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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: r2 ]8 }" W% _% z
netlogo自带的social science--traffic grid这一例子当中,
' @. k  Y: Z( N3 u$ ^3 T  Nglobals, r* U- S1 O/ q* E( l
[$ H7 w+ i" X: m0 L1 g
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
* q+ p/ @% k' U0 E, \  grid-y-inc               ;; the amount of patches in between two roads in the y direction, o2 K. T% u9 J: p0 P' U1 r! n
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if% P6 f& m6 [7 O* X* U- T
                           ;; it is to accelerate or decelerate
: t) q7 N8 D) }, ^6 x  phase                    ;; keeps track of the phase; M+ B1 r& ?$ D) v
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure& C: }$ U, [* G: A* X, W; S8 ?( F7 {
  current-light            ;; the currently selected light
8 S7 t, c( A- E& _" N& ?# K! y1 j
: L; u# Q3 O. ^9 a! a3 A& f  ;; patch agentsets* ^( F& A% x  O% P- Z2 x, A& O' t
  intersections ;; agentset containing the patches that are intersections9 o2 c/ L. M$ A6 \. s
  roads         ;; agentset containing the patches that are roads
; @! @& E+ J5 a! L  D]
: D7 E0 G* N- o' @% m' J" B
4 G' n9 @" z$ Eturtles-own
) y% e5 x! k1 M& u6 \4 Y! m[
* r" G9 I6 O- c  speed     ;; the speed of the turtle
' b3 G5 G5 J: W  up-car?   ;; true if the turtle moves downwards and false if it moves to the right  V) R) E/ ^8 p# K  w5 v* z
  wait-time ;; the amount of time since the last time a turtle has moved: Z% L) [$ T3 G0 i( `
]
0 E$ K$ Z" F" l4 Y: {( d0 F3 ^9 j$ H- e6 Z
patches-own; F. u7 C& o  A9 T$ `* y
[
( b1 j  u8 P1 f# o/ I  intersection?   ;; true if the patch is at the intersection of two roads/ R& R+ I; P1 U0 `: t' |1 c/ g4 z
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
+ H% P( {. |! e, C+ }                  ;; false for a non-intersection patches.
# g* F& B9 c. M4 k7 O2 U  my-row          ;; the row of the intersection counting from the upper left corner of the
) h3 e1 d7 t, {5 R2 @6 ^                  ;; world.  -1 for non-intersection patches.! x- o% ?  e4 @' T! L
  my-column       ;; the column of the intersection counting from the upper left corner of the
5 }  X8 ~- d9 K, |, O8 r  f% |                  ;; world.  -1 for non-intersection patches.
! D3 H8 I' [5 J" m2 @& Y; o0 v% Y  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
  m8 S7 |$ U: J7 ]: f  auto?           ;; whether or not this intersection will switch automatically.
, x/ E+ n6 E& \0 B, h/ U                  ;; false for non-intersection patches.
. W1 q/ ~7 e3 u- A]
5 Q+ O/ F$ E( I/ U
4 f0 T* S& N: S+ u( ?+ E0 P
( _  S- P" Z6 Q" R;;;;;;;;;;;;;;;;;;;;;;
" h8 h, I0 O- t; `;; Setup Procedures ;;) v0 e" \" g* g
;;;;;;;;;;;;;;;;;;;;;;% m" Q, U0 T% g5 h3 j8 t

8 s8 ?" M" }; M6 `# D- T! I# D;; Initialize the display by giving the global and patch variables initial values." J" T9 X. V4 V0 c
;; Create num-cars of turtles if there are enough road patches for one turtle to; D# D7 ?' a8 H' B
;; be created per road patch. Set up the plots.- {9 n3 X% S, J( ~8 `5 h4 s! ^' y2 T( G
to setup. e+ O8 |5 n: @8 ]# Q
  ca3 Q/ F8 W& ~8 \- F& o
  setup-globals8 V2 L+ j& J4 G# }% S$ _% ~
& x. D( F' ~1 u8 z* n1 v
  ;; First we ask the patches to draw themselves and set up a few variables
  M/ z5 @( ]) Z6 D/ }* h; i  setup-patches" Z7 j8 j( e* {- k. o
  make-current one-of intersections' [/ n1 X8 q1 e: n" n3 U9 v/ @
  label-current
5 O. Q3 B, C4 w2 X
: ~" E# u$ p/ @% _0 ^  set-default-shape turtles "car"
; J7 Q) j" y- ^' y0 E! I1 y7 C! A, t
  if (num-cars > count roads): k/ ]. b, E7 v- t4 V! ]
  [. Q! D7 c  E: o; O, \7 ^$ o  n
    user-message (word "There are too many cars for the amount of "
. M8 L( f$ u  x1 t# f- g                       "road.  Either increase the amount of roads "
3 ]) Z4 G! \% H9 R4 z4 f                       "by increasing the GRID-SIZE-X or "
" l) q9 C  [% h0 f4 H2 C                       "GRID-SIZE-Y sliders, or decrease the "" R, B2 p3 o5 K; p" |$ x! s
                       "number of cars by lowering the NUMBER slider.\n", a% R" O4 F" @1 n
                       "The setup has stopped.")
2 r. O8 U5 \' {  q" A" p    stop
. k! S7 f, p; X  ]
( o- p" f: d3 O# n, Z' X
4 g: l. L& O4 A- o6 E, P  W9 p  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color: M1 U/ N% n% j3 N6 K  I! B
  crt num-cars  m3 X$ T- j$ k! @- f6 d
  [
& u! C' b( Y2 \0 P8 n    setup-cars: J! {% h7 q! @6 Z7 ~5 d
    set-car-color4 y* ?/ G5 X! X0 q' z# J  f+ g
    record-data* R# Z% f0 P  n3 X$ w
  ]3 D7 Q2 H) z. b7 X7 p4 A! D

" Y& |6 f5 ^7 I$ x/ b& ]  U  ;; give the turtles an initial speed" n. n( x1 \% s
  ask turtles [ set-car-speed ]4 w  E3 ]- @  s( d* ~; X# d
" ]* E6 B# `! Z/ M7 e
  reset-ticks3 K0 O( E% i& T6 _2 |. ^
end/ ~/ m, I# K, k" t" A' F
% g/ y! w' W6 z$ Y
;; Initialize the global variables to appropriate values. ~; v! g/ s* Z) a2 n
to setup-globals
+ K; |$ W- [  B3 u  set current-light nobody ;; just for now, since there are no lights yet! v* z6 z/ C0 R0 ?$ I
  set phase 0+ V5 {1 I2 V9 }  `4 e0 d/ T
  set num-cars-stopped 0" n" k; l3 k/ X. q: e1 X' a
  set grid-x-inc world-width / grid-size-x; I6 }7 |, k( L) u
  set grid-y-inc world-height / grid-size-y
+ F7 G1 k6 K( H8 b. i4 g9 _
) t$ W9 b/ a' i9 y  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary' L: u( y. j* y6 d) y4 c: V
  set acceleration 0.099* X: ~4 y. o3 J+ {
end
* _3 a6 M" z6 r8 o
9 n  N$ D) F( \;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
. c$ u. @+ m+ s, @% n;; and initialize the traffic lights to one setting! E+ a) @' J: T  _
to setup-patches. Z* j! G$ U, [& P
  ;; initialize the patch-owned variables and color the patches to a base-color; Y( v, E! A5 Y  M( ]1 M
  ask patches& |, x' v% @# [( f& G
  [. C: `4 T  x3 C, Q% p. o) x! g. g
    set intersection? false$ {8 U" S0 W9 T1 y8 f
    set auto? false
2 w5 G" [) x+ ~, ?* h    set green-light-up? true
$ h/ P2 p; O7 h: |' X! M7 A    set my-row -1! [5 G; ?& t5 j) `
    set my-column -1
) ^# e  s/ d, F  C& V, _9 o! _! c    set my-phase -1
9 e9 K+ t1 e+ y! |    set pcolor brown + 3
0 u8 i% \/ S  O1 ]( V  ], `% G3 B4 j6 P% V( e0 d0 s

# ?$ `4 x1 G: o) e  ;; initialize the global variables that hold patch agentsets1 t$ ?5 D% A) r. w( E: L) |
  set roads patches with( q8 ?9 @: R% ]- w+ o8 m% k9 w7 z
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or1 H3 Z! ?9 E- E: _9 k( [' [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
' j2 G0 [5 A" \9 w4 X8 r8 v  set intersections roads with' Q2 R+ a6 f' m# ?3 q3 o$ Y
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
. k4 Y2 Q) l" E    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]3 @& J, E# F* M
7 y6 W! W9 g6 h; h2 C
  ask roads [ set pcolor white ]* k5 i! f' p* E0 r1 J
    setup-intersections
( t; @" p1 t5 O) bend: r, H1 X) ?) b* P7 p
其中定义道路的句子,如下所示,是什么意思啊?& R. W8 \# ^/ k  H0 X
set roads patches with
9 h, {$ @6 @4 [    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ n8 `$ ]+ O4 P4 e- w) R    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]% B5 ]) Q( @+ ]
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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