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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。+ y3 X. ^& \# C6 l2 d  e
netlogo自带的social science--traffic grid这一例子当中,
( z, o) q6 Y$ u7 k% rglobals9 H" [( \, P6 H4 S& q- h
[
$ @: Z2 o. h$ @3 V8 l- v& w6 ?  grid-x-inc               ;; the amount of patches in between two roads in the x direction
0 k5 }7 r7 r  E) V0 k. J  grid-y-inc               ;; the amount of patches in between two roads in the y direction
, h2 u( v7 r5 V$ A3 E/ r! E. I  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
/ V6 q3 z! V3 o, Y                           ;; it is to accelerate or decelerate
) I7 n; ^9 k! h. o3 ~; B0 t  phase                    ;; keeps track of the phase
7 ]0 l& u/ v* `- X7 }$ x  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure8 _3 S- s; n! I0 P
  current-light            ;; the currently selected light+ a1 V, b6 S1 t( M: X6 C
  U6 q% v6 U. |$ x+ y: Y4 o/ ~
  ;; patch agentsets+ M. W' n4 t: I& M& Y6 g& u) M
  intersections ;; agentset containing the patches that are intersections' C0 `& ~! U) ~) c! _) M9 p! F" V
  roads         ;; agentset containing the patches that are roads! h$ T9 O' a2 j* J5 m3 b
]5 y$ U! X) o# f2 S* D
& l$ O; `6 y) S$ Z$ j5 `2 R* X& s
turtles-own
- f9 H8 h% l  M8 h* N7 H5 Q# `3 P[
  y+ Z3 @+ g) \' I4 X  speed     ;; the speed of the turtle
( y& J  v) j, c$ O+ z) J; Z  up-car?   ;; true if the turtle moves downwards and false if it moves to the right6 W: q, j( Z2 L
  wait-time ;; the amount of time since the last time a turtle has moved. F' ]% F% z4 m
]
3 _% a3 M: D6 W7 s5 C  n' D, D' [( m+ [' A
patches-own: @( b8 R9 {: W+ G9 v- x6 G2 h
[$ J9 P( X  o: j8 j7 Z; [4 v
  intersection?   ;; true if the patch is at the intersection of two roads
, L) \+ k: x; Z6 m/ t* b  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.. u! X: E, V& k+ J3 k5 W
                  ;; false for a non-intersection patches.  V  I5 U! `/ G. \
  my-row          ;; the row of the intersection counting from the upper left corner of the) O/ D" J; r7 ^: h* k
                  ;; world.  -1 for non-intersection patches.
) H. u/ e+ u9 a6 j5 ~  my-column       ;; the column of the intersection counting from the upper left corner of the
" j% i( j8 u8 h* @6 `                  ;; world.  -1 for non-intersection patches.
0 B3 {/ M/ }5 v( K. V; h; N  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
& ~8 m# J, ^2 Y" y. H  auto?           ;; whether or not this intersection will switch automatically.8 Z; r; X- W, Q& {% s& Y
                  ;; false for non-intersection patches.
5 _1 e6 T8 w9 a) `- `; w  p4 E]
9 _: y4 }1 R2 P7 B' v: o7 N0 I9 k& q: Y% d; O( v! W, |
6 Z9 C( R9 `7 Z% ^! }; K8 c' q
;;;;;;;;;;;;;;;;;;;;;;
2 y/ J1 x" {: x; e) a5 v: }0 B;; Setup Procedures ;;% ^& x! N- y" `) s# @- g% Z) I
;;;;;;;;;;;;;;;;;;;;;;
3 F7 u# F, s2 A; v9 H
) o: G/ N2 @/ |7 `, |6 }1 K. Y& o+ p;; Initialize the display by giving the global and patch variables initial values.
, F  R# m! |! k1 S;; Create num-cars of turtles if there are enough road patches for one turtle to
3 T1 b: y+ J3 B  g/ d/ t% J0 s/ ];; be created per road patch. Set up the plots.
; n, j/ d2 M  Z  W+ T% k; Q+ b8 |to setup
7 O/ k4 I. q6 B* p* U( U5 T+ P  ca
5 ?6 J& f! ?- i; t+ g/ }  setup-globals) a! x) K4 U! B7 I! v4 R7 H

- Q: R1 a- a0 g6 I/ o  ;; First we ask the patches to draw themselves and set up a few variables8 y; y3 b2 v2 {- z( @- P
  setup-patches& f% S' A; V7 b$ K
  make-current one-of intersections
+ h1 F* G/ w; K/ t  label-current# Y2 W1 y6 S) M0 g1 B

9 K! F6 y, V' V7 X0 @) A2 F  set-default-shape turtles "car"' h$ f$ k2 i. \4 D- k) y2 h3 L% j2 v
/ M$ d1 O1 Y/ j" }0 e5 l1 ^
  if (num-cars > count roads)
9 w) `6 Q. ?0 L! n' R& ?3 l  [
1 r0 z4 r, I2 J9 G( q4 e    user-message (word "There are too many cars for the amount of "
* C- T! W3 v* l6 v                       "road.  Either increase the amount of roads "
1 j" R3 A# C! m5 |4 z- c                       "by increasing the GRID-SIZE-X or "5 m; F/ q2 l( s+ Y% a0 L2 O( ~6 J
                       "GRID-SIZE-Y sliders, or decrease the "
8 S5 K0 A9 `+ P0 P# y. |; l                       "number of cars by lowering the NUMBER slider.\n"
6 K2 ^8 e/ q' X7 _0 i/ i, P! }                       "The setup has stopped.")/ a: q# R$ S  L5 k: q5 w1 l8 C! M
    stop
2 X8 E& q4 a- c- p: h  ]& I: R* A5 w! g' J( Z, a% M* Z9 X
' c5 d5 R* z& I2 w
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
! S+ n3 j7 j4 i# c+ t, ^  crt num-cars
" n; O* M$ j7 v6 u  [
; S: A- [/ r- B5 F1 }" v' _& S    setup-cars9 x! a; M. Q) l* _( Y
    set-car-color
/ Q  Q2 M- \0 [    record-data
0 \0 M3 B* F! Z" ?. ^+ e3 ?' t  ]
% d( k) x2 ]+ H7 o$ `+ M+ V5 g8 b- g5 Q& F5 X# S
  ;; give the turtles an initial speed
% W7 n2 S2 q6 [$ h  ask turtles [ set-car-speed ]
- `: E% d( Y) v& k; J% L# ?; z
8 U- W7 s7 ^6 W$ o% m  reset-ticks) x; v6 G5 E. m1 [( d# h
end1 A8 t; k! l) N, O- {

( a$ h# A) J2 m( r;; Initialize the global variables to appropriate values& \* i! {/ Y* b
to setup-globals, @  ]1 X7 y! C8 Q& Y9 I
  set current-light nobody ;; just for now, since there are no lights yet1 P: G3 D, V8 l) w+ d9 O
  set phase 0' O9 g1 o3 v2 x+ o8 {/ B. ?
  set num-cars-stopped 04 P$ c" F: m6 e, P" v- j2 N
  set grid-x-inc world-width / grid-size-x
- I& n4 W) e# W* M, `0 k: E$ U  set grid-y-inc world-height / grid-size-y2 c) G6 N4 v& B# {" i3 z3 f/ R% P( U

7 F! W8 C' N8 D8 W2 C  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary, D2 ]  ^- m3 L, s7 y9 A# b' f
  set acceleration 0.0993 L8 b, Y2 ^9 t& J/ m1 x5 V# b
end8 [* K6 X: q! `8 Q' X# X( D2 \) X! f+ y. T

% e7 M2 p; }: t& S4 ];; Make the patches have appropriate colors, set up the roads and intersections agentsets,5 k. A$ ^1 e1 x2 u4 ^/ o4 {
;; and initialize the traffic lights to one setting
3 P! N/ t+ g- Q! y8 a) D& Xto setup-patches9 E5 J3 S9 o' S8 y
  ;; initialize the patch-owned variables and color the patches to a base-color
; n4 p5 W& @6 N! B  ask patches
$ A9 O; S# k% y- H  [
6 s  J7 K& B0 I  F: m2 _    set intersection? false
$ T$ R; X1 U, J7 \# q2 ]& U    set auto? false
/ ?/ J" O% Q$ |( c- S( t3 m    set green-light-up? true% M* A5 |9 v2 t; J: c0 n8 M0 P, W
    set my-row -1
" q9 S( a. w3 Z" z1 t) d, h+ E$ |8 L    set my-column -1
1 `; L% Z  {5 z# `/ K& p& n    set my-phase -1
5 o! {+ w6 k) Q6 e2 P    set pcolor brown + 3$ u* ^' ^+ Y/ v" E$ u& g% \
  ]
9 P& d# v% ^' L* m& \% a' H& Q* p, c3 @+ I  m
  ;; initialize the global variables that hold patch agentsets% l, x$ [* r: {( A9 y5 p
  set roads patches with8 e7 B, ]! i: l8 G( \& W
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
# a0 |3 |1 Z" o% T5 A    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]6 T. p- {; m; s# ]
  set intersections roads with
- k4 U, w" n+ }; F3 \0 a3 I    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and4 l5 i" ~7 i* X: ^
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
: c: Q5 M, c& A$ N& a, w
  e$ G& `) K* ]2 c4 {2 h( m% H  ask roads [ set pcolor white ]1 k- q; T* b0 E' m+ U1 [/ L
    setup-intersections+ w2 s+ v' E; l
end5 J8 w, A2 V3 G! S2 P# U# _
其中定义道路的句子,如下所示,是什么意思啊?
$ e/ P; o+ w7 r set roads patches with7 h* z+ T! z, C/ ]7 M9 J
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
5 u- c& q% b. Y- \    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
# I, `. H8 N4 Q9 l% g+ f- 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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