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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。/ M. }! k2 F% q0 Z
netlogo自带的social science--traffic grid这一例子当中,' o$ N! e, M# s( E2 P7 B
globals
6 Y' ^* [% t; m# O5 V  ?[* y0 K0 t. y  P# R
  grid-x-inc               ;; the amount of patches in between two roads in the x direction+ ~4 R' t5 ]. h$ o# S! [
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
3 Q/ [& x0 d* j  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
" w4 ~9 `) _  H* d3 {1 Q                           ;; it is to accelerate or decelerate
9 W! y7 b9 e  H1 S; d; ^$ S  phase                    ;; keeps track of the phase
3 `) v0 H4 o( W, `& V  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
% S# ~. y9 X, W1 b  current-light            ;; the currently selected light/ C  _. n6 J, a! D4 M
  R8 }8 [% M+ W6 s$ Q, S& Q
  ;; patch agentsets
' S' r* w/ ^0 d' c  U' A  intersections ;; agentset containing the patches that are intersections) G1 L( @2 N8 D# C* Z# e: D0 V" p
  roads         ;; agentset containing the patches that are roads6 z3 H8 a* q; _
]
6 o, T6 o, U3 c
, ?  K& H" {% k( p' sturtles-own% {2 U  N: n; C$ f0 e
[
7 p+ B1 O$ z6 l. z  speed     ;; the speed of the turtle
7 ^, H9 U; O( _. N- I  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
5 _- K) o* h# I3 i5 }  wait-time ;; the amount of time since the last time a turtle has moved
, l0 ?' W7 I4 q- V]
- O- I4 G- z' L/ A
+ j0 J8 ^3 o- l5 H1 V" Lpatches-own6 T5 c$ F9 t5 I1 v$ P2 ?. W* n+ b
[
) E( P5 Z' O2 o5 g; @& W  intersection?   ;; true if the patch is at the intersection of two roads
; k1 w9 s' M' @  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
, G: p0 b! _1 A  Y                  ;; false for a non-intersection patches.8 o; D- p8 n1 q. A  W- \
  my-row          ;; the row of the intersection counting from the upper left corner of the
- ~  K# Z  L! t) S. {* d6 o( g9 t                  ;; world.  -1 for non-intersection patches.
; L" i9 a* t6 B' N4 c/ e# K# G. @/ A  my-column       ;; the column of the intersection counting from the upper left corner of the
* {& |7 z# C8 u6 c% ]9 T. S( d& Y                  ;; world.  -1 for non-intersection patches.+ @  P6 c  j* s  S7 r
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
6 b3 D! J, r# {4 c) N  auto?           ;; whether or not this intersection will switch automatically.0 W$ b# c1 T% J$ J& w
                  ;; false for non-intersection patches.0 x( s$ G( p2 O/ y6 O1 _
]
7 c% e6 g; U, @$ y+ n; y
0 ]  B6 ^8 Y$ T  Z( ~: x/ X1 b5 C" D$ P) l$ Z, g
;;;;;;;;;;;;;;;;;;;;;;/ Z+ P5 n) ~% D. T
;; Setup Procedures ;;+ _% k, }, {3 P9 ~( @8 [! r) ~
;;;;;;;;;;;;;;;;;;;;;;
6 \7 m" T" L4 m( {! @! y
* W" `1 o8 i' j$ b% l;; Initialize the display by giving the global and patch variables initial values.3 e4 r; R1 N6 e4 T7 {0 w( D
;; Create num-cars of turtles if there are enough road patches for one turtle to. ~( X0 f/ n$ {" r
;; be created per road patch. Set up the plots.
' C! i, _1 C; Eto setup
3 L0 L& ?1 D+ ~" N* U  ca
% i0 o7 D3 B2 W% x9 }5 l" V  setup-globals  J3 c8 o5 D: S

4 N/ e, ?8 q: J+ }  ;; First we ask the patches to draw themselves and set up a few variables
; X+ |" X& X) S  setup-patches
3 G1 p6 \+ v: r  make-current one-of intersections
" e3 W! a  `: O  L9 B# N9 ]  label-current
4 t* t# \3 X5 }% l; d+ N% u, x
( \. L2 i3 v' D* k  set-default-shape turtles "car"
( K4 G- `% l) S) H8 L# d% @+ I/ Q, B
  if (num-cars > count roads)2 K, X+ z8 L$ _8 k% {8 a
  [
* t1 R2 f/ U0 ^    user-message (word "There are too many cars for the amount of "3 Q3 W: u4 k' M. @" v0 c
                       "road.  Either increase the amount of roads "
9 r* [! z0 _  k6 a1 m8 ]$ h                       "by increasing the GRID-SIZE-X or "3 `9 _- w4 I- o
                       "GRID-SIZE-Y sliders, or decrease the "
& g3 D% U1 ~" z; C" `                       "number of cars by lowering the NUMBER slider.\n"; }  R" i& ]$ g& D
                       "The setup has stopped.")" `1 r9 V0 W& [( V# @8 J
    stop
& X+ S; S! n7 H. i  ]; A% b% \4 Z0 M+ j2 b& E3 C

) N. Q% K- }& E5 n9 m  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color# H5 z& y3 M0 n1 K
  crt num-cars
5 O$ L0 x; h: u: r* a  [: u) g) z- k( k( j) l, `. ~
    setup-cars
4 b$ k- \- h) J! r7 E9 T    set-car-color
9 K$ d% P9 a6 n- u) ]' ]    record-data
8 {- J: \/ H5 r1 W6 G0 o3 _  ]
7 i, n7 U+ x1 v. ~/ s
, c& s$ n+ P2 a9 l  ;; give the turtles an initial speed
3 m( h3 h( ^7 P' c9 X1 _5 J  ask turtles [ set-car-speed ]
! _2 T8 b9 g- o7 s
1 P0 S5 J7 ~3 z" s& C  reset-ticks" a5 Z4 c1 [3 M6 M+ F
end
# w2 L4 S5 i6 \/ R5 ?
1 I0 u, k2 z9 B/ x0 Y' A! \8 K( J0 u;; Initialize the global variables to appropriate values
5 q: J* t, p2 a' ]" ]1 Gto setup-globals
$ Z8 j% [: a' s) Y6 _; U& L; Y' d  set current-light nobody ;; just for now, since there are no lights yet
% H: |) j" v; k; b! U8 l! J; P  set phase 0
9 x+ D5 {7 ?- b  set num-cars-stopped 0
/ Y+ u( Z* ]3 [) }3 n) D9 Q  set grid-x-inc world-width / grid-size-x! [0 |$ t6 U1 P# @
  set grid-y-inc world-height / grid-size-y
  t# I( L5 f- n) Z3 G& w: I) @& h0 k6 n
5 N* E; `9 d6 A* |9 s9 b, q) V! H  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary/ G0 ~! T0 v' {+ u  B& P" l
  set acceleration 0.099
% D. A+ c  t: S* \. E1 d/ Zend2 ?" G: j# X) N" P
- g$ F! c4 d% A& J9 T; y9 y0 [
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,6 k9 Y, S" b9 @, z
;; and initialize the traffic lights to one setting
8 @8 I2 G2 ?% l& O' V; |to setup-patches
& w5 `" C- j* a" V3 L  ;; initialize the patch-owned variables and color the patches to a base-color: x) U& l8 r! K& }; {" n
  ask patches
9 C" K' q; p' U! b( E- _8 D! [. Q* D  z  [' P- y7 H* F- v6 B& Q7 I' i
    set intersection? false( T. i; A0 d; {: V! S- X  `' V" h
    set auto? false6 U1 ^3 k7 ~% s+ m& g9 L6 w/ r- ?4 v
    set green-light-up? true) w  I4 N( }' G6 k/ }
    set my-row -1* ~% @4 K! @+ @/ R
    set my-column -1. x. B3 I8 T4 @5 K/ J
    set my-phase -1
, L: H  S7 \1 d2 r( O    set pcolor brown + 3# G/ S, d; }' h* K) R! u
  ], i1 |* H/ r' O+ g

( `% f9 k6 N/ a, u: F  ;; initialize the global variables that hold patch agentsets% T# F8 w4 p1 D9 S: J) [
  set roads patches with+ u! n9 C0 U6 _& P0 Z7 {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or- R" z8 t, _! c3 Y) p* M2 c; c
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) b" z, G# J$ r+ r! `
  set intersections roads with- I5 h# c% D" B& ^
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
* l4 k* Z4 J: m6 y    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]6 N6 I% l* ]; y

8 u( [4 V9 }0 f5 O( t  ask roads [ set pcolor white ]
! c2 U+ o! M3 |& x+ o0 d    setup-intersections4 J9 _- y% @0 U  L
end
3 d5 f7 U4 o" H3 c/ d其中定义道路的句子,如下所示,是什么意思啊?. C5 }: C+ L9 x
set roads patches with6 d! n9 t, z  X+ x
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
; x* i0 ^+ j8 Z. u& k    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
, X9 Y7 C& H# k" ?% K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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