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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。) y8 _. D) q7 [+ L! @1 L
netlogo自带的social science--traffic grid这一例子当中,
, J, H, U- d  C$ N1 H8 fglobals
2 c* d' Y2 y$ W[
8 I) `, R4 y' g. \! E  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 R0 T3 H8 h8 ~1 q. b
  grid-y-inc               ;; the amount of patches in between two roads in the y direction1 }0 D: C! c1 f: y; F
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
. t# z" N3 }& J7 O/ I4 D) r1 d                           ;; it is to accelerate or decelerate+ U6 k) g1 t$ R4 {$ z3 ]
  phase                    ;; keeps track of the phase6 e. O" ]. b  R9 D
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure2 j0 K( [7 F5 z: B: N6 E
  current-light            ;; the currently selected light' R1 o7 o- C- z2 t" H  C

9 K; Q5 B" m( P2 f9 U! k  ;; patch agentsets
1 u1 [# G$ x: V: w& w  intersections ;; agentset containing the patches that are intersections3 ^* F- M4 I+ }! a# d7 m
  roads         ;; agentset containing the patches that are roads7 [. O2 {6 k7 ]# L% x: X' M
]
" |/ i. A4 x! `" }( X' o
4 G6 w0 g+ b! Y! q5 k! _turtles-own( R" k( N! c, j
[
' M2 Z9 @# U$ ^7 R' Y( U$ S  speed     ;; the speed of the turtle3 L* n2 _& j4 @
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right8 o: S) V1 x. D: t, P, \+ N2 B
  wait-time ;; the amount of time since the last time a turtle has moved) k2 q1 ^4 j& ~3 s- ^' K& d; b, O
]* Q2 I- b, F6 E6 p9 o% X" a6 Y: U
, ]1 l; C  g. K: O$ x+ i) J
patches-own
8 L% u  S" `5 J3 i/ t) A6 h[
- Z6 a/ w2 B& ?5 b$ Z  intersection?   ;; true if the patch is at the intersection of two roads. L, j' h3 j- w0 a; c
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.6 r7 i  l8 s6 K* d' L3 b7 D
                  ;; false for a non-intersection patches.
; s! Y+ D: R2 E: ^& [6 `6 a6 Y  my-row          ;; the row of the intersection counting from the upper left corner of the
: D* O9 G3 M  W0 Y& e% G                  ;; world.  -1 for non-intersection patches.2 y/ Y0 [+ Y# q8 [" F* r
  my-column       ;; the column of the intersection counting from the upper left corner of the
. Q# }0 O2 m: R: X) E! D                  ;; world.  -1 for non-intersection patches.: l* |2 `" @9 |) X! [. X* |
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
  r( K; C3 q, d  auto?           ;; whether or not this intersection will switch automatically.
6 a$ U. g0 A8 X: Q3 X                  ;; false for non-intersection patches.; |$ y- _4 A( T+ Z! X
]! Z( j% P* ]4 p# x

( o* g' R- q4 D- i/ u- Z/ J5 [2 w2 \, n
;;;;;;;;;;;;;;;;;;;;;;( z  O: ^5 E$ v  y
;; Setup Procedures ;;
  g- |5 |- a5 ?1 W- S;;;;;;;;;;;;;;;;;;;;;;  F" Q0 P$ m& A; l$ ?) P

5 X* I8 i) O% H5 O2 U$ y;; Initialize the display by giving the global and patch variables initial values.
* K2 p# y: ^- b3 D; B( h2 g6 ^;; Create num-cars of turtles if there are enough road patches for one turtle to
  r. Y/ }1 \4 b" G$ Z; A3 Q;; be created per road patch. Set up the plots.
- _/ F$ d) G$ G% A  d% W1 Ito setup
/ u8 w+ C0 z0 |& Z7 B: O7 x$ r* Y7 |  ca" G# T) [& U3 n  M; Y
  setup-globals
( a, z, L  Q/ I7 J
9 p) a3 H; A! f" R+ s  ;; First we ask the patches to draw themselves and set up a few variables
  \: A9 Q+ B  g7 y+ _  setup-patches! g0 O- L4 J3 i/ U( i
  make-current one-of intersections, j. ~9 P! p) F4 |9 s% o
  label-current/ H! z( p  [/ z$ s' t) s) \+ [
, S8 o) B" _% b
  set-default-shape turtles "car"
" ^, n9 F! b8 Z. k: ^
( b9 G/ g; ^- o( q9 R! R% F  if (num-cars > count roads)5 E3 A, m. q! G3 [5 u& S0 I
  [
- x" D7 ~9 p9 e5 ~& @  ~% N6 E5 P9 V0 O8 d    user-message (word "There are too many cars for the amount of "  E0 j' E+ F0 G9 ^( Z
                       "road.  Either increase the amount of roads "! {* k3 H. o( e3 j* G
                       "by increasing the GRID-SIZE-X or "# {5 X( J# _1 }# j
                       "GRID-SIZE-Y sliders, or decrease the "
/ Z2 _( @) n$ W$ l% m' j: r1 ~9 @/ |- ~: h                       "number of cars by lowering the NUMBER slider.\n"
, u1 z/ |4 [" R4 e6 F                       "The setup has stopped.")/ [* L8 S# W, W8 ]! H! g2 c% C$ P1 b" F
    stop3 c; G9 O5 j6 z4 B+ P" O7 Y
  ], _) B, L4 G# g* e( y

# H( C( v3 x" e* o  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
/ B* F# h+ r+ \% w6 V! u  crt num-cars) N- `+ ?2 W1 r) B
  [
4 j0 t9 c% m; k2 @' Y# o4 c    setup-cars
; L+ q- B6 X& }2 \; b+ A2 P0 Q+ z    set-car-color
; ]- p- N$ x  G    record-data
. C1 A: X, i# ?% a  ]$ A. T# O& H' U% t! e% t; @
/ H- P9 g5 ^0 `* U5 H; e
  ;; give the turtles an initial speed
: J/ c* W4 i2 H3 B5 W  ask turtles [ set-car-speed ]
8 H5 R* P1 r- q
$ g$ H3 \4 \- P# }8 X2 {' ^- R  reset-ticks/ C! g2 j2 B! }2 x3 X6 d8 }
end
! T+ [: G+ s6 ~5 E- v
7 q3 x7 i. X: ?/ A8 J;; Initialize the global variables to appropriate values
. \. s  g0 n& S, {to setup-globals' d# G4 R* @8 ~( t* D
  set current-light nobody ;; just for now, since there are no lights yet* W" s2 [2 j% X5 a$ e& }" l
  set phase 0
; ^0 W" P/ N! J5 A# l9 h3 M  set num-cars-stopped 0* {4 I+ z2 U/ C6 o
  set grid-x-inc world-width / grid-size-x8 g3 @7 V' K; I& e% K* i4 B
  set grid-y-inc world-height / grid-size-y+ H6 I; B: b( V1 N
  _; h7 }+ M  R8 v5 R6 b9 K  X5 r6 B
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
% p- k# B4 P$ V( b  set acceleration 0.099
& S8 F. n- s+ I. G" g- P% xend5 z/ q9 }6 |2 I
& l1 t+ ]; g1 u. A
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
( G- l, _8 G! r" v;; and initialize the traffic lights to one setting
9 a  ^- ~9 ?+ R( d0 X- F8 Fto setup-patches9 f, L* y8 C/ j8 _: o4 Q8 ~5 Q
  ;; initialize the patch-owned variables and color the patches to a base-color5 {' |# q8 Q: ~( Q- p3 Y! k
  ask patches
# u1 H/ l1 k1 e3 @% a1 a  [
0 \0 y* j8 d: o9 y2 C( e    set intersection? false
! Z1 n$ E$ n  v/ A2 b9 _9 h    set auto? false4 f  o. s0 P  w+ _0 \( J1 w) ^) g/ H
    set green-light-up? true4 s2 \; A+ F! h, ?1 N8 G  _7 X- j
    set my-row -1
% g  |% _8 B4 H- P% D! {! k    set my-column -1& G9 T* P! m$ Z3 s' _. ~5 \1 @
    set my-phase -14 p6 B7 W( j7 {6 g3 E8 s
    set pcolor brown + 3
- N# }7 H, ~3 [. F* n! `  ]/ j( n: y4 W4 ^+ C# f  w5 K" }2 d

/ T6 V9 M  D/ l7 }9 Q1 G  ;; initialize the global variables that hold patch agentsets
" P* e6 L; q+ ~9 ?+ b# ^2 a  set roads patches with& D( X. n6 S7 _! V
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
% L/ }& s9 e& H# T: J( V% ?' L, h    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]* k1 y4 c% O6 X
  set intersections roads with
3 x( |9 p$ W6 h8 I+ _    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and$ X* G5 P, K+ T5 Q( [, [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
6 o8 K& c& Q/ w. }6 u) ]* f3 w2 }6 A8 Y, e0 l6 y9 `7 V/ j
  ask roads [ set pcolor white ]; V+ e( S6 M! ^9 h* r3 w, u2 h
    setup-intersections5 N7 A4 b! P# i! |7 [
end8 I; m) a3 Q- }# Q" x8 d' Y
其中定义道路的句子,如下所示,是什么意思啊?
, [* M1 j7 D) H2 i, x; ` set roads patches with# s. t8 g) A1 Z3 _" k' {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
1 g2 F2 E; r" ?* q$ q% e, O1 ~    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]! M, f  C0 D, `( r
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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