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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。
. s+ A$ s! L: Q7 {netlogo自带的social science--traffic grid这一例子当中,
0 q9 ]) [9 }  [% N- }globals* |; O+ ^- z: L- T
[
8 z; n8 j+ e& B: L5 X8 b  H  grid-x-inc               ;; the amount of patches in between two roads in the x direction# H) s0 p0 b4 K" o6 H% o! l/ z
  grid-y-inc               ;; the amount of patches in between two roads in the y direction  Y$ L) w3 b! \- L3 t0 d
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if; @! O: I6 J! L: M. ^3 R0 h
                           ;; it is to accelerate or decelerate
! b1 `/ Y, d+ u5 y  ?8 n  phase                    ;; keeps track of the phase  e# V: v* R% Y, E( H9 w
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
5 q# w  |6 B  m( o. H( `4 u  current-light            ;; the currently selected light
  F4 Q, u) ~1 M6 P; N& J! O7 m; A% \# |: M% `% \, K5 z( H
  ;; patch agentsets; |& g. g  O( R, B  u: R8 R0 a
  intersections ;; agentset containing the patches that are intersections
" c1 y) _6 Y+ z2 I  roads         ;; agentset containing the patches that are roads+ o) P2 o5 t% O) ?
]
) n. ?- g7 \7 p6 k  L) d
5 L; u% J" H. [/ r9 ^0 {turtles-own
0 |, u; ?3 s$ k& l( |* X+ S9 H! ~[* K, J$ A( b# W( N. A
  speed     ;; the speed of the turtle
1 I; A$ y& D$ `, F) I/ s2 P  up-car?   ;; true if the turtle moves downwards and false if it moves to the right9 A' v6 k! `! e* B1 Y" c6 X% c  E
  wait-time ;; the amount of time since the last time a turtle has moved6 O6 \1 C+ B. j6 }9 r
]
+ Z: X% ]: }4 ]# k$ z$ Q( q+ _' O( [# j% _/ [4 r/ m
patches-own
. j8 |" i' o  k+ _5 f* o/ _- J' E[! O7 ~; C( m; Y$ M7 ^! Y
  intersection?   ;; true if the patch is at the intersection of two roads: c+ q& N5 [0 c# q4 f  `7 Y* y
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.' D' u  x' q& e& J
                  ;; false for a non-intersection patches.
5 [; W! n0 `1 F- r6 }! G8 u- c  my-row          ;; the row of the intersection counting from the upper left corner of the6 G0 a* L! r2 G8 u  M6 |  b3 ^
                  ;; world.  -1 for non-intersection patches.' b2 c" K0 B' r* Y+ l& _
  my-column       ;; the column of the intersection counting from the upper left corner of the' t" |3 i# M3 a- [6 I2 ~
                  ;; world.  -1 for non-intersection patches.# e& L6 T- T# }4 T  i/ b) Q, v, j
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
# N' {6 w: E% s4 q3 [0 c* R: @  auto?           ;; whether or not this intersection will switch automatically.
! X% l) L) O; d6 f3 S  c2 l                  ;; false for non-intersection patches.
5 z1 r) C9 U7 B' Y: c' W4 M]
1 n6 t  A1 r- {5 u6 b* ~9 p6 t- f7 Q* j9 O: @4 R- z
: C2 F& Q& z; R. J! N# l& X
;;;;;;;;;;;;;;;;;;;;;;) h8 ]4 L2 i) H" e" h, z8 ~
;; Setup Procedures ;;  q4 [6 z2 x5 ~4 C6 `8 x- I
;;;;;;;;;;;;;;;;;;;;;;
) e) m7 R+ D1 \1 b4 U9 R- h1 I  y% D7 ?5 A& w
;; Initialize the display by giving the global and patch variables initial values., Z: f' `* {% o/ N. y3 e! Q4 M
;; Create num-cars of turtles if there are enough road patches for one turtle to6 i4 e$ }* ~8 M$ q4 B6 x
;; be created per road patch. Set up the plots.
$ t" N: K1 E- O! N! p/ G# S: z& eto setup
. T5 z, x/ [0 X+ ]- D  ca
' N; ?9 ^" U; V  V7 N  K. {3 K  setup-globals- r5 [7 l5 }  [" ?. \( e1 O5 @

1 ~& i) c% ^5 d( @' K# }  K  ;; First we ask the patches to draw themselves and set up a few variables5 A4 V: y7 a! `  y
  setup-patches
: ^$ p1 L; @. c% R6 T  make-current one-of intersections
/ D6 a, f. `' p  N( c' l3 o- J  label-current
; _+ T2 [. X& {4 x+ H  Q- @# c7 w2 a, ^9 \1 L5 K) T( h/ O
  set-default-shape turtles "car"
0 r+ n+ c: n6 c4 Y0 c) O  b; c( W, e1 B% Q. L/ L$ p
  if (num-cars > count roads)
! n  v+ F& L$ n- b# `( R" [  [- ^3 A. y( m8 I& ]( c2 P4 f
    user-message (word "There are too many cars for the amount of "
) F0 n* k4 V1 c& ?                       "road.  Either increase the amount of roads "
) g2 N; u1 p/ v4 k/ R4 T2 G, P                       "by increasing the GRID-SIZE-X or "
* h0 h7 j3 _) [* {" ^                       "GRID-SIZE-Y sliders, or decrease the "" `- `9 ?# [7 x
                       "number of cars by lowering the NUMBER slider.\n"$ j+ C. P' o( w4 ]" ^5 b( B" G. K
                       "The setup has stopped.")# A1 z# \; }& k* [  O2 N5 G  j
    stop6 `, r0 E! `) U! M3 H0 h9 p3 c9 U
  ]
7 N$ I3 d) j  c
+ N+ |- g( h" B* Y  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color; m# x7 a8 `/ r9 |% Q
  crt num-cars
' w* A( b9 x2 X; ~. O  [
" d: R$ _9 T7 b- j2 _$ @* S    setup-cars
  }" w9 N# p$ Q4 B9 [: R    set-car-color$ j7 g- N5 f* L! T4 P5 u% N
    record-data9 z( G4 ?/ ]. y% |! Q
  ]3 c$ _# w0 J; a

5 U4 C+ O  C( P' J% r) V5 K5 H" h  ;; give the turtles an initial speed. f0 T6 l' b) c5 ]" ]8 c
  ask turtles [ set-car-speed ]
& }; B" J( M0 v2 @& X1 L$ w- H# A* G+ u6 t/ I2 e
  reset-ticks
. L' ]+ T5 l9 y0 \7 W& Lend( V7 m9 ~* o. @& `  J
- a- [" ?4 L; l; b
;; Initialize the global variables to appropriate values
/ Z4 S; {" K% a/ a) k) nto setup-globals) w# w  l& j& v. d* ^" Z4 J' y; l
  set current-light nobody ;; just for now, since there are no lights yet
% \& U: B) s% s; g4 e3 ?' F$ K  set phase 0
) u% o" h8 l/ }9 J- Z  set num-cars-stopped 00 ]7 r+ I; P8 R+ O- C
  set grid-x-inc world-width / grid-size-x
, _5 Q/ T6 Q! X5 |$ e; G& `- }  set grid-y-inc world-height / grid-size-y
, p5 d/ \9 N5 W3 f" S+ O8 ^2 O# a# K/ d
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary7 {0 B  F( O2 Z' [6 R* M
  set acceleration 0.099# T% j' O; a. J) E
end
1 f( j% ^1 n* {# ]
7 R6 C/ M, _' O; U;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
  G* d/ D- d) w; B2 k;; and initialize the traffic lights to one setting
& y4 O) b+ e' Q, _6 ~to setup-patches
/ S9 P: N, W- K* [* B  Z: ]( x5 I0 a, k  ;; initialize the patch-owned variables and color the patches to a base-color
1 z) G. T5 `+ J8 `  ask patches
8 j7 D. }- ?. a9 G1 C" ], Q) i  [9 F1 R. F- I6 b1 @$ Z# N5 V
    set intersection? false
3 l2 Z4 a: e: W) t    set auto? false
' ^3 W* ^; ^' ^& s# A  \3 Y5 |; U    set green-light-up? true3 z4 l, {, ?* o) U$ q$ _
    set my-row -11 {- k! C  m9 H; F! K. h
    set my-column -1: H: K/ Y( ~, C8 m& h, E' B, Q
    set my-phase -1
* `2 L0 N) X( v    set pcolor brown + 3
/ ^; ]7 Q# H% `8 e/ G& ]  ]
# B; ]; S: T7 D  Q9 `
: X  o) u% H5 A% u& f) s  ;; initialize the global variables that hold patch agentsets/ A* M" ~6 f  E! x; b  D9 o
  set roads patches with
* @1 `4 H, n( O0 \* _/ {" j    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) _% A. A3 ~# A2 S* {) |
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]" n# v2 ]8 q0 p2 W3 {* g
  set intersections roads with( G: v+ [! |, _# N
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
  b3 k( \) S9 C5 L8 ?# s* J    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]8 f) K7 z- ~2 g6 L: U

( ?+ c+ a$ o0 ~. x; g* j) N" t, w  ask roads [ set pcolor white ]
1 [3 R: H# D2 C0 ?2 E# g% d    setup-intersections
- d* ]3 s; ~) Q: `end' h$ i+ ^, ~' X. u" I
其中定义道路的句子,如下所示,是什么意思啊?( l5 d  ^  r# s4 P& W
set roads patches with( u9 s  V% T: u9 U3 G# V4 e
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
9 @! K( d/ n4 a    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
# n3 o: j4 H1 h' u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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