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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。5 s7 i. Q6 m' w
netlogo自带的social science--traffic grid这一例子当中,, ^9 @/ i7 t; D. v. K& |! h) Z
globals# N' s3 f1 N/ g* u
[
" e% J5 v- j$ \8 V- f  grid-x-inc               ;; the amount of patches in between two roads in the x direction
' Z, }" b* P6 x; W  grid-y-inc               ;; the amount of patches in between two roads in the y direction% I) z5 [4 \0 r! ?& ^
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if( [6 ]1 y7 J, ^0 S% F
                           ;; it is to accelerate or decelerate
! T8 U- L) z2 ]( m& w  phase                    ;; keeps track of the phase* ~! P/ d3 U( C0 n; p0 D, Z
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
& W; N: Q. L. j# _, _, u" p  current-light            ;; the currently selected light
9 d; _- u' _  I* w0 l$ H$ c1 o' l3 y' R/ W9 r' L
  ;; patch agentsets2 b. a, `+ h' O" t! e
  intersections ;; agentset containing the patches that are intersections
6 s" P: Z' w2 \- a$ _  roads         ;; agentset containing the patches that are roads
" y% l% R* H. M2 R; o- E$ g5 X]
+ d. t9 }# O/ a/ `* r& H$ o1 _# S3 O8 ?
turtles-own( v: g+ M3 ~5 b
[
2 d; }7 u, j* y1 g# M4 h  speed     ;; the speed of the turtle
& ~' T* z, h$ m' J  up-car?   ;; true if the turtle moves downwards and false if it moves to the right; W" C+ S* N' Z- u& \
  wait-time ;; the amount of time since the last time a turtle has moved9 b; g9 j9 J# J; R6 g5 m2 w4 c
]
! {* X# T+ d" J- h+ P
  o$ b3 @; m$ E: h) rpatches-own' N& ]% m! S; S: t2 i
[
# |) [1 b$ Z( y0 h) q% G7 o  intersection?   ;; true if the patch is at the intersection of two roads
, `# q$ P  R/ d4 R+ F7 R  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.! x5 E) }: i1 d/ M6 P% I
                  ;; false for a non-intersection patches.
3 R+ q6 }% T" s" D  my-row          ;; the row of the intersection counting from the upper left corner of the; o, a* j4 U' G4 z
                  ;; world.  -1 for non-intersection patches.
7 U& e: w! I1 b: C  my-column       ;; the column of the intersection counting from the upper left corner of the  a+ I! T6 h& e# n! X5 b, |# K
                  ;; world.  -1 for non-intersection patches.7 K  O. ^% \+ ]
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.% L) ?, {9 u9 [4 e% A; n! x
  auto?           ;; whether or not this intersection will switch automatically.! o' x* h* o* m
                  ;; false for non-intersection patches.
- ?) v& A0 e9 f]
5 |$ @  {+ I( [6 Z0 H% x' c$ l9 j' p( l% x- a: j! g

# L3 N, z* i& W;;;;;;;;;;;;;;;;;;;;;;- s9 A" S2 N, B0 M1 Q9 D
;; Setup Procedures ;;
% T* E' k" b# G6 ]- P! a6 ~;;;;;;;;;;;;;;;;;;;;;;
  f2 _* a# K3 a# l  D, d, ^# V" A+ t' D$ }3 k& J1 I- j. ^
;; Initialize the display by giving the global and patch variables initial values.  ]  Y/ M! j. h5 ?& U2 L
;; Create num-cars of turtles if there are enough road patches for one turtle to4 P( \- i0 c" R& d8 S; x
;; be created per road patch. Set up the plots.# d3 V0 W5 k5 k- K( e. a6 w
to setup
7 \; _8 _9 G- w4 `$ Y  ca
* Q# d9 a1 f* l. f  setup-globals8 \3 ^6 n& f! G
4 w" i3 Z; K* E4 u
  ;; First we ask the patches to draw themselves and set up a few variables' }: z. C" v- O  ~
  setup-patches+ |' h& i- H7 D, |1 F6 H) ]
  make-current one-of intersections
7 H) n* _: F6 G2 s/ q; W  label-current8 \7 J7 S* w* V) b6 Y

: B$ Q- C1 X2 a+ M+ z6 ]  set-default-shape turtles "car"( S( R; E1 z. x1 ~
+ Z, E# U& w  f3 {/ C
  if (num-cars > count roads)( X* Y8 k( {5 H/ w6 g
  [
9 H; R# w; }9 r; h8 s1 U* X    user-message (word "There are too many cars for the amount of "' D4 p  g/ W% @' k
                       "road.  Either increase the amount of roads "7 M0 m8 @3 a2 [5 i5 n2 {; z( l: [) J
                       "by increasing the GRID-SIZE-X or "
& z4 O" J* ~, _" X5 \) S0 V6 Y                       "GRID-SIZE-Y sliders, or decrease the ", k0 K0 o% ~# l% j, f2 c
                       "number of cars by lowering the NUMBER slider.\n"
* r& L' L/ T6 g: q, z. P4 A2 v! X* |* K2 `                       "The setup has stopped.")
: U+ |. x/ p8 @# u    stop: P# j! F+ q9 B4 W' y! K  k
  ]9 T9 F# S  B1 m) m' V
! `$ K; N, R: Y" b% d+ N, C
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
1 o* o/ w8 Z. u: Z9 {$ ^  crt num-cars$ b  `! B' @- u% `: F
  [3 A; q0 a$ y4 p
    setup-cars
0 {( G5 `# e9 |* c" h% V: h3 Q    set-car-color) O3 J9 J3 \) ~" }' W( k
    record-data5 t( }; {( S8 H2 P. U
  ]$ r6 y# m7 J9 b0 b

: a% ^- B7 P7 Y) r" ]  ;; give the turtles an initial speed# w1 R8 n: S0 {( M, u* q
  ask turtles [ set-car-speed ]
9 P1 ?5 |- Q* ~+ Q
; t( p; v% Y9 E* X; c  reset-ticks
( L& I# O9 @6 cend- l( I. d2 G% D, Z- I- O# O6 X7 Z: C

4 p7 B& K3 Z' V: Q3 _& \8 G;; Initialize the global variables to appropriate values( w+ ^* s* }; u  l% W% I- e
to setup-globals
+ A9 Z& [5 {1 `+ C8 C: [0 F; Q  set current-light nobody ;; just for now, since there are no lights yet' T- g: l0 U' j( q- D' {/ ]
  set phase 05 d9 r& B9 H, l% ?+ @# u
  set num-cars-stopped 0
8 x: G6 G7 }! U* _6 r0 G( R  set grid-x-inc world-width / grid-size-x. u: H# v+ X6 }8 F
  set grid-y-inc world-height / grid-size-y
: n$ }6 V1 [" l5 X# |
% Q; l7 Q2 B' c4 e- M2 h3 c  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
- B" s3 z. ^9 p* W  set acceleration 0.099
& N3 J2 U& `1 K) ~end8 m% D, H) f+ t8 ^( ?2 p
& ]" @9 r- `6 y- k& f- t+ s
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
3 q: W2 X8 w6 J;; and initialize the traffic lights to one setting
( m9 v- s$ l2 [4 A3 S1 cto setup-patches
/ f! z5 s4 }$ F; ~* G  ;; initialize the patch-owned variables and color the patches to a base-color
3 T# q( A. u$ K3 w  ask patches* [* Z& b+ x/ V6 r
  [
. y8 S- i- a3 u0 Q  y    set intersection? false, y# v7 |# a, T
    set auto? false
+ L" v6 t( ~! e9 l" M$ I    set green-light-up? true& @; c' M/ y$ ], [1 q% D7 x
    set my-row -1
  V% i- m% q: Y8 k3 [    set my-column -1
2 E% W6 N% E& z- o8 y4 W% @9 J    set my-phase -1- o- m7 u7 K2 k) [) y
    set pcolor brown + 3" j8 T1 X2 k8 X& ?
  ]  `* {  j7 w$ X5 i4 n3 k0 F
& s7 Q) r1 X1 A$ Z1 F' A( h$ l: U
  ;; initialize the global variables that hold patch agentsets
" K) |* w7 Q. ?: X7 n. D  set roads patches with( K5 s% u1 U: H" v* ^) Z0 R9 V! I
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or. n$ J! t$ i7 z) O) ?7 t
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)], m4 n  T* @) y
  set intersections roads with. h0 ~1 H/ Z. {* r5 ]
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
8 j$ l* X8 |0 ]5 n6 M. C* N" T    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) ^* e) Q: \9 ^0 w

  \8 |, s5 z5 N  A4 c  K/ p9 v  ask roads [ set pcolor white ]
3 x+ n8 e7 X' {8 G4 f: k6 _    setup-intersections7 E! D+ y" S. x, p3 |
end
& ?: {* u# `" a* o* ^  l# u4 @其中定义道路的句子,如下所示,是什么意思啊?/ g( \6 }5 h/ T0 X
set roads patches with6 L) p& \/ e" [
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 [' o  M& x! f& K' ~- ?
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]  e- C; e7 l9 {- Q
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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