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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。
( D# Q5 B: Z; w$ C3 Hnetlogo自带的social science--traffic grid这一例子当中,! S) h) d& H0 D9 T
globals
4 k7 m: \. y) L* ^- t- O[
4 v2 [" y% N' t! k& H; r9 w3 y  grid-x-inc               ;; the amount of patches in between two roads in the x direction
6 G) q6 `9 k' }7 g% N. O  grid-y-inc               ;; the amount of patches in between two roads in the y direction
( Y; M( h( T; q& w& n; v' `6 ^, z  acceleration             ;; the constant that controls how much a car speeds up or slows down by if+ a& H% a; x5 ^
                           ;; it is to accelerate or decelerate' d  i, _6 A# G; K
  phase                    ;; keeps track of the phase
( i7 v6 N) G' c3 A) z/ C( S  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
& v: J/ @8 n4 g: |4 m! W  L  current-light            ;; the currently selected light$ E7 g7 n9 o* |
/ w4 q2 e% p9 @) ^8 y, f
  ;; patch agentsets6 F. F( d, L: W9 Q+ P: K* _" a* x
  intersections ;; agentset containing the patches that are intersections
) ~& T- C& y' t1 S* R% y  roads         ;; agentset containing the patches that are roads+ Q8 H! m" |- W; W
]6 t/ l/ g. u' j2 P0 Z0 {* O# ~
+ ?2 }! l( }# ?5 s3 s
turtles-own
% U# S/ S1 M  i[" I; ~" A. m! v) M4 I8 M
  speed     ;; the speed of the turtle+ f( g- v5 Q( x5 |# p4 D$ q) j
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
* }8 P+ T9 P$ S4 r  wait-time ;; the amount of time since the last time a turtle has moved+ P- p8 {0 \4 T6 S4 O) y6 k
]
3 s; ~! l3 g/ C9 d3 U/ E1 h$ |, u* c; X7 N+ m1 w
patches-own
+ {/ B* x! O% e. K[- h" f0 _/ m  ~3 ^  i8 _3 z
  intersection?   ;; true if the patch is at the intersection of two roads
! j: b4 I, B6 B9 A( w1 O  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.3 G6 r% s6 j4 O6 D  z5 ^
                  ;; false for a non-intersection patches./ M* Q, i, I3 |( {6 E0 T5 ^
  my-row          ;; the row of the intersection counting from the upper left corner of the
( W6 B, ?& ^. w- w0 }  L6 h6 L                  ;; world.  -1 for non-intersection patches.
* F2 C0 |) L+ |3 a  my-column       ;; the column of the intersection counting from the upper left corner of the
: L% `/ ?; l/ H% Y                  ;; world.  -1 for non-intersection patches.% r" d% F/ `. ^& }/ {7 A+ r
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
( O; q0 ?! `% R  H8 a; h  auto?           ;; whether or not this intersection will switch automatically.1 b8 T; z& Q3 a& h
                  ;; false for non-intersection patches.
5 m" h' C0 T6 L7 h]
1 `" Z! y- ~5 L6 R+ a" |& v) Z1 m5 w- j- W+ c1 }8 i

& Y% O: ]* M8 j7 u1 {;;;;;;;;;;;;;;;;;;;;;;
$ B/ `$ w/ @1 p+ h. R;; Setup Procedures ;;' }( M1 J3 I; Z; B. |+ V
;;;;;;;;;;;;;;;;;;;;;;
3 |5 L- k! ?5 S: s- o# e. s- p" G" w, L& r- F/ C# u3 o
;; Initialize the display by giving the global and patch variables initial values.9 [4 }, G8 b, j8 d
;; Create num-cars of turtles if there are enough road patches for one turtle to! Y( ^5 s; k* i7 P2 |- }
;; be created per road patch. Set up the plots.! a$ P; C) E% J" H; t7 m7 X! \
to setup# `2 e$ ~" O$ `$ t, J
  ca
; [0 }  P$ Q: z# ~+ X4 S4 ~0 k  setup-globals
- |+ ?: i* y: v
* P; s' w* O! v. o( o: U  ;; First we ask the patches to draw themselves and set up a few variables% x5 j9 Z6 y3 D3 B
  setup-patches  B9 R" n4 h9 D9 z- ]% N
  make-current one-of intersections2 l1 T: ^2 N3 ^+ f8 ^
  label-current
4 R( C3 ?, P/ O( j2 ^
" n5 V: V( ?9 H9 \  set-default-shape turtles "car"
3 J3 h& @6 V! I6 I
! l' e5 n( \+ m2 k; O  if (num-cars > count roads)
1 j' V3 U% @; S: A# g/ }  [
  ~6 J6 A0 J( o/ Y# X2 y, c( b$ Z    user-message (word "There are too many cars for the amount of ": v( a0 s& z% Z( c7 p. T" T- |
                       "road.  Either increase the amount of roads "
4 V( u8 f! l- e  ]                       "by increasing the GRID-SIZE-X or "
! Q( d+ Z/ t$ `3 C$ R4 R                       "GRID-SIZE-Y sliders, or decrease the "
2 `) Y8 G# e/ E                       "number of cars by lowering the NUMBER slider.\n"
3 r7 J. ?6 O, _1 |8 Q! R                       "The setup has stopped.")
: i4 c# E  ]* W+ Q+ ^    stop) r2 [& |% p9 Y- M; q+ a
  ]. j6 V# d9 l. e% E& n
7 f3 Z1 x' V' c$ Y) F
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color7 j4 ?% ~3 S# K6 M- f' j- Y
  crt num-cars
! i; z' K, A* C- U2 c% H# }, Z. t  [9 x/ c% g9 `5 s% C+ P: U/ Z
    setup-cars
4 z; i% f$ V9 g    set-car-color
5 P6 C0 p  r0 I/ e    record-data3 @: y, }1 k2 \7 n% ^! A
  ]6 V/ l! }7 z9 R, A. n! \# v) R8 i* P

* s( l+ p; u( H: i+ S  ;; give the turtles an initial speed/ r0 |9 I% K$ i' G; I2 K
  ask turtles [ set-car-speed ]$ t0 U+ P; F/ [) p- |

. b; d: N* T2 [* \) q: S  reset-ticks
+ l' N. f% _3 H, V- Bend
! {: o' |% P, v6 C
4 t9 G6 ^6 x; s;; Initialize the global variables to appropriate values/ q, Y$ @2 |$ x
to setup-globals2 Q% X$ u$ G8 I5 K; I. C
  set current-light nobody ;; just for now, since there are no lights yet
) H: ?2 ]; a/ a' v  R. X3 v  set phase 01 G3 S" U$ k. D" [. e* }0 Z
  set num-cars-stopped 0
4 [( T" B- _7 H# j& e/ N' o& Y  set grid-x-inc world-width / grid-size-x
2 y0 K$ B9 p. J* w8 M( L; z  set grid-y-inc world-height / grid-size-y5 C( S& F% V6 D) a! M* m3 z' C
/ }5 n6 B1 L! q5 ]) T: R' t
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary2 {, A3 `  y6 A6 g  `4 @
  set acceleration 0.0995 T9 _" y1 }. b/ q- S" N+ }
end2 I& h& i: g4 V) C  @
- V0 K7 y: U, [/ t. _+ H( ]9 W! {
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,9 u% g* k: ]% x
;; and initialize the traffic lights to one setting
0 _) ]/ Y; b2 r( jto setup-patches
& y' A( Z, |# z" P, J" \' H  ;; initialize the patch-owned variables and color the patches to a base-color1 N3 X- w; f" V4 D  V, U0 ]
  ask patches
( N$ b. E4 q* s# z  [' t% |  M$ b0 z4 U
    set intersection? false9 l# T  V3 W& O! R" l
    set auto? false4 c5 E# e4 ]$ a* ?5 X2 k( E1 [3 m% }# U
    set green-light-up? true% [: I: O  f$ {" I
    set my-row -1
; y4 q( J- ~/ _& `' ]    set my-column -19 @/ u+ ^! Z5 r* G1 {7 q
    set my-phase -1
  y& Z" x) H( Q" \# w    set pcolor brown + 3; t: M- i* q3 [# B8 i0 B/ s
  ], N/ A* b8 Q- w9 a

* d+ E% J4 q: R6 b5 T/ }" h1 o# I  ;; initialize the global variables that hold patch agentsets
# ^8 p4 @# v% y* T' [  set roads patches with
/ g0 Z2 Q! r4 u    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
& O* F1 B$ m) a1 s) P    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]; h; R  w6 ]' l# Z
  set intersections roads with! C6 p; }9 \) M3 ?7 b% t* Q7 g( ?
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and5 k; ~9 v2 C, E* F& p* ~
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ w7 Z# c! ]% R( t9 P
- e" b) @4 j1 W  V8 F
  ask roads [ set pcolor white ]
5 b1 y+ p7 d( O1 {. V0 Y    setup-intersections7 s* D0 u1 ~! K) a/ W% {4 i
end' J1 I) V% N7 ^/ L6 k2 c. {
其中定义道路的句子,如下所示,是什么意思啊?
# X5 C3 v9 x' R8 C  w9 y; n. v set roads patches with
/ b8 y; n  Z" [0 B7 v7 F' r' g    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
, S9 B4 M8 Z- y7 C- i, p* v. n% S2 I. D    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) Q/ B) c" X, W* i  J9 P6 {) 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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