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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。4 C0 `, r) H  \1 E& @+ O* ]
netlogo自带的social science--traffic grid这一例子当中,1 W' F1 `2 d8 H% O% Q6 ?/ r2 {
globals
8 N( B5 n3 F& @' i[) \* J- L. |% ]( |, K% S
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
% u1 P7 T/ J9 T4 m' E/ u  grid-y-inc               ;; the amount of patches in between two roads in the y direction, S" W+ l6 E, k8 Z7 d% }
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if/ V  X: n! m8 N2 _8 ]4 V
                           ;; it is to accelerate or decelerate
# c2 H' J2 z6 e0 W" q0 X  phase                    ;; keeps track of the phase
0 Z9 v. [8 V1 p2 N& z/ X  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
( H9 v8 _! A, r/ @  current-light            ;; the currently selected light
) v$ z3 {3 D* {+ w) y) u; P; a
  ;; patch agentsets
" x$ n; k0 _+ Z( u2 I  intersections ;; agentset containing the patches that are intersections/ r* {8 N/ z) `; {, ]' {
  roads         ;; agentset containing the patches that are roads
& z: z% M5 o) F$ T2 o& z' V]3 }6 g( f7 y* Q6 y
5 n: G: p: K! r4 a+ j
turtles-own
4 K- M. _: [: @( l1 `7 D[
  P7 P9 o2 v: ?$ X( T  speed     ;; the speed of the turtle& V1 g- Z" r  b  H( |
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
  G5 h" c2 J* J- f; T  wait-time ;; the amount of time since the last time a turtle has moved
) v" H. E9 {$ v; `( S4 c]
7 _( z  R$ I, `9 x& b) t) _8 e  {. N5 [% q2 _, T
patches-own+ E* A) F" n/ R: H0 i* A
[: \9 r( g6 v6 v6 P2 p
  intersection?   ;; true if the patch is at the intersection of two roads
! @0 n5 K/ K( t8 H# }" T9 L  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.* @" p7 i1 b' K1 q4 U
                  ;; false for a non-intersection patches.' ^4 M" C, [( O" K6 f& Y
  my-row          ;; the row of the intersection counting from the upper left corner of the
8 z$ q4 i- m+ B' F0 u                  ;; world.  -1 for non-intersection patches.; }* X% W, \- z5 k7 S# m" G3 p
  my-column       ;; the column of the intersection counting from the upper left corner of the
7 l* r5 Z/ P, j" @$ V                  ;; world.  -1 for non-intersection patches.
" D1 v4 y5 R$ T" b  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
4 y) f5 @6 E& A! u0 I+ o  auto?           ;; whether or not this intersection will switch automatically.% `  z% x6 t1 O0 k9 ]; D
                  ;; false for non-intersection patches.) {4 q! C* w& s3 Y" `3 ^
]( _5 V! j6 l0 a

9 |# G! K+ V; Z) [- ?
- H  u% ?+ l, v;;;;;;;;;;;;;;;;;;;;;;
4 }7 Z0 M* |. e7 w$ j5 a;; Setup Procedures ;;" r) h" a% h/ Y3 i7 d
;;;;;;;;;;;;;;;;;;;;;;
& m) H0 T, j6 f% S
0 n& H; s: W  A7 p;; Initialize the display by giving the global and patch variables initial values.( C1 |, m! t. [. R. `5 ?: V' o
;; Create num-cars of turtles if there are enough road patches for one turtle to
6 t: @6 {2 n& {$ l( P# r$ C) O! k' C;; be created per road patch. Set up the plots.
# F) {; n! L0 @6 Z1 @to setup
$ H8 l' y6 g$ S  ca
+ E, u- ]* o7 G: i! K& R  setup-globals& L6 _9 q( }8 P0 u; ^
! v; @* B  y- q8 m5 p* F1 S8 C
  ;; First we ask the patches to draw themselves and set up a few variables. ^' m( T" K6 M2 D! G5 ^
  setup-patches
; w0 f7 L$ p" v- t: w. W- f  make-current one-of intersections
: \$ p* g, X+ b/ \+ `  label-current
: S; h8 _. v% Z7 k% }
9 x7 H9 m* }" j- R3 y  set-default-shape turtles "car"- @( q- y6 n) f

  }6 f+ A/ m; _" D  if (num-cars > count roads)
0 k4 b) z0 u. W6 K  [. \0 V2 R, }& G# \8 e9 j
    user-message (word "There are too many cars for the amount of "
5 d% B( |$ Z. q, a( ?                       "road.  Either increase the amount of roads "
% E1 ?# n) Q6 v" @                       "by increasing the GRID-SIZE-X or "
( n- f4 A1 S  p- F* R                       "GRID-SIZE-Y sliders, or decrease the "
, i+ c+ w6 x5 V2 c                       "number of cars by lowering the NUMBER slider.\n"
4 U+ o7 U2 u8 W2 a: O                       "The setup has stopped."): j. e, T7 {6 m" E6 Y
    stop
5 l8 r: F" q$ v6 t7 B  ]
6 [) u: ?' @" G1 H) h
# z# K' p7 E: d  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
1 {9 K7 m* K& |4 {9 q  V; r  crt num-cars$ {' t. d; Q/ A# a) k
  [. g( O7 J# t4 E! d6 b8 i
    setup-cars7 R6 y- q: l: |; ]2 n7 ]
    set-car-color6 `7 s# w8 P+ y3 U  L
    record-data& K! e8 M# ?. H7 H3 u9 w4 O
  ]$ l' \' `5 o  l( X

3 U# y/ A5 Z! v& Y3 G+ v  ;; give the turtles an initial speed
: {  w, q, r3 E3 I  ask turtles [ set-car-speed ]
7 U7 p4 e" j: }/ \. f6 w$ W# ~% Z, Z: k3 E! f0 {
  reset-ticks
1 p) H4 L8 ~) B8 k; u- T: [. ]( [end0 _# O: I& j. A1 p! M

& N$ W& E, n% Y8 |5 [;; Initialize the global variables to appropriate values
3 L: v( c, E) gto setup-globals( p6 m* I& k: T
  set current-light nobody ;; just for now, since there are no lights yet
: }3 z/ ^" q$ u9 ~/ C9 y  set phase 0
" |) z  J% ]0 D4 f, c+ S# q1 h  set num-cars-stopped 0
4 T. B' ~$ E0 f. g3 c" a  set grid-x-inc world-width / grid-size-x- y7 b; R$ L3 u
  set grid-y-inc world-height / grid-size-y3 J/ j* ]1 @- x/ g7 `2 K* d  A3 ]9 A  _

( l8 _: N  k' j- T; v/ w) n  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary& Q% v& W+ F& V+ [
  set acceleration 0.099
7 ~8 g5 X( v3 Q! s( m. L; {; @end& d8 z; }2 F+ n7 }+ c1 M

" `. V- o5 [4 H5 B/ o9 \, N;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
) m( w+ u, }, O0 P3 w( C! R7 M* v3 p;; and initialize the traffic lights to one setting
: S& |! v6 E0 \9 Eto setup-patches
  s1 y: o5 Z, W5 q% S" s9 [2 W  ;; initialize the patch-owned variables and color the patches to a base-color
% I( ^: [# \, W% H! K  ask patches
' I- v% T; u: J' }8 e5 s( l  [) p5 `2 y# J" Y% ^  E5 _' k
    set intersection? false% y* @0 ~( W7 {
    set auto? false
+ _* ?# D, f/ N" F7 _. M    set green-light-up? true! P# N9 g  `9 C' J, z( X* I
    set my-row -1
/ ~0 W% P& ?: P. L% i    set my-column -1
/ L+ J! x/ n4 F4 S' L/ h    set my-phase -1
/ e# c) W, ], r: e    set pcolor brown + 3
+ c" ~8 t( v/ i3 r. Y- A  ]" r" S+ N& {6 e0 K- a# N

- ]  A* Q) @2 i2 N6 X  ;; initialize the global variables that hold patch agentsets% a" N6 Y3 b' J) I) B
  set roads patches with' j. C5 l: B* p4 \: H3 ~
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or5 [# e8 \5 P# w6 N' `8 X# c9 p
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]0 ]! V6 s$ x/ o) a
  set intersections roads with
7 g+ c5 y8 q8 q+ p    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and+ p" S4 E6 J  E: G9 h- i# s
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  e/ p3 E, r# S$ }6 y& ^0 t+ Y! [; u, N) Q
  ask roads [ set pcolor white ]1 Y. u; q5 n' b2 ^& L& s, n( g' S( \
    setup-intersections
1 G; g4 O: P" x$ r% o7 x+ Y# w5 L, wend
, P: n+ ], `& U7 B: ]( u% {6 b) P其中定义道路的句子,如下所示,是什么意思啊?
! K- ]: r6 K! V3 N8 [5 I set roads patches with
) X9 Q9 |! p4 m5 [, {" @$ v9 a    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
8 x9 t! U. y) R8 }# x8 E9 f. p* c9 W    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 ^0 j! P3 \( a9 @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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