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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。* P# h2 z: g5 Q0 V$ v+ g& a
netlogo自带的social science--traffic grid这一例子当中,* m) t/ i8 r4 A% t; k
globals
  Y* M) L+ C: I5 f$ R7 c! y& ?[# y$ w5 ^2 z1 z: t. o4 p' G
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
- }8 Q1 R6 Z. c( [$ |; D  grid-y-inc               ;; the amount of patches in between two roads in the y direction
' S! N9 @/ d0 F! @  acceleration             ;; the constant that controls how much a car speeds up or slows down by if, W3 N& d9 a6 y0 q+ m' Q# K
                           ;; it is to accelerate or decelerate$ {6 @" C1 @) E9 `
  phase                    ;; keeps track of the phase
6 N* z3 o  w% m  T  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
+ F+ @8 U8 h; V  current-light            ;; the currently selected light1 u8 ^+ k+ I) l! d4 E3 b3 T
( x: b) M+ S* m/ }8 `* w
  ;; patch agentsets4 [/ I7 Q2 f9 Y! m7 a! `
  intersections ;; agentset containing the patches that are intersections2 n. p* Y/ s* a: \
  roads         ;; agentset containing the patches that are roads
5 m; d5 h8 [! H+ ]" ^% W7 K]
) r9 u$ W# ~. ?+ O6 J- J' @; _% Z: `3 t8 q
turtles-own
! D" W+ V$ j9 n1 U: N[' b' c- i  j) e$ Y
  speed     ;; the speed of the turtle3 r$ X. {. U. F- E# @+ |  @
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right" |% g( `4 U+ @& j$ g4 _
  wait-time ;; the amount of time since the last time a turtle has moved
' k! |- i7 P! ]4 |]) D' h! |! r( w
7 F$ i: _+ @, q/ v# b  _
patches-own9 Y5 a/ ?4 z: ^9 f$ x7 V  T/ N  \
[
- ]/ W0 K! {) K" Q. t" n, o7 C  intersection?   ;; true if the patch is at the intersection of two roads  Z1 \" \) X- H3 h
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.( r, I- A, {# Q7 Q- L
                  ;; false for a non-intersection patches.- u, W; ?# h- R' Q1 x4 a6 W, J
  my-row          ;; the row of the intersection counting from the upper left corner of the
) r" ^6 a/ t! F2 |( y( T                  ;; world.  -1 for non-intersection patches.6 _5 [5 T6 r% J: R$ u9 M, w
  my-column       ;; the column of the intersection counting from the upper left corner of the
( V9 s2 k& r8 r/ h3 F3 R& o                  ;; world.  -1 for non-intersection patches.4 z$ C" ~9 }: M4 R0 _
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
! P. C0 E& k; H+ [  auto?           ;; whether or not this intersection will switch automatically.
8 c9 ~! ?3 }5 h0 T. o' K                  ;; false for non-intersection patches.8 F) d$ b! t8 Z( U
]9 G2 ^) E2 r: `, c- {, [

1 Q$ M, m, ^; G( {
7 \& M4 Y6 V/ F8 r( h;;;;;;;;;;;;;;;;;;;;;;
+ _" S) |" D3 s# t8 `+ V( S% V;; Setup Procedures ;;' {% o- D# E" J! j
;;;;;;;;;;;;;;;;;;;;;;% I: z* s2 }& _  N8 ?5 |6 P

+ A" y0 L0 {  }& K;; Initialize the display by giving the global and patch variables initial values.3 w$ |0 A8 g6 r- ]* z9 ]* _
;; Create num-cars of turtles if there are enough road patches for one turtle to
# O% x! w0 v- p) Y) b;; be created per road patch. Set up the plots.
7 l) C* b+ W3 }to setup' [! Y: g1 o) P/ G
  ca
# _8 Q8 A; N8 N/ y& z$ D" g  setup-globals
/ i  m/ I( q* X2 c) m: \/ [2 O0 ]. m- n: U: t
  ;; First we ask the patches to draw themselves and set up a few variables8 p$ h9 t4 T/ z* e. O' c2 Z5 V2 f
  setup-patches
) ^. r8 Q5 G8 e2 S# u4 z3 x; P  make-current one-of intersections
! K6 F) y/ ?1 Q- A1 U3 }  label-current7 e* t; a& \. P
; i" R, p) {) {
  set-default-shape turtles "car"/ J. ^' b+ N3 Z; p7 V8 v
4 t& ^4 [4 c) M3 V0 l  Q7 k6 Q
  if (num-cars > count roads)
6 L1 ?8 s. ?. k6 v  [) Z- x9 k5 z- f  `. t0 O2 j) R+ m
    user-message (word "There are too many cars for the amount of "
! D) b- d; s8 ?; j/ F' f                       "road.  Either increase the amount of roads "
4 F+ ?( G( b6 z/ N                       "by increasing the GRID-SIZE-X or "& Z% Z6 V/ O; N0 {& N% C
                       "GRID-SIZE-Y sliders, or decrease the "
  S- @- p! p: Y                       "number of cars by lowering the NUMBER slider.\n"
0 D& M7 y7 o+ i, I% b                       "The setup has stopped.")) S4 Y( \- ]) v0 A5 Q7 D1 d. ~
    stop
, _- w9 q2 {* V8 M+ V! G% j  ]
1 X& P0 P7 {$ D7 ~2 a5 c4 P( D9 x- m: W" O0 W% u5 F- D. X) F
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
! u# z8 z3 q* Y# f- p- Y) R  crt num-cars
, t0 I: {+ U% n/ A7 Y! g  [
" \2 H% L7 z$ m  [    setup-cars2 X! K. e' Y- {& C1 v2 r7 c
    set-car-color) u9 b' h$ t/ \' o- h
    record-data! u/ b6 Z8 `- S
  ]( X9 t9 e: _& T
  _+ B/ Y: f. ^9 o1 ~$ H" p
  ;; give the turtles an initial speed
8 v# p3 @0 v- I' G3 W# b$ Y  ask turtles [ set-car-speed ]1 n) K2 B- c6 n# e/ z5 P; q
8 U0 k" P4 R4 g& r+ _
  reset-ticks
7 S, S' w( _4 Y0 Zend
" _& @  ~) _1 W
; G6 }/ R: `' t( [$ x;; Initialize the global variables to appropriate values4 v& L# t3 v: g6 p6 O. @
to setup-globals
9 ^* ?4 E! n- p; S! N+ H  set current-light nobody ;; just for now, since there are no lights yet
3 l3 j. X" V' @" ]  set phase 0
5 Z  g! x+ U. c  D5 E5 E/ _  set num-cars-stopped 0& Q! }4 ^' U+ Y0 _- w+ w
  set grid-x-inc world-width / grid-size-x  t! Z1 p/ q, Y$ E# q
  set grid-y-inc world-height / grid-size-y; v6 S* ]7 l: c5 G. N. d; G0 u; r
; P8 b. \( V& g) j
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary+ V' F* x: ^6 T9 x) T" {# r
  set acceleration 0.0998 D6 w+ [- }8 c2 S7 k' J
end; R# ]% n6 c4 h0 ~3 E' `) z
0 Z2 u1 t1 N, ]8 R& }) q# ^& _5 f
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
" }6 H6 I- O3 V0 C% h;; and initialize the traffic lights to one setting; x5 W/ e0 a. F9 n8 M: }
to setup-patches( y% R5 c0 R! }6 m
  ;; initialize the patch-owned variables and color the patches to a base-color$ V6 K- K( J! U/ U0 G) j; h& m! j
  ask patches# {% s0 ^) e0 S" Z9 v# N
  [/ S3 f$ d* n! f% w9 c
    set intersection? false& b/ Q. d) ~& Z6 ?. E) n8 b. s" f
    set auto? false
! p: ^* G* A4 K% P+ x: U    set green-light-up? true
$ i) r3 v3 M8 G8 j7 S3 W$ }% Z    set my-row -1: ?; f" J" j# V5 L& S9 r8 d
    set my-column -1
! m) I4 }, X" c4 G1 Q2 e4 S+ k: g    set my-phase -1! k  O* s: e: G7 G/ Y; M/ j
    set pcolor brown + 3, @* [. X, C9 p! f* C4 A) v2 r5 R
  ]; \  Q4 Y8 _0 C- K8 y

& ?- v# t) S, p  ;; initialize the global variables that hold patch agentsets
6 R* `# G% ~0 c' U( c  D/ l  set roads patches with" c# P+ n6 ?/ H
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or: }. v- C, X' W: K; h
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]7 c8 u# z/ f6 x0 k( M& ]1 A
  set intersections roads with: a& U- k& q, i+ z( \+ Y& Z# T
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
: F8 g# \* k9 U- J, h  L/ w  v    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]  Q- ?3 }: h: x0 ~6 Q6 Y8 h

9 b1 @' t) e4 L! `. d' O  ask roads [ set pcolor white ]
2 M: s6 ?* G* E0 y0 Y; k- D; Z6 p    setup-intersections
/ J9 _& G" `9 K9 q5 H0 ]$ L: r6 qend
5 P' F# @2 J7 E其中定义道路的句子,如下所示,是什么意思啊?
& J; @- [" O2 b. R4 H2 V; O) S set roads patches with
; x" F1 w5 W. i& g5 u    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or5 \5 W. X" G) `% i- I" r: c
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
& C( W' K1 j# _: d) m+ w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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