Use the 0-if-null defun

diff --git a/math.lisp b/math.lisp
index 405669da10f545a2aedb39b144036016e8a5f6c7..ec68ded266e1cfa02437e81fbcfb7f2865f775b2 100644 (file)
--- 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))
        (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)
                (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))
 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))
        (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)))))
     (list (- (* ay bz) (* az by))
          (- (* az bx) (* ax bz))
          (- (* ax by) (* ay bx)))))