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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。/ t0 U; L. I* B6 X8 L8 C
netlogo自带的social science--traffic grid这一例子当中,
1 g) Z! X- g% R6 B4 u# p  h/ Bglobals: n( C" G3 k9 B8 f+ J& X" m8 X2 Z
[
2 e2 c* J6 h1 ^  grid-x-inc               ;; the amount of patches in between two roads in the x direction2 y( [0 e! ?- `  w3 P0 b& E/ h. k0 W
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
6 v$ x( {3 ^, s: C; s3 Y6 ^  acceleration             ;; the constant that controls how much a car speeds up or slows down by if4 r! @. c% w" O7 a, n1 y
                           ;; it is to accelerate or decelerate
( m, P& X6 q$ b( _$ N  u5 u) a  phase                    ;; keeps track of the phase
% x, @  X- f8 y% T* r, K  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure+ S/ E7 Y4 [0 [
  current-light            ;; the currently selected light
. i2 F: n% E* I; ~* s+ v
3 d5 [6 a" ?' a; _( ?# j  ;; patch agentsets
  p2 b: q  B5 F- \6 K! q  intersections ;; agentset containing the patches that are intersections
; P$ m; i8 @2 `  roads         ;; agentset containing the patches that are roads3 k3 _9 U7 _. n3 h
]+ O7 ]6 m5 [& M3 W

7 p7 @) a4 F0 xturtles-own- N1 C3 _0 H# o, ~4 w& L" S
[( S: u" r4 K9 _% I& J$ q
  speed     ;; the speed of the turtle
- ?) z8 @9 H. h: O& r& \/ `$ x( _) P  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
( J2 F" W- }6 `' C2 T: h  wait-time ;; the amount of time since the last time a turtle has moved
8 H* U& ~: }* `8 E4 q% y! L]
1 T. W8 `6 W3 V. W- M4 O4 h$ q: o, p! Q, j5 s) x" \- I
patches-own
3 `5 {- h6 Q3 _/ A) H( d% c* v. E[
; P6 B8 p1 F4 A' E/ e% e+ i  intersection?   ;; true if the patch is at the intersection of two roads
5 C: W$ V4 _) Z# i: H3 _+ u, i  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
8 ]8 A) ?2 u7 S1 q+ I. ?5 I                  ;; false for a non-intersection patches.1 V$ r! ^# k" b
  my-row          ;; the row of the intersection counting from the upper left corner of the
4 Z: t$ f' n+ U0 L; e6 c5 ^                  ;; world.  -1 for non-intersection patches.9 u! C7 K, ^* ~# H( O$ O8 h
  my-column       ;; the column of the intersection counting from the upper left corner of the
( ^, l  A: ?/ L" S$ N" H                  ;; world.  -1 for non-intersection patches.6 [, n3 L+ l' L- N, W! P: t
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
& F4 |* \% R$ Y  auto?           ;; whether or not this intersection will switch automatically." x- |# v: v6 y, a
                  ;; false for non-intersection patches.
8 g3 m  d( a2 R8 w$ T) w  u]
: n/ L. x/ _# Y6 X/ A7 @/ \2 `1 R) M1 N/ i

! E# ~! M& N% T8 u2 e;;;;;;;;;;;;;;;;;;;;;;. |' q: [- F5 z2 \6 J; c
;; Setup Procedures ;;  A+ l4 J, L" r' ?( w* G
;;;;;;;;;;;;;;;;;;;;;;5 H% A& F1 C, c4 u2 I& g: s

, T' C1 ~, D+ Z;; Initialize the display by giving the global and patch variables initial values.9 [0 Q6 R$ ~$ y/ u( ]2 B  R6 X
;; Create num-cars of turtles if there are enough road patches for one turtle to9 G7 e; O7 V0 L: d9 e& Q1 X
;; be created per road patch. Set up the plots.8 j0 f3 r6 @* t4 C( @& I
to setup
: y: E) m& R+ Z7 D1 b5 c  ca
/ W( R+ P2 \7 U& Q4 l: D1 b  setup-globals
. m5 N* `) e/ [& X5 D4 w0 Q' n1 j
% x8 a; p# y  x, L7 i& M' @+ _8 [& w  ;; First we ask the patches to draw themselves and set up a few variables
3 @" r1 w9 S$ |, o  setup-patches
2 J* G: p  p+ v$ W7 _  make-current one-of intersections) G- \" j) g! M4 M, d8 @6 f
  label-current$ _+ w$ `6 d  v8 F* E0 P& e$ K

6 O  a' [3 M8 q  set-default-shape turtles "car"1 d  L/ U% Z: h9 q3 |' e* X

+ u7 f  u/ D' o" u8 x; ]0 T- s1 V4 F  if (num-cars > count roads)
+ t! V5 {' n3 T' W1 I5 i; t) w  [  g  k% a2 C7 q: F% n$ D
    user-message (word "There are too many cars for the amount of "
# ^& Z/ M9 S4 C! j2 d9 y9 Y                       "road.  Either increase the amount of roads "
& T& M; g9 [  P, _: g                       "by increasing the GRID-SIZE-X or "
' }) @. ?5 @$ k                       "GRID-SIZE-Y sliders, or decrease the "$ E; ]" a( u3 X' N0 ~  m: U; }  Y. S
                       "number of cars by lowering the NUMBER slider.\n"
# c  t- Z" g, V                       "The setup has stopped.")$ y5 A3 H6 D2 Z! A
    stop; b; \; \2 I6 f& }
  ]
' i% t+ {# J4 C/ I/ r8 X. Z. ]9 r9 U9 v* h6 N$ M  w, n
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
; k( l, }/ h% @' L, h# x) d  crt num-cars
4 M' V) T- V7 v: L" f  [
4 C. h* T2 v) u  \    setup-cars
: Y5 s* k9 {+ E  i. s/ a    set-car-color
) z' ?# W( M6 U# @! p* u! m7 x    record-data5 a- m  f1 `7 N& V2 r0 K
  ]
/ q0 w& b; }- |! E$ a8 x5 I( r/ l/ ]& ~! {) f
  ;; give the turtles an initial speed
) U8 ?1 c6 h% x9 x/ ?  ask turtles [ set-car-speed ]
. p5 s% C" n! a+ ]$ h. N2 T7 `& f5 N: n
  reset-ticks8 @, i8 t: y5 _8 R3 C$ h
end0 J, \% R, E& e! c
: @6 ]4 r. ]4 \0 Q1 Y4 l) c
;; Initialize the global variables to appropriate values& h1 w& V5 D% j; d9 R6 j
to setup-globals$ \: g* r+ f  ^; X% g
  set current-light nobody ;; just for now, since there are no lights yet& K: g1 O3 ^& `- p6 u5 D( f
  set phase 0
* m) \# h( V+ t7 u! G- P  set num-cars-stopped 0$ U5 x8 Z+ j, f( w4 @: m- J! D& w
  set grid-x-inc world-width / grid-size-x9 u; s1 X8 ]; D7 b
  set grid-y-inc world-height / grid-size-y
* E7 X6 F% f0 I( g5 u7 F3 Y0 \/ E$ H. }" `, d
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
" B6 X6 i9 R) i6 c& Y% Q3 S3 _  set acceleration 0.099
+ T5 _/ j  r' Zend0 d' u9 s: D5 t) Z4 v9 r
( u$ b% r6 K' _0 O
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
9 T# b5 X% g# \% t, e  `: L;; and initialize the traffic lights to one setting
2 v4 q; _( q+ ]  [6 W7 [to setup-patches" x. S$ }! Y3 H# ?0 X2 p2 h" G
  ;; initialize the patch-owned variables and color the patches to a base-color8 Y/ s, T& K: g
  ask patches
6 b/ L% {1 N. G* H# n  [
* \5 v0 B4 g4 I" c$ y    set intersection? false
/ f5 X- Q# S2 t" Z6 }3 |    set auto? false* D/ A# c8 \: z; J1 ~$ |1 F% v
    set green-light-up? true1 ]% s4 l8 i! ~5 h, L- n
    set my-row -1
5 T3 h- _, e" b3 [( V    set my-column -1
! H' C1 R2 O1 X    set my-phase -1
1 h8 D3 Z- ^' p) F8 i3 f+ R    set pcolor brown + 3
3 S2 C4 F  n! s+ a  ]
* E" S; }3 u, q/ I8 E* S' |% s
5 s7 v1 h8 c' ^4 B4 n! e5 L/ L  ;; initialize the global variables that hold patch agentsets1 {5 {2 i( @. B* R
  set roads patches with
8 k0 ]2 v- d" |% C    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or0 H* H# ]; f8 L, U4 T
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
9 ?7 O& }  i9 ?8 a; m" Q  set intersections roads with3 m& E) r6 ~' ~$ |% F
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
! D% w" n. {* }4 i3 n  @    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 [* c% a3 J) |3 N! Z
# r1 E; K. t0 \
  ask roads [ set pcolor white ]( y: w0 u# y( E  m
    setup-intersections
% Y  m; a" u0 ^4 W4 r, k9 ^end4 p9 d( A9 @" v( E( @
其中定义道路的句子,如下所示,是什么意思啊?" E3 R2 b2 a( r4 h1 Z
set roads patches with1 t' N% i: I% x% ~
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
: @. T: h# q- h5 M& t9 N    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 Z2 ~6 ]0 E* I3 B) [2 u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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