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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。
8 R; N( C, i& Z4 Knetlogo自带的social science--traffic grid这一例子当中,
7 \8 Z, {& O" m( p! iglobals
1 z" u% x8 z; I8 v; u[
9 d- O/ Y: {* k  grid-x-inc               ;; the amount of patches in between two roads in the x direction* o) N' d4 H0 _- R- Q# J6 [( n
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
  I$ Z# E; Q# L; C  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
' T; v8 ~& w* h+ r& x; V                           ;; it is to accelerate or decelerate9 V* O1 j" s; G6 Z2 s* q
  phase                    ;; keeps track of the phase
) E; Y& h. d/ P( o9 N  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
; r, l+ y3 Y6 c  current-light            ;; the currently selected light9 r- G9 i8 W- {/ F/ U" ]& C) F/ l* k& r

- {7 C) p8 @- G+ R! B  m  ;; patch agentsets
; ]+ \* Q$ a4 K" N* i7 K6 ]  intersections ;; agentset containing the patches that are intersections
' V6 r* T, f6 h& _6 G% D  roads         ;; agentset containing the patches that are roads  C, a: `1 V/ \2 H" y9 ~( @
]: a, y' x" _" x1 g# Q; s/ l3 [7 V
7 R% m5 k1 _3 w4 u" E0 o
turtles-own
- Z( V. ?/ G' Z6 f/ o) C$ X[) j9 b: t; r$ }: f- L1 P
  speed     ;; the speed of the turtle
' N- p5 @% U- P- T  Z0 {; F  up-car?   ;; true if the turtle moves downwards and false if it moves to the right6 N9 p, ?3 V* g( B6 ^) D& I
  wait-time ;; the amount of time since the last time a turtle has moved& n+ D5 Q& `5 t4 X
]
2 Y! V( i8 O1 D
3 e5 s3 `, w. B/ Jpatches-own
2 |; H- }' L- m[# F1 i% D, @: u5 ]/ w& X
  intersection?   ;; true if the patch is at the intersection of two roads3 ]+ O4 [3 o, A& p3 n5 {
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.0 R* U0 z$ m6 L- w3 a, h( @" u6 D
                  ;; false for a non-intersection patches.2 r+ D7 R5 @# ~# n$ c
  my-row          ;; the row of the intersection counting from the upper left corner of the
  ?5 x: \' S4 R9 w, S0 e                  ;; world.  -1 for non-intersection patches.
/ k7 D3 F/ {% W2 z# z  my-column       ;; the column of the intersection counting from the upper left corner of the
2 D: S, m# ~# l( O, F/ w" ?5 H; C) Q                  ;; world.  -1 for non-intersection patches.
* _2 @0 {0 X* K3 C) O0 i  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.3 e6 D/ c2 N" j# ^4 t; }. l
  auto?           ;; whether or not this intersection will switch automatically.6 r0 K; L6 M" _
                  ;; false for non-intersection patches./ d7 k0 y7 h7 D: G7 _9 e
]3 J6 z! d- y5 e! Q  e/ ?- W9 v6 _
# ~4 M: I: Q- o5 N( ]  R0 q2 o

6 P3 C' u! S) g8 ?;;;;;;;;;;;;;;;;;;;;;;
4 Q7 ~) u& a+ d9 u( i* z8 F; K;; Setup Procedures ;;
& V& f/ Q: p; O1 L;;;;;;;;;;;;;;;;;;;;;;) q8 \8 y1 I8 g* p1 u
5 ]' I5 F( W4 c: Q- ~8 A
;; Initialize the display by giving the global and patch variables initial values.
$ i% u, X7 R5 m8 r) o7 n; E5 W;; Create num-cars of turtles if there are enough road patches for one turtle to
; G. m7 z2 N4 Q4 b  ^1 F;; be created per road patch. Set up the plots.% e+ p* [( ~" _! Z
to setup5 T' G, E: q8 v; J2 H& n
  ca- P. k# k' F9 x+ |
  setup-globals9 ]1 }3 `. o& B/ x; D
8 R7 H, c6 T6 Q. f* P8 f
  ;; First we ask the patches to draw themselves and set up a few variables
; K7 d& K2 p9 z( M  setup-patches
' e- y) A, G  p0 I% d+ s  make-current one-of intersections* E' Y5 |$ `3 h# k( v
  label-current
' _% U* s- Q% M4 b( i0 w! P" ~4 K) f( _: \/ x, `. g
  set-default-shape turtles "car"# m3 J* a) A, `* K$ P

3 D$ H) ?  s; @/ Q5 z9 ?. d" p  if (num-cars > count roads)- V0 I5 D! H: f! r6 b5 M
  [' r/ f9 {3 R) L) M, J
    user-message (word "There are too many cars for the amount of "
& I9 i6 j8 L' T                       "road.  Either increase the amount of roads "
7 k" H. F! L/ K# r- @- q! L% @                       "by increasing the GRID-SIZE-X or "
/ i, i5 _1 K; G' `. N                       "GRID-SIZE-Y sliders, or decrease the "
- x# R( u: G2 h4 o+ d0 h                       "number of cars by lowering the NUMBER slider.\n"
. G9 ?. o/ a  S' O! T" Q" @                       "The setup has stopped.")
- l7 V3 t3 k; D- V    stop2 S' J4 y8 \2 n7 I, k: b: k
  ]
- \0 J$ G; y5 O6 @0 K( \: Z, P6 E; |" K( q
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
" n! T! H) j5 ~. I  crt num-cars1 @9 m* Y8 D. ^- u( v' c1 K/ T
  [
( a1 s  k# @4 R2 H6 ?    setup-cars) D. D2 j& a& r7 R
    set-car-color% b1 l9 O& s1 c' H5 K3 j8 g  G
    record-data
/ [( y9 A1 x  T, N  ]& ^7 n* M/ O% S* V
) r: o. l/ G9 N) r9 b0 v
  ;; give the turtles an initial speed
! U4 E/ d0 d  ~2 r, r5 U  ask turtles [ set-car-speed ]% P& ~3 i2 b6 L6 }
# ~0 R5 A( e; a5 e
  reset-ticks
  g0 M# z. b) B' c7 R* [end
3 C9 B$ L- S: N4 g& l( `1 y8 i$ y6 @' I. P4 j- P8 ^
;; Initialize the global variables to appropriate values% N% J. K# o. D! |3 h5 G7 M' B
to setup-globals
, }! U: M  j# q7 @. y  set current-light nobody ;; just for now, since there are no lights yet9 {( y6 D0 D( F
  set phase 0
2 B" \1 c; i: `3 H6 s' E  set num-cars-stopped 0
! l$ d- [" w5 q$ ]  set grid-x-inc world-width / grid-size-x% j& k( h: d) e
  set grid-y-inc world-height / grid-size-y
/ _. |7 _+ I& \2 w; u* K
2 }8 |7 d. h7 j3 ^  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
6 F- f- h* n  ]+ h& U  set acceleration 0.099
$ M0 d5 O" i" U+ Pend0 F( `8 w- Q0 ~+ O  \2 J7 o9 a

+ b! f; ?3 k* u; F5 B;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
7 ~" }3 m  x! `% Y# y( t" j% M;; and initialize the traffic lights to one setting
8 v6 T- J$ e+ D6 Rto setup-patches" e/ G' A& }! O) K; H' N. c
  ;; initialize the patch-owned variables and color the patches to a base-color
# n+ _& i, @6 X; N+ t3 Q( I4 _  ask patches1 p3 U7 F8 J6 z' g7 G
  [% `, U( z# F& E( ~6 \- l
    set intersection? false  ]0 t; X2 ~% w5 k$ e; s& O
    set auto? false( K) M- F$ N9 ?2 r  N- {( f' B
    set green-light-up? true
7 K7 m! C' U  }0 \    set my-row -1# h; c9 k( b. d8 p( M$ G
    set my-column -1
5 }8 j  b4 l' S4 h3 o    set my-phase -1  x8 `4 W+ l) c2 X0 ^
    set pcolor brown + 3$ }8 _& a" b" e  Q9 |- h
  ]
: M3 N: n4 L$ G) |# c# r
% T# ]: z% e( @  q  ;; initialize the global variables that hold patch agentsets
7 S, g' l, A5 @  set roads patches with; D' n4 a, S( ?3 D4 e+ w
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or- U7 @% c6 o7 y! F( w' @8 `8 ~
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
# G, w" E# D( ~' N1 E/ m  set intersections roads with
8 h4 V! Z8 a' U1 N    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and& ^* f( C" j2 Z9 I! y7 K; }" q
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ J# y$ H8 _7 O0 [6 d' q. Z% |2 Z

( l% M2 l& X. Y  ask roads [ set pcolor white ]
, _8 ^8 B  f! f    setup-intersections
7 i; C. F1 d5 \: H6 S/ p. qend4 S2 j0 u3 K- G/ t& B8 E7 i) @
其中定义道路的句子,如下所示,是什么意思啊?0 S( J1 Q. j4 x- T
set roads patches with
& G$ h0 \" J2 e, [    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
1 n; L3 }2 f6 M( k    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]" T) f/ W. _9 U9 O  H1 I! d
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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