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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。5 n3 p' E" I, i4 H, I! x8 q" D
netlogo自带的social science--traffic grid这一例子当中,/ z; S7 B( W5 P  \
globals
, |. C1 _2 S9 k[; G8 L$ e5 r9 o3 k" R  G
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
; l* z3 ~/ r7 e: j) \  @, f  grid-y-inc               ;; the amount of patches in between two roads in the y direction
( D# n) o  x. }9 I  |* T  acceleration             ;; the constant that controls how much a car speeds up or slows down by if5 S$ |' y  v, e+ C
                           ;; it is to accelerate or decelerate  Y8 [  P' z/ t2 T9 m
  phase                    ;; keeps track of the phase: S. {% H1 N9 R9 c, j- d1 [
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure. H! K$ X9 R- t( X
  current-light            ;; the currently selected light, A  w# W9 F7 ~0 ?& @: P

$ S2 X, L5 O- ^7 a9 f" a3 g; c  ;; patch agentsets
+ ]2 X5 q; L/ v3 K! t2 k  intersections ;; agentset containing the patches that are intersections" R2 P& X0 w8 z, r  F
  roads         ;; agentset containing the patches that are roads
# s1 }  H8 o# P' m4 Q! b/ @( z7 _* x]
- c$ B% ?  `- x- S5 _
- q8 j- f- E* Lturtles-own
2 v9 R+ Z* z' Z3 A7 G' c# Q[0 W) e" x  q) D# h2 D
  speed     ;; the speed of the turtle
  i) I1 f2 }3 r4 R' P  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
! c, q7 W2 B) X- j  wait-time ;; the amount of time since the last time a turtle has moved
+ }' v# j( a" X) D2 T; K5 B6 H1 w/ F]
2 i7 _& s, Q& w5 M
( m  c0 \# g* }( F0 z3 a4 qpatches-own
! E5 o0 r8 Q* r[0 _* v# Y1 m7 Q
  intersection?   ;; true if the patch is at the intersection of two roads6 v& v/ ]! c( {. ]' K4 M% k+ S
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.8 \6 z* U4 ?  W# p3 r6 g
                  ;; false for a non-intersection patches.9 q& D. k) W3 A1 ^( n% C, C
  my-row          ;; the row of the intersection counting from the upper left corner of the" ?( ^# j* {7 Z! m4 n/ d
                  ;; world.  -1 for non-intersection patches.  o8 n( A& q" ^7 K8 G9 v
  my-column       ;; the column of the intersection counting from the upper left corner of the
* H. K# k' H; M8 r8 ~1 X4 E                  ;; world.  -1 for non-intersection patches.
2 j  ]. h8 T9 ^  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches., Y  D9 K5 x" k8 s6 F$ o; C& O' o
  auto?           ;; whether or not this intersection will switch automatically.* E- n9 L, M# C- |
                  ;; false for non-intersection patches.
; x+ @7 R% R  b. v9 n  [5 K( q+ z]; Y/ r4 u+ V6 ~+ B' e
/ Y7 w" x7 e0 K

, C, U* p; {# ~3 ~& L;;;;;;;;;;;;;;;;;;;;;;2 }$ E# A; x  a9 k6 j. ^( y$ ]: S+ q
;; Setup Procedures ;;3 R; ?2 t; F6 s4 Q  d, ?, ~" A" q* I
;;;;;;;;;;;;;;;;;;;;;;0 h1 O8 l1 D& ~+ E

& C6 h* s8 u2 q% x2 y;; Initialize the display by giving the global and patch variables initial values.5 F: D- O! q8 c: Z# ~
;; Create num-cars of turtles if there are enough road patches for one turtle to
6 O5 _/ Q! R6 b/ z& j;; be created per road patch. Set up the plots.. X( T: }  c3 t: b" W$ }, w1 U0 o
to setup
! l2 ^. [7 q4 D6 u2 V  ca
' K& ~$ Z) p" a. h2 {  setup-globals
$ _8 ~  u/ e4 ^! `# [
; ~, R' e. U4 w: N9 Z  ;; First we ask the patches to draw themselves and set up a few variables# m+ b# I+ _* g  x
  setup-patches
, a) r+ i: u$ U3 N; V; g4 @( p  make-current one-of intersections
2 E' q8 @6 A+ k- `+ ~) {! o6 ]  label-current
& S9 Y! e% w" u2 _' {
0 A" x/ p, A- h4 R  set-default-shape turtles "car"
# W9 Y9 [1 e+ c, M/ Q" K- I, o3 O7 r3 a
  if (num-cars > count roads)
  p) N) y. |  w  [: b; ^; u) a4 J6 n) p/ r- u
    user-message (word "There are too many cars for the amount of "4 Q1 x+ R$ k; L, t  G$ z
                       "road.  Either increase the amount of roads "
( S1 i& F$ o) }2 J2 z' U! f                       "by increasing the GRID-SIZE-X or "
* v% _6 Y2 n, g1 k7 k                       "GRID-SIZE-Y sliders, or decrease the "
6 x+ ^  B% S4 @3 \                       "number of cars by lowering the NUMBER slider.\n"7 h- A0 n0 b8 h7 ?8 w& C. @' s, N
                       "The setup has stopped.")
2 ?) E6 H( q9 T  w! X* U2 H5 `    stop
8 ^( _9 f. J3 t2 [/ y  d  ]5 W  c' ^  u4 d5 K
# L! P* O( o# K! m# Z% X3 N# x
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
7 h; J& a# _! U. o  N$ ?  crt num-cars3 L+ u$ A2 j: E& z
  [
* o6 C9 l) H" J) w/ W0 G2 K% X( f( j7 I    setup-cars
$ @- g, Q6 V3 E# h4 r8 p8 Z4 G    set-car-color( |$ z3 U2 S% Y1 [
    record-data
- b+ O( K6 R! }  C/ \* ?  ]& ]2 L  m. P& ^) x
5 C1 [8 |" o7 M5 D
  ;; give the turtles an initial speed
; o$ L& @" _  w8 _" H6 Q  ask turtles [ set-car-speed ]4 z- ?9 v1 g6 t' \0 R

0 {7 w- h% L& n: j# I  reset-ticks
2 q3 o2 Y& F: x+ ]+ iend. ^* D2 m* H" {- }

6 J, P9 v3 \- d/ j;; Initialize the global variables to appropriate values' Y: X3 y. T8 i6 z* V. h2 J2 u: D
to setup-globals
! G) ]( _% N  P5 K3 I( b  set current-light nobody ;; just for now, since there are no lights yet" {' a  S' u* _" a! J' F
  set phase 0
% M" T' D- ~' N$ K/ c* h  set num-cars-stopped 0
+ ?( O, B/ p* I& C7 a+ [- R; o0 M$ O  |  set grid-x-inc world-width / grid-size-x
9 U5 ~' ^) p& h' D+ }& s% S  set grid-y-inc world-height / grid-size-y
: o- U1 T& Q7 U( g, S! h
. d5 G. w  j/ s. w" `0 `0 z. a  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary- `( X# r- S  N1 j: m. C
  set acceleration 0.099
+ J0 _4 n2 U/ Xend# N1 X! L1 K" k' y2 }! v
( s7 E/ M* C2 I
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,6 j& z& {- B5 K/ |/ ?
;; and initialize the traffic lights to one setting
" i8 H, N3 M' E9 cto setup-patches
& Z# I, q, Y' A6 f1 \2 R% H6 _  ;; initialize the patch-owned variables and color the patches to a base-color: c& d8 p/ _4 O* U& W+ ]% I
  ask patches
  c+ c8 w& c' v, c  [7 `4 D- M+ ~. `) ]! x8 R$ x- R
    set intersection? false
$ P' q, l  i; f/ R. F2 Z6 y    set auto? false
, q  s; {# X$ |5 ?: f$ S0 I    set green-light-up? true
4 m- Y9 e" a/ d7 ?# [    set my-row -1" `7 ]7 u# q/ @  P# V
    set my-column -1. W3 Y: ]$ c/ j8 a6 R0 R
    set my-phase -14 g; D7 _8 R# |( @  R
    set pcolor brown + 3& x1 r/ F3 x5 `1 v) G; g
  ]- z( y- z3 R8 m- Y% j0 h

6 q; W' K0 Z5 |- Q+ ?: y  ;; initialize the global variables that hold patch agentsets
- e8 F2 s& X4 D9 z7 ~  n  set roads patches with* P2 Y0 ~# z; J- K- B$ u/ L$ Z
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
' {/ j# M/ I- ^1 W! i9 d6 r2 w    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ q& _; ?8 j7 ~+ [
  set intersections roads with3 m: U, `9 O  d5 s
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and, I( L* D2 _* T, j" R
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
- K. F: F: p: Y$ @: L6 j/ E0 o" V# P) K. I$ M- z# E( M
  ask roads [ set pcolor white ]
1 [* z/ f2 c/ A    setup-intersections% O9 M% a/ \5 `( k8 o- Q
end0 m, \+ i+ Q& u1 i5 B
其中定义道路的句子,如下所示,是什么意思啊?
, ]5 h) M& ?  V: ~( V9 H set roads patches with- i* F" b" I! P% T
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or" r  i* y# M/ v- @! R
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]3 v% E; c9 N+ `% D' o0 z
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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