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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。
$ i" j. ]2 K# H8 N; |netlogo自带的social science--traffic grid这一例子当中,- N' J# x$ V* h% D4 Z
globals% D# S) P0 |2 r; K( O8 e/ R
[
  P6 N$ l. ~% B  grid-x-inc               ;; the amount of patches in between two roads in the x direction: g- L# w# v+ G% P
  grid-y-inc               ;; the amount of patches in between two roads in the y direction% V9 w; V! B6 T0 z0 x7 g2 p; ~
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
' Q3 O% Z/ j. \" F$ w                           ;; it is to accelerate or decelerate  D: q# x) Y/ H3 d9 R
  phase                    ;; keeps track of the phase
- }5 ?, x7 |* B  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
6 d7 w  k, d, u* X5 M1 `' U3 `  current-light            ;; the currently selected light
: d! u& l0 {6 Y6 N6 m$ I
$ `7 R, I% T7 l4 x! X. t0 e  ;; patch agentsets
! l( x9 `. X; ^' Q( f. J- |  intersections ;; agentset containing the patches that are intersections
8 L1 L# k2 H* ?9 m' q$ x0 Y# r  roads         ;; agentset containing the patches that are roads$ V8 A, k. _3 N! G" G& e
]
# c/ h# g& P2 X2 l, }
. E% j( D# b; Nturtles-own& Y0 ]4 g8 O/ B% T  V. a& t; e5 A8 k
[6 Z8 I* G3 W' p
  speed     ;; the speed of the turtle
; T/ h& d9 X8 \; L' C2 z" X  up-car?   ;; true if the turtle moves downwards and false if it moves to the right, x5 L5 H& E( p; U; s, D
  wait-time ;; the amount of time since the last time a turtle has moved
- Q; I2 D2 n" P]
' L, |3 ?1 P9 t# L( v) w' ]6 N& V2 e5 ^
patches-own
4 J9 k9 {* T& s) G[
" P3 _1 J. P2 ^) F  intersection?   ;; true if the patch is at the intersection of two roads
9 ^( }/ |% x& T, S, k4 p5 L$ B  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.# x9 v1 |; Z, r, t
                  ;; false for a non-intersection patches.
' f$ m; V5 k% @% P- K- L9 M" {* S  my-row          ;; the row of the intersection counting from the upper left corner of the
0 P2 I- F3 E0 T4 b3 o                  ;; world.  -1 for non-intersection patches.
4 o+ w' Q1 G7 U% }- U1 q3 Z  my-column       ;; the column of the intersection counting from the upper left corner of the% R2 O8 ~( }( c6 k" F' H9 N
                  ;; world.  -1 for non-intersection patches.% ^& F2 v' G  s9 j* s
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.# c. T( D1 ^7 w. W# H
  auto?           ;; whether or not this intersection will switch automatically.
! v  O) w2 D; T) J) {( n                  ;; false for non-intersection patches./ S5 t( @) I: c! O. j, q8 v- l
]
7 m" }0 O% ~' `7 `3 o, ?! O
5 n! h# K- _) ^% c6 D
5 G' e8 E7 X8 J, S" S) R5 r;;;;;;;;;;;;;;;;;;;;;;9 s# g2 B" J2 @( y# N) _4 b
;; Setup Procedures ;;
; d8 v; ]" Y& c;;;;;;;;;;;;;;;;;;;;;;
% r0 Y" K7 h$ F( C7 P6 R; m! X/ w
4 |! [; s; C' ^1 d" c;; Initialize the display by giving the global and patch variables initial values.  u- x  ^' h  h
;; Create num-cars of turtles if there are enough road patches for one turtle to
( c0 Y8 x; r  h( n! H  K' O" i;; be created per road patch. Set up the plots.& O0 |" l6 u+ m" T( F
to setup
( I" {* C* \( z. ?/ o; |  ca; E: R8 W2 j& g9 s( E
  setup-globals
2 K# |. m4 ^4 v; t
) w) l6 D3 U8 ^- F- s6 o  ;; First we ask the patches to draw themselves and set up a few variables4 d' }& Y3 h6 @$ L; `+ U; \3 @
  setup-patches
9 H; t7 C) W$ i7 Z- N2 ~+ x/ |  make-current one-of intersections
6 O+ E6 @4 s+ O  label-current: t& b8 S# p. {9 f# @

3 d  g! C+ Y1 j% U0 R2 A" p5 u  t  set-default-shape turtles "car"3 \  {  r7 d( w8 V2 F, T2 r
* M/ D4 l$ ]' }+ Q
  if (num-cars > count roads)) L  v1 z' c& O0 m$ L8 d- G' K% T
  [& ]6 n) b5 a: r$ X
    user-message (word "There are too many cars for the amount of ", h" ]0 {8 N+ U
                       "road.  Either increase the amount of roads "
6 J4 m% d' s2 [4 B                       "by increasing the GRID-SIZE-X or "
: `9 f! `/ r. p                       "GRID-SIZE-Y sliders, or decrease the "
6 Q1 z0 \( D6 [) d5 {/ S- X/ Z: v                       "number of cars by lowering the NUMBER slider.\n"9 R9 T0 h, |, m
                       "The setup has stopped.")- l- @5 C! ]& |; _# \+ U
    stop/ e3 |( y4 h5 d9 t
  ]6 u% j( ?0 B& A
6 B9 i: q2 o$ g5 \: ?% |' H
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color0 q0 @- t& S% I+ w! {8 v9 n. f4 z
  crt num-cars& j7 J  S  |8 @: R+ y8 z
  [
2 K' E6 a. J3 b8 y9 _/ D    setup-cars
$ j8 n- O: q# y+ X2 ~" n% W    set-car-color, g" i; p7 Q  e* b, d
    record-data: E1 M' }+ ]. g! {
  ]4 R6 q0 H) X! V! B! h
! e2 x* f5 g& H$ m0 h% a$ |6 `
  ;; give the turtles an initial speed
! t4 F; s5 C+ o* _& u! ^& |  ask turtles [ set-car-speed ]
% c) M, m( i" r+ L
! m& @" I. Q% n* c$ s* P  reset-ticks4 Z- ~, c, A- R, r0 Q7 s5 \( o
end
6 i* r( E6 _2 |+ h) u5 @
6 ?! x/ p5 b- N6 }$ J3 A4 \' h;; Initialize the global variables to appropriate values
# w- l  E# M, u9 k7 a  i/ l/ bto setup-globals1 w9 f7 m) C- Z4 }% g. _
  set current-light nobody ;; just for now, since there are no lights yet( H6 v) o7 n0 z3 |) [( f
  set phase 0  E' J: i$ S) z
  set num-cars-stopped 0  b' K- j$ ~! V' I9 J$ e. A
  set grid-x-inc world-width / grid-size-x- ?4 a% c6 l* ^' `* H
  set grid-y-inc world-height / grid-size-y  S# p5 e' H% ]; f, k
; m6 H2 ^' }3 n' {( P
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary* f. w) y- s* B" s
  set acceleration 0.099) e: \& q2 E  W4 ]) [
end
8 }9 T& F/ F- U* [) w8 m! g5 _
% r4 @5 S5 s# O! a;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
! T$ K4 S' m1 {' T) J4 Z" ^;; and initialize the traffic lights to one setting
' g4 \& m! W0 l0 bto setup-patches9 X# w9 Z6 t1 m/ S( b
  ;; initialize the patch-owned variables and color the patches to a base-color
* [, }% A5 M7 |; V  ask patches
8 q% j  V( y# M; y0 f2 g6 F  [/ m3 U2 Q- @, \% m4 K0 |
    set intersection? false
8 I9 C1 }9 Z7 t) Y: s& \0 n9 c    set auto? false
; d2 M0 G( `; p  b" A& X    set green-light-up? true
8 j( y( r7 B1 X: r2 k    set my-row -1
* [# [1 |/ f6 b  l" I; F) Q    set my-column -1
  z3 y) X$ z  Y: O    set my-phase -1: j. v) T% _$ I$ T9 }5 n/ e
    set pcolor brown + 3  Z# F$ {6 h8 q9 O7 y' H
  ]
, e$ v8 E2 v# B7 g; b) A$ C) R0 K7 B8 ?3 \. L. T5 D
  ;; initialize the global variables that hold patch agentsets
# s- c& D8 L& }* c# A  D+ P  set roads patches with& s; ?4 Z- c+ g, [0 L( L
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
; a1 \% t. {% M. _    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
9 W/ d' ]7 R- l, ?. G2 |+ V/ m  set intersections roads with
+ ]" l8 O+ h  N/ @" n1 U    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
: Y8 d; f* `" [" L7 ?    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 y; p- q- G) f7 M0 U, N% {1 s: I4 R% t2 m
  ask roads [ set pcolor white ]
7 z$ O0 F5 _% R1 W( P! E6 V    setup-intersections; f6 a/ [5 C. P! w0 T  f
end4 k; H* c" G$ B
其中定义道路的句子,如下所示,是什么意思啊?2 s0 A! v  M6 ?. b% g" P  V# A9 ?
set roads patches with" ~' n0 s, S$ S- s3 ^3 [( e
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
: s3 Q; u( S3 C6 l0 W    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
$ ?3 d- I4 Q8 ^4 c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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