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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。" U- o7 A$ [" V3 ]8 `' d8 z  A
netlogo自带的social science--traffic grid这一例子当中,' D1 W- {. N! r. n
globals; n3 y+ L$ G. r* R- Z7 q8 a7 H+ M
[
& q& K' Y- y# T" U- e4 y0 M  grid-x-inc               ;; the amount of patches in between two roads in the x direction9 X3 N+ i9 K, v: J
  grid-y-inc               ;; the amount of patches in between two roads in the y direction1 S& a& r2 d/ \8 `/ l
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
% P& J  w0 Y" K8 A$ z: H: p% O                           ;; it is to accelerate or decelerate9 g" V2 R: v7 h0 |
  phase                    ;; keeps track of the phase
1 M7 N9 \/ M# v( J8 G  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure7 w# c9 k) Y8 C8 c' g& x! a5 D
  current-light            ;; the currently selected light
9 F8 `: C; e' t5 R0 p/ H) _5 B7 w, K' x' O! g
  ;; patch agentsets' U* `; B" |: a8 W! N4 N6 x; h; t$ Y
  intersections ;; agentset containing the patches that are intersections
2 C$ x+ E5 a4 R6 m+ H! p3 b  roads         ;; agentset containing the patches that are roads
: k+ {. P0 c  h" y$ c0 T' W]" J* A! v/ Z) w- L# i1 |

4 t+ I9 G7 e$ P# y" o& q. ]' Gturtles-own: j/ Z: @) p2 o
[
  V- o. D/ i2 o% d; q3 a  speed     ;; the speed of the turtle
0 A% Q8 H! f) l- E7 N; X  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
4 J2 ?8 V, e9 n8 ?1 ^' Q3 B  wait-time ;; the amount of time since the last time a turtle has moved" M, Y$ E* a  z+ B* G5 C
]
: x$ n& ]0 ~" B9 @
7 R; M4 v, _& Apatches-own
5 w1 `8 R" e! \; ], q- }( w+ N[0 G# ?5 a) A6 r) r
  intersection?   ;; true if the patch is at the intersection of two roads8 Q+ O) P' t9 k4 [
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
' A% A& X5 j( M9 i$ a" F                  ;; false for a non-intersection patches.: B! u; k* H" l) M9 r; h7 y1 D
  my-row          ;; the row of the intersection counting from the upper left corner of the& `6 C8 H9 p6 o8 x/ L/ A
                  ;; world.  -1 for non-intersection patches.
8 @: G5 N$ _' `1 a  my-column       ;; the column of the intersection counting from the upper left corner of the
& A( K) l  {, E4 o% x                  ;; world.  -1 for non-intersection patches.& ?9 q! u0 J5 h* `, D* _- r  D
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
  x% T5 S' T7 g* Z5 o4 C  auto?           ;; whether or not this intersection will switch automatically.9 ]7 f2 w; E8 {! {: a
                  ;; false for non-intersection patches.
' |( B1 V7 p4 E5 W. `  ?]5 u2 h' q; P1 b4 R( C. @" U
$ g; Z$ d- b' H; ?: G$ o) J  D! A
( W+ W* D$ }7 D" [1 g) r6 R
;;;;;;;;;;;;;;;;;;;;;;
" Q- [( x& D0 I* L;; Setup Procedures ;;
8 Y$ A8 z6 M  r2 O( Q;;;;;;;;;;;;;;;;;;;;;;
( b$ ]: f6 ?6 e2 Y: I9 c& q% X
0 ]5 I5 u% S8 c7 r4 F;; Initialize the display by giving the global and patch variables initial values.( F- w3 ^+ d+ J2 B  A: f
;; Create num-cars of turtles if there are enough road patches for one turtle to
+ P( b7 a9 O( `5 r7 E  X' L;; be created per road patch. Set up the plots.# r" v9 W9 Q* }' x+ u8 K
to setup
: Z( S  L' o/ L9 ~: |1 m. X  ca
1 d$ Y) C, Y+ X, n" @* m' t$ J  setup-globals+ C: a3 |/ P! Q5 i# c
" f5 d' Z0 j- T, ~1 I
  ;; First we ask the patches to draw themselves and set up a few variables9 H! `4 G# l9 J9 S5 L# m2 A; i
  setup-patches" _% U5 ]* ?& Y" u2 R1 f( r4 B- {
  make-current one-of intersections
' j' X/ f. I  v+ p5 }5 K6 A  label-current1 x+ ?# Y4 J& c/ `& ?$ D1 }! Q& Y

( {- X* g2 f5 Y" R  set-default-shape turtles "car"
- y2 O+ X0 V+ |" N. e( }, H3 n6 _8 j. i0 ^: r# ~  f
  if (num-cars > count roads)$ d! g% h+ o3 D- l
  [- M/ J4 Q$ o' w; m# b: y
    user-message (word "There are too many cars for the amount of "+ K* z2 ^( ?4 b( n7 z
                       "road.  Either increase the amount of roads ") ]% J, B& N; t: _3 }. g( {
                       "by increasing the GRID-SIZE-X or "
6 g6 k1 }( p4 V( Z2 [8 r! ^                       "GRID-SIZE-Y sliders, or decrease the "# q' `1 D- Z9 f  T* O* d8 p5 x7 Y
                       "number of cars by lowering the NUMBER slider.\n"6 \0 Q" D( z& x+ L
                       "The setup has stopped.")# T, m+ q6 I/ Q
    stop, X: R# k  g. H4 h
  ]0 ^1 I" l8 F# v0 W% F2 \6 u. x
; U7 u" X7 z3 |7 ~
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color/ }/ R; A! h% T. G0 G
  crt num-cars
' I. `/ `8 _. k' G/ `. q' S  [$ J5 i1 F7 \6 O5 g! j: Q) D
    setup-cars) ]5 J. v; z0 d4 W' i
    set-car-color
2 N9 D6 j0 ~2 t9 E9 u% p    record-data" g; f# [3 p6 ~7 I
  ]
5 ^) W) {. Q! q: n2 |: I  W* {  W: b* H+ M
  ;; give the turtles an initial speed; D: D" J7 }9 K5 [- H$ s! t8 c
  ask turtles [ set-car-speed ]& L( g. M0 v( d* b  I" q- }- ~
% s  o/ }: i5 g1 s8 M7 z( X8 B
  reset-ticks
0 s% a+ [+ i; w+ {. tend8 u$ @7 }- O  i  j9 F

! }7 Z! z/ j/ q;; Initialize the global variables to appropriate values
9 A- K' t6 x* E1 p3 b1 Lto setup-globals
3 q& p1 u% h6 a9 `/ h, K  set current-light nobody ;; just for now, since there are no lights yet
! g8 M& y1 g# r# k, a1 \' G  set phase 0% g; l9 e8 C# N# U! _6 `
  set num-cars-stopped 0
$ j1 t. p" L/ m/ p# m  set grid-x-inc world-width / grid-size-x
7 h" `1 p- k5 v1 \  set grid-y-inc world-height / grid-size-y3 i" _+ s, J' p. Y7 [, x! T
- v) S, O* x# A3 d" }
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary; p  g! O: G) c) B! `7 \2 a
  set acceleration 0.0991 a3 M" d. i1 k, V
end* ~) v! N9 c9 ]5 v4 `
4 q) d/ h2 U5 m( S& e7 U" J
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,  o; z4 m# ~& r. ^$ ]/ m
;; and initialize the traffic lights to one setting" n7 f7 k% ]3 r/ C2 s6 ^4 @
to setup-patches  a, X' T4 o) z: I& L$ Q
  ;; initialize the patch-owned variables and color the patches to a base-color/ D- t; G/ p7 b$ I7 j9 f- R9 y
  ask patches" R% M" f: s# M( }; k- v# l/ R( \9 t
  [
& G: T. q8 P, y" b, {" Q: C    set intersection? false" l% F2 Q& R7 x  W
    set auto? false$ f. [0 L8 t+ s1 S8 K3 o
    set green-light-up? true
$ Z" G9 W  o. K; x' p9 m  n' o5 W3 X    set my-row -1
2 V3 u) i: ~  r# R) t, |6 L3 x2 \    set my-column -10 I0 n- O! w3 u7 \  }0 o# C
    set my-phase -1" v2 Z2 f" l3 z. J
    set pcolor brown + 3& L* f: J* Z! x; k' q
  ]3 _" o# p( H+ i( _' k
# L( ^4 B0 g& c5 o) q* L8 s+ C9 B
  ;; initialize the global variables that hold patch agentsets, x, U4 }2 C1 d; Z
  set roads patches with
/ O( s: ], {  N' Q    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
- u. b9 T0 w- ^    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
, E  B2 p! D: Y  }$ p: a  set intersections roads with
, q% c: N1 H! N    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and$ k( }; L( r0 Z; Q0 M' W3 Y) ^
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]. @8 S1 O, v( Y1 B' w. e  t: B
  w$ w' Z1 _0 o, T
  ask roads [ set pcolor white ]
1 V6 n% [& y8 C% Q" O5 u8 I: H9 w    setup-intersections
" |' i2 S) R9 c; v" [' Xend5 N. ^8 X/ ~" A8 X) w
其中定义道路的句子,如下所示,是什么意思啊?
! A4 W4 h1 r- F set roads patches with6 O8 }8 `. Q9 F& m# J8 `
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
% h5 H& ^6 _& b6 u- R, Q% {2 E    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
" M) h. v) r) ^1 R# T9 P& c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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