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[求助] 在看例子时有几个问题看不懂

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发表于 2012-6-20 08:59:43 | 显示全部楼层 |阅读模式
新手,在看netlogo自带的例子时,有几行程序看不懂,希望高手能够指点。8 m  l: N2 K4 Q
netlogo自带的social science--traffic grid这一例子当中,
0 M. x4 I( f* ]% pglobals" ~% M, w- a2 s- H/ a: H
[( M# r  Y& r& C
  grid-x-inc               ;; the amount of patches in between two roads in the x direction! K% T1 i' l5 y/ D0 A" A
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
# Z: D5 |1 a: [' u& I  acceleration             ;; the constant that controls how much a car speeds up or slows down by if1 z0 c. H0 Y+ `! R8 J  Y* `
                           ;; it is to accelerate or decelerate7 D, p6 z4 s1 g# }+ g  v
  phase                    ;; keeps track of the phase
+ U- I* ^3 Q* M: Q+ X* t! f4 A  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
1 |1 z$ N+ p* I  current-light            ;; the currently selected light  ~: h0 {: F8 ]* s3 ?: g5 s# x+ z) F: ~
5 g  ?0 m; p6 b, y  B" [8 k$ `
  ;; patch agentsets
# E2 z' z; E9 s2 b! P3 F) T) c  intersections ;; agentset containing the patches that are intersections
! O4 C7 R0 Q1 I! p/ B  roads         ;; agentset containing the patches that are roads
2 l2 I5 J% q- f$ y* R6 T" x# r( o]) W! E: {! |" D

  ~; n" Z  ^! a, H8 ^turtles-own2 }& p5 @! N5 x: ^" j' w# ~
[1 I( u/ r4 ^% n+ l; a
  speed     ;; the speed of the turtle
5 D) F  a* u1 s' W. V: D- ]# X  up-car?   ;; true if the turtle moves downwards and false if it moves to the right0 d$ m; O/ g+ u& d: ~+ d5 S$ p
  wait-time ;; the amount of time since the last time a turtle has moved
: K0 F3 M: }; Z4 G: t4 ]' d# H+ E( V]  l9 c0 @% R5 @2 h: h

/ m$ w+ h2 P- Q' A) H2 ~patches-own
* e; }- m6 l7 ]! q) E$ T. D[' g6 R: \8 N% S0 }% R8 _- Q
  intersection?   ;; true if the patch is at the intersection of two roads% a/ q1 b3 h; {4 U' o) `% r1 ?
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.' R% j2 W$ h1 f* T; J
                  ;; false for a non-intersection patches.( x  ]$ w! y8 Q6 o8 f
  my-row          ;; the row of the intersection counting from the upper left corner of the
# S7 x! M0 C9 w, a! ?, ^/ S                  ;; world.  -1 for non-intersection patches.! i2 }- b3 l% J, ~) L$ w3 t
  my-column       ;; the column of the intersection counting from the upper left corner of the8 p# f5 f( k( K. R
                  ;; world.  -1 for non-intersection patches.
% h8 Y6 q, p$ n; f( @' L* t9 a  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches." K5 ?, L: _! L. G6 q& V: R9 ?2 _
  auto?           ;; whether or not this intersection will switch automatically.
4 ?: l# |9 ^5 N$ D5 ^. h  [; v                  ;; false for non-intersection patches.$ U+ t& }1 W* T* m. r1 g7 K4 U/ y
]: c2 Y! F# B1 ~4 ^" B

* t! [' |& V8 O. G' L5 }7 a& `- b, q% J" |
;;;;;;;;;;;;;;;;;;;;;;
" I& w! W+ N0 X' J( T' ]0 [* L;; Setup Procedures ;;+ z1 P9 O6 x4 X% [
;;;;;;;;;;;;;;;;;;;;;;
2 @" d' J% ~( Z1 i* {5 T8 L$ g  {! y! A
;; Initialize the display by giving the global and patch variables initial values.
* ~7 d+ F2 @1 W7 Q2 G, ~;; Create num-cars of turtles if there are enough road patches for one turtle to& w3 H. G- x) w4 R) x$ E; `
;; be created per road patch. Set up the plots.8 H9 V1 _3 K0 J* X: m& ]
to setup
8 ]) \, [  ?- ~9 o' Q0 D  ca0 L. i* @$ E& L3 ~
  setup-globals
( v2 ^/ G( s4 h0 L  c' a
2 k: ?' i" n5 n/ P; x  ;; First we ask the patches to draw themselves and set up a few variables2 x/ o. i# I' P  y- b. P& D
  setup-patches
6 m$ [5 M; O, @( S' l! t, `  Q. X: z  make-current one-of intersections. K3 {! u6 Y# @
  label-current7 j" a9 }2 [8 w( v& [4 |8 O7 [

# f3 M6 n, A; l5 f  set-default-shape turtles "car"
, g. M/ _6 T" V+ x7 {& i
! c1 p/ n+ {% [& ?( M  if (num-cars > count roads)+ `: j! V- h" A! [- I" ?
  [
4 p( i- s& Z$ J8 @/ V& c    user-message (word "There are too many cars for the amount of "9 M6 c1 J9 ~6 w: C* }2 m+ \
                       "road.  Either increase the amount of roads ", w( R! D" q% O" v, y. e, i
                       "by increasing the GRID-SIZE-X or "
( {# b5 d& ?, W# s1 M                       "GRID-SIZE-Y sliders, or decrease the "' p* D8 U) S+ K) p7 i8 f( ^$ @+ N
                       "number of cars by lowering the NUMBER slider.\n"
( r* _  M5 D0 o' {                       "The setup has stopped.")) l0 }. s5 k- U# I5 O/ o1 ^0 c
    stop
9 P& t- h' J0 @- g7 w+ e  _  ]- E+ \0 ~/ ~5 v3 E3 Q
' H6 f  A1 q: `9 |! F
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color) R2 D, y* @3 ]; |% x
  crt num-cars
3 m9 ?6 J! p9 }. A  e! g  [
# e, |- w6 q5 y9 C; S- s# q# J7 `    setup-cars- O9 z/ C0 ~, S. M6 K' e: S* z
    set-car-color- V4 u/ b; t2 x- e
    record-data& Y0 m0 n) ~8 \6 U" G3 G
  ]: v, T7 H; b1 |" v- l- W. s

. j) W! d$ e5 D2 Z( }) a- e  ;; give the turtles an initial speed
$ f9 l9 m. G- L) U1 k3 n- r; P. R/ p  ask turtles [ set-car-speed ]
! ]. L+ t, C7 m7 u" x2 Q: [6 P/ h! x$ `4 j: O* \
  reset-ticks7 ~. x, \+ q) k" W$ B2 s, @
end2 W, Q) ^* L& ~
9 {$ K. r8 Y: r3 L' N  f8 x
;; Initialize the global variables to appropriate values6 w. c8 v' O0 {( `4 q
to setup-globals- W7 [, v* ^' ~* e
  set current-light nobody ;; just for now, since there are no lights yet0 ^. g; T; y! ~
  set phase 0
2 J' Z! b9 O  t3 X  set num-cars-stopped 0
; U6 A) C. d7 {& ]8 |  set grid-x-inc world-width / grid-size-x; u) ?% r8 G) p  [* J$ ]
  set grid-y-inc world-height / grid-size-y
$ z! c7 Q% D7 }/ _6 m/ w6 Z) y
  q1 b5 N2 {  I1 q0 n7 f  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary7 E, E* Z2 a9 o1 P( {* a5 H% s, M
  set acceleration 0.099# Z! s& x' u9 `/ W/ W* l8 d3 v
end( Z4 N# d* Y$ g' C

6 l: B( g# P5 Z- W;; Make the patches have appropriate colors, set up the roads and intersections agentsets,9 D% y& f, O2 X' K
;; and initialize the traffic lights to one setting& R, s  ?! g7 Z3 F% K  v9 G8 U
to setup-patches" w; |. U0 v5 }2 ]: j" |
  ;; initialize the patch-owned variables and color the patches to a base-color- Z- F4 \3 b, v! E5 [7 l- J  p
  ask patches% s0 x( y+ s0 r& m  X7 K
  [6 y4 q- k* w. E
    set intersection? false- j# A5 Q% s) `. h+ _4 u, J- J! O; N
    set auto? false# J6 ]* H, T/ y
    set green-light-up? true* j9 J- A+ \  y6 Z" Z& Q0 H: i
    set my-row -16 D9 B4 W% _# R8 o5 g0 J2 s
    set my-column -1
3 W, E. x  t9 j0 e  @    set my-phase -1, [% x( R: c- s# w$ t; i4 I$ R% D
    set pcolor brown + 3
& W2 i3 v8 C, f8 p+ X/ c  ]( ?) H. o; P( f

/ }2 W& t4 ?4 i4 |  ;; initialize the global variables that hold patch agentsets
# G% S  I! y# o3 ?; a5 F  set roads patches with
; \- _5 x: j# I7 T$ u: h1 S% ^    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
9 `8 H% G+ N6 J    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]5 c- V0 U5 O7 i! c( a
  set intersections roads with/ u1 k- X% X1 w" V" C9 O
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
  a6 a5 d  Y2 k) \% p    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
& T/ f, F1 @7 R; T) u
  R5 E( n8 s' i. P7 [  ask roads [ set pcolor white ]1 X! K7 C" O6 l6 O/ i! x
    setup-intersections7 c  c5 j1 e& g6 K9 J: i& L8 ?* a
end  u+ j- }' d; z
其中定义道路的句子,如下所示,是什么意思啊?
% W" `/ O) Z9 I" F7 p' Z6 ? set roads patches with
& ?% Y, y- D6 H/ c7 ?3 U) \, a, z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
) q1 {! N8 a, C% K$ g% T    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
1 w+ N* @. d/ e% _& F" \9 `9 h谁能帮我解释一下[(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0)是什么意思吗?
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