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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。0 a. v7 w3 t. {$ s+ d0 c; v
netlogo自带的social science--traffic grid这一例子当中,4 F5 O; H% o, v4 }" z" M
globals
5 _' b% q/ Y: V- o& M; W[2 }4 J5 r/ T% A% q) P4 x
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
. x$ {* O; o4 [  Z( I5 \, A$ E  grid-y-inc               ;; the amount of patches in between two roads in the y direction
% a1 ]% e' W* Y* I: F0 ~# r! a  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
, `+ D! m, p9 L# z! r& R                           ;; it is to accelerate or decelerate
# m, N: v5 {! A  h/ \' n  phase                    ;; keeps track of the phase1 h/ T; B% P' j* Q* S( g* h0 L. X5 x
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure+ h( Z/ c# J% D( D( `! V# K) r& G  O1 I
  current-light            ;; the currently selected light
$ i. F' U$ q+ m( a
" W$ Q6 z+ H1 w1 }; H& k: s  ;; patch agentsets! m! H! |+ D2 |9 Z& @/ t/ Z
  intersections ;; agentset containing the patches that are intersections
7 A/ ~3 r5 c8 s; B& X' J% p7 [# j  roads         ;; agentset containing the patches that are roads
. f" u- {+ B( L, i; L3 c]
; e4 M0 S# i0 N' [/ f# w: Y: R; S4 t$ k0 N
turtles-own, ?% E$ H: T6 o2 R2 i# W  q
[" i, `5 D+ Q; p8 F9 `- m) ?+ g3 ^
  speed     ;; the speed of the turtle0 ?9 Q2 {' b6 k* H9 M' Z* C! u7 F1 l
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right" f7 X2 q' l- B) ^+ s1 p1 n
  wait-time ;; the amount of time since the last time a turtle has moved; z- H3 [  B1 `: A; a1 Y
]* r" n' G# q5 `" [+ u  @
6 ^+ d; y" |6 i2 r1 \( {
patches-own0 T9 X: V+ p5 {$ Q/ ]1 \
[  J7 ?1 Z" S( z- Y4 s
  intersection?   ;; true if the patch is at the intersection of two roads) ^' ]2 a& X$ D9 W2 S
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.$ R; i  G' m) ~4 u$ s# U& F% R0 Z
                  ;; false for a non-intersection patches.& C2 \0 H- v. d% F5 l
  my-row          ;; the row of the intersection counting from the upper left corner of the
" g; W+ U+ H  S3 A- \                  ;; world.  -1 for non-intersection patches.5 N0 C, b6 j* q* g6 e  b# K" V
  my-column       ;; the column of the intersection counting from the upper left corner of the: u& ?/ b/ J4 t- n
                  ;; world.  -1 for non-intersection patches.
9 d/ x4 ~; s6 b: ^  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
" {5 b; v/ S5 [3 U) V$ g8 _  auto?           ;; whether or not this intersection will switch automatically.0 Y7 r% U# l, x
                  ;; false for non-intersection patches.
& h! O/ r+ S! o) a, q8 v: }]
9 t& J$ s( Z: S8 j/ }& A% y# X; c- x+ [4 o3 _: A6 e

2 E6 R& ?; x2 m) r! T( i8 u;;;;;;;;;;;;;;;;;;;;;;2 C5 L/ m. `, U$ q: S; J
;; Setup Procedures ;;
7 U6 q" L% w7 r/ C8 F4 {, H3 Y;;;;;;;;;;;;;;;;;;;;;;
4 Y; V: r: o; ~& L' d+ J4 @' \
- \2 f* A. D0 G' S2 ?1 N0 E;; Initialize the display by giving the global and patch variables initial values.
% P7 h, `# _+ G$ {5 |6 O;; Create num-cars of turtles if there are enough road patches for one turtle to
. T, x/ Y1 Q1 Q! A$ p;; be created per road patch. Set up the plots.- V7 a$ D/ d" J$ f
to setup: X; l9 x4 d$ ]  S, R; T4 f
  ca# X, g, f& {& ~% V
  setup-globals, b- a+ K4 T1 M- b0 r9 C

# h6 A" `* l+ G7 i( Z: o7 ?  ;; First we ask the patches to draw themselves and set up a few variables
7 @3 d4 K' f6 ]8 [% F5 q  setup-patches
* H: g4 F; Q6 `' D) z# u& f  z  make-current one-of intersections
# y- ~3 ]6 \  a/ h4 J  label-current9 U" ~  ~/ E( ~9 {) x% z
) {& W4 C. K& E# g/ o# K
  set-default-shape turtles "car": H. ^( T' q% [1 p( ]

3 ?) b; _1 k9 ?) ^0 @  if (num-cars > count roads)
; q) E' o6 v& j3 |  [- q5 F- c+ e7 L; X4 j
    user-message (word "There are too many cars for the amount of "- _. i- o, E  [1 x
                       "road.  Either increase the amount of roads "
6 x& C, ~6 ]' z; u2 t; G! X( s6 z                       "by increasing the GRID-SIZE-X or "
: K$ e$ a8 c7 @% Y                       "GRID-SIZE-Y sliders, or decrease the "6 [$ b% ^: a8 E$ i- n! k% b
                       "number of cars by lowering the NUMBER slider.\n"
' ?9 V. y) I! U9 N8 K                       "The setup has stopped.")9 m5 D8 F! {/ i( L
    stop
- i% w8 j: h9 ?+ Y) a  ]
* S& ]8 s8 P# n+ @8 D, V6 F. e' y6 i
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
) ^7 b; P5 j7 a$ o  crt num-cars( n# P0 Z) H8 p# a, l
  [4 w: r3 ~1 v) H! ^* \2 o
    setup-cars
5 t& d# Q9 b$ o$ u$ L" w    set-car-color
* C( V& u/ u3 |% R    record-data
% A  ]3 S0 E9 j& }: v. U* j: P$ K, k  ]3 }' n. Y& @1 i' f+ u0 w+ L
8 F2 n. c: a/ G; T
  ;; give the turtles an initial speed) }, M% f! s* w  o1 L
  ask turtles [ set-car-speed ]
: @& c! O5 H8 A) D* I$ ^" d& S, @- Z
( d% ?2 V  k9 r! u7 j8 F, @  reset-ticks
$ u6 Y$ H$ N5 J2 h$ Tend
( c7 f% R4 R$ d/ r. W, l3 G
7 g" k) b9 u0 Y;; Initialize the global variables to appropriate values
4 a$ N8 d8 n7 P' T+ gto setup-globals  i, c% _3 g. }9 J1 F, L$ T7 {, b
  set current-light nobody ;; just for now, since there are no lights yet4 B/ X- g1 R( Z0 r' U- }
  set phase 0
/ I+ S; j) p9 t/ j* @  e  set num-cars-stopped 0( t! z$ }$ B! _4 h
  set grid-x-inc world-width / grid-size-x
2 i# `0 \0 ^/ ]- e+ ~  set grid-y-inc world-height / grid-size-y
) U6 u8 x, w3 h* F: ], d& K, s! g4 u
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary9 c' M' |8 @0 M5 I4 Z; T
  set acceleration 0.099
" b( ^+ N8 f+ H% F" ~; Q) Iend
! Z# x. w/ `8 h6 D: V; X  G9 ]
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,1 q- u: G- H2 J& x4 w& S
;; and initialize the traffic lights to one setting1 y8 _; Y7 E- _3 h" _5 S
to setup-patches& h( y- I0 }' m5 R8 K8 H$ r9 p; p
  ;; initialize the patch-owned variables and color the patches to a base-color; K: \# U* N# L3 l5 ]6 I, D
  ask patches& ]* y+ R8 p* Z; J; E, o1 G- v
  [* B' l: b. h5 f0 ]; A) l
    set intersection? false
/ Q0 y: r9 d7 V! s: x2 a6 ]* A    set auto? false* V7 K$ Y6 g( w( o9 O6 S1 d
    set green-light-up? true1 o8 }& m" v* Z% ~4 X6 q8 j
    set my-row -1$ }$ x7 U8 b/ I" o( L
    set my-column -1. `. @* S8 P9 ?6 z& e
    set my-phase -1; U, i% o/ K$ W! P* Y
    set pcolor brown + 3
- M, g" e' e2 a* n, H  ]
  E& N) {9 y* g$ s0 \
; ~; B8 t. N- W! y  ;; initialize the global variables that hold patch agentsets( L* v1 [7 _5 X
  set roads patches with
+ m$ \6 G7 e6 F" L, n8 E! l' N. ^% E    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or  z8 i1 d4 a; D
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  U. z% u3 P9 x8 V6 Z, e  set intersections roads with
1 L) m: G+ s1 \3 h    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
: h4 a( m! s  A- {    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
. F% A; ]4 N4 C# {* l+ U6 ^$ W
: S2 B& x: @  I$ b% b. G  ask roads [ set pcolor white ]& ]2 H( ^. C0 q! H2 L' `; [1 U6 W
    setup-intersections& w0 v3 z& f& q& J! q. j+ T9 a4 W9 |+ [( f/ h
end( J# U9 i0 |3 g8 Z3 V# Y# S% l
其中定义道路的句子,如下所示,是什么意思啊?
/ n2 V& ?6 H1 j( n set roads patches with; j5 f$ Q4 ]2 _
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or. f+ Y6 C5 e+ j4 a( ]2 F7 E2 T4 p
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 D* f3 q' X0 X: @) B! ?* ?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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