Turtle-Geometry-Book/chapter-2/predator-prey.scm

(import
  (scheme base)
  (scheme read)
  (scheme write)
  (scheme load)
  (srfi 27)
  (yasos)
;;  (macduffie alsos)
  (turtle turtle3)
  (turtle vector))

(include "./animal.scm")

(define (make-prey starting-pos)
  (define t (make-hungry-turtle))
  (hide! t)
  (pen-up! t)
  (set-pos! t starting-pos)
  (pen-down! t)
  (show! t)
  (set-food! t (lambda (turt) #(-20 -20)))
;  (set-strategy! t (make-strategy-random 5 10 -10 5))
;  (set-strategy! t (make-strategy-smell-3 2 6 20 10))
;  (set-strategy! t (make-strategy-circle 10 20))
  (set-strategy! t (make-strategy-direct 10))
  t)

(define (make-predator starting-pos the-prey)
  (define t (make-hungry-turtle))
  (hide! t)
  (pen-up! t)
  (set-pos! t starting-pos)
  (pen-down! t)
  (show! t)
  (set-food! t (lambda (turt) (get-pos the-prey)))
  (set-strategy! t (make-strategy-smell-3 2 6 20 10))
  t)

(define max-delta 200)

(define (execute-together pred-proc prey-proc)
  (let loop ((i 0))
    (when (< i max-delta)
      (pred-proc)
      (prey-proc)
      (loop (+ i 1)))))

(define (main)
  (define t1 (make-prey #(100 100)))
  (define t2 (make-predator #(-50 -50) t1))
  (clear-screen)


  (execute-together
   (lambda () (step! t1 1 1))
   (lambda () (step! t2 3 1))))