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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。
$ O- i3 N  a0 e! f+ {netlogo自带的social science--traffic grid这一例子当中,
, T( t: F) ?& e/ g7 j8 E( ^8 tglobals4 Y  |* n4 ?$ E" A- X0 k6 `
[: ?$ ^3 F$ J$ Z* n( r. H8 p
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
6 C. s% h1 |* c* h4 W! `% X) Y9 V0 _4 X* }  grid-y-inc               ;; the amount of patches in between two roads in the y direction! C* r# p# \$ j* W( C
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if* h6 M& _: F/ ]8 D
                           ;; it is to accelerate or decelerate
4 M0 z0 l% z# H" j4 S6 {/ t! L7 K$ F) \  phase                    ;; keeps track of the phase( z8 C* Z3 f& E- A# U$ n
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure6 O. b9 c' P- Z1 S& U
  current-light            ;; the currently selected light0 Q7 T) I& p" P- t3 F  h, Y

7 v6 F( q3 r0 M1 f5 T* x# L1 v: `  ;; patch agentsets
8 t3 t! O2 m: \" M# J" Y  intersections ;; agentset containing the patches that are intersections
' U) i7 d- w& ]2 Z  roads         ;; agentset containing the patches that are roads6 y0 |  |5 }* K8 W# n4 f
]0 u+ L# ]. N7 Y* c! L# _$ m5 }

/ r4 V- Y" l6 c1 d8 E+ u1 Vturtles-own/ }% [  u# H/ h  C7 n& r
[' @+ }7 Q3 J) m' y' z0 r5 e2 a
  speed     ;; the speed of the turtle
* x% Z4 R! m4 l4 t: s7 d" p* q4 V  up-car?   ;; true if the turtle moves downwards and false if it moves to the right9 E2 t* l% z: O7 l$ n! w* I
  wait-time ;; the amount of time since the last time a turtle has moved% N, m  q3 D- w' V  T! A
]! S& K7 ^/ t" u) t* `$ `1 x, c

6 I" \7 J- J5 K( p( Y7 Y6 R2 h; z- Lpatches-own5 Z1 b/ X7 }" S5 K! e/ M
[( e  ^* u) y0 ?! ?- e4 P+ s
  intersection?   ;; true if the patch is at the intersection of two roads! r2 V4 W% ^" {8 i( A/ \
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
; d0 {& n1 L5 t5 l8 w8 m( M                  ;; false for a non-intersection patches.
6 Y/ H8 P! t, B3 x3 V( ~! H  my-row          ;; the row of the intersection counting from the upper left corner of the
! Z" G  e+ z' g( S                  ;; world.  -1 for non-intersection patches.
# N- X2 E& G- O  Y7 i$ E# i$ }" e  my-column       ;; the column of the intersection counting from the upper left corner of the
2 t! H$ u" z, q0 Y/ w* i                  ;; world.  -1 for non-intersection patches.% ]2 ]) H' m9 v7 E) o6 z
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches./ k3 k- H2 e7 i% q8 q
  auto?           ;; whether or not this intersection will switch automatically.% `- f9 L+ ?, @6 z/ }9 t: m
                  ;; false for non-intersection patches.: S" p" F; a3 z; |9 K0 N  K
]
) @$ U; O4 i3 V9 g2 h3 r9 u
: F: C" W5 k9 a/ Z1 `0 S: l) J6 \. Y, r1 O7 q/ u
;;;;;;;;;;;;;;;;;;;;;;" ]2 R5 l) V" u; A
;; Setup Procedures ;;
1 Q) j3 |: g3 z. O) S$ e;;;;;;;;;;;;;;;;;;;;;;
0 l0 \# c- i+ Y( g
- k3 R/ z. Z8 }8 I;; Initialize the display by giving the global and patch variables initial values.
; L2 [) C- y6 N3 ?" u) L;; Create num-cars of turtles if there are enough road patches for one turtle to1 q( ^5 `( {4 h8 m- S
;; be created per road patch. Set up the plots.7 m0 X) \0 J% O& _/ S
to setup* ?4 Q8 z1 \* p4 a! c$ {, B' H
  ca8 K+ ]2 ~5 V4 R! j1 N3 K. ~
  setup-globals
: g2 }4 g, u$ H) u
$ s* ~* X4 z% ]: N" ~) _  ;; First we ask the patches to draw themselves and set up a few variables
/ ^: w0 f- c  e7 L3 b) ]! `  setup-patches' v8 l. i! y5 Z% j
  make-current one-of intersections
. C0 i! H; @6 y4 }1 l' Y  label-current3 d7 i7 R9 d9 e2 T  D% s
0 S, A* ?2 W4 V/ E/ T
  set-default-shape turtles "car"
& Q( n* U5 ]4 E" Z! u) c% x& v2 j( o6 c0 D3 V3 s! k, f
  if (num-cars > count roads)
  l: i0 f; u; q) `$ n) d/ v7 d" K! f  [" U) p7 i, e3 \0 X0 E2 ^
    user-message (word "There are too many cars for the amount of "
$ c. {" O+ X' U1 Q, [                       "road.  Either increase the amount of roads "0 v4 o! f; d6 a
                       "by increasing the GRID-SIZE-X or "1 Z% D, B8 c$ k8 h- |
                       "GRID-SIZE-Y sliders, or decrease the "# c% Q5 I  u" f% [9 y3 z2 m9 m
                       "number of cars by lowering the NUMBER slider.\n"
+ l7 l& K) @( D" B8 @( l9 O                       "The setup has stopped.")4 E5 M/ u+ ~  z0 f
    stop4 H  S. l2 W' t  e4 w* L
  ]
# m0 i, n  c3 s/ B3 y7 j
* I5 p4 {, }  d" m  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color9 ]" J8 M1 i3 m% `* D. g
  crt num-cars5 j# W3 W- I# W+ m
  [
! Z* P: v; P+ c; Z' P, J    setup-cars
% }( c& Y- e& M0 z6 E: V    set-car-color
3 |9 X2 b$ }6 t! K6 q* v4 Y    record-data
% Q) x( h, S. M& I  ]
) x# e; U0 Q: j0 Z4 `, a, ^. m6 W( }3 P  f: X0 t4 C0 X
  ;; give the turtles an initial speed
/ K6 W+ _& x4 o0 C2 g  ask turtles [ set-car-speed ]
, u! W- O' j8 P1 T) [( t+ }
* m3 F! {7 \# o9 w- ^7 g( D. `  reset-ticks
! B0 r# l" }" }0 Rend
  l; I9 l; t0 a- U- `
( i* ^8 }: G9 G* \* }" n+ B;; Initialize the global variables to appropriate values
1 D+ n8 V5 [4 ]& p0 ~/ C- ?" z6 Pto setup-globals5 r. m; u1 n% }) v$ P. f" B. o
  set current-light nobody ;; just for now, since there are no lights yet
3 ~  X2 f: K( P+ N7 h4 L6 j  set phase 0* P7 ?  b% Z4 ]' m
  set num-cars-stopped 0
; n- {2 i1 g9 T! j  set grid-x-inc world-width / grid-size-x
5 O' P, Z) s( {$ A/ b8 u, s1 [  set grid-y-inc world-height / grid-size-y
- w* i' l8 `( H8 w4 t& O; G% \1 S& J+ q/ e- b$ ^: ^, F8 h
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
, K, k: l) u! A: y% M% K3 ~9 V  set acceleration 0.099
- R0 I" }3 I* \  ^8 f+ s1 l  Wend5 [- E! f9 X! k' b; Q) F* F9 _

7 P& N. L4 n# u3 I1 A3 u( x8 E;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
/ u7 k7 @8 G. Y7 J;; and initialize the traffic lights to one setting
( o/ Q; \# n- qto setup-patches
; D1 ]" q; ?2 Y4 l: B/ C" p  ;; initialize the patch-owned variables and color the patches to a base-color
. K2 e: u% [8 A2 K2 m- l7 \5 v  ask patches* z- ]5 ^4 X# R2 c  G7 J$ y
  [6 `2 Z4 K. _0 _5 T$ s6 F0 r
    set intersection? false" k! }& y+ U' h" x" J; o
    set auto? false
# H: ]  V; Q+ B/ z' z$ b$ s. t    set green-light-up? true
0 {. q& g' {; l( Q" a    set my-row -1# A; o' A" s3 k  g  P
    set my-column -1) ?: @) S' m6 T
    set my-phase -1" @- w* X) }+ w: [* m3 X: h
    set pcolor brown + 33 v" A7 a5 Y; g5 {$ i' k1 W
  ]! e/ N& C7 a0 N# o9 _/ y% R* n
" u; |7 ]0 {7 e+ O' [
  ;; initialize the global variables that hold patch agentsets
- _- g* D8 U9 m0 z  set roads patches with" \9 P- A6 Z' ^
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or0 X4 q; x, i' ?2 K
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]4 b5 J8 K7 Z. u
  set intersections roads with
) J) E1 e# I: b3 v% K/ e    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and: `' z- F5 L$ f6 a
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)], ], w7 T# U. V( C3 F

2 v2 l. x$ l' H  ask roads [ set pcolor white ]! }- t. {0 O9 n' u; `0 C0 J
    setup-intersections" D6 u3 @6 k/ H
end$ T' y) ~$ t, C: B: X/ ~
其中定义道路的句子,如下所示,是什么意思啊?
( U$ `/ M. x; { set roads patches with- ?8 E( B2 g1 F4 E
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
' s" l1 _5 t* O7 [. G% Z    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
, P$ C; b* L0 D7 O/ U- B' d% _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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