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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。! j! i/ L/ R! B+ m1 @) L
netlogo自带的social science--traffic grid这一例子当中,6 P5 Y9 V5 \6 ]% p
globals% W' C  B# }7 o5 l# O% n
[! N$ N$ n9 X$ T( _. M! R* _
  grid-x-inc               ;; the amount of patches in between two roads in the x direction" b% ~) Q! F  p- d  f7 w% P
  grid-y-inc               ;; the amount of patches in between two roads in the y direction/ D2 ?7 {  M% R' V* ^9 C5 f
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
7 R% U; P' l2 ?, {: O* D$ z                           ;; it is to accelerate or decelerate
- x0 R- Q& t3 h  phase                    ;; keeps track of the phase, b0 O7 v2 \( h4 v/ w; W3 G
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure. V1 T( J$ n3 c
  current-light            ;; the currently selected light
( J5 K! ~5 D- m! Z9 m6 [) S3 m. M: H4 u! |
2 y* ^  [3 P2 E. E" j  ;; patch agentsets% `7 l# m4 O6 h# S  s, Z. l" a
  intersections ;; agentset containing the patches that are intersections
8 F, l' X3 E/ s; Q* R- D  roads         ;; agentset containing the patches that are roads
7 H0 B" {( E2 g0 d/ Z2 c! l! Z( d& @]
/ L1 Q9 J, W7 t) V7 O! }
. L' @. a5 r' `$ Eturtles-own
6 `. l4 V3 ]# f2 h3 o- X& T' g9 g: j[; ?/ ^  q' o1 @# @
  speed     ;; the speed of the turtle
( z$ I$ }! `! v6 Z  up-car?   ;; true if the turtle moves downwards and false if it moves to the right4 {, J$ S2 t5 t3 t
  wait-time ;; the amount of time since the last time a turtle has moved4 h  m( n& S9 h0 @
]# J/ l3 [7 |; Z$ k6 @0 e
: e6 P1 g! o/ c/ Z7 B
patches-own/ S. X1 i: @- g6 S. F
[- O& l1 w. i' t$ j: o4 q
  intersection?   ;; true if the patch is at the intersection of two roads
, E6 A" x/ r/ i1 l. K1 n/ U  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.! _1 b2 o, O0 d6 \& T( v( N
                  ;; false for a non-intersection patches.4 ^3 k/ X6 O( A. D& C
  my-row          ;; the row of the intersection counting from the upper left corner of the% ^! P  G/ J* y5 F) e
                  ;; world.  -1 for non-intersection patches.
9 F+ e9 |9 V! K. _: V  my-column       ;; the column of the intersection counting from the upper left corner of the5 Y" D) E- d: y
                  ;; world.  -1 for non-intersection patches.& @% _8 \- u" A. f  }
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.% Y2 [6 b. Q6 n3 S
  auto?           ;; whether or not this intersection will switch automatically.
9 n6 {- F1 ?& q5 P1 g                  ;; false for non-intersection patches.
# q& E  o; D3 L7 V3 g, V- i" G+ l]
) q  D% w; @$ ?  p1 a& A3 A# Y% d& H6 E; L9 O. t

6 a, L; ~3 U* F! n;;;;;;;;;;;;;;;;;;;;;;5 G6 N9 q, h! P" z' }) }
;; Setup Procedures ;;$ }/ z  _& ?5 x* |6 z$ e: I
;;;;;;;;;;;;;;;;;;;;;;/ D' y, g5 X8 `6 Q( G8 t& E! c

& T5 S+ E2 W. R& n: j( X# O1 b;; Initialize the display by giving the global and patch variables initial values.
+ S" N% p/ i! W0 t3 M;; Create num-cars of turtles if there are enough road patches for one turtle to6 \9 a+ P# ?3 i2 n
;; be created per road patch. Set up the plots.
5 U% L3 ^# m& v# Mto setup
7 u7 K! U/ s4 `1 y  ca
3 t6 d0 p% I% N: N# u, _  setup-globals+ j: H, G! E+ b* v) K7 n

2 n" g( d. N! _. I0 k& g. z" P  ;; First we ask the patches to draw themselves and set up a few variables" \. Z2 t- Z" z& c( d" b; k  T5 M2 o* H
  setup-patches2 o# x6 U# l  l6 z" S8 X
  make-current one-of intersections+ J% e4 T0 q5 ]& O( O! J2 C7 h# S
  label-current+ ]; o- q( R! ^& L

  T1 ~' q# S" `6 Y3 \( V4 u  set-default-shape turtles "car"( t1 _' H4 e$ [6 F, }9 ^% h

! K/ Z& \* O7 z$ r- N# u, c9 Y  if (num-cars > count roads)3 @+ A% P& ?4 X/ `
  [
0 N& T3 w1 C0 ]* Y  |9 t3 [    user-message (word "There are too many cars for the amount of "
& G4 |- H8 O+ c                       "road.  Either increase the amount of roads "$ L5 r! S. a& L) \- `& Q* U
                       "by increasing the GRID-SIZE-X or "
$ }3 D9 X( L8 n$ J                       "GRID-SIZE-Y sliders, or decrease the "
3 Y5 E. |) q( v) h  y/ H                       "number of cars by lowering the NUMBER slider.\n"
+ [7 N! M8 w' M7 W% r) |                       "The setup has stopped.")$ W0 W8 l- {- N, H& S
    stop) w% c1 C, G3 l5 f- O& ~
  ]
7 D+ D7 e/ C. }" v9 e! W/ T3 E
; E* }3 r) v: {4 c0 q0 N  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color+ {/ m2 a$ Q( d0 l. N: B
  crt num-cars! T' }* _( x* P5 a, q( X0 w
  [
9 V$ l" V! i; ]& U# g3 P    setup-cars
1 n. p. e; L1 j5 Y& @* V) W    set-car-color, z0 a$ H. E: m" W4 w& u% [) ?
    record-data" C8 T! J. F7 g8 h: e# ~  m
  ]4 z8 d2 y, [9 e! ]* M# T5 H
- ~7 ]  j  U' ~( K& C7 `
  ;; give the turtles an initial speed
- j) B/ T, X$ s$ N: b6 ?% f) r) b  ask turtles [ set-car-speed ]
1 {% s8 q1 r+ p8 p' }" d: d& |2 q
  reset-ticks, {; Z( Y4 }* t$ I
end5 f; i! Z- Y5 l5 {

+ r' x% a" X, l- D8 w;; Initialize the global variables to appropriate values
0 H4 ~3 {9 y. r7 n! yto setup-globals# R. [+ K7 v2 G7 F- o+ g
  set current-light nobody ;; just for now, since there are no lights yet
% U; x5 I! o- F# Y  set phase 0
1 ]! X0 W0 {/ E' C5 e) j  set num-cars-stopped 0
& Q* P$ h( ^/ L: b7 E; n  set grid-x-inc world-width / grid-size-x
- B) ]9 D- `9 u9 B$ {! ?* S- h( ]0 ?0 P  set grid-y-inc world-height / grid-size-y# p9 r7 ?: w- e+ y

. i6 x) F8 N' s4 w  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary+ s$ w/ @' S/ \& J+ h
  set acceleration 0.099, d" x/ y, T" s0 N/ N- J8 t
end& o9 \& i! q9 y+ D  c4 v

& }7 Q# G  G1 c;; Make the patches have appropriate colors, set up the roads and intersections agentsets,- i1 N4 \; @7 T/ U5 m4 ~2 x
;; and initialize the traffic lights to one setting
/ E5 X' r  v  I  U1 y% eto setup-patches
5 v5 M6 C) h  m1 y9 J/ g% K; U  ;; initialize the patch-owned variables and color the patches to a base-color
! h5 h, J& x+ m) W9 e, H- u  ask patches
; I8 h% ]  [# @  [1 v) T$ B9 L0 i2 G& `+ X
    set intersection? false
6 [5 E) v8 O; S. R! y: ]    set auto? false
5 f/ |0 c, E& v    set green-light-up? true
; Y; C! E& Q! f9 O& {) k    set my-row -1
. N6 ~) A7 f" \1 t2 R5 Q5 B    set my-column -1) `2 }+ l5 A/ V  `' `3 e
    set my-phase -1. V( P8 c5 S8 G+ A4 {6 W
    set pcolor brown + 3
% q" I( v3 ?3 ]! F) |4 m; _  ]* U: w2 ~- e2 V! L2 w
+ @( s$ e- k& d1 x: t
  ;; initialize the global variables that hold patch agentsets; j% x" G3 I: m4 j
  set roads patches with
/ ~) f9 s5 Y+ D0 ?6 R    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or% `9 N0 l% a0 n# o/ H% R% g
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% C2 \* r6 L- V  set intersections roads with$ Z- m2 |7 X7 F  t0 M- J7 q* a, {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and* y% T5 J8 |$ ^) S7 ]3 Y
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]- s4 u+ @# B9 B  d
! g+ m5 f6 m4 ^7 E, a/ V$ g" G
  ask roads [ set pcolor white ]
" N! f7 A) u0 H    setup-intersections
( @. o" _! [) ?. ?- P/ Wend7 w7 J3 D! |: I1 }1 s/ ^# L: @
其中定义道路的句子,如下所示,是什么意思啊?
$ ~( A" C! z: |0 [; C set roads patches with
# B  c* m5 j4 j5 h. r5 P% x# D  m    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
7 M( U$ O, T+ Y8 Y! G    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
; d0 P" s7 l: T1 M( G1 B8 \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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