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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。; j; x+ i% v5 L  Z2 e% _
netlogo自带的social science--traffic grid这一例子当中,
/ s" g8 S" V/ D8 p1 Wglobals7 x7 M+ E, Z: r4 x& b4 j' A/ o* N
[
; k* Z; N; Q0 _6 _. B7 t5 Y, F; G  grid-x-inc               ;; the amount of patches in between two roads in the x direction7 H3 V* Y  l& x
  grid-y-inc               ;; the amount of patches in between two roads in the y direction' J1 I7 v' R, g# p+ [
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if  q# \. ~$ ]/ U4 j3 D, I
                           ;; it is to accelerate or decelerate
" Z- r  q6 Q* Z! @9 }( T% F  phase                    ;; keeps track of the phase" C$ R3 t. F7 |! _! K" f4 A* I
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
  ^! [- \1 u( `7 n0 r  current-light            ;; the currently selected light3 ^( r' }5 D2 `+ j! G2 ~1 q& ^

7 ?2 H6 K7 v" h; F, u$ Q  ;; patch agentsets
; T% e1 @( Z+ r. |% f% H  intersections ;; agentset containing the patches that are intersections, n3 Y7 O/ S+ U4 b+ ~
  roads         ;; agentset containing the patches that are roads
% k/ o) s+ w# V2 w$ J]
3 ]+ _# z+ D) ?  P2 n" u
$ M1 p) K. `/ d8 gturtles-own
7 {& g3 r" x: L7 r% ~4 {8 p( B[
% `* P8 W* H( C4 w. }  q' p- C( X" K  speed     ;; the speed of the turtle
3 m9 J7 K0 I+ [  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
8 N/ A8 ]4 Q8 Z/ d( }4 s: A  wait-time ;; the amount of time since the last time a turtle has moved
" p; `( ~- r+ V' W, q9 E* X$ I0 A]. b% M4 t4 x* S/ R: m
. U5 z/ B# n) I- ^
patches-own
( I  o! ]/ Q$ R* U+ R$ ~1 o6 x* y[) }7 P* @6 J! w$ Y6 S) ]
  intersection?   ;; true if the patch is at the intersection of two roads
7 }  E2 ]  H1 c7 [& q  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
; B! o7 K1 k& l- ^                  ;; false for a non-intersection patches.
6 V4 c; W; @! K/ {" P  my-row          ;; the row of the intersection counting from the upper left corner of the( b% z$ X% n1 L3 }0 x4 m0 {+ D
                  ;; world.  -1 for non-intersection patches.
) D9 z- o9 l2 e  V" I9 n$ X  my-column       ;; the column of the intersection counting from the upper left corner of the
9 K5 \+ b& S3 c; |                  ;; world.  -1 for non-intersection patches.
) f+ G5 [% n% ]- ~9 h1 j# T4 c  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
1 \! K4 R- z! y2 i/ X, [' I( K  auto?           ;; whether or not this intersection will switch automatically.
2 T# l$ C) K% o3 C" A; m                  ;; false for non-intersection patches.
7 [9 @) j: `7 ]4 V% o9 e4 d]; D# a5 B0 T1 H' t: n- @$ t

2 {+ f) E2 t0 k8 \/ C- h* x7 t5 P4 d$ s1 v) L
;;;;;;;;;;;;;;;;;;;;;;
3 O& A% b$ A2 {6 u;; Setup Procedures ;;
( P1 c8 y9 |2 K& W;;;;;;;;;;;;;;;;;;;;;;2 Q9 H% n' @- n8 a% M5 t

- |! Z1 }8 d7 o$ z;; Initialize the display by giving the global and patch variables initial values.
) O) f6 W) @0 t& ?/ p. A9 ~;; Create num-cars of turtles if there are enough road patches for one turtle to
  M5 g! ~9 J7 `/ v1 g* r;; be created per road patch. Set up the plots.+ s7 p( I$ k4 G! V5 [$ L
to setup
, Z0 }3 E, X  |/ Q! L2 F) `1 ?" @  ca( M& S( a: {' W7 t. k6 c, w
  setup-globals+ g! N& U! d, k" Y: C$ U

( |$ ^2 x( I- C6 D1 Z% U+ m  ;; First we ask the patches to draw themselves and set up a few variables
1 C4 ^$ T  u% {7 M2 K! V  setup-patches
* z  V, y% D3 \  make-current one-of intersections$ t" F8 @6 q- z8 \% i6 ~
  label-current
% |! R9 z4 u3 N7 T  X0 ?% C9 T) ?7 a  k1 G/ T. \3 Q1 z
  set-default-shape turtles "car"( F8 o% m4 `) B0 ~6 J9 ?: B

4 ~! t1 C' U6 C; n  if (num-cars > count roads)
: w& p5 @+ \9 ~: w% h4 |$ ~  [
* ]# r/ Q; B) o" r& i, S1 I' H    user-message (word "There are too many cars for the amount of "& w/ X" Q6 v5 Y& O
                       "road.  Either increase the amount of roads "
" |# ]' R, q; w( H' f1 m1 c: \$ W                       "by increasing the GRID-SIZE-X or ", D$ q7 L( ^  U3 z" b
                       "GRID-SIZE-Y sliders, or decrease the "
- A) c; \5 s" f0 b                       "number of cars by lowering the NUMBER slider.\n"
: t" S) E% W; D* P                       "The setup has stopped.")
7 ^9 Y6 f5 X! v6 X2 F: J    stop- E1 N- \" I$ ?% g# y/ Q6 F/ V1 k
  ]
1 x4 `1 L3 _/ N$ q" r' U# q6 R& u$ s
6 r6 @/ f  k! u  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color2 ]# T  {- r; j: a' Y$ ?
  crt num-cars
# d4 X6 A$ J% q. l% c) d  [
1 I+ {" G- C- [8 W7 A, q, L* r  v    setup-cars
( r% ]. Z( s$ R7 ^7 F+ t5 ]. E    set-car-color* f4 W$ S' |0 s8 a- x
    record-data8 Z; n% b3 a9 G+ `
  ]
: |8 ]; |3 }* Z* X4 m/ F2 n  K) M1 L& B; P- V' \: W
  ;; give the turtles an initial speed
( r$ x+ h2 _  w2 _  ask turtles [ set-car-speed ]
8 h4 ^3 c; x4 [6 W" o
3 U9 x  K8 v/ Z  D- a; S# F/ _  reset-ticks9 Y' G. O& K" S! i
end
4 ]! T+ w% ]  @  {* i! k0 J1 k
5 v8 X( _/ y/ S;; Initialize the global variables to appropriate values. V$ A, E+ [! d0 o! g8 ^$ E0 R5 g
to setup-globals
4 [& C- A% m0 \5 S  set current-light nobody ;; just for now, since there are no lights yet
8 ~4 V: v# h7 ^* p0 h* G9 R9 D  set phase 0- C; u& S+ t: J& R" N) [' ?7 V
  set num-cars-stopped 07 ^8 y5 N* M$ ^* h
  set grid-x-inc world-width / grid-size-x- Y- a) L4 c( n- s0 {* ^, P
  set grid-y-inc world-height / grid-size-y0 q" h# x  s& T" ^

, S. p% T/ u% F) H( w  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
" g9 B+ @  O. J" w1 F  set acceleration 0.0991 a5 Q1 y4 ~( [% c- ?/ S
end" G( ?% j' |% u

- [7 _5 v4 ?7 x# a% G;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
: e0 m. c/ V! L;; and initialize the traffic lights to one setting
" Q9 p; g% n8 v/ q; Z3 g% p0 Mto setup-patches3 D7 N' G* c' d9 L( A8 x
  ;; initialize the patch-owned variables and color the patches to a base-color# c- C# K9 M& i- x$ S; H5 P
  ask patches  z9 E2 _7 X" u! F# l5 E( @: D
  [
% H: Q3 `1 l" q9 ]: J2 ]    set intersection? false, k# I# w0 y$ e  y
    set auto? false# T+ w4 Y3 y, {- A) T
    set green-light-up? true2 I% p- ~9 `+ U! v
    set my-row -1
1 y' O2 b9 b8 \' ^, Q. T" ~; o    set my-column -1( K- {3 G! c' }
    set my-phase -1: i0 C4 I, i) [& }! H9 z
    set pcolor brown + 37 p+ V7 e4 h  r3 j1 C2 ~8 o
  ]% I. g" y  a- W' O' i

, Q. u# z2 y' ~# x  ;; initialize the global variables that hold patch agentsets/ P2 k+ v4 m( d: ]( D- E& H9 l. g
  set roads patches with
3 _0 X. Z& G' ~' a6 l0 c( J$ e    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
7 b* W+ G# f# A( T9 d    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
9 O0 I$ |: ~  R2 \2 D  set intersections roads with0 W; R6 D2 o, r' }( V8 @
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and# Q  g& ~& h/ W6 L
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]# C: w! g! ~& u( Y

' e( G0 n7 G5 I# h  ask roads [ set pcolor white ]5 d- E' a+ {+ u$ G
    setup-intersections4 N8 M" Y% B: B" e& S
end4 L7 x9 p/ c" I, R
其中定义道路的句子,如下所示,是什么意思啊?* y- e9 u$ b+ k, _
set roads patches with( R3 G8 o6 f& r  Y% f
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
% b/ U6 j# \- M. O$ t1 D# M    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
( ^" v! r7 S. V" [$ g0 K- h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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