Find the intersection of two lines: Difference between revisions

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Inline

@@ Line 966: / Line 966: @@
   (defun calculate-intersection (line1 line2)
-    (let (int-x int-y)
+    (if (= (plist-get line1 'a) (plist-get line2 'a))
+	(progn (error "The two lines don't have any intersection.") nil)
-      (setq int-x (/ (- (plist-get line2 'b) (plist-get line1 'b))
+      (progn
-		     (- (plist-get line1 'a) (plist-get line2 'a))))
+	(let (int-x int-y)
-      (setq int-y (+ (* (plist-get line1 'a) int-x) (plist-get line1 'b)))
-      (list 'x int-x 'y int-y) ) )
+	  (setq int-x (/ (- (plist-get line2 'b) (plist-get line1 'b))
+			 (- (plist-get line1 'a) (plist-get line2 'a))))
+	  (setq int-y (+ (* (plist-get line1 'a) int-x) (plist-get line1 'b)))
+	  (list 'x int-x 'y int-y) ) ) ) )
   (let ((p1 '(x 4.0 y 0.0)) (p2 '(x 6.0 y 10.0))
@@ Line 976: / Line 979: @@
     (let ((line1 (line-prop p1 p2))
 	  (line2 (line-prop p3 p4)))
-      (message "%s" (calculate-intersection line1 line2) ) ) )
+      (message "%s" (calculate-intersection line1 line2)) ) )
+  )
 </syntaxhighlight>