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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。. d+ A, r" ]/ @0 r
netlogo自带的social science--traffic grid这一例子当中,
; l7 W  u8 I- d' C$ W# z. W$ {# aglobals
6 r9 _: u& [4 X  z[
9 _. U& y6 g, P$ R& W  grid-x-inc               ;; the amount of patches in between two roads in the x direction
4 B# D; Q) B% y% n( j  k  grid-y-inc               ;; the amount of patches in between two roads in the y direction% x0 [0 v' i9 f0 q4 m
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if) s$ l2 v7 ~4 D: M3 }3 O' e4 H
                           ;; it is to accelerate or decelerate
* h/ y+ c. F5 S  phase                    ;; keeps track of the phase; m7 y0 L) y2 \
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
1 j- c8 x7 M9 `  current-light            ;; the currently selected light
6 {) w" g* E6 A) K4 ^! I0 f' J: K! J# }
  ;; patch agentsets- e) F* G3 B3 y7 z9 S+ f
  intersections ;; agentset containing the patches that are intersections- g. W$ `- j: ]) A: y8 H
  roads         ;; agentset containing the patches that are roads
4 i& G: J% Z: Z6 t]
* ^  g9 J4 g2 n3 H1 _5 {, P# e3 E8 m. K
turtles-own
# E' L4 g% L4 T, c& C1 I% R[) {0 X4 y, I: p4 Y
  speed     ;; the speed of the turtle2 C, O# w" d! s/ V9 s- f
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right$ t4 w3 Q+ ]7 r# x% A/ \/ y& Y, X
  wait-time ;; the amount of time since the last time a turtle has moved
# M8 J0 u$ n1 [/ ^. D# W- l]
! l/ f1 S0 E! h& X* E9 ^
5 r$ _7 L9 i' U4 o+ Qpatches-own
% X: }5 r$ A! y[
! X  G2 k; \8 a/ q6 @7 G/ _  intersection?   ;; true if the patch is at the intersection of two roads% i& ~6 I$ k+ @1 \4 k( o6 k6 i
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.; K" A$ l1 T7 ?) W) E# u" Y
                  ;; false for a non-intersection patches.
; }" F* g$ _1 a- {6 Z" ~7 y+ U- J, o% y  my-row          ;; the row of the intersection counting from the upper left corner of the% V( R8 z% t5 ]8 O, `
                  ;; world.  -1 for non-intersection patches." X* ]8 g9 D) h- W
  my-column       ;; the column of the intersection counting from the upper left corner of the
6 z9 U+ }" R4 p' F, C                  ;; world.  -1 for non-intersection patches.
& m2 c- j* p  S% W8 L, b  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches." y2 ^; n6 B, I+ T% m
  auto?           ;; whether or not this intersection will switch automatically.1 k- `7 ?# c5 {! [
                  ;; false for non-intersection patches.4 A, L' Y" M7 g; K( |( D  D: {! d
]
$ }  ^  m. f$ \( a, k# Z, K- h5 }# A  l- o: d* }' R' W
- @- F9 Z" J6 z( M
;;;;;;;;;;;;;;;;;;;;;;
& A. }8 r' |. V+ l;; Setup Procedures ;;+ L5 b, c" [& B+ D
;;;;;;;;;;;;;;;;;;;;;;
2 M  q: v) r: G& {6 c3 F
, ?, b0 w: _6 |9 y$ Y9 Q;; Initialize the display by giving the global and patch variables initial values.
- j9 f5 S2 s- I9 M* M6 i' m;; Create num-cars of turtles if there are enough road patches for one turtle to; I2 m! L: ]; R
;; be created per road patch. Set up the plots.: ~- m+ I3 H+ e) J& P5 d
to setup" H) a0 a7 X/ v
  ca& ?: M- n/ f9 \6 W7 w
  setup-globals
  e9 q& l7 o4 b% K: Q1 T7 B
( o* E. _* q% V  ;; First we ask the patches to draw themselves and set up a few variables
# ?7 F$ K9 U+ ]) }7 a  setup-patches
. W1 R0 T# V  j! W) ]  make-current one-of intersections! b) q6 n2 A  ]1 k5 o+ Q2 z
  label-current/ a/ \" [2 |. Z/ _# {
+ _* F4 Y0 n# }; W" m
  set-default-shape turtles "car"
/ a/ _/ i5 t; c& _* u- g( R( F7 }, o' o, x
  if (num-cars > count roads)) W) i# K* c9 C; z* a( u
  [* S7 t6 Y; }( f
    user-message (word "There are too many cars for the amount of "
$ ?% N( J3 R! h# M4 L2 H* K7 {                       "road.  Either increase the amount of roads "4 _5 Z/ V6 [& s  o* I
                       "by increasing the GRID-SIZE-X or "
1 F( y# e, E1 g) s0 _' p: o8 U                       "GRID-SIZE-Y sliders, or decrease the "" f& R9 Z, m; A
                       "number of cars by lowering the NUMBER slider.\n"
0 g# X4 e: ]2 f8 I3 S( G* ~9 i0 Q                       "The setup has stopped.")
. U$ N0 v" o# w# U3 X' V8 k    stop& e3 L/ I  F' p; _4 O% w
  ], ~5 g. M$ [5 T3 g3 c
9 f4 f# _% c9 D0 @, w& Q/ ~2 L
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color; {0 S# X) e, ]
  crt num-cars! r, A# g5 I; _1 R+ Z: A
  [
6 ]8 g) p# R1 K- ]    setup-cars* m7 M. c/ p  @
    set-car-color8 ]2 v) X2 J4 K8 \; D6 J
    record-data
  i! D- ~  `1 e# L4 R  ]
9 x# _6 w- z) B% r, z
2 r8 }7 U9 V2 l. l6 h  ;; give the turtles an initial speed
' G* }; D$ Y: Q5 [& h  ask turtles [ set-car-speed ]) b+ R- P9 d1 z
* u( z# g% l" j& A. z/ `+ j
  reset-ticks2 }4 v1 j9 D$ U1 m
end
, s$ \1 _- `1 d3 u. h* X# }, ]
0 ~/ M+ E" t: [. V;; Initialize the global variables to appropriate values6 q  C9 w5 m2 {* ^9 y7 M8 e. ~9 Z
to setup-globals# v! g, A5 t/ j" S
  set current-light nobody ;; just for now, since there are no lights yet
% s" r$ b( F$ d/ p  ?2 L5 h  set phase 0
8 p; O$ @/ a$ O6 M3 f/ `  set num-cars-stopped 0
: Q5 b9 s+ i( s7 a  set grid-x-inc world-width / grid-size-x
  w' ~8 E6 [& A$ \. C7 A$ t  set grid-y-inc world-height / grid-size-y
- X. ]' A# l( i, C- n* x7 L
1 y# S/ k; r  n8 y5 m  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary' v) [  B2 [; \, j! x  }
  set acceleration 0.099+ Q5 d6 h) I/ W) t$ c
end
$ Y* P1 H/ H4 Q. e  i9 [+ I0 {6 w
4 n& q, J0 n, b' z;; Make the patches have appropriate colors, set up the roads and intersections agentsets,; C# D2 f# e5 r7 s
;; and initialize the traffic lights to one setting7 s& X! y0 t) }( Q$ l, S, W8 e5 k1 F
to setup-patches- p- s4 {6 ?( @1 I0 f
  ;; initialize the patch-owned variables and color the patches to a base-color- w+ c8 t% K2 w$ m' ?
  ask patches
6 v$ {( u9 _6 C0 B5 G  [! j4 n$ O* Q$ H
    set intersection? false2 \' @4 i: q: x/ S$ D
    set auto? false) j' g  a2 J  n  M- L4 X2 \
    set green-light-up? true
9 w$ g7 {$ j) E7 A' o% S    set my-row -1
: Y* O/ o0 T- \2 c% }    set my-column -1
& v( M0 d( \4 R* w3 d* u$ M. H    set my-phase -1. S. Y2 S6 ~2 y1 \3 @% I" z
    set pcolor brown + 3
: X" D" C* }' j( E* L( ?  ]
) Z/ y( d$ l$ F0 C3 H6 D1 u
. `( z3 p9 I! R1 K% A! P  ;; initialize the global variables that hold patch agentsets# u  h+ [+ A5 n* g3 T  Z
  set roads patches with
4 q: q! L0 y7 i7 q2 b2 k% u  b    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
8 u. E1 |- v) `4 x; U/ o    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  o3 M8 \! n- P4 y( w3 f* L  set intersections roads with
# i% y7 P0 D" ?' w" _! s" Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and; J) n, G/ H0 ]* _. _
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 S' f( Q7 a7 P! \0 H; g' X6 A1 s1 `8 ~
  ask roads [ set pcolor white ]
/ c& r' Y4 r* n* p. L7 ~9 D' v* Y5 s    setup-intersections
! l; e7 k: U9 g) A. |end+ U, s$ w9 b1 G" P! Q5 N% G: u
其中定义道路的句子,如下所示,是什么意思啊?
9 ~, r; C! f, p set roads patches with% S- u  D7 {. V- G/ x* Y# }
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or6 A& m# D  G6 t. K: v0 w
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]! X# D/ V6 s/ w3 P- T
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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