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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。
$ b) x8 W& l6 Ynetlogo自带的social science--traffic grid这一例子当中,. M' ~) O9 f! C1 n
globals
" c$ s  X! h" N- t, b4 y[
# M7 l. P2 s& |  z  grid-x-inc               ;; the amount of patches in between two roads in the x direction3 x2 x1 [' @* Z( m
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
2 y, W( I3 s! l  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
3 _/ Q* X' N8 ?% B                           ;; it is to accelerate or decelerate. ]3 W; J# ~1 n$ S7 j1 l+ [
  phase                    ;; keeps track of the phase
5 d$ S- Q7 J! t! f8 I( v7 X9 e( @) H  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure6 ]7 M& }# F; ~$ _
  current-light            ;; the currently selected light
, V# @. r1 F1 ^' p5 M
) K' e3 m% d" H7 L) F" o1 S+ f& f. g# N: ]  ;; patch agentsets2 o+ D/ o; n% s6 M& N! W
  intersections ;; agentset containing the patches that are intersections
) L+ L( ~6 L) h  `% [/ z" Z  `  roads         ;; agentset containing the patches that are roads
( E# ~7 H0 v9 F/ d+ t+ F) `* r]; G1 w* t& H! R% W( U! _

6 u1 v6 r2 a* }" @+ O* E; yturtles-own
9 U/ i  b' Q7 E! l7 O' b! z1 l[
% i9 _, _) Z* l' K  speed     ;; the speed of the turtle
) p" q, C& b/ ~$ {! T  M  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
9 S8 f' q7 r1 y& Y2 h  wait-time ;; the amount of time since the last time a turtle has moved( ]" \, m6 p: q  J0 U  r1 H
]
7 n: i4 P/ C6 ^  r6 F4 C6 B) `5 c! U5 N7 T7 s# f5 q  o* }3 {
patches-own
/ h- ]( s# |. E1 M7 m) s[
* M$ q  f. t8 L# f  intersection?   ;; true if the patch is at the intersection of two roads+ k- I+ x* M  t% Q
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.6 a% e/ z8 j8 m# N5 n  U
                  ;; false for a non-intersection patches.2 T- i# O; |! G* N6 A1 V( h
  my-row          ;; the row of the intersection counting from the upper left corner of the# `( M6 p! B) ?) g' O' P
                  ;; world.  -1 for non-intersection patches.6 l# s, N0 Z5 t1 C0 N+ _( R
  my-column       ;; the column of the intersection counting from the upper left corner of the6 {9 Y+ x& K% R' D" q
                  ;; world.  -1 for non-intersection patches.0 {2 u& O$ ]. n4 j+ U
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.* ?5 }! X/ }: K& O
  auto?           ;; whether or not this intersection will switch automatically.5 {9 Z4 P# c6 F% g8 K
                  ;; false for non-intersection patches.
" a2 l0 e$ L. Y  J]
' P* S2 t( t, k) r6 X$ c- ^/ e, z1 b( f

1 p$ @# R& z/ S4 ?% c;;;;;;;;;;;;;;;;;;;;;;  E/ h0 l, }* H. ]
;; Setup Procedures ;;
" i' y( V" O2 X+ r;;;;;;;;;;;;;;;;;;;;;;+ T" l  t( g* Q0 ]. t( ^

/ f& c; T7 z2 o# ?; [; ^8 n;; Initialize the display by giving the global and patch variables initial values.6 v, h4 _2 i8 |
;; Create num-cars of turtles if there are enough road patches for one turtle to# f) ~# I! f2 y3 v  w
;; be created per road patch. Set up the plots.9 l' c* S" l+ Q" m4 G( K# {
to setup
) k0 m9 o' N$ Y- v" }+ v  ca
# x) {' s3 m! u3 p  setup-globals
6 z0 f1 a8 L9 F7 r0 f# W2 F1 j% O
6 C( |! x' ?) N  ;; First we ask the patches to draw themselves and set up a few variables* `# p5 {7 t/ K3 I3 f' H6 h
  setup-patches
) O) @3 n) N# ?: v4 O0 W: u" g, J, k$ Y  make-current one-of intersections2 {7 p: |: R& f% g, q% O, U
  label-current
5 V% i) P8 U2 T) d
; H) \- s0 s/ D( T  set-default-shape turtles "car"; o# w! h  H' p3 K

! u8 `1 C) `' G2 q5 a9 k  if (num-cars > count roads)
# h$ m  }7 m6 ^; H% u! E$ F  [
( n; h: m3 c3 Y  n/ C    user-message (word "There are too many cars for the amount of "
8 _) z1 ^1 F! `: \8 ^" E* `                       "road.  Either increase the amount of roads "8 x8 }$ o" P% k$ O9 H# J2 M. q
                       "by increasing the GRID-SIZE-X or "
2 g$ m4 u9 x4 v( G                       "GRID-SIZE-Y sliders, or decrease the "& G$ n# C3 R" K0 Z
                       "number of cars by lowering the NUMBER slider.\n"( T1 {7 }' {" M5 T# r& r4 m
                       "The setup has stopped.")/ B$ j; c& u* j3 K* Z. m
    stop
0 ^; g6 l- i+ M: |9 G8 s8 n  ]; \8 z3 O6 m  B! X
$ R( t' x' q7 k1 f
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color7 t% {( Q1 ]3 j5 K8 p' X' u
  crt num-cars
+ W7 w5 a% N- W0 s7 a) f! Q1 b! D  [- ?! w3 N4 t/ }! z: ^( E
    setup-cars
# Y3 s7 b/ y' Y8 q, ^; L    set-car-color
1 `8 B! r2 F+ A# Z! b  W    record-data) M( R4 c/ O! r5 m3 a
  ]6 O( J6 W- v- ]6 H

& \8 [: U; J0 B) a" \+ I( @5 S/ I  ;; give the turtles an initial speed- o' `! g: T6 u/ {; I
  ask turtles [ set-car-speed ]
6 _! L7 K% h2 [0 Q
2 u7 r* z" E/ S) M3 c0 i; ^# G  reset-ticks
$ q5 v, X$ n1 V6 S" q9 fend
* `6 M* n  s! H- |9 r8 N
& i, g+ `" N" _/ s9 x- t;; Initialize the global variables to appropriate values
3 r! {+ \: |5 ]  u; nto setup-globals9 O7 c  G, D; g6 R. z! b+ G" i
  set current-light nobody ;; just for now, since there are no lights yet: o6 \" T4 ^; c
  set phase 0
9 }) Y2 T$ _* s* i: f2 H$ R) o# x0 D  set num-cars-stopped 0. w3 L1 W2 v+ U
  set grid-x-inc world-width / grid-size-x
+ s- d- @, |1 o8 ]  set grid-y-inc world-height / grid-size-y  b" y# P/ r6 V) x- Z1 {  |/ c
8 T8 j. u% d/ y: q: y
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary1 o5 B; g1 M' s( s( Q
  set acceleration 0.099
* v: \7 z# d% a$ i4 y/ q" bend
+ }! H! K0 i% Q1 k4 w6 t& L& d& Y2 b- r/ K7 L
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,. C  R& @7 m1 I- x6 S2 x, ^/ {9 X
;; and initialize the traffic lights to one setting+ @4 F1 `' m9 [/ X8 W. d
to setup-patches7 A: `: x; K2 R, ^# V
  ;; initialize the patch-owned variables and color the patches to a base-color
. a8 N+ a  a, W2 t+ J  ask patches7 ^5 _+ u- b( y& z% n
  [& }) Z" I) `/ h6 j( o' q
    set intersection? false$ t/ F: k2 R# M- w
    set auto? false; F  z4 g+ r0 b+ O! M
    set green-light-up? true
  I5 Y5 T( |  m    set my-row -1
  K! h# l' s, ~6 x3 P    set my-column -1
1 C* b/ Q! F* c& N) g* _    set my-phase -1
# e) u2 p0 P+ J. z7 ]$ i    set pcolor brown + 3  b- T* O( O9 w) P
  ]& g3 E. [7 a5 f# |% I

! \" t; r3 X. K, L) |$ `7 }% o  ;; initialize the global variables that hold patch agentsets
) W, ~' }8 g8 l# P  set roads patches with
( |5 I. D8 }/ S    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
% L' ~1 T9 A) d: b3 z' ]4 X    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
5 Z  P  ?% y( u& P* e5 u  set intersections roads with/ H; M7 N" N( m- R
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and  h% k3 k) Z0 Z' U# {  `
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
0 Z* H: b  A+ o! Q; n2 |3 w: b/ U* T9 U) O+ ^2 |6 j
  ask roads [ set pcolor white ]
9 Y7 g/ H# |" H: S3 k- w7 D    setup-intersections
3 u- E  t) f5 X4 V5 J& L9 Wend
) b" z: W% r) r2 c# @其中定义道路的句子,如下所示,是什么意思啊?' S- W" H' q# B# o; @1 v+ I0 z8 V" [
set roads patches with
/ l% q) G; \$ R4 Z0 t+ I* a    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or; Z! `- M" y+ q7 e' `
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 t& P# i9 B  H8 i1 v9 o9 C7 J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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