . items)
@@ -47,19 +47,19 @@
   (:method pend (self . lists)
     (when lists
       (let ((st self.tail))
-        (rplacd st (append (cdr st) nil)))
-      (let* ((tl (last self.tail))
-             (cp (tailp tl (car (last lists))))
-             (nl [apply append lists]))
-        (usr:rplacd tl (append (cdr tl) (if cp (copy-list nl) nl)))
-        (set self.tail tl))
+        (rplacd st (append (cdr st) nil))
+        (let* ((tl (last st))
+               (cp (tailp tl (car (last lists))))
+               (nl [apply append lists]))
+          (usr:rplacd tl (append (cdr tl) (if cp (copy-list nl) nl)))
+          (set self.tail tl)))
       nil))
 
   (:method pend* (self . lists)
     (let* ((h self.head)
            (pf [apply append (append lists (list (cdr h)))]))
       (usr:rplacd h pf)
-      (set self.tail self.head))
+      (set self.tail h))
     nil)
 
   (:method ncon (self . lists)