#lang racket
(require "vect2d.rkt")
(define (my-relaxator)
    (define c1 2)
    (define c2 30)
    (define c3 (sqr 30))
    (define c4 0.1)
  (define (this methode . Largs)
    (case methode
      ((get-c1) c1)
      ((get-c2) c2)
      ((get-c3) c3)
      ((get-c4) c4)
      ((set-c1) (set! c1 (first Largs)))
      ((set-c2) (set! c2 (first Largs)))
      ((set-c3) (set! c3 (first Largs)))
      ((set-c4) (set! c4 (first Largs)))))
    (define (force-e fpos node-id1 node-id2)
      (define v1 (hash-ref fpos node-id1)) ;; fpos = function de placement
      (define v2 (hash-ref fpos node-id2))
      (define u (vect-unit (vect-sum (vect-scalar -1 v1) v2)))
      (define d (sqrt (vect-sum (sqr(- (coord-x v1) (coord-x v2))) (sqr (coord-y v1) (coord-y v2)))))
      (define k (/ (- c3) (sqr d)))
      (define fe (vect-scalar k u))
      fe)

    (define (force-m fpos node-id1 node-id2)
      (define v1 (hash-ref fpos node-id1))
      (define v2 (hash-ref fpos node-id2))
      (define u (vect-unit (vect-sum (vect-scalar -1 v1) v2)))
      (define d (sqrt (vect-sum (sqr(- (coord-x v1) (coord-x v2))) (sqr (coord-y v1) (coord-y v2)))))
      (define k (* c1 (log(/ d c2))))
      (define fm (vect-scalar k u))
      fm)
    this)