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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。5 j7 D5 D) s+ V* a& @8 c
netlogo自带的social science--traffic grid这一例子当中,% B6 V* I' B$ _* j8 o9 Q" u3 E) R
globals
( @) r% p  C1 ]: g" q. c9 b7 B. r[5 g- I9 Q6 h4 J' L) k& j/ B
  grid-x-inc               ;; the amount of patches in between two roads in the x direction5 R6 }( T& e/ p( Y& X2 z$ Z
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
* a, }% T3 k1 |8 O2 A* m; r4 b  acceleration             ;; the constant that controls how much a car speeds up or slows down by if! |1 x, d, g# G2 d. C7 T
                           ;; it is to accelerate or decelerate6 z0 j  X4 P: @. |  o
  phase                    ;; keeps track of the phase, f2 a: ~, p  m! q6 o' Y
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure3 J. c/ e; t4 q- k3 n
  current-light            ;; the currently selected light# N2 p5 l3 f- B. f/ D- P  }

$ f& Z& i! E  h$ b9 u  ;; patch agentsets
, E' j! Z% a( A' F+ s3 h8 L+ C  intersections ;; agentset containing the patches that are intersections' {2 L8 j! z! T0 ^
  roads         ;; agentset containing the patches that are roads
  B; V+ u- \9 b8 N# m+ [. ]]( Y$ F& }% S3 Q: U' `+ a* }$ B
$ i! N- q$ L5 k3 h
turtles-own* X, I3 D! V8 {
[/ [5 i; T9 G. C9 r
  speed     ;; the speed of the turtle# }% H3 ]1 n2 e5 N7 P( T7 f$ w
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right$ t1 l# r* X$ |% ~9 {
  wait-time ;; the amount of time since the last time a turtle has moved
" U- f2 j+ Q1 `, k) V1 @* d]. D* u1 m! K1 }% I' l% X8 `, A

) P* q' w: J/ I: }7 d) Fpatches-own
& e+ G5 v/ C1 ~, E2 P0 z[. C0 x5 k6 y! Z# x$ e
  intersection?   ;; true if the patch is at the intersection of two roads3 p2 V, }# m& v' ]5 H
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.. ?: _+ X% v' ^/ M) V- P! Z
                  ;; false for a non-intersection patches.
  z* m% _7 Y5 y- u5 U  my-row          ;; the row of the intersection counting from the upper left corner of the/ Z$ d/ ]4 G% T: z
                  ;; world.  -1 for non-intersection patches.
0 V" ^. ?. Y# c1 c  my-column       ;; the column of the intersection counting from the upper left corner of the
0 \5 Z& I4 G9 F1 [                  ;; world.  -1 for non-intersection patches.
- r+ d' J: j) S$ [# j) W  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
1 r6 I' q/ ]6 r  auto?           ;; whether or not this intersection will switch automatically.# Z4 A# b7 G# j, r( K$ M; ^8 y% z# Z
                  ;; false for non-intersection patches.- O* D$ b' `! D2 [( {7 {/ Y1 ~3 f
]
5 y( t( W' I! s1 f* N- [" c$ A
) C0 L0 r  J2 [- s7 w! i! s) j' ~; B5 d. c* |& X
;;;;;;;;;;;;;;;;;;;;;;
; m1 |+ x0 _2 z" U) K;; Setup Procedures ;;
( C1 L' |! A4 c5 h/ O3 p;;;;;;;;;;;;;;;;;;;;;;7 d, E7 u9 e+ D: b" q" B
  {5 [* T: |- E1 h; ]: g4 \
;; Initialize the display by giving the global and patch variables initial values.. p5 B2 e/ I: H( g- O: J. H4 Y
;; Create num-cars of turtles if there are enough road patches for one turtle to* n4 [$ o+ e, e* s8 W/ V
;; be created per road patch. Set up the plots./ {5 ^/ g! q1 d% k6 V
to setup
! x! V$ g3 y! L' ~' A9 q  ca
! M  S/ |# z% F  setup-globals
- A& V* ~8 \- z2 O- y) @7 F$ {+ i& T% e0 o
  ;; First we ask the patches to draw themselves and set up a few variables
" u  H& i- `! s  [0 a  setup-patches9 u3 M0 w3 _" M: g2 S- g
  make-current one-of intersections  K6 f4 s. |( ^2 w7 o* K" g$ I9 G
  label-current* j' P0 M/ T2 a  C

4 H% w) C& ^7 o, V4 c  set-default-shape turtles "car"
2 B  w4 H  E7 |+ @
" q/ r- |# \) z: q/ h' ~  if (num-cars > count roads)
9 s; j. ^# [) F- J% Y, O1 d! z. M  [
1 C& {/ i' ]/ L- B& Y    user-message (word "There are too many cars for the amount of "
* v( u+ L6 D0 `  B# i1 ?                       "road.  Either increase the amount of roads "
- D  z% y1 V5 V                       "by increasing the GRID-SIZE-X or "  J+ O8 e6 ?) I& G
                       "GRID-SIZE-Y sliders, or decrease the "9 s! e$ \0 ^; O8 ^7 g  N" Y$ u% {
                       "number of cars by lowering the NUMBER slider.\n"
) A- ?$ i! Q' v, u! V                       "The setup has stopped.")
/ S  I( I# o, m4 O) [3 S    stop
5 Q8 v8 H5 q' V$ Z. J' ^* k  ]
  Z5 Y( C0 h& [' A2 g  g" ^: G+ m; f1 |: r2 b) W; p; M
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color- e) V: _1 X  A% V( ]( ]
  crt num-cars% B5 H* ~0 n0 k
  [) _& q, \+ i6 r% X: _& D
    setup-cars
7 W/ T' y# O6 Q/ w! \. d+ I3 b& p% o    set-car-color
' y/ v6 N2 w& |' O; ?: B    record-data9 A. K7 y  N+ X: y; C3 Q. I' r
  ]
# m* z$ N. z- ~5 e# i" U2 H
  e0 y* s+ I( T0 }1 G; q9 h2 Y  ;; give the turtles an initial speed# G+ ]0 T$ c, U9 X3 x/ r: _" _
  ask turtles [ set-car-speed ]2 w7 `. l1 g" C: q! j- M

5 E; J( r4 z$ f" V6 o3 R# M  reset-ticks8 r1 t7 ]- o; m: W
end
  d$ ^9 W+ v4 G& A1 v$ }9 T2 l- p& v: B. \" P
;; Initialize the global variables to appropriate values
+ A* @4 p9 o1 [0 oto setup-globals
- Y: }6 p* R( P4 _  set current-light nobody ;; just for now, since there are no lights yet; a4 R& F# a3 g1 I1 e! D
  set phase 0$ S8 Z( M3 H$ d3 p6 p
  set num-cars-stopped 0
( C% l7 Z0 h" _  set grid-x-inc world-width / grid-size-x
# w; e! @0 B' _3 G  set grid-y-inc world-height / grid-size-y( Q: S6 D) H$ I" Z3 q

, |$ U& |  \8 ~$ D  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
' b4 L! f+ M2 c2 _  set acceleration 0.099
( R7 E2 C* {8 K5 r5 C$ h7 v1 }/ B( _end& S4 ^& q- H( T% w
4 F. `. K, I& U7 l# d3 B, n+ Z' e
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,' h4 F6 Q( }- o9 Q( ~" ]! M4 B/ h
;; and initialize the traffic lights to one setting8 p* Y$ F- h8 A4 y# k+ A3 s
to setup-patches' A) N% M( G1 o, d# z$ }
  ;; initialize the patch-owned variables and color the patches to a base-color/ r' M; }7 @9 p& p; m, Y
  ask patches
, Y0 p; k, f9 O  B  [  ?! e9 w! N$ U% U7 T! p( X
    set intersection? false# g1 W5 o# R" u& y3 ?
    set auto? false. f! L7 i; e3 m
    set green-light-up? true; U( p" z9 P7 K7 b7 X( e
    set my-row -13 @# h5 Q" N2 r0 M( N
    set my-column -14 M) e* W  x* D, N
    set my-phase -1  Z6 I( r+ u; p/ B; p
    set pcolor brown + 3& C7 X; H; y' |! S0 b; ?+ d& D
  ]' `" R  K7 ~6 V% S& H) F# K' D
; F  f' O& h. g2 q( R) q" y
  ;; initialize the global variables that hold patch agentsets1 F* i' ~3 c" O/ ?( X: ?( i
  set roads patches with! k5 j- F6 S; i& ]
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or0 V( E! O. h+ ?9 ]+ m
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]" r: q6 m+ w8 x4 X
  set intersections roads with' c$ o/ Q/ N: D: d$ o+ p( e( u
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and, \. `2 ]- F! ]( t% C, m2 c0 v2 [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 K+ y' b6 Y6 H# z! q- @4 Y
  Y& k! E; d) ^: o9 @( P* {9 v  ask roads [ set pcolor white ]% w2 f3 h" d6 w. F9 N, d
    setup-intersections2 f: f5 }7 G% Y: t, [
end4 o! z& z- A5 g7 L# ~8 N2 ~
其中定义道路的句子,如下所示,是什么意思啊?
) ~1 r3 ?( m% b5 K7 d set roads patches with+ V6 k3 z& o* G0 @; x2 X
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
; o/ @+ _; U, L/ D    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
! b6 ]/ {6 \$ M' F8 C) c3 b$ Y6 G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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