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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* w; b  t$ E8 B1 `, bnetlogo自带的social science--traffic grid这一例子当中,1 x+ A+ |. X  j) W( N
globals" g4 U" }6 P* T) P: {+ Y
[) J" ^3 o0 J( i
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
( R! N% N; c* v4 G  grid-y-inc               ;; the amount of patches in between two roads in the y direction
% f' ?; w0 c( _- n4 h0 d  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
2 M* M$ t. }" V4 m' f  @. O' l                           ;; it is to accelerate or decelerate7 k/ \' m+ X9 Z; e+ y5 n+ ?
  phase                    ;; keeps track of the phase3 l+ _: g* \# \+ ~" n4 M  V; O& b
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure5 b4 p' |- H5 t& J( V  R6 d6 E
  current-light            ;; the currently selected light
/ K* \2 K4 m. `8 u4 [9 z. s$ X" j. n
  ;; patch agentsets# ]5 ?$ F/ d3 f# }; O0 I
  intersections ;; agentset containing the patches that are intersections1 r$ a$ w; j" K
  roads         ;; agentset containing the patches that are roads
+ T3 r7 @/ v6 y& r]
5 \' n2 ~- K" F4 P2 F- I$ Q2 V5 p" u7 A6 ]  a/ e( P9 \
turtles-own9 L: f" C6 g; _
[4 B! `# P. ^- f' h- P/ s
  speed     ;; the speed of the turtle
) x5 t3 x# [+ ?  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
1 G7 W% I! |$ C, D" c  wait-time ;; the amount of time since the last time a turtle has moved
1 s6 u, a$ ^2 s) p5 P$ q, n]0 O" Q" s# a1 _. E4 U; [+ \- [* O

; L7 _& l; P' ?- `, ]patches-own
' J& G% c+ h9 z/ T6 T& g[
/ n$ N/ `0 q+ I! s% v8 f: I  intersection?   ;; true if the patch is at the intersection of two roads$ l' ?% D3 h; [/ L; N
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
* Y8 ~4 ?9 e" B! _; m                  ;; false for a non-intersection patches.
$ W6 j7 k" \; h, E  my-row          ;; the row of the intersection counting from the upper left corner of the
: A7 v0 i; P8 t# i) @) y; [                  ;; world.  -1 for non-intersection patches.
; u. @  ~+ Q  ~2 u  my-column       ;; the column of the intersection counting from the upper left corner of the
6 Q* u0 Q/ ]: l% W* _6 p                  ;; world.  -1 for non-intersection patches.
" o) K; f7 X* r. b3 R/ V& A  q  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.* J& l0 m3 l$ r6 w
  auto?           ;; whether or not this intersection will switch automatically.8 x; a- |& W  s' d& h
                  ;; false for non-intersection patches.
: y$ u. B$ D9 o. q]- b" q; X7 D! W: c/ c
' ~4 c, b- Y7 l2 B8 M! ?

2 Y, r: L' j# p+ X;;;;;;;;;;;;;;;;;;;;;;
- P$ u8 V1 q1 v& I;; Setup Procedures ;;
. G- ]+ H2 v! h. H6 j( {5 W;;;;;;;;;;;;;;;;;;;;;;
6 L% C. H; J( Q% J: P, R: G2 d' l3 z, @  }2 G1 p" l3 z
;; Initialize the display by giving the global and patch variables initial values.7 k5 I$ W9 s# Y8 E/ K( {$ |
;; Create num-cars of turtles if there are enough road patches for one turtle to
/ u2 m( b% a, u+ a- l4 }% G;; be created per road patch. Set up the plots.3 S$ B! O' U! R- o  n5 o3 G% J
to setup
) U6 ~1 J6 X: c* D; W9 W  ca, C0 s" E; B9 l8 _* }
  setup-globals' }0 H) j% H8 ?3 c  i( h9 F

7 n" \/ W8 Y0 Z  ;; First we ask the patches to draw themselves and set up a few variables; p& k2 |+ k* B4 w" I
  setup-patches
2 E* v" Y' j; r' P( a  make-current one-of intersections% H7 [. N4 `  i1 P, `& O7 J( k# M
  label-current
, a: p; T; x1 v* T* ?/ V8 p5 p8 W& T7 w
  set-default-shape turtles "car"% ^( L5 b+ r/ N9 @2 i$ K- _
" r: H8 [, D+ V5 p1 u; t, w
  if (num-cars > count roads)
- O' K1 r0 T% }: w; A  d  [, _0 c/ R. ?1 f# g  M  y
    user-message (word "There are too many cars for the amount of "
4 c6 V6 f) B6 I! x0 Q5 b                       "road.  Either increase the amount of roads "
) Q* J- r# ]$ Y4 M                       "by increasing the GRID-SIZE-X or "
# ~4 ~/ i0 l2 w( f                       "GRID-SIZE-Y sliders, or decrease the "
; c$ V" A) L6 [                       "number of cars by lowering the NUMBER slider.\n"! r. r& Z, ?7 r
                       "The setup has stopped.")" l2 X4 o, |( S+ ~$ @- F
    stop5 y/ V2 T7 [3 i: |" P: V
  ]
; a3 W' S. l' O
$ G" C1 w6 H, F, T; j  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color0 o4 c6 h4 ~; J* X6 H( P. e) ^0 j
  crt num-cars- K8 c: w" r' S/ A
  [" v1 K1 ]/ U% \; g; q
    setup-cars
3 W% z5 S* o* K    set-car-color2 s6 D# u7 X9 n; C3 x
    record-data% s9 ?; o7 d+ ?% F8 T
  ]' u! V4 ?# H7 S
1 k8 ]3 @  C$ s' g( [/ a
  ;; give the turtles an initial speed
5 @, ]8 a% T$ u: y* v3 s  ask turtles [ set-car-speed ]
( r& L+ k) S$ L$ t! i4 T1 V( I; W) f: Y+ u8 z, Q
  reset-ticks+ J4 j; f# s7 b" u/ O5 b* b. z
end. \+ r9 Q5 \& c8 P3 u. S' A4 w

6 O, {2 |# X% d9 D. F! L9 E;; Initialize the global variables to appropriate values
6 R: v6 z8 O4 T, S( w8 uto setup-globals' ?5 `6 J* z8 l6 P) v/ u, i
  set current-light nobody ;; just for now, since there are no lights yet
  Z- l" d" N# ]; [/ [  set phase 0
# E2 V7 k3 A4 C$ ?0 i! O1 C  set num-cars-stopped 0
0 y, b: D( G, [0 a; y% T  set grid-x-inc world-width / grid-size-x; Q3 s. p7 U3 v; ?( F( f
  set grid-y-inc world-height / grid-size-y% B( [3 Y' Y2 M" j+ ~" Y

9 U( \) n7 k: {: ~# O$ p6 l4 A  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
8 X* A% F$ l6 D: D! Q  set acceleration 0.099
0 U0 C: \* k! @( S- J' ]2 u* H* ~end% ?- D& g' {2 R" W% ^/ |0 [
) e0 D7 i0 B+ [9 d# z2 h# Y
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
* N4 |2 p4 ?4 U( x" u& b;; and initialize the traffic lights to one setting
7 o) S6 V2 t% x0 P# U6 s4 K. Dto setup-patches
6 c% f  E: h1 M: P5 N  ;; initialize the patch-owned variables and color the patches to a base-color
& W! |2 S6 i2 f  ask patches
4 j* O9 j( ^) ?. Y) g) S$ \  [! {9 F2 t9 @" ?1 Z# t  {. U0 b1 J
    set intersection? false! W9 w2 s9 O. R* D% R
    set auto? false$ {2 ^0 P) Q5 O/ ]1 _
    set green-light-up? true: Y2 n6 Z$ e6 M% i" B8 N
    set my-row -1" k" l7 `# o& v0 V  B  o
    set my-column -1
! o  Z. S) R$ T5 z+ P3 A    set my-phase -1
, A3 c' N1 F' Q& i7 U& D    set pcolor brown + 3
2 K% q4 ^+ k1 s9 ?! c* _  ]* {, ?8 ?7 W" v/ R4 X- O

" u1 P. d3 \" p' [. ~4 ^7 n  ;; initialize the global variables that hold patch agentsets+ ~; s! S1 w) x3 K
  set roads patches with
& Q" g# }1 K; k8 K. M/ Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or& e% M2 Z1 h" I. z, _( ^( r3 }$ s& B
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
2 }) I2 y/ a  Q, e  set intersections roads with2 r  t$ I+ I9 _7 S/ v9 P
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and- [2 Y$ K" T- f$ a3 y- A/ d
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]; C' ^4 u+ W9 W- [
- g- o3 r3 _5 c& [4 `7 j  X
  ask roads [ set pcolor white ]
- }5 ~6 M* m9 `* w    setup-intersections* G& [0 _% Q  w5 }2 Z. D
end
# S9 E/ s0 E, V- }/ k$ _其中定义道路的句子,如下所示,是什么意思啊?
! ?, c8 C2 A  ^% Z2 U7 K' v- U9 w set roads patches with
) z/ t# ]4 Z. I, u    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
) O) `* I" c) x    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]& g. S: t' }2 M  N# j
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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