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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。5 D. g1 }' k. t( m* L
netlogo自带的social science--traffic grid这一例子当中,, z3 o& w% D* `3 Z. o
globals
8 Z! K: ~5 Z+ c$ G; Z8 m$ A[6 x; y6 t" ?9 T; U
  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 y$ `! i+ ?( w  X8 F; X3 s" c- i
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
; A  j% Q9 Y6 }! S% D' }7 u, \+ N8 k  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
: S' _; h: x$ |" M                           ;; it is to accelerate or decelerate) M0 |8 j' x& A. W" I2 w
  phase                    ;; keeps track of the phase
9 C# `2 m% B$ T" v4 A  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure) {& o+ |# Q- R, G
  current-light            ;; the currently selected light
5 ~/ p( G' [; L' B+ I9 e, s( _. ]! ^2 v( G, c
  ;; patch agentsets, n$ q/ w0 i2 ]! d
  intersections ;; agentset containing the patches that are intersections
  W7 m2 ?/ L! W& @- h  roads         ;; agentset containing the patches that are roads  H  b9 ^2 i; S: }4 d" x
]1 \/ [9 V: k; O1 [4 p* Z$ Y7 [
# S) ?8 @. c# J# i# T' Q
turtles-own
- Z' y1 C# D) A# D. R[  }- i3 I$ X" B# _* {
  speed     ;; the speed of the turtle
$ {: S& i4 B5 l) F  f  up-car?   ;; true if the turtle moves downwards and false if it moves to the right! E, h& w. F1 C3 A" G* c; H" Z
  wait-time ;; the amount of time since the last time a turtle has moved
( |( n, U- ~. v( ^4 X0 g4 ]. V3 C]
$ A" w" s& h$ F1 A4 j
2 b) ]/ o; W7 n1 [( @patches-own$ B8 z0 w9 Z1 D: [
[# i; c7 X; ~( P8 s. _: k4 p
  intersection?   ;; true if the patch is at the intersection of two roads$ l* d9 y8 p) P! P, a1 u" w, E9 _
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
; q. _7 m+ r6 f9 Q* D                  ;; false for a non-intersection patches.
% @% c& E" \- u% P( ?) O0 e, O  my-row          ;; the row of the intersection counting from the upper left corner of the& }; \$ E) p6 D  H0 d; H# l; g
                  ;; world.  -1 for non-intersection patches., ?/ m& P: V4 [
  my-column       ;; the column of the intersection counting from the upper left corner of the
& Z5 Z6 e  Y  L" D' G8 D* o                  ;; world.  -1 for non-intersection patches.
. P6 U* y( o% |  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.; y3 W: F! o* }! I$ @/ R7 a
  auto?           ;; whether or not this intersection will switch automatically.- a: Z- c/ V% b2 C
                  ;; false for non-intersection patches.
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9 B; s: R6 E1 a* n/ s1 O0 O6 ]8 P

4 P2 s5 x% Z& U* ?;;;;;;;;;;;;;;;;;;;;;;
/ V3 K% d" x9 f& L! o1 G5 n;; Setup Procedures ;;
& P# I, O/ t' `) u1 n- };;;;;;;;;;;;;;;;;;;;;;
! I9 y+ ~' b9 k1 u, W! R% D0 [$ H6 Y! x0 a: K' l
;; Initialize the display by giving the global and patch variables initial values.
% m) ]& z- n3 ^2 t# Y6 @) i* m;; Create num-cars of turtles if there are enough road patches for one turtle to
, B! S1 d" M- @7 R: y;; be created per road patch. Set up the plots.8 Y& y3 i# C: ^" @: x( d) Z) q
to setup3 E9 r3 H9 G6 j) u
  ca4 W+ o5 v, T' ^
  setup-globals
1 @# b$ E- m; e  `( |5 Q
6 O9 D! ?8 p6 y& d  ;; First we ask the patches to draw themselves and set up a few variables
4 e/ J* Y; b4 O: s: C- x' @" p, [  setup-patches
* ?+ ~! Q( B# ~  ~$ w0 W  make-current one-of intersections4 s) G$ t; s$ x7 x, s" A! p7 D
  label-current( _! x( n, d) F6 F1 S6 H
' @; ]0 T" @; ]& Y& k. P9 K
  set-default-shape turtles "car"
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8 }0 O7 _; Q" c1 v  if (num-cars > count roads)5 c  C8 P% K6 ]4 F+ w
  [: j$ F8 V2 ]% Q4 K$ S% o
    user-message (word "There are too many cars for the amount of "
3 l& _' y0 w8 B7 N/ y                       "road.  Either increase the amount of roads "
) W: B. w- W! h6 T& S/ b' K                       "by increasing the GRID-SIZE-X or "7 q( x3 i' I$ p
                       "GRID-SIZE-Y sliders, or decrease the "' Y2 f' J; O( i
                       "number of cars by lowering the NUMBER slider.\n"
9 d' H$ N! V: L8 T( t/ ]9 c0 \) `! m                       "The setup has stopped.")
9 c3 S- E! [4 v% W8 b& `    stop
5 k. \$ h" v$ Q$ r" Y  h& }  ]
7 ~" N- Y. Z1 O' _. I# R0 o- C; Q# y6 G5 C! C
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
* [# W) Z" E* O' p( t. u, Q  crt num-cars
5 I( U9 Z2 e) O0 R  [
% G8 y. ?8 p/ K3 d) D    setup-cars7 Y) w5 M4 P. [" `5 K
    set-car-color% e. L  o, T5 Y6 P1 e
    record-data9 k0 f: D0 k1 j5 }8 c, s: K
  ]
% N, O, @, q" g! U5 i1 R2 B. U8 M/ E+ ^: M, ^! y3 p  K
  ;; give the turtles an initial speed# d4 v+ c# r4 ]" B$ n
  ask turtles [ set-car-speed ]
! Z& x" e  _) N1 q- g# }  p0 G+ W% P; S, q. A+ J! f
  reset-ticks
# X5 ]0 ]& z3 u5 Iend5 b! U' [: k( g: f

* ^4 \0 o. O) A;; Initialize the global variables to appropriate values
# B/ p+ x9 m- R% x/ N9 qto setup-globals" ]# _9 b3 y9 c# ^. w/ u
  set current-light nobody ;; just for now, since there are no lights yet) |, w9 M) ?3 |( b* T
  set phase 0+ z, o8 |5 ^- x( P# Y5 n
  set num-cars-stopped 0
4 }, w# o  y# V/ H: Z  set grid-x-inc world-width / grid-size-x0 z: V6 ]7 m; R2 z# F5 I9 M
  set grid-y-inc world-height / grid-size-y0 {& [% S5 G6 S" |7 w! _
$ B& @. |6 {3 x1 p6 k  r9 o
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
* i; A  z( I5 d7 G, K/ c  set acceleration 0.099: E  A% ^" r, O: ^- Z" H* [7 f
end6 Z+ l) q3 S0 O# B

2 Y) r: v& Y, q, o;; Make the patches have appropriate colors, set up the roads and intersections agentsets,& ~. _" g" f% s- u5 w
;; and initialize the traffic lights to one setting& F- I. b! ^% }/ j0 g8 ~: `
to setup-patches
: F* M& n7 S# X' n  ;; initialize the patch-owned variables and color the patches to a base-color0 H) Y" P' m9 e4 p! Z
  ask patches( Y" F9 h% w. F: h
  [
+ Y# e# g, A% u, @- J4 I: m    set intersection? false2 o  z" K( m% a1 E
    set auto? false
. m& h8 V; I$ @    set green-light-up? true
. j+ r& k& f- b! \% b* M    set my-row -1# L, y- l: e7 t4 s" d6 H
    set my-column -16 b& |4 A; [* T# K
    set my-phase -1. ]( }$ f: m# m8 f/ _$ G
    set pcolor brown + 3  |4 O. @, K" U3 t5 l
  ]" ~' O1 w5 j" J! n# `

( n" |: r9 C% h" ?, b, _8 y9 A0 i  ;; initialize the global variables that hold patch agentsets6 B5 H, Q7 j# [7 |( I+ C
  set roads patches with
5 J4 M' t$ `, Z' B" I8 u    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ A8 V  L( n' p# Z. E    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 C; y3 H' p% l( R/ {6 V; Z3 f
  set intersections roads with( J, D/ T0 V4 M& |8 B  X; p
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and: m+ B) U2 \+ ]4 T% \( V) @6 f
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]6 E4 \; s# F' b+ Q
# R5 X. H* v( A/ X8 H6 b; ?1 s$ m9 S
  ask roads [ set pcolor white ]
- T* r2 N# {, q2 W/ r4 l# r4 ]    setup-intersections
* q# q1 `3 O  Z" e. Q1 uend
" F6 ~; W5 v1 x' t! K1 g其中定义道路的句子,如下所示,是什么意思啊?
; Z7 @. a% D; g3 z; Q set roads patches with
6 n% G) ^* c  i& H4 B/ w; I3 A$ F& T    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
& ~# Y# S4 d  E  F( S0 q  P: Z) A    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 r; O% d; _; b# [- F' F
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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