From: rearman <rearman@r717.net>
Date: Mon, 13 Apr 2026 21:15:54 +0000 (-0400)
Subject: Use the 0-if-null defun
X-Git-Url: https://git.earman.xyz/?a=commitdiff_plain;h=26a90ab6c4a32dbb3e549009fddda936d7f57100;p=lisp%2Fworkenv.git

Use the 0-if-null defun
---

diff --git a/math.lisp b/math.lisp
index 405669d..ec68ded 100644
--- a/math.lisp
+++ b/math.lisp
@@ -29,9 +29,9 @@ If a 2d point is given, it is converted to 3d with z=0."
 	(mapcar #'/
 		(list (apply #'+ (mapcar #'first points))
 		      (apply #'+ (mapcar #'second points))
-		      (apply #'+
-			     (mapcar #'(lambda (x) (if (null (third x)) 0 (third x)))
-				     points)))
+		      (apply #'+ (mapcar #'
+				  (lambda (x) (0-if-null (third x)))
+				  points)))
 		(list numpoints numpoints numpoints)))))
 
 (defun dot-product-points (apoint bpoint)
@@ -67,14 +67,10 @@ Inputs are of the form '(ax ay az) '(bx by bz).
 The function returns '(cx cy cz)."
   (let ((ax (first apoint))
 	(ay (second apoint))
-	(az (if (null (third apoint))
-		0
-		(third apoint)))
+	(az (0-if-null (third apoint)))
 	(bx (first bpoint))
 	(by (second bpoint))
-	(bz (if (null (third bpoint))
-		0
-		(third bpoint))))
+	(bz (0-if-null (third bpoint))))
     (list (- (* ay bz) (* az by))
 	  (- (* az bx) (* ax bz))
 	  (- (* ax by) (* ay bx)))))