How to resolve the algorithm Find the intersection of two lines step by step in the Emacs Lisp programming language

Published on 12 May 2024 09:40 PM
#Emacs lisp

How to resolve the algorithm Find the intersection of two lines step by step in the Emacs Lisp programming language

Table of Contents

Problem Statement

Find the point of intersection of two lines in 2D.

The 1st line passes though   (4,0)   and   (6,10) . The 2nd line passes though   (0,3)   and   (10,7) .

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Find the intersection of two lines step by step in the Emacs Lisp programming language

Source code in the emacs programming language

;; y = a*x + b
(let ()
  (defun line-prop (p1 p2)
    (let* ((prop-a (/ (- (plist-get p2 'y) (plist-get p1 'y))
		      (- (plist-get p2 'x) (plist-get p1 'x))))
	   (prop-b (- (plist-get p1 'y) (* prop-a (plist-get p1 'x)))))

      (list 'a prop-a 'b prop-b) ) )

  (defun calculate-intersection (line1 line2)
    (if (= (plist-get line1 'a) (plist-get line2 'a))
	(progn (error "The two lines don't have any intersection.") nil)
      (progn
	(let (int-x 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))
	(p3 '(x 0.0 y 3.0)) (p4 '(x 10.0 y 7.0)))
    (let ((line1 (line-prop p1 p2))
	  (line2 (line-prop p3 p4)))
      (message "%s" (calculate-intersection line1 line2)) ) )

  )

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