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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。/ L: M$ T5 k( D- Z, i6 l
netlogo自带的social science--traffic grid这一例子当中,( z& E5 d/ u0 Q2 {( E0 B
globals
6 D0 I7 s3 k: T5 _0 Y, U; Y( F" N% m[
  E0 `2 f8 Z) E  grid-x-inc               ;; the amount of patches in between two roads in the x direction1 v& ~! c! |, I) t. K/ ]
  grid-y-inc               ;; the amount of patches in between two roads in the y direction" A* L' ^* F: w  \1 u/ Z
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
6 `" u7 T3 Y2 Y2 x                           ;; it is to accelerate or decelerate. m6 n$ l  {% [# f' t3 c
  phase                    ;; keeps track of the phase
" z/ j1 c% G5 ]& Z, G6 p  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
6 _* R. C" A' l* N2 V  current-light            ;; the currently selected light
1 D, t+ S  K: s6 [, @7 F) h/ v; X9 V' A$ e
  ;; patch agentsets
8 ?! H5 O- n, a2 w% }9 {  _  intersections ;; agentset containing the patches that are intersections
, d1 L& f: H& M. f  roads         ;; agentset containing the patches that are roads
* n; K- q( Y- \. g8 t9 x' I]1 U0 G3 S' ^2 Z8 A$ o

  \1 K9 u2 J) R- Pturtles-own1 B% e* ~( z: ~$ u8 i& A
[
- W/ K; W, s& T  A( _9 R  speed     ;; the speed of the turtle2 Y% a" `, T5 _  [8 s
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right0 j+ j9 t/ g- x
  wait-time ;; the amount of time since the last time a turtle has moved* V( ~/ j1 W4 D. x5 V
]
( R! ]% m; y- e  b+ Q# u9 ^8 L- C6 g& H$ i) K
patches-own
0 R) a+ O+ Y0 v[
+ l: \/ R  y  b& W& L0 [& O. T  intersection?   ;; true if the patch is at the intersection of two roads. z- Q) |7 O3 j5 o9 g
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false./ E' Y9 J- d+ `$ q" }( `( a
                  ;; false for a non-intersection patches.
& N. r6 A: B2 b4 B6 X  my-row          ;; the row of the intersection counting from the upper left corner of the1 J- R% h) E5 K2 X( E! e
                  ;; world.  -1 for non-intersection patches.' p! n. I9 e: e1 k- v0 e
  my-column       ;; the column of the intersection counting from the upper left corner of the
- p4 p' Y% m* c. Q  t7 f8 X                  ;; world.  -1 for non-intersection patches.
( i2 M, [: E' S# ], k6 i. v  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
) i+ s5 [# ?6 B, q0 j  auto?           ;; whether or not this intersection will switch automatically.
' ~2 q+ z* J; q+ J8 T% p                  ;; false for non-intersection patches.* \" |* n' f% \
]  e) g; E; {# u+ {1 M2 M; y# r
8 m- {# _& Q+ v+ O4 F1 o
* U+ R2 K% g  V( C& ^9 d
;;;;;;;;;;;;;;;;;;;;;;+ M6 e9 U6 m2 k+ f0 M) P9 o' v
;; Setup Procedures ;;
; e: @6 k& \  l/ S( |% q: B+ n;;;;;;;;;;;;;;;;;;;;;;
4 U) I1 V7 j; \$ {* Z( A  D/ L
- ^$ N" b6 p- b" b0 L  d4 Y6 j- D, f;; Initialize the display by giving the global and patch variables initial values.
& t& e8 R9 v; g4 M' }+ X4 m% n;; Create num-cars of turtles if there are enough road patches for one turtle to8 O$ o- I! w# b5 f, K' e+ ^; x
;; be created per road patch. Set up the plots.
4 U  \( E0 p# ]; P/ X. J* _to setup
- Y% h' i. E2 B, N9 w  ca5 A% u' _- j* @  C2 B) n2 \) y
  setup-globals8 A  i& Y' _; b1 B/ q
: |# ?3 z; T3 z' j$ ?9 s! ]% g
  ;; First we ask the patches to draw themselves and set up a few variables
4 B. a9 t3 n- }' X6 e1 c  setup-patches* h) r' q  e/ @2 `2 L
  make-current one-of intersections
$ m& ~' a2 }8 T8 V6 `% g  label-current7 j: O: w, v/ q$ ?" H* t' T

, V# V6 n7 E3 T8 U+ Z  set-default-shape turtles "car"
! Z) w! p( T) t5 k# K7 p+ [, I( T% q$ r# ]
  if (num-cars > count roads), Y1 r$ t9 X, X3 F( C; V5 V; O
  [
: O9 O$ ]$ ?! h( C0 P    user-message (word "There are too many cars for the amount of "
- W- N0 e8 I- C0 N, |# W! Z                       "road.  Either increase the amount of roads ". @; J" I  V. f' ^5 H
                       "by increasing the GRID-SIZE-X or "
# M6 [4 E: e' z! K, s                       "GRID-SIZE-Y sliders, or decrease the "4 ^, G/ T  B# d4 r# t
                       "number of cars by lowering the NUMBER slider.\n"
4 Y8 g! Y2 Q! B$ M! g7 J3 I6 `                       "The setup has stopped.")+ Z% |4 }6 K0 t
    stop  W- G( s1 ?& W( p' Z$ b
  ]
* s0 _( w) J8 _" t2 U
4 t, u+ E( C* I# T  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
0 n& o) {* @. m8 t  crt num-cars% e, U+ w) q  E: }5 E& m& {" Y  v' ^
  [9 ^; T5 Z* B$ s  L9 x. C0 f# }
    setup-cars$ ~) W1 y' o* L
    set-car-color* b0 W/ w; ~. f+ X$ g
    record-data
% e. k+ n! G. [* @: ?( T! S  ]
- J( j6 T- K  s+ ^
  u* r$ V7 W9 Z( o  ;; give the turtles an initial speed. y& x7 l" ~7 l
  ask turtles [ set-car-speed ]6 u/ U8 x/ X2 y- v0 p

* s3 a' k8 K" a1 p5 A  reset-ticks0 t+ ^2 I4 X& T  o  C1 a/ w% C2 Q
end
# d5 ^% N! M% ]5 p  R0 f
$ _+ c6 E* e( f! k: _  E$ A  i  Z;; Initialize the global variables to appropriate values
& q/ u! {/ b! _to setup-globals/ Y, M, ^& K) L# b) t
  set current-light nobody ;; just for now, since there are no lights yet# u+ n( N0 ]8 o( P# l' V8 ?' M
  set phase 0
  v9 Z' S1 _4 C7 K) d& n. h  set num-cars-stopped 0
4 C& [7 f" `# N* H  set grid-x-inc world-width / grid-size-x
' g- ^& ?+ ?( I7 D" b* u  set grid-y-inc world-height / grid-size-y
3 J6 M) }) i3 ^8 y
$ O# q& R1 S4 y4 T! q8 p  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
& j$ E8 Y9 u6 c2 D- W  set acceleration 0.099, E4 M7 I+ h  a' H* ]1 Z9 x
end. `2 l2 S- Q0 s. _6 Z  Z

! o2 X6 V5 d( h;; Make the patches have appropriate colors, set up the roads and intersections agentsets,! f4 ^9 _0 B, A  |/ K
;; and initialize the traffic lights to one setting! d, `. L! D# D  l
to setup-patches3 q6 u- Z7 X, W+ U
  ;; initialize the patch-owned variables and color the patches to a base-color  v# W5 v- I! K9 |
  ask patches5 C! U4 l4 U0 C
  [
1 L0 O) f2 W$ q& ]2 \: {! H8 }3 d/ u    set intersection? false
+ C  u8 T$ {% g6 d) V0 K8 D! R: q    set auto? false
  {) n( U9 Q& w2 w    set green-light-up? true
( A5 D8 y- w% x1 L9 a( ], o    set my-row -1
5 {0 f- I2 z- k) F# O    set my-column -1
3 B8 R. s5 b) H" ^- }% r    set my-phase -1
, a7 Q7 y! j, ~+ F) K' L    set pcolor brown + 3
7 m$ d/ W  a2 d* R  ]0 O" }- N; Q* ~+ V9 J  |4 U5 J  ^' J( Y
2 a2 z$ d4 S1 o( w3 n+ q; f
  ;; initialize the global variables that hold patch agentsets# c) {8 a4 q# O/ Z& t: l+ R
  set roads patches with
7 Z; h& s. a& ~$ h' R    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
5 ^% E% Z7 |% R! k0 `7 t- E  k    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]2 a, S1 _9 q5 y+ A/ v1 |
  set intersections roads with
  \* R( m+ ~4 v    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and: G2 m  H* I8 X4 [% t( z2 e
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
5 E- m8 j6 O) o" e: C+ s& F4 E
8 }" p" S, \& T8 b  ask roads [ set pcolor white ]( W9 {8 M0 A& J; b7 F3 A
    setup-intersections- e" u" k9 `, W" q, L; {( q
end
' R  r2 K+ v) k9 C3 N其中定义道路的句子,如下所示,是什么意思啊?4 M0 W: A  B/ T3 q8 _, b" R9 R  b$ j
set roads patches with/ g- R8 U% K9 B8 P
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
2 T8 K4 x) C3 T2 ]    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
# b7 H5 H1 g3 D$ ]* R9 I' F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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