;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;                                                        ;;;;
;;;; Copyright (c) Jun. 1996 by Takehiko Nagakura.          ;;;;
;;;; All rights reserved.                                   ;;;;
;;;;                                                        ;;;;
;;;; Do not copy, use, modify or distribute this software   ;;;;
;;;; without written permission by Nagakura. Nagakura will  ;;;;
;;;; not be responsible for any consequence of its use.     ;;;;
;;;;                                                        ;;;;
;;;; Takehiko Nagakura  (e-mail: takehiko@mit.edu)          ;;;;
;;;;    Massachusetts Institute of Technology               ;;;;
;;;;    77 Massachusetts Ave. 10-472M, Cambridge, MA 02139  ;;;;
;;;;                                                        ;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;; Last updated Feb 28, 2005 by TN for true color sample
;;;; Last updated Dec 29, 1996 by TN 

;; The following pseudo-random number generator was
;; adopted from Kernighan and Ritchie's "C Programming Language"
;; second edition, p46.
;; If you want to use a random number in your program, you can just
;; copy this whole program into your program and use the function,
;; (rand min max)
;; as described below. It works, but do not ask me why this code 
;; can generate fairly good randomness. If you are curious
;; to know it, some discussion on peudo-random number generator 
;; is found in Paul Kohut's web page,
;; http://xarch.tu-graz.ac.at/~rurban/news/comp.cad.autocad/rand.lsp.html.

;; functions and their descriptions                                     
;;
;; (rand16)       : generates a random number between 1 and 32767, 
;;                  that is, a positive 16 bit integer
;; (rand min max) : generates a random number between min and max.
;;                  Min and max must be an integer between 0 and 32767. 
;; (c:demo)       : demo function to generate random points




(setq *SeedRand* nil) ; initialize the global


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun rand16 ( / s )
  ; when this is used for the first time, initialize the seed
  ; from the system clock.
  (if (null *SeedRand*) 
	(progn
	  (setq s (getvar "date"))
      (setq *SeedRand* (fix (* 86400 (- s (fix s))))) 
    ) ; progn
  ) ; if

  ; To generate a psudo-sandom number sequence
  ; I use the routine described in Kernighan and Ritchie's
  ; "C Programming Language" second edition, p46
  (setq *SeedRand* (+ (* *SeedRand* 1103515245) 12345))

 ; trim off the bits left of the 16th bits      
  (logand (/ *SeedRand* 65536) 32767)
)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; generates a random number between min and max.
; min and max must be a non-negative integer smaller than 32678. 
(defun rand (min max / r16 range quotient remainder result)
  (setq r16         (rand16))          ; random number smaller than 32678
  (setq range       (+ 1 (- max min))) ; number of integers to be produced
  (setq quotient    (/ r16 range))     ; result in non-neg. integer
  (setq remainder   (- r16 (* quotient range))) 
  (setq result      (+ min remainder))
  result
)

; test it
; (rand 5 7)


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(defun c:demo   ( / x y n)
  (command "plan" "")
  (command "cmdecho" 0)
  (command "zoom" "window"
            (list -10000 -10000) (list 40000 40000))
  (command "pdmode" 65)
  (command "pdsize" -2)
  (repeat 500 
   (setq x (rand16) ) (setq y (rand16))
   (command "point" (list x y ))
 
   ;AutoCAD takes color numbers between 1 and 255
   (setq n (rand 1 255))
   (command "chprop" (entlast) "" "color" n "") 
   ;(print (list x y n))
))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun c:demo2   ( / x y n)
  (command "plan" "")
  (command "cmdecho" 0)
  (command "zoom" "window"
            (list -10000 -10000) (list 40000 40000))
  (command "pdmode" 65)
  (command "pdsize" -2)
  (repeat 500 
   (setq x (rand16) ) (setq y (rand16))
   (command "point" (list x y ))
 
  ;AutoCAD true color uses numbers between 1 and 255 for rgb channels
  ;I use 100-160 range to make pastel colors. 
		
   (setq r (rand 100 160))
   (setq g (rand 100 160))
   (setq b (rand 100 160))
   (command "chprop" (entlast) "" "color" "truecolor" 
     (strcat (itoa r) "," (itoa g) "," (itoa b) )     
    "")
   ;(print (list x y n))
))