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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。( z& V  t% e5 Q, W1 V9 c2 Y, f6 R
netlogo自带的social science--traffic grid这一例子当中,3 L- L# u1 @4 y
globals
: }& i+ {9 @% F" K% p' j[9 c; |) v- ?  l# O! Q" r
  grid-x-inc               ;; the amount of patches in between two roads in the x direction7 r( I4 |9 L) x3 [: @$ `
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
4 A  q+ b1 Y# S. b  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
3 |  @" J9 i; h. h( {2 L5 y9 l                           ;; it is to accelerate or decelerate! q+ j9 h9 Z/ O- i! R4 R
  phase                    ;; keeps track of the phase% O! m* j7 x0 x! ~
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
( P5 D2 r& P  g) ~3 k  current-light            ;; the currently selected light8 T$ j7 }+ V7 T0 K1 G$ u) s
2 M4 X5 r8 d: M7 U
  ;; patch agentsets) A( T% }' w# Z) [6 Z. }
  intersections ;; agentset containing the patches that are intersections. g" }" n1 t; \! v: T; `) _& ~9 P' Y, t
  roads         ;; agentset containing the patches that are roads% R" T$ p2 {. H" m
]
6 r0 A5 ~# X+ q6 F8 A+ o# C. V  {- i, W# T
turtles-own% D+ R, a% I) m3 D" ~" g
[6 X0 M6 q9 g" Z$ E2 }! f
  speed     ;; the speed of the turtle. Q9 j  O6 ~" D6 O" E
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right7 `# K5 e  Z# T+ @- |
  wait-time ;; the amount of time since the last time a turtle has moved
& r2 W# P& ^1 K  Q. q]3 {1 z- w& q: J  W, o+ S

4 n4 E. V+ i' p% ^+ @3 }. ?3 o+ ypatches-own
8 ]1 b$ }" T/ f7 E, Y7 d[
3 b" u0 M- \! @. m/ q4 n7 b0 s2 a  intersection?   ;; true if the patch is at the intersection of two roads" \% X) [- ^, K* S' N
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
6 ^1 x5 {  J) K9 J5 e                  ;; false for a non-intersection patches.
. {% Z/ U: D) W7 a( s1 v: R; u3 n  my-row          ;; the row of the intersection counting from the upper left corner of the' ]+ P/ t. {1 T1 e$ \6 U
                  ;; world.  -1 for non-intersection patches.
; Q3 v7 W% H' j5 n1 C  my-column       ;; the column of the intersection counting from the upper left corner of the9 C: w" z$ v3 @( Y8 s% j% B! S5 x
                  ;; world.  -1 for non-intersection patches.1 c3 Y9 X3 B, s3 H' H5 H
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.  I1 O' @  _8 o6 U3 h. Y) _
  auto?           ;; whether or not this intersection will switch automatically.
6 [& D0 |( F7 r3 ^                  ;; false for non-intersection patches.
' v7 F# [9 N- d, Q$ g7 E* m- s]
$ j3 a& ?4 D8 m6 H8 f& M! _1 I, H2 T- z6 x7 R; c* J5 L+ z
" F, U2 p+ ]& A9 X, S
;;;;;;;;;;;;;;;;;;;;;;
" C6 m, j( _* A;; Setup Procedures ;;" `* Z0 V) V+ Z. D# }& G
;;;;;;;;;;;;;;;;;;;;;;
  T8 k) u5 ]" X8 w$ h0 k0 p" r8 ^
& p2 s# l! h+ F( L) R! W- ?;; Initialize the display by giving the global and patch variables initial values.
2 g  x- k- T1 a$ F9 `+ w- h;; Create num-cars of turtles if there are enough road patches for one turtle to3 W' l3 P9 `4 D) n7 i4 {
;; be created per road patch. Set up the plots.
3 j. ]" m3 {. ]7 @/ \7 gto setup
2 ?) }: }$ Z- ]  ca
3 W/ n, T1 q, B9 Y, f7 F  setup-globals
6 l: ~" o4 [, x, L: u( n& {- G- N$ I# x
  ;; First we ask the patches to draw themselves and set up a few variables
+ z$ Z" B; d6 Y: b4 i& k  setup-patches2 s# ]0 ^! U* u$ P/ s
  make-current one-of intersections4 F; |$ }# N+ q
  label-current9 }, G: b+ i. D7 X2 V! l
5 E# ]0 D# Z9 _1 v" {% x; U
  set-default-shape turtles "car"( u$ F4 ?* D0 ]( N! R* k
* K) f# y6 a2 N
  if (num-cars > count roads)
+ y* W; ]8 |4 ~$ ~4 }0 ?* {+ w  [
( V- M$ ]% t/ [" X# R0 U    user-message (word "There are too many cars for the amount of "
$ D$ o1 G7 V' X/ Q                       "road.  Either increase the amount of roads ": E7 J- P* r# {5 E1 S8 a( K0 E
                       "by increasing the GRID-SIZE-X or ". F* i! q) J6 w7 `/ |! a- p) y
                       "GRID-SIZE-Y sliders, or decrease the "3 u  a2 |: n2 c" G  r
                       "number of cars by lowering the NUMBER slider.\n"8 d# o+ L4 I) f* K' u- B( s" p
                       "The setup has stopped.")
% {4 _3 O- m2 k( |. g$ j) Y* B( J    stop, y: q. O  C  L% r3 C( H' \" W
  ]! [: A+ H9 |# V% ^0 Q7 a7 U
3 a) [+ {+ C4 k/ k, H5 \
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color8 T: X: ]. D6 a% h- z& v
  crt num-cars
& ?( q" x$ p8 j2 ?# q' _, m  [+ j6 g1 k: P$ Z4 E& c; k7 j. d5 y
    setup-cars
1 z: y6 h0 a) U    set-car-color
6 P( b1 M7 N6 Z5 K% C# S+ j    record-data
' {# [, _& Y" g8 A  ]
+ s1 |/ P7 o, }/ g
3 F" E% P* x& r% D) x  ;; give the turtles an initial speed5 B! P) V0 m. D! c" z+ ]1 _/ U# M
  ask turtles [ set-car-speed ]9 `0 l. E4 K* Q2 L  C. b' Q

, J' ~4 P& w! A$ u8 P- @  c1 G9 H  reset-ticks9 e4 c7 z. {" p, j  j+ R5 c( X
end
8 v3 h& ?* k& y; b$ ?2 }" ~# w5 [+ h
;; Initialize the global variables to appropriate values
/ o  M8 G+ U* x' U+ T$ Y' Ato setup-globals
9 h$ Y2 P# n" O: I4 F, [  set current-light nobody ;; just for now, since there are no lights yet
) k" B2 \5 q: H7 f- D( m  set phase 0" x$ [# f+ v) m
  set num-cars-stopped 0
. M3 e) D8 s' H# B( y% J4 i3 H; c  set grid-x-inc world-width / grid-size-x
( u- ]2 ^) K. @7 d* `, O3 c8 H4 F  set grid-y-inc world-height / grid-size-y
5 Q( }8 v' z! h5 x- i. ~0 o$ v
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
) r9 A2 d  t! L  set acceleration 0.099* W$ A1 h" V. i7 {, y
end8 d( T# g/ s4 J# _& v% l

  Y1 X0 B* t! B. Y, Y;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
  L9 W$ ~+ B. Z% P8 k4 V;; and initialize the traffic lights to one setting3 w$ [- ?: W  m; k" b0 K! i) p
to setup-patches+ H6 d3 s2 S2 N4 p/ l
  ;; initialize the patch-owned variables and color the patches to a base-color
! Z* R; q& z7 b" K" ]' {  ask patches
! U- Z  B" g3 B  [& V8 ]% |4 X& `) F; Z' L# e3 @6 g7 a
    set intersection? false
) W  W6 h7 o/ K/ I) _    set auto? false2 A: F5 B, d+ ~1 Z
    set green-light-up? true
, H, J; {  K$ n) K$ \    set my-row -1
, m- u& z' m/ [9 w, x# g" V$ N    set my-column -14 H9 n- V9 q+ }* z8 \  h  `
    set my-phase -1
% l7 t: U" D" K. X' ~    set pcolor brown + 3
2 o4 `+ ~; R- p" `# L+ P  ]
* i. h: S$ M% \3 N1 b9 N4 R: l4 F
  ;; initialize the global variables that hold patch agentsets  L$ }' d5 l8 O0 O8 w0 i
  set roads patches with
6 S4 k3 |* x: C5 u9 G* ^( I# \& Y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or4 y' Z, {7 J; q( H
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]6 _2 f* e9 X9 Y; N0 X
  set intersections roads with
' l6 v: U- w, P7 {! N. `! Z+ S    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
! X& S# Q5 J" D  \& i    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 {8 P1 W2 F. I9 q$ d  U  t

# d9 w( e' F8 Y3 z" ^, |9 m% }  ask roads [ set pcolor white ]
4 [& W* ?4 F) R: ?! ^8 Z    setup-intersections: C3 v/ }( r' w3 H8 r
end
! ]* ]1 G0 l6 p# M其中定义道路的句子,如下所示,是什么意思啊?
7 M* }0 U2 F+ S+ \4 u% v. [9 T( J set roads patches with
0 f, ~( i. {3 D1 d: g$ H% @    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or. e6 b6 f0 G4 K, U7 p5 _* _6 L& V
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]& M" S1 G7 D6 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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