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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。! G" Q/ N8 c: g# y$ t  k. _3 e
netlogo自带的social science--traffic grid这一例子当中,
  ^1 s  ]2 i5 H$ ?globals
# k% s4 D$ y" B- v6 j[
  E: G- }- H8 H" J" A+ J  grid-x-inc               ;; the amount of patches in between two roads in the x direction
' S5 {( r- B1 W) [: Z  grid-y-inc               ;; the amount of patches in between two roads in the y direction
, I* Q  k' b  g9 d# P  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
3 b: N6 T  F! }2 t                           ;; it is to accelerate or decelerate
. k& n+ N, ?  M% ~" S' v& Y$ _, A. g6 F  phase                    ;; keeps track of the phase
  d9 a0 Q8 r! U7 P5 `  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure; v. L: Q: ^! E7 W& I9 }
  current-light            ;; the currently selected light
4 o  Z) x! t6 \- X! z; a' V; i4 l: B& |
  ;; patch agentsets7 y0 U5 O2 D8 V! V7 _4 J, ^( E- A$ e
  intersections ;; agentset containing the patches that are intersections) w, K+ J- H+ j2 t( ?$ U
  roads         ;; agentset containing the patches that are roads, f: ]7 d8 \5 x1 @
]; r) K/ c  r& ~
7 j& Q5 }$ P- C  h( v+ D% v$ Q" Y
turtles-own
% t: z6 W: \( x* m1 ?[( \( A. d# X1 d8 x+ M
  speed     ;; the speed of the turtle
! q3 W; D2 e3 F+ l' V  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
) w4 P# m  d) {  _  wait-time ;; the amount of time since the last time a turtle has moved0 A1 W8 l5 C* D  E
]
; {- w* j; q* h% y* J- \
3 h' Q) I3 E8 h/ W9 npatches-own3 Y( E- V, r( @7 n" D5 \
[
7 a9 X4 O; d2 J6 Y; f% m; H  intersection?   ;; true if the patch is at the intersection of two roads
# G6 W4 ~% V" U( B& C8 |" l' m6 ^' M  green-light-up? ;; true if the green light is above the intersection.  otherwise, false." o4 t3 z5 `' `) ?' u. ~
                  ;; false for a non-intersection patches./ {4 a! V3 s9 }& @' r3 U1 b
  my-row          ;; the row of the intersection counting from the upper left corner of the
9 Y( q" a# ^5 i# ]* G- {                  ;; world.  -1 for non-intersection patches.+ N' S  a: R, K# ?8 p! ^
  my-column       ;; the column of the intersection counting from the upper left corner of the
, a: N9 u- l7 b9 P1 W9 F5 k& H1 O                  ;; world.  -1 for non-intersection patches.* W1 I0 q. }/ F9 X+ A
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
( b4 K6 N% u, Z! c8 J  auto?           ;; whether or not this intersection will switch automatically.
/ M3 u/ t* L" j/ ~2 Q/ h+ P                  ;; false for non-intersection patches.8 M* [0 r. I7 f' i, W
]
- w0 }. ^  `/ e. }, h6 m- F
& w# c( L/ M" T7 f' ]4 |3 [/ ^" J& l% G& A
;;;;;;;;;;;;;;;;;;;;;;9 {0 P' P+ x$ l, x
;; Setup Procedures ;;: t' x; d' H% j; t
;;;;;;;;;;;;;;;;;;;;;;8 K% d' T. w# s- L8 m& r
' q5 P, N' ^3 H" L9 J) U! [# L  ~
;; Initialize the display by giving the global and patch variables initial values.
+ c8 x1 L. B% A! R: n; Z7 k4 t% e9 Z;; Create num-cars of turtles if there are enough road patches for one turtle to
5 @+ u! |" J8 R. Y9 n;; be created per road patch. Set up the plots.
4 q' X8 r7 w3 W* ]to setup
  y! M) K, ]! k, @+ P5 D  ca
! K/ }3 r# H% F* l4 h  setup-globals
2 }/ w: v: P* S6 ?) d# F' r
) L1 W4 z7 o/ [; g, D  ;; First we ask the patches to draw themselves and set up a few variables
& q' B$ @3 Z$ }8 r8 I9 w. p/ \  setup-patches* v" N. f$ Q& O  `4 Y- P
  make-current one-of intersections
1 w% v8 X% ^2 B6 }  label-current
1 I- i: Z6 G4 F; y& r2 [/ Q- K# Z: a  g  D
  set-default-shape turtles "car"9 q. V1 @1 W  F5 A- {" x

  P+ @. S7 O( l9 }. a* K- x  if (num-cars > count roads)
$ v( z7 V, a: [6 I0 N0 [+ c  [
. h3 |0 L6 }/ f; k/ k    user-message (word "There are too many cars for the amount of "/ p$ J, [( M: q5 t' w
                       "road.  Either increase the amount of roads "3 h; d$ l% J, O3 ^4 g* X: `; \
                       "by increasing the GRID-SIZE-X or "
4 F, ?0 B: ^) c0 h; b4 _                       "GRID-SIZE-Y sliders, or decrease the ") F/ w4 L. \$ l' Q, \
                       "number of cars by lowering the NUMBER slider.\n"
! ]: p7 L2 J& A. q- |$ V4 v  H' n# w                       "The setup has stopped.")
8 S2 p: L' L3 e1 _8 \9 y2 E/ C    stop1 v5 `2 w5 R# C* s1 Z  n( @, f
  ]
. }8 x* J4 w& @
/ q7 B  E) X# R3 b; [  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color, }# F4 Q* l" o# R' ?- m7 Z
  crt num-cars! e7 M6 K; b  L; W
  [! Z# N2 S, W) x5 t9 f+ u
    setup-cars& C$ S2 z* Y$ g' P8 e
    set-car-color
7 }: t/ i, m) T; f2 J    record-data( ^5 e9 R- {6 r
  ]
3 o( g6 Y0 T) o% J+ H" w  i( d1 \- J( R0 z
  ;; give the turtles an initial speed9 W2 x! T9 M! I* Q6 ]3 ?0 f
  ask turtles [ set-car-speed ]: d& w# x% q2 y$ N+ s; n7 N

1 q$ I# I. S/ t; i  reset-ticks: ]  {, J9 M( ]- @9 ^  N
end
7 r6 b) F% i; r! Q9 C
" V  T# V& ~& |; j* `9 v;; Initialize the global variables to appropriate values
$ V. i- p$ {+ h: sto setup-globals
5 }4 E/ ?# [0 V/ u  set current-light nobody ;; just for now, since there are no lights yet5 m4 i/ X8 Q+ n+ J- C9 n
  set phase 0" v( B" t' G( X5 ^
  set num-cars-stopped 03 s" s( n& A1 p1 @$ |/ C
  set grid-x-inc world-width / grid-size-x& k+ ]2 t! E8 ?- }" W
  set grid-y-inc world-height / grid-size-y( `7 k# @5 L7 P- X. O. ]

6 x; _3 a' k+ q# R6 u  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary* a$ P7 V% ]! h9 u1 ?( [
  set acceleration 0.0998 h* J, E$ ^* \: z9 U
end
) u. Z# H) L; I" t
" S* _; b+ z& E4 [# \;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
; E" Z/ W8 e& I; k; N4 N* R;; and initialize the traffic lights to one setting+ {! L  B" [7 v, e! r
to setup-patches0 A" [; M( |! F1 a' i2 u
  ;; initialize the patch-owned variables and color the patches to a base-color- A* A! ]* l! p  U1 r: h& y
  ask patches0 o8 T* E2 d" \: [4 h1 a
  [3 q" a0 w- [6 Y8 n
    set intersection? false. k8 Y3 l6 \4 v3 U3 s- y4 M
    set auto? false
( ?5 D0 Q% F1 ~2 a; s1 S0 z. C% u    set green-light-up? true, E0 c& R. Z* M6 D9 [& c
    set my-row -1+ B0 \8 `$ w, n
    set my-column -12 U, ?+ x2 D0 s5 d2 ~5 U2 k
    set my-phase -1
1 d3 c) T- z8 u2 z0 N' L    set pcolor brown + 3, X1 s1 d! O. b+ i
  ]; f/ F1 y! y1 w5 {8 L, Y; z
% y  l. o5 d' {, a
  ;; initialize the global variables that hold patch agentsets3 k6 M) ]# Y3 t5 G# B
  set roads patches with8 z' _: E+ V$ g( T" F) [! y
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
6 B5 q( K$ ~8 |) G$ e1 e    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]' H/ P% [; H8 U% X2 |. {! P) o! O( D
  set intersections roads with
/ {1 l5 X2 j; s6 v    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and* h& M0 u: p; ]4 u0 C7 Y- n) ?1 e0 [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]  t  `" S# d1 _& c* E4 Z' r3 V# H( [
9 x  c& g/ O3 U1 K7 ^8 h: i6 T0 @
  ask roads [ set pcolor white ]; M$ H$ G3 x. B
    setup-intersections
+ s( Y/ }! z8 }$ \( |% }, B4 Eend; k9 |5 h' P' ]& x/ F5 ?
其中定义道路的句子,如下所示,是什么意思啊?3 B- X# f6 K' l
set roads patches with1 ?! M7 i" g0 K+ F$ X
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
- A. U" V& [" M3 {' \! u( I    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 V% K. r5 ~! [4 x$ b0 t; X7 n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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