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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。
- K: `- L6 V; O) f* r' Snetlogo自带的social science--traffic grid这一例子当中,3 [' W5 j8 `% g) u9 R
globals
- l! c, F  C. c( a5 l! n[
  S" F/ u1 E$ h: ^& \. o$ H  grid-x-inc               ;; the amount of patches in between two roads in the x direction
) G+ u" F: D4 ^$ s  grid-y-inc               ;; the amount of patches in between two roads in the y direction
% ?9 J$ M$ F2 l* P! ]8 N, R, V4 B  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
6 v  d  d( I# u7 y$ l1 Z) i                           ;; it is to accelerate or decelerate6 B$ F% m2 m1 X$ M9 f( n. a
  phase                    ;; keeps track of the phase
5 c1 h' }7 a/ \0 h  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure( ?+ @7 X: P: @$ n! s! e  v
  current-light            ;; the currently selected light
  }  s+ D  M+ B# m8 w
& J, ~1 t- b  t$ R' _  ;; patch agentsets+ c% x+ E7 B) q$ _1 _& E
  intersections ;; agentset containing the patches that are intersections
* _0 b' q* I- Z  roads         ;; agentset containing the patches that are roads1 r" E% @$ [$ C/ o. d; B
]+ U0 ^  S2 K0 `/ {7 p% C7 T! g9 ?
+ h' f0 Y: E4 F. b) Y' K2 X8 S
turtles-own
$ U* v7 M) r- k9 I/ t[" A( A3 R8 k- p/ m1 M
  speed     ;; the speed of the turtle
2 S8 j6 S. Y( @  up-car?   ;; true if the turtle moves downwards and false if it moves to the right# B) f/ X& {4 I( o3 b
  wait-time ;; the amount of time since the last time a turtle has moved
9 I* \! h9 S- C" s# n& M0 w]
! b4 |' P# A- J" V! @# G7 o3 S' l2 g2 k. U
patches-own
" s6 M& x0 k8 \! a6 i0 S[
* B, @- }. |  B  intersection?   ;; true if the patch is at the intersection of two roads
3 G- ~3 ^9 X; V+ j+ t" J  o2 Z  _  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
; ]9 K$ C2 T2 ~" L7 e+ w/ ^9 d/ A                  ;; false for a non-intersection patches.# H, x& M2 c$ R2 u
  my-row          ;; the row of the intersection counting from the upper left corner of the3 t" M* @, L. a/ I# ^. l
                  ;; world.  -1 for non-intersection patches.
# U. F- M* p- l7 Y0 @# u+ |  my-column       ;; the column of the intersection counting from the upper left corner of the
8 Q* f4 I7 j: Y9 z                  ;; world.  -1 for non-intersection patches.
; W  p( Q$ c  Y/ F7 R  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.0 X; y- W; [) `, k8 d/ w4 g( a
  auto?           ;; whether or not this intersection will switch automatically.  T6 r( V7 l$ t( \, |
                  ;; false for non-intersection patches.2 e9 j$ P; j( {  x3 q/ k
]$ @! F/ L' Z2 [! R, v. s

+ @3 y# `9 l0 O9 l
2 ~+ S- p% u& E* s6 l9 ];;;;;;;;;;;;;;;;;;;;;;& b- h) l  R/ X" C, y9 v- g
;; Setup Procedures ;;& j2 F4 m  i0 k  o  D
;;;;;;;;;;;;;;;;;;;;;;
- V0 o& M5 ^# k. W  s' @/ `; E5 p) X, N* x+ o$ d; J: C
;; Initialize the display by giving the global and patch variables initial values.* l; h" ?9 X& s3 X3 j' J* W+ V
;; Create num-cars of turtles if there are enough road patches for one turtle to
1 p& c, X- K: O8 M  h;; be created per road patch. Set up the plots.8 D4 l# X% X7 [" p& R7 B
to setup
4 T4 h& x8 r, B( G7 y2 n$ K  ca) k/ t, u3 _: z
  setup-globals) h. l$ s5 \( F/ ^
9 D4 ^8 Y" ^2 H, P) x
  ;; First we ask the patches to draw themselves and set up a few variables
: ^; q1 t  A6 @  setup-patches
* i: J/ p' t* d' w2 ?; ]5 K  make-current one-of intersections
, m. W" c1 I- D  F! {& i/ {  label-current& y3 ^5 l. {0 D, c, n2 [9 }4 q

( Z5 Y7 \0 ]& _6 s7 P  set-default-shape turtles "car"
# q$ k& X8 x5 E3 I& j# x
1 O" x- m+ J2 ]  _3 L! c& v  if (num-cars > count roads)( k% @6 A' O9 [& c2 c( [* s
  [
& g: P$ K5 M* ?3 T8 u& r: {    user-message (word "There are too many cars for the amount of "
8 o5 {, K0 ]! n2 O4 s8 v                       "road.  Either increase the amount of roads "
9 S+ j2 {1 a5 o4 C% c! g                       "by increasing the GRID-SIZE-X or "$ t# s) [7 U% |2 o! x' {
                       "GRID-SIZE-Y sliders, or decrease the "$ ~! A) P/ ^+ @0 k+ N
                       "number of cars by lowering the NUMBER slider.\n"
5 y2 G0 O6 E; v2 x                       "The setup has stopped.")
$ @+ O9 e! T; J' j/ _    stop$ i  n3 o9 ^* n' b( M8 g$ U8 t6 ^
  ]
* C$ m6 F- c5 J  F4 ?- ?' C% C! q" b3 G- r. C' `' u9 f! X  G
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color2 P" _  d) j2 F9 n, v4 `6 i; j
  crt num-cars
  b$ N8 ?4 C/ ~; s5 }0 C( z  [4 k- F4 q* p  d" {. G' P1 F) B
    setup-cars
! A( Y7 ]* M# b( W    set-car-color, c% F# Y! K  B% t6 s& j
    record-data
% M8 P. ~2 x& `9 H6 q' q5 D" |  ]
: P' ]* t/ x2 u5 h6 p# y1 M
! o) s7 K. j% A2 _& ?7 ?" M  ;; give the turtles an initial speed
' L4 O; p5 B2 }) z" L% m  ask turtles [ set-car-speed ]
0 d% \5 d3 |/ B% e) h. y, f' h( k
2 Y( u8 R0 Z3 z! F9 r& [) a  reset-ticks  k9 B: b9 o- j3 w6 [/ ^9 T7 Z
end
% _; [7 Z5 `* b: _2 t% O) ?% e
% V" R7 K; g5 j" d1 x;; Initialize the global variables to appropriate values
* G7 ~* O, u0 _! q: Vto setup-globals  t1 R! \' {6 O! f% M2 }
  set current-light nobody ;; just for now, since there are no lights yet$ |6 A! E, P8 |5 e: j
  set phase 0
# y" e' M) C' F# J# B. [  set num-cars-stopped 02 o! g& q8 e, n3 S8 B  W
  set grid-x-inc world-width / grid-size-x
) N5 y" W5 s& d! b8 S  set grid-y-inc world-height / grid-size-y. j! Y3 E6 Z' T* h' P& ~( g
7 a  t" M; ?$ ]3 I" ~. s/ F
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
0 j: H- g& q2 s6 Z/ g* v  set acceleration 0.099
0 r' Z3 D( i6 m7 rend
& k6 T5 `+ D, X4 t& a6 C3 |2 l  Q2 @9 q4 T" C# D
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
9 v" R- s6 T. a1 L8 g- _, g;; and initialize the traffic lights to one setting
. F& b+ _6 E( E0 C8 ]. Uto setup-patches# x5 C: n; R" e7 R0 S
  ;; initialize the patch-owned variables and color the patches to a base-color
0 `  ]0 k- y: @$ b  ask patches4 }7 l4 I) |. Y) }0 j' X
  [
8 g1 D/ Z  _* U$ u$ y    set intersection? false  x/ i3 d# [) q. [' u$ X8 w" N
    set auto? false) n& z9 H. S+ ?* M. D
    set green-light-up? true
; F5 i  E! b7 n) N& {: D9 ~) D/ z) W2 J    set my-row -1
/ e" E4 f  A2 L( P6 A) x* X. S    set my-column -1
- k1 N3 G1 S- @9 Q" E6 c    set my-phase -1
) w/ {& L. n+ s) v0 r    set pcolor brown + 3
  h& T- k5 K' c, m  Z: N7 V  ]% s3 E0 |9 ^4 F. J7 u! h5 `# F

0 x: z2 `  o1 m7 f  ;; initialize the global variables that hold patch agentsets- s' J5 L' }0 m
  set roads patches with
  F8 o' N) F( _    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) x0 B5 f6 b5 X. G/ W( `9 f
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]% V5 x5 B/ r) i( m
  set intersections roads with/ u' f" k; b/ [/ ]
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and9 ]( f# f8 }) G7 o* v" B7 Z
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
7 r! Y0 l+ _% b0 J7 m6 F
4 ]# U) s. R" i  ask roads [ set pcolor white ]. g4 Z3 C' g2 T; Z: C
    setup-intersections5 ~# \" ~; K! A  s) U% p
end
. o; [8 ]5 O. t3 W* J其中定义道路的句子,如下所示,是什么意思啊?& {3 h0 J* A# x
set roads patches with
1 i1 g( Z! L9 X) I: C/ u; ]    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or9 u% l/ F( `6 A5 W) E" l- O. h
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% @8 q  c7 \- ?/ \7 F) R7 ^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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