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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。, v) m2 r: ]& }5 T7 X
netlogo自带的social science--traffic grid这一例子当中,+ S6 i9 @. _$ \9 v0 Q* G
globals/ R. i$ y7 U/ k/ O1 g. Z* N5 R
[' @  `# ^/ n/ C. I8 P6 y# V
  grid-x-inc               ;; the amount of patches in between two roads in the x direction& H5 ^( e+ H: T& u8 K2 C
  grid-y-inc               ;; the amount of patches in between two roads in the y direction: J2 d) b8 P/ d$ _4 V
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
5 b. n  e5 t1 h8 K9 e9 o5 V                           ;; it is to accelerate or decelerate
1 S; h! q3 I4 R  phase                    ;; keeps track of the phase- G) [9 h8 i* U8 r, u1 K% m
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure% I8 v9 i& g( n3 R
  current-light            ;; the currently selected light( f- o* N0 z# r; n7 M" H4 P1 _7 @
- c  [4 _, ?  d4 x3 U1 k2 H( |+ G9 ^
  ;; patch agentsets3 [$ A+ h# a) C4 v
  intersections ;; agentset containing the patches that are intersections/ c/ u9 T- |/ o- |% }: d
  roads         ;; agentset containing the patches that are roads
  S' X" S8 e. |! y5 s]( u4 |  V, r4 u8 U$ ^9 p

& e9 F- l6 z% D9 Uturtles-own
# r" ~4 z. _5 q8 l1 q- C& i% U7 X[
& h1 i5 J5 U1 b5 [' @4 D- ~  speed     ;; the speed of the turtle$ P& z/ ^7 `; }
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right( ~5 ~1 O1 X' y7 D
  wait-time ;; the amount of time since the last time a turtle has moved/ _4 H9 l; n" j4 u6 r. I. p+ F  Q
]
' u) Y$ I. Q" M8 ?& `2 c* X6 B0 }& ~; M
patches-own
& P2 T! X" y5 r3 I3 ~; r[$ L3 @. `" R% A2 d
  intersection?   ;; true if the patch is at the intersection of two roads5 ]$ l0 c/ ~0 n3 Y, G3 x! O
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
" ]# ]* v2 @, c9 c" ?, Z% A  l8 I7 ^# b/ }# A                  ;; false for a non-intersection patches.
  m. o: E0 N+ ~' d' y1 k( x  my-row          ;; the row of the intersection counting from the upper left corner of the
9 j* G1 [* a9 P                  ;; world.  -1 for non-intersection patches.
; \: C7 ~1 @" B! Z  my-column       ;; the column of the intersection counting from the upper left corner of the
  x% g' C, q, X* G- n                  ;; world.  -1 for non-intersection patches.
; b" s- e' U( G  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
6 x. {# M. L. N6 s2 u! Y$ S/ E  auto?           ;; whether or not this intersection will switch automatically.
* C- J! r7 U5 I0 G! ~                  ;; false for non-intersection patches.' p, [( e) M: n3 Z
]7 S+ U# D" d  E; O

& H" G9 Z: N* m7 Y
; P- r# H/ b3 d4 G;;;;;;;;;;;;;;;;;;;;;;
  o/ Q3 O9 T2 b: J, [;; Setup Procedures ;;+ W2 F  T9 J2 g6 g  M% S
;;;;;;;;;;;;;;;;;;;;;;+ T! w9 {) |& Z1 V
! Y6 U) k3 i0 D, Q8 [, ?) }
;; Initialize the display by giving the global and patch variables initial values.# M) ]# t/ E) V2 P  s8 Z, s
;; Create num-cars of turtles if there are enough road patches for one turtle to1 S: s5 R  k% L+ n
;; be created per road patch. Set up the plots.& v8 R3 P/ t$ L
to setup
7 v' ?8 T5 W) b' o3 i" m! z7 \  ca
% l1 n) j9 E! z0 m3 \  setup-globals
' W  z) x$ X+ T7 r0 h2 E8 z$ @1 G. G5 Z
  ;; First we ask the patches to draw themselves and set up a few variables- a# ]5 A* [) [' u, T' |* z
  setup-patches# |8 _9 `2 r0 F0 q
  make-current one-of intersections" U3 K* `5 T+ R( f9 b0 k, W
  label-current, }% L, k0 G/ K! g8 V) H

) K. ?8 O$ N3 Z6 c& X( y8 i7 c  set-default-shape turtles "car"8 ]4 d" C* G3 X
" T1 ]+ M" u6 r) Z7 @: W: m6 g
  if (num-cars > count roads)
+ L4 l  X8 z$ t8 A  [
! t+ f: Y. m3 D3 f    user-message (word "There are too many cars for the amount of "7 D; Z% P) i) U, x
                       "road.  Either increase the amount of roads "5 _! ]$ v) N, b% L* b* d6 R
                       "by increasing the GRID-SIZE-X or "& i. U1 O5 N$ s* o
                       "GRID-SIZE-Y sliders, or decrease the "
5 t7 F6 r, J7 C! o( j1 \                       "number of cars by lowering the NUMBER slider.\n"+ C+ T7 ?" Z; B' e
                       "The setup has stopped.")5 Y) N0 `5 x3 b6 E$ p7 p' ]+ [  \
    stop8 T. i" G$ l9 p' w( j/ [
  ]' T) V! W0 i8 g. S5 L* p

$ f' z/ P3 ?- ^; B5 d' D; e  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
7 v8 V* g0 U  z" }) a( N- K* y( J  crt num-cars% z. M* u7 {$ g9 y7 F
  [
7 u! k" E$ W( |0 L% C+ R    setup-cars! z' M; _5 \# `( Z/ @9 h9 |
    set-car-color- s" C- D! u& p! H, D
    record-data
  z) r- w: [: O  ]
' y3 |' c5 i* _# A) D% T4 w, n) V+ r# ~+ z
  ;; give the turtles an initial speed$ Q" @, U. @# Q% t. p! W
  ask turtles [ set-car-speed ]
) W' Y. D, X7 A# L5 h
$ l8 W* a1 p9 p' |: R$ J  reset-ticks
! _. K5 ~/ ~9 lend
( p! A& J4 {% t- ~
4 }( M' Y: b' u: n5 t" v$ `2 p;; Initialize the global variables to appropriate values5 D  ]0 A' T8 z% r1 Z
to setup-globals
& |- a- X; B3 z, F9 M  m, f; n  set current-light nobody ;; just for now, since there are no lights yet
* Y! I5 n5 {1 r- [9 t' M, W  set phase 09 [+ ]% L  l& C6 s+ D5 m% B+ F7 [
  set num-cars-stopped 05 S& f+ {& q# ?8 B: P
  set grid-x-inc world-width / grid-size-x5 D: w/ Z4 W; j, f
  set grid-y-inc world-height / grid-size-y0 i0 c! f4 e) G
/ ]1 r3 D$ M( q( r$ |' b
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary- I4 F) n* b, E* i$ v2 K' ^
  set acceleration 0.099. H7 b+ Z: Y9 j# \
end
9 T. T8 j8 Z4 x. _2 f2 W: I7 I1 a4 u1 f# C
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
1 J: B8 }1 K5 S6 U! F;; and initialize the traffic lights to one setting& _1 E- Y7 s. P2 ~+ ]) s2 w
to setup-patches
' w: N. j+ f  P# d# B  ;; initialize the patch-owned variables and color the patches to a base-color* q: R% f; v8 T  H& X
  ask patches
7 D# ^' O( W0 u0 D! B3 X/ h  [1 i4 o" i8 |! H* @" k6 E/ K
    set intersection? false4 I# y; [" ?% z9 x
    set auto? false
5 K' T8 j, A$ @" p0 H! U5 L  k' a    set green-light-up? true2 {$ p% c) O3 O- e
    set my-row -13 [) X0 `' H8 B+ t
    set my-column -1/ E/ S6 W8 ]3 B" E/ ?- R
    set my-phase -1
4 o3 U6 E6 B+ e3 }2 T    set pcolor brown + 30 t$ p$ d& d+ K' [3 }+ M8 X( Z; [
  ]2 t5 C- J0 b# Y- c% i' _

2 m1 S% ?8 a  e$ s, w. C7 X; L  ;; initialize the global variables that hold patch agentsets
; \- |* i  s6 Q: T/ u6 O; D  set roads patches with
8 }1 J& `. E, C3 y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
2 b5 W+ C$ x. ]5 }) q- }    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% A5 F  S: y1 F( A  \0 R0 O0 y* m/ {  set intersections roads with
8 y1 V5 u9 x- z$ Y7 k    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and8 _! l: n" [1 c4 q: T, p  a
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]3 h0 E# d+ Z0 n3 c7 a# h: o

3 _+ H- a. s6 x4 a+ v1 ^+ z0 T  ask roads [ set pcolor white ]
5 k+ l; }% \0 U, B, E9 k    setup-intersections  x( q. r& X7 `: R# [2 i- M
end9 L" u7 ~7 e8 t4 u
其中定义道路的句子,如下所示,是什么意思啊?
4 e& @  `) T! R set roads patches with
9 ~8 Z+ F2 S( b1 `3 D7 W( Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or0 K& _. L' Q  n1 N0 [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
" {& r9 J8 m$ X( I( h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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