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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。& O& i" \& f1 \" ], R3 R
netlogo自带的social science--traffic grid这一例子当中,
5 }3 B, x$ g! w- B4 O. qglobals9 b! n$ p# i  b6 b( v8 Z: V1 \/ F9 U
[
$ H$ @4 x, V( F0 j0 `( E# ~  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 [; f% @. E! h9 `9 u! ]
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
3 O2 H' v' }! L& i3 A  acceleration             ;; the constant that controls how much a car speeds up or slows down by if1 z3 C3 ^' D& p7 K
                           ;; it is to accelerate or decelerate- O6 H# }% P0 m) T
  phase                    ;; keeps track of the phase- i2 K9 }9 O! B8 n; V8 J
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
' {3 ?4 \- \- ^5 \  current-light            ;; the currently selected light' b  n+ [, E% t, ]9 x; p2 u1 c; x

5 r* y$ K; v  m, f  I  ;; patch agentsets) R5 d# z$ S+ Q. z  t4 {
  intersections ;; agentset containing the patches that are intersections
3 B# j5 f9 u4 w" G% n) X# y0 @( I  roads         ;; agentset containing the patches that are roads" H; f& g. R/ t  H' F3 c, C
]! }1 `* c9 i' a# l( C* h) p! o

3 k) Y5 l7 S. N5 dturtles-own
* l6 T& I- e) l: `/ b- R[
$ G8 f2 j$ D( S% U. P" `  speed     ;; the speed of the turtle
5 t4 |6 J. ~7 U. x9 \0 n  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
; j/ B# F# T6 Q0 _  g' B1 o) `  wait-time ;; the amount of time since the last time a turtle has moved" K  ^6 a8 W7 O2 I9 E- U
]! @7 N8 D+ @4 r! v2 ]
& i% J+ S* U4 d/ B; h
patches-own
* R1 Y- [3 w$ f' O$ r2 y  E% c5 f# R[% J' J. y3 c1 K7 q/ v/ v3 |
  intersection?   ;; true if the patch is at the intersection of two roads! l7 g7 a6 f2 o8 B# N
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
- @% B8 R+ k- D8 S: s5 m                  ;; false for a non-intersection patches.
3 b6 V4 F9 I0 t' b5 a# w! v  my-row          ;; the row of the intersection counting from the upper left corner of the
( s! T+ u2 u/ P" u5 {% C                  ;; world.  -1 for non-intersection patches.3 G; i2 m& i) x& l
  my-column       ;; the column of the intersection counting from the upper left corner of the% ?2 m1 E6 Y* ^% S, {
                  ;; world.  -1 for non-intersection patches.' C" v* M) h  o0 _' ^8 M: ~. |
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
" n6 M: Y0 ]; W) E8 @1 B! B, t  auto?           ;; whether or not this intersection will switch automatically.& \' Z$ C4 m' _) T; G
                  ;; false for non-intersection patches.
6 R& O1 f# ?: j' s: O7 o]+ v8 x  r5 C3 N! @# P! [1 v. c. ~
% ^% J& `3 v- P& j4 o! }  J
0 p( E2 O( k( _7 k
;;;;;;;;;;;;;;;;;;;;;;
( T/ @4 g# j4 A# K8 p, V& \;; Setup Procedures ;;
/ \4 V- u, ~4 A;;;;;;;;;;;;;;;;;;;;;;) q2 J  D1 Q1 f( D. s& R
6 F8 y# \2 r& D) i- Z8 w* Z
;; Initialize the display by giving the global and patch variables initial values.# ?& o6 O2 l8 h: s* L! I
;; Create num-cars of turtles if there are enough road patches for one turtle to
- d2 G. c# D/ d4 A; N+ y. E;; be created per road patch. Set up the plots.+ _: p% P6 k0 s- F- U
to setup
% r, E+ s7 A- L3 L  a7 U. ]( k' Q  ca
! l" U# E8 H1 s8 i, P  g! U  setup-globals0 ~7 `( l8 O0 c4 z1 p  v$ |

7 Y% b0 n) R/ c4 F  ;; First we ask the patches to draw themselves and set up a few variables
) Y' J  L- I, I  setup-patches) h* i; G7 F* u$ }5 j. r$ u- x
  make-current one-of intersections
, j; o5 a/ g. E4 y: P  label-current' c& W; f- H6 G' Z$ A

+ k) A& S9 A0 j$ ?+ g: U9 m/ q  set-default-shape turtles "car") C5 [$ B6 F6 `% ]1 B* r+ y
" c' m2 M. [7 H; [
  if (num-cars > count roads)
9 M. ^! a0 {8 V; [8 a% T* G  [
9 U/ A/ x3 I! ?4 x) @5 `& |! ^    user-message (word "There are too many cars for the amount of "
' k" M5 p- w* r4 |9 V, j6 N                       "road.  Either increase the amount of roads "
( M* q2 n; I4 v) h: @  H4 _0 y1 d                       "by increasing the GRID-SIZE-X or "
7 l3 B" @3 M( q' u! J5 h                       "GRID-SIZE-Y sliders, or decrease the "0 M( `4 `5 I! O- Z8 q1 p
                       "number of cars by lowering the NUMBER slider.\n"1 x8 h. p. U% }& N; f
                       "The setup has stopped.")- v$ L8 `2 n7 }
    stop
: S9 I4 Y  y1 j% T- v8 U  ]  k: `% O% `- K# c

4 r  C5 b7 o8 G0 t. q% s3 K  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
/ {5 W6 S3 G% U  crt num-cars
2 W! z* x* T' a4 Q% q* D1 U  [
4 z# ^9 K: N% ?; v( q" I    setup-cars9 O, E4 J' U" ~9 ], c
    set-car-color4 ~0 r7 r2 M3 Y3 I# W+ t, R3 p
    record-data$ h+ p* ]! _- R* X( v
  ]  i* s$ v4 O! l- l6 \  |" b6 u

* [/ d; n  R" V" h5 f, A1 M% D  ;; give the turtles an initial speed* a, I# K: X$ E- k2 G
  ask turtles [ set-car-speed ]
* X! ~5 O' u- x& h! s7 s, @, e  }" J0 J4 e3 h: B7 U
  reset-ticks' M  W( {! x) s* h8 Q9 O
end
8 o, X$ d  n+ D3 T% \4 Q0 g% g6 F% D$ a6 q
;; Initialize the global variables to appropriate values
' P5 n' B& ~0 I: W" Qto setup-globals' x4 e) q& ], q  R
  set current-light nobody ;; just for now, since there are no lights yet0 Y) h& s5 N  r0 y
  set phase 0' [- Y8 [4 [/ y9 f0 v
  set num-cars-stopped 0
* Q9 ]2 x! \& X* k+ R. O/ k7 g  set grid-x-inc world-width / grid-size-x
. `. ~* P, `4 v  set grid-y-inc world-height / grid-size-y& \; Z! ]$ B" Z( b* G
% {! p* E. z! [
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
. ]- u4 \0 k. n9 t7 k  O& y  set acceleration 0.099' B% ]. P2 ]2 o* `
end
/ K* r( D4 D7 [8 d7 t. y; S  Q3 P( a. d0 _9 R1 f0 Y" t
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,% i! D: W+ g) Z
;; and initialize the traffic lights to one setting
4 p2 A& Z/ I+ P9 Uto setup-patches
6 ~+ G/ S( P4 m+ B7 `  ;; initialize the patch-owned variables and color the patches to a base-color
4 F8 d+ U2 D8 o# w4 T# |  ask patches8 S+ X2 \- H% c  f8 P& \4 v) S. }
  [9 ~/ o9 v: r& a# E& d5 P
    set intersection? false0 _3 H2 V* _# U8 c) m6 `. q
    set auto? false. C. B8 B" H: H# h8 C) L, ?0 ?
    set green-light-up? true2 ^$ Q0 y" [5 s7 L0 u
    set my-row -1; J& t/ r# q" e- i' z
    set my-column -1% s: r7 M/ X9 q9 S. X5 `/ [
    set my-phase -17 [9 x$ N- f5 V& y( |" N
    set pcolor brown + 3
+ j$ I  n! S8 m# b  ]. Y/ f- x3 B/ {* i" P# _$ G) T  j

( b1 _/ G& A4 n( T6 F6 s  ;; initialize the global variables that hold patch agentsets) x7 Q" ?! h! F0 z% o! S
  set roads patches with8 f  ~, n$ q# ]
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 L! ]0 c$ C7 \2 ?
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]$ W6 ~8 O2 r" e. R
  set intersections roads with$ _5 @, q3 x6 T9 L$ {7 \
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and; M" B$ g' r1 k! b
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% W' _, f: e, ~& d% q& W- [6 y" h. }9 M' M# S8 H+ }) v
  ask roads [ set pcolor white ]
4 ]$ G8 R7 B( @3 j6 \5 K7 l; F    setup-intersections
2 V. F3 p6 A! l2 k# L* j( gend
) q3 l" j, C2 }. i2 d& W" C( K其中定义道路的句子,如下所示,是什么意思啊?
1 a) p" i- Z4 i' P& {0 R set roads patches with
4 f1 {' `0 D) n3 D5 S    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or* s, w, s( ]* K% x7 Y- G  a& [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
. Q! @4 q' K+ {# X" N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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