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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。/ a! M# [" M5 \/ r: E. X) F" C
netlogo自带的social science--traffic grid这一例子当中,
2 Z% a# B0 W' G" ?globals
4 `! w/ \* D& B# i, {" P[
- I. ?$ Y4 r' Y' M( b8 n  grid-x-inc               ;; the amount of patches in between two roads in the x direction7 O. |: K" x# M1 j* q" h
  grid-y-inc               ;; the amount of patches in between two roads in the y direction. N( _$ {' \* a* {0 {
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
' H$ H1 ]5 Z" R) I# h# R& N& v                           ;; it is to accelerate or decelerate
/ B: X8 s( ?  P! w4 o  phase                    ;; keeps track of the phase! w" M8 t! ~3 c# M
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
4 w: v' f! p' _4 B3 ^; K  current-light            ;; the currently selected light- r/ ~) ]! S' }% K; M7 R" H1 P" h

+ r, w  `2 R' p7 s$ t  ;; patch agentsets) v& x& L/ ~0 Q9 u' D0 n* G* ?
  intersections ;; agentset containing the patches that are intersections
( O# P- \8 L# m0 m" R8 n$ C8 P$ f  roads         ;; agentset containing the patches that are roads
- |/ z# D' S2 q% j+ E& t$ r]
. G' d0 T% `6 ~7 I
8 }- f' i4 G0 ^turtles-own! {) h6 S6 w5 q
[
8 f6 f' J4 f  j1 Y' s  speed     ;; the speed of the turtle
5 m% N3 |9 r0 A  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
) I( ^4 E/ G: c/ |# U  s3 x  wait-time ;; the amount of time since the last time a turtle has moved' Q! g! x2 _4 C8 }. C8 E5 v
]
( R( [* M4 T" I$ M! q& ?5 ^# N+ K2 V6 H  J; U
patches-own
& b9 a! W7 J# Z$ Z( A! U[& ~& |  V1 _  z: i, {, s8 P
  intersection?   ;; true if the patch is at the intersection of two roads( D8 `% M5 K% Z2 Z
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.2 T& i# ?" z4 x  E. U5 z$ N: x! |
                  ;; false for a non-intersection patches.
' s: {1 C) U, L/ U7 ]7 r: r- K" L  my-row          ;; the row of the intersection counting from the upper left corner of the
2 R& h3 [& `  j5 F2 |( j  x. b+ s. R                  ;; world.  -1 for non-intersection patches./ X! D* ^( ^+ j: m
  my-column       ;; the column of the intersection counting from the upper left corner of the- ]; x2 }/ r9 ^0 G( C
                  ;; world.  -1 for non-intersection patches., ]1 s% S0 i' f# T
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.4 P& V: o3 o9 y3 R) p
  auto?           ;; whether or not this intersection will switch automatically.9 N& ]1 W7 P  A; V6 l% j6 q0 f) D2 B
                  ;; false for non-intersection patches.
7 B  o) ]% [; `; Q, o& l]
( e0 ^! `6 j% y# ^2 ]# B  c) J7 B
) l) R: J9 X/ c9 t( n6 |; a4 o) f5 e0 ^! Z# ]7 u$ C: E' k( O
;;;;;;;;;;;;;;;;;;;;;;
7 v% }: y& H9 ]& i6 q;; Setup Procedures ;;6 f) S" W. p8 a/ d; ]! \
;;;;;;;;;;;;;;;;;;;;;;) i% X! b6 D3 T7 V
8 |+ u  ^4 u$ I6 r5 f4 o  y
;; Initialize the display by giving the global and patch variables initial values." {- X! J- p3 Y6 i
;; Create num-cars of turtles if there are enough road patches for one turtle to) y( D7 _# `) B. S) _9 }+ h7 R
;; be created per road patch. Set up the plots.
) w3 S& i: m, ~7 n' B  A  s& Mto setup
: ~+ `; j# g6 R" ~3 b  L* G/ h  ca8 w3 j; e6 Q% R, n  w# e
  setup-globals, A8 V' C- I2 y" b$ F

2 e/ c$ K- `' @. L1 j  ;; First we ask the patches to draw themselves and set up a few variables. o; `- ?9 {8 A( V$ C, A" y
  setup-patches, {( R8 o& s5 k
  make-current one-of intersections& a9 T3 q" i: S$ G2 @( e! m
  label-current
- J9 f4 Y- P3 ^# N8 F1 o' E' ~# z" S: J
  set-default-shape turtles "car"
+ z7 o+ `  f% r9 ?8 Y! l- X3 ?  p1 ~- v- V& U
  if (num-cars > count roads)( X3 E9 C. l6 A  O# W+ r
  [
4 _: h. P0 P" n* T+ K7 T: `. l, s4 ^9 {    user-message (word "There are too many cars for the amount of "
' x2 x* Q7 h- d: q: z2 [) ?# |                       "road.  Either increase the amount of roads "
3 n7 \6 `+ ?3 ~; w  |                       "by increasing the GRID-SIZE-X or "  w! P" G3 ?2 a7 R' h  A7 @
                       "GRID-SIZE-Y sliders, or decrease the "
% o8 j8 l6 S% B4 `) h! N2 o                       "number of cars by lowering the NUMBER slider.\n"5 q* s( a( Z# j! t% w
                       "The setup has stopped.")) n  y* V5 \& h& T' v  R
    stop. w$ u9 E0 K$ ?" G% c/ Q
  ]# h8 i0 k2 x5 n5 |* o& ]

# o* i" x* |, f6 d, r7 O  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color, |* N- n- t% _) W0 ^% d
  crt num-cars. ^( J! S8 ^; f+ q3 e9 c/ h
  [
/ E' \/ s  P' S    setup-cars! M4 q" b8 H+ \+ ?1 `: x$ |
    set-car-color1 [- k' t- {! F, u
    record-data3 k% @+ j/ s0 h
  ]
9 b  Y: _/ s: {" j/ B0 r3 u" e
; f5 k5 E6 f# p# T5 B  ;; give the turtles an initial speed. f5 Y1 X$ w" \6 [; U  e% r5 ]
  ask turtles [ set-car-speed ]4 H4 N0 y6 c8 M

- H; S9 ~. R3 B  reset-ticks* [0 g# B2 p9 D' _: Q
end# H9 A" b) V4 C. w& p% Y1 V: s
5 L9 x5 q% S  A5 o5 ?/ ^* f
;; Initialize the global variables to appropriate values* k) X' q- {( c+ c
to setup-globals% g! W) x& E& ?9 Z
  set current-light nobody ;; just for now, since there are no lights yet
* D( S0 i7 H4 ?# b# n1 z  set phase 08 R2 z; J$ t% l  w
  set num-cars-stopped 0
9 r, r# D' E. w* _( P  set grid-x-inc world-width / grid-size-x1 n0 l8 x+ z0 u& k+ X! F( C
  set grid-y-inc world-height / grid-size-y
2 H7 ?7 q& g7 V2 n/ A
8 Q% Z1 _' y7 p. T% g5 g6 {  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary. m- H5 y$ Q; L* _2 r+ o1 H# E
  set acceleration 0.099
3 r8 o5 i$ a& ^: H1 N& e9 N0 L. Lend
0 x- U: K, m% u, f: ]1 l  K# _* @/ f* t2 n9 u% L1 S
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,; P9 s4 E0 I9 q: H
;; and initialize the traffic lights to one setting
2 Q7 Z8 Z/ C) i: o. E7 X+ ito setup-patches4 k) }5 {  E- N0 j8 i2 j6 V, F0 v
  ;; initialize the patch-owned variables and color the patches to a base-color
0 z. e. j" H, J- A# c  ask patches
- G) D( X6 a) ~# u; w  [: l8 k& T6 n+ p- ^5 g) G9 T0 V
    set intersection? false
$ W0 f8 U* ]* Z! _' A9 _% l    set auto? false  M( f/ Y, C' @! E. l& [- B* E- c% a
    set green-light-up? true/ D6 N  r# F) ~( b
    set my-row -1
: I. _1 `4 }- Q    set my-column -1
5 E# J& M# `9 B" t9 m    set my-phase -1
& m) }8 D5 Q5 R! e' D1 p    set pcolor brown + 39 @. D4 {4 C& T& z
  ]3 D4 c5 X& d3 d* g

% g. t* s1 U3 U' z) Y! e5 F) E  ;; initialize the global variables that hold patch agentsets
. X5 `0 ^5 S& L4 c2 A- E  set roads patches with
% O$ M, L' Y2 k. ]2 O5 {: I    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
$ j5 x" x; g7 ~5 N. j6 Z    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
* _4 ~1 v! Z" I" i/ t: d  set intersections roads with3 @- Y( K: Y1 y" ~/ a: y0 o9 S
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
" [6 v4 Q6 r* N* J    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) n3 s0 ?/ _6 F- Z- q) V) {/ ]
5 `4 }, r& Q6 X$ z3 s# y9 B
  ask roads [ set pcolor white ]+ ]" u! v- d+ I0 X+ _% E  T
    setup-intersections
& s- J$ M' z$ }3 Yend& {' p" v. i$ K: O3 T9 G2 N
其中定义道路的句子,如下所示,是什么意思啊?. d" v  ?2 r, {8 k6 D7 _  y
set roads patches with! _3 j6 S. {$ X
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or+ W! V  ^- w9 F
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]0 I* b$ q0 t, y2 u2 \" Q2 E& ]
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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