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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。
$ a! G$ Y: v0 b2 k8 Snetlogo自带的social science--traffic grid这一例子当中,! t$ `# g) ], s( L, v
globals
) Z! r. o% G6 t# Q2 z$ T[
3 J+ f& _8 C, t% R1 |9 J5 P; @5 q! n  grid-x-inc               ;; the amount of patches in between two roads in the x direction* X# x' J* p4 E3 t" ]2 F/ B
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
/ Q( }: Z' C* v& c  acceleration             ;; the constant that controls how much a car speeds up or slows down by if7 Z$ l% o7 M, W. p9 r$ f9 Q# x
                           ;; it is to accelerate or decelerate" B8 G9 Q' z6 L
  phase                    ;; keeps track of the phase
$ N) t, \0 k: M  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure7 ?: A& l0 |1 a) F; K  |
  current-light            ;; the currently selected light' g/ A/ ~3 R! {% D9 M; A

; D- a) X2 R8 T* ~, y0 s  ;; patch agentsets
& r$ u' h* P5 a) ]8 @* s. k  intersections ;; agentset containing the patches that are intersections
  g0 C+ C3 {4 \$ Q  roads         ;; agentset containing the patches that are roads6 z: C% d0 C2 ^, x
]2 Z, Z$ k* Z' J- X- C
! e% d' v% E6 }+ }
turtles-own
% H9 s  E6 t3 W  C( _[
' W& E3 i: q5 b6 k4 l  speed     ;; the speed of the turtle
4 @! f! `5 @2 f) M  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
8 A7 i6 C, Y. q  wait-time ;; the amount of time since the last time a turtle has moved8 P5 u* @; V9 I. r
]2 a9 i* Q! Z) Y# v- o% F

7 j' e2 I2 P; O8 _* e) `patches-own' o5 Z4 S+ X) p4 b1 P
[$ B3 L6 d& V- T
  intersection?   ;; true if the patch is at the intersection of two roads
1 m$ y. u# T+ L5 l4 v$ h  green-light-up? ;; true if the green light is above the intersection.  otherwise, false." a/ U6 T2 l* U) G! I
                  ;; false for a non-intersection patches.
5 j- `" P: y4 x1 I6 d2 {  my-row          ;; the row of the intersection counting from the upper left corner of the( I! Z9 b1 e  r  Q9 S
                  ;; world.  -1 for non-intersection patches.8 {, T: A7 @2 F
  my-column       ;; the column of the intersection counting from the upper left corner of the9 R# u$ R' V, c. r2 t* _
                  ;; world.  -1 for non-intersection patches.
8 q! L$ W; b3 B( I' H' O& z  L  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches./ l/ n8 s" p/ ?/ I  w
  auto?           ;; whether or not this intersection will switch automatically.
1 G+ N6 x: u& P1 Y0 }                  ;; false for non-intersection patches.
; E% m, b3 t8 f* ^; i]
- I+ ]9 `' g* F7 {% b' O+ Y
  ]1 }% p" K: X- o! V9 h
, [/ [% y, ]( L;;;;;;;;;;;;;;;;;;;;;;
0 r) T; C* r; Y9 P( L, B4 N6 o;; Setup Procedures ;;9 ?' d5 m- U. N
;;;;;;;;;;;;;;;;;;;;;;
4 f+ l8 F7 x, F' T1 V& ^4 {" K) T8 w4 _( ?: X
;; Initialize the display by giving the global and patch variables initial values.1 P6 H' u- z) b& l! x+ ?4 f
;; Create num-cars of turtles if there are enough road patches for one turtle to
& ^; [+ b+ r6 a6 A;; be created per road patch. Set up the plots.
; p* Y: N3 Y* L+ A7 c" kto setup8 R# Q& b8 b1 {8 N( m. F6 g' [7 y
  ca
. u& C( S4 q& C  setup-globals' j; i' ^4 i) m9 Y7 h7 S8 _* j

, Y  d* f( w: Q# b  A- C1 X  ;; First we ask the patches to draw themselves and set up a few variables9 L7 ?0 x' K' c! W, o, m
  setup-patches, O( g! u8 ]$ [
  make-current one-of intersections; j+ Y$ s7 l6 N/ J
  label-current& s! W! m4 u) K+ l* _: V

# B( C2 E# M$ x8 j8 \+ s, |" n! ^! Q  set-default-shape turtles "car"6 {7 Y; n8 s. r( ^7 Z6 i4 M

% G, y$ y7 Z6 U( ^; _' L1 }7 b( U  if (num-cars > count roads)
; @* c# b3 B/ X: ]2 ~5 ]. x  [
* [0 P" D% s- Y5 ]. j. b. _0 v    user-message (word "There are too many cars for the amount of "
* J* d5 K- Q$ p+ u# e( k- j& D                       "road.  Either increase the amount of roads "
/ V( \  M, C' M+ B/ N6 w                       "by increasing the GRID-SIZE-X or "5 _: `, N. L; Q1 V
                       "GRID-SIZE-Y sliders, or decrease the "
7 |9 W$ J5 l. ?. x/ z. h                       "number of cars by lowering the NUMBER slider.\n"
5 _" F) h: Y( }5 c                       "The setup has stopped.")0 k: F$ m- }. x1 B1 K0 W
    stop
9 S7 G- d- K% b) @: O. x  ]( d$ I* c0 r( D/ }

3 h* ^% e( T& u; L  ^% Z  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color2 C4 a% w8 i/ O) D: X" U4 r
  crt num-cars2 E* i& [. _$ D3 ?( m' s) Y
  [0 n0 D8 W3 l- V& A4 |: a
    setup-cars3 M: h! `9 ^, I- |" e/ n9 z
    set-car-color  o6 P9 A% |  e0 i
    record-data
8 N  m8 X6 N; M- U* q  ]
" j; L, F0 K+ Y' v9 Y: G  v! l5 Y
* X" e( i3 d! q' v, c! X8 x  ;; give the turtles an initial speed
0 ]6 m" e+ b) Y) D  r! \0 @  ask turtles [ set-car-speed ]& |. s9 {* s5 \7 E% _/ h
; D" A9 R4 I- [; y. g( T' w9 P
  reset-ticks$ h: p$ }" y; u
end0 k0 X! x! I0 F# p
2 f: `. ~+ e+ D3 e3 j+ n/ d
;; Initialize the global variables to appropriate values
& ?# `' ~' k/ u7 M' E: ^to setup-globals
' N8 K5 w% i4 E  set current-light nobody ;; just for now, since there are no lights yet
) j" g/ V7 {/ }: O$ d* _3 D1 U# U  set phase 0. L& |0 k$ f, D) c
  set num-cars-stopped 04 J3 q9 p+ i6 k8 O, r+ s/ P8 ?9 T0 X
  set grid-x-inc world-width / grid-size-x
" m+ I/ e. s% O( g+ L& W  set grid-y-inc world-height / grid-size-y+ ^) w# e* a$ h% P1 Z& L, d* f
) H) U: f% b. |+ W7 Z$ a
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary  q1 ]2 x# n  p! Q3 l, N
  set acceleration 0.099
8 U9 u8 w  I+ x5 Z- Eend% c& b4 f' h& v, @
- |$ ]1 v9 ]8 |; u& q
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,  Z, U4 S$ R" Z: V# y2 n
;; and initialize the traffic lights to one setting
/ e: U" l+ I, `to setup-patches
' B) D6 V, ^. ^( S  a# f1 n0 p  ;; initialize the patch-owned variables and color the patches to a base-color
: M! d) d/ F* {) @( p8 x6 y! ~  ask patches: k4 J: i; R7 \4 ~1 Y' M7 o
  [
# U; Y3 G! S% g& n    set intersection? false
( j- Z1 u$ D1 f& ~; i    set auto? false, R+ C$ z- w4 X1 L
    set green-light-up? true
8 i9 G0 o/ {! g    set my-row -1! q) g0 v4 r" y, ^4 \% i: i
    set my-column -1
7 ?4 T1 ~3 ]" V    set my-phase -1
9 ]; t: L, a8 T5 e0 l+ n    set pcolor brown + 3
2 X7 _1 R& B5 j; r9 y1 p& O4 W  ]
- w% G% V3 ^% z3 E$ o, g6 X  H1 V! @4 h2 i7 h' v: C
  ;; initialize the global variables that hold patch agentsets
  H0 x' r: W- B0 [4 F. ^2 I  set roads patches with$ W! f: L2 d/ o; ~" Y( ^
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
. u2 O* R2 x1 ?: R+ k# J, M/ n    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
" P4 `6 O6 n1 Y# @3 G4 P1 z3 L  set intersections roads with
4 b) ~7 q/ n$ C. T    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and$ A( J4 T3 G, x" F$ P4 b) M4 v
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) M" Y' S1 [+ @
1 s: E  e  c0 h- `, B+ O
  ask roads [ set pcolor white ]
, }. U' P" }- C" P8 |& n    setup-intersections, v$ `) M; _0 m
end8 k, {" l) M+ f/ k0 p
其中定义道路的句子,如下所示,是什么意思啊?
, [/ Q( p) Y* o0 i/ I9 ` set roads patches with
4 V8 E0 K: N; k! Z  d4 ]' c! ?    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
0 ~8 n9 S" {! U+ J! \5 d1 i2 G. s    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
0 C: @8 U, n0 W* g2 x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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