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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。
! y0 U5 p6 ]; o5 ^, o" b% }. onetlogo自带的social science--traffic grid这一例子当中,
. E7 Z7 U* ?, y1 S2 `globals
2 ?4 b$ V1 m+ X[
7 s+ K3 C2 B) ^% j, |3 N$ @  grid-x-inc               ;; the amount of patches in between two roads in the x direction7 ^9 v9 n1 f3 p5 ^
  grid-y-inc               ;; the amount of patches in between two roads in the y direction( P; L5 Y. Q0 A$ d
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
/ S4 P% ?! W. ]# c  b# D2 H                           ;; it is to accelerate or decelerate* K! C1 @3 _) G( l5 X
  phase                    ;; keeps track of the phase' X. t9 n% N6 w, u& R$ w1 Y/ M9 m
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure* `9 s" v' S6 S! ]: \: U
  current-light            ;; the currently selected light; n7 r$ ~" w) X4 Q3 ?

1 }4 d  m0 e( i5 N& r8 m( ?# v  ;; patch agentsets
9 n0 ]& J: E2 b7 v. y1 I3 F) ]  intersections ;; agentset containing the patches that are intersections" B1 i. a- n/ V5 Z7 \9 E: y
  roads         ;; agentset containing the patches that are roads
1 ^+ P* x+ Q  Q& h+ G* a  Z- X]/ x, {% u5 F) w$ L+ S* t

# ^9 c: z& I, q7 i+ x3 i& `turtles-own, w2 @% L0 P: |2 d3 T. J
[
. O! z6 I1 r+ \! C% R  speed     ;; the speed of the turtle
3 b9 _- \: Q2 t8 A1 K0 U  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
4 p% E+ l& H. }! u) [2 @' Z  wait-time ;; the amount of time since the last time a turtle has moved
% ]2 h0 h" X0 h. v]
2 [2 X7 w  \2 P/ H1 Q
& V! D9 t9 A7 @" x: ]7 w, Rpatches-own5 B5 w. s8 s1 w7 |. b/ u
[9 }$ y% j8 A# }, B
  intersection?   ;; true if the patch is at the intersection of two roads9 }' \, ^" y: H# |$ \* a3 S5 m
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
3 P1 O9 x6 Z2 |# d! m: d  t& i# C                  ;; false for a non-intersection patches.
6 a- U  l/ C/ C  my-row          ;; the row of the intersection counting from the upper left corner of the5 c3 R( i! o( v" p
                  ;; world.  -1 for non-intersection patches.
9 T- B9 k0 L' c8 X* f1 z  my-column       ;; the column of the intersection counting from the upper left corner of the) [" T2 |1 B+ J) I# S
                  ;; world.  -1 for non-intersection patches.8 H6 @5 {+ d/ N7 G! g/ `
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
2 N) P3 J( o$ t$ v8 A  auto?           ;; whether or not this intersection will switch automatically.. j! j" E9 t6 E3 Y+ e/ Y* w, d
                  ;; false for non-intersection patches.
, K1 I4 H: B8 Q1 u]
8 [) ?5 ?1 u! j. s9 c
  J1 J0 @- v7 J/ V' {# C4 J' k" y# ^0 j1 h* z
;;;;;;;;;;;;;;;;;;;;;;
9 F# S+ x, ~- ^+ {; L;; Setup Procedures ;;
5 \0 p$ ?0 h' Q& o;;;;;;;;;;;;;;;;;;;;;;
$ p, C! B% f8 T, B3 q9 f" I- R4 {8 c' ~6 [! H
;; Initialize the display by giving the global and patch variables initial values.
& K+ O0 C6 W1 ]" X;; Create num-cars of turtles if there are enough road patches for one turtle to
( E# k/ x7 `) j7 `: R! e/ q;; be created per road patch. Set up the plots.3 V& ?- `" h$ t. _( J
to setup
" O  t1 g: M( G9 ~  t  ca1 Q( w1 E8 o8 I% H
  setup-globals
% p# L# u- `# U/ x
4 F) O9 T+ @7 o5 Q, p: y+ v  ;; First we ask the patches to draw themselves and set up a few variables+ l: N9 S- ~  @8 g
  setup-patches
# \4 I; e6 Z" x- P" Z6 j' o8 x( Z3 n  make-current one-of intersections
0 X; B2 ^! o( V  label-current3 \! B% Y) Z% t9 t% v* b
; S$ R0 c6 V( \2 D: L* L
  set-default-shape turtles "car"0 R$ e1 k1 R+ `4 `

9 N3 j0 e# H1 T  {4 i  c8 M  if (num-cars > count roads)
& e4 g' d" D+ e; J3 j  [& M. Z# j+ u& q9 I
    user-message (word "There are too many cars for the amount of "
4 _1 V, r% y6 g# {                       "road.  Either increase the amount of roads "
/ g4 _4 k1 ^: F                       "by increasing the GRID-SIZE-X or "
! h) _4 B/ _7 ^7 D) {8 M: P                       "GRID-SIZE-Y sliders, or decrease the "
1 u1 V9 X* a7 B9 w8 [: J                       "number of cars by lowering the NUMBER slider.\n"
/ Q, p4 ~8 T! v% A; v/ k& w& H                       "The setup has stopped.")* P( J  S- W# t( J2 N4 }1 p' n
    stop& h- O/ e$ h9 t! y+ k2 i2 r) E
  ]' A# E4 ?1 [4 c# h7 H% P
* `+ o% `. y3 E5 a1 A1 M
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color7 H+ S- ?% a% s5 j* W
  crt num-cars0 R7 @1 j& q+ ~1 h; k
  [1 v, T( H9 M9 u$ y( M( f$ O% L* u
    setup-cars1 d2 B7 [* @. O, J
    set-car-color
3 O: T6 }  d3 k: i    record-data9 x2 Q2 o. M4 t
  ]
0 t, \2 r- a2 a3 ?( V" |* P+ U" s# d  d
  ;; give the turtles an initial speed: W5 f+ q+ {: X/ Z: X
  ask turtles [ set-car-speed ]
2 S" W  s, B" F# N
. j" x* O& f9 b  reset-ticks
- E% W6 s5 j) r# L% u$ send
4 B$ s& m# _  s( g8 M+ @- o- \# R( X' J. m- ?- r
;; Initialize the global variables to appropriate values
' v0 l, w2 K0 F9 u! rto setup-globals: R" C+ E& v0 ^( v9 c. n
  set current-light nobody ;; just for now, since there are no lights yet
* X' N: h  L  D7 n; [+ t) }  set phase 04 y; t$ ^+ |9 S4 ]
  set num-cars-stopped 0$ q) d6 C) r+ s9 f/ e6 k6 s9 B
  set grid-x-inc world-width / grid-size-x& z% N! a+ n0 W" P+ ?
  set grid-y-inc world-height / grid-size-y8 K; A2 Z( {! t

: T! N+ U# \5 y  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary* F9 J+ b# L" m7 }- b
  set acceleration 0.099
- t. n, H! h, g* _; d* e- ?end
" V% x/ j  K  ?* J; M- |
$ l1 |) D/ N$ y) [9 B8 v;; Make the patches have appropriate colors, set up the roads and intersections agentsets," i& _7 i3 f8 k/ e5 u# u
;; and initialize the traffic lights to one setting" a5 A# B6 W6 s& q2 M0 {+ g
to setup-patches: o; p' K0 c6 E7 S* X/ q/ B. J
  ;; initialize the patch-owned variables and color the patches to a base-color/ U. j2 y$ g/ T- Y9 G0 K  x
  ask patches
6 `% z  l* a" M# X4 q7 |  [
  z7 |0 Y" c7 V( A    set intersection? false) K) L5 s; B$ g4 a0 c
    set auto? false  ]9 f, E$ P4 ~' }( c
    set green-light-up? true
( X. W- c6 s0 a6 u3 N! P( H+ U    set my-row -1
1 |- ]1 ~1 h1 x/ y# G    set my-column -1
. ]$ ^! L! L1 |% H    set my-phase -1+ v1 G- v- n+ B( u: ^! l$ A9 G
    set pcolor brown + 3. ~  @/ k% t0 F; x, H0 ]
  ]' ~: F$ `0 u: {1 @  c3 @! j& w, k

% v) E' @+ `) j  ;; initialize the global variables that hold patch agentsets# p* g" P4 }0 O1 w4 Z4 {
  set roads patches with7 Q' z: B7 m& z' r! _" ]+ |' U
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or2 M  A0 j% V2 e8 u; O7 C% g4 a
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
0 j$ k  ?4 u/ D  set intersections roads with
; i8 @) j6 v* ^0 t( s. L" k% x    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and6 `% @* {' r( |6 ^
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]6 v( O* d) a) x# ]- C
, L' F! q7 ]" r' H- T5 D
  ask roads [ set pcolor white ]
: B) `* c* Q  e0 M) [4 l    setup-intersections" o& f1 T. ^. v  I
end
7 I6 T0 P6 z! L( j, J: q5 O3 \其中定义道路的句子,如下所示,是什么意思啊?
! t) {9 V, q7 f5 m% r- Q set roads patches with
7 `# E! b3 ~. L8 o' y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or. O* X/ `; N4 W% t  v5 N. Y
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% E0 n, ~$ I3 r1 ?( P8 w+ I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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