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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。" i' K  |1 U0 X  H+ C( i
netlogo自带的social science--traffic grid这一例子当中,* C& |3 i) y% P/ E1 ]0 O
globals
8 J; X7 Q# t/ _- S7 }) x1 r8 Y[2 P* x% z( o% q) v9 s7 y$ D# E
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
& V' H2 ^0 k7 l+ w  grid-y-inc               ;; the amount of patches in between two roads in the y direction
; c# f' g- _3 r2 [9 A  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
" L; g  X5 ^( L6 g                           ;; it is to accelerate or decelerate. B# R, A) P/ ^+ R! u9 w3 u
  phase                    ;; keeps track of the phase
3 ]* J( x9 t* O7 c  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
$ ]* J* g: @9 q$ Y4 v2 C  current-light            ;; the currently selected light* N: X) f& m/ ?  s
; B8 q  y( V/ k
  ;; patch agentsets
( Q7 ?6 P0 q1 Q% V  intersections ;; agentset containing the patches that are intersections
7 u4 r/ p& l( L3 l. P  roads         ;; agentset containing the patches that are roads
+ O$ F. M% T. a. ?]' Y6 |# w: r2 [' f# s* {

: [1 ^( h! N2 [/ w$ Kturtles-own& |. V' g2 Y4 g6 c
[9 T7 w, {# B/ g1 ?, ~
  speed     ;; the speed of the turtle6 c& c# y3 K7 }
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right, B  p' b$ y) t+ b/ [
  wait-time ;; the amount of time since the last time a turtle has moved
- _! U7 p* [% H]! E4 i! [; g, e5 b# X
8 y4 V' L  u  z: [# X$ J6 e0 T
patches-own
! b# K& a' J, i[
7 {, p) ]: H3 w4 L3 j9 l  intersection?   ;; true if the patch is at the intersection of two roads
  m) P+ M& O. {" m6 l# u& e  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.2 u5 Y; x2 v/ Y( I. Z
                  ;; false for a non-intersection patches.
3 E+ v' x. y4 g; q  my-row          ;; the row of the intersection counting from the upper left corner of the
) \% P+ q* e) I: n$ q$ E                  ;; world.  -1 for non-intersection patches./ X# j5 B) y! u" B( D
  my-column       ;; the column of the intersection counting from the upper left corner of the% O: p0 u" U7 Y& P
                  ;; world.  -1 for non-intersection patches.
8 J4 _6 q0 P) ?  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
7 H2 a7 d# w' B2 }" S  auto?           ;; whether or not this intersection will switch automatically.
, H- q' ?: G3 g, p1 o% S# r                  ;; false for non-intersection patches.
. I3 A$ D8 n; Z. q]$ l. k( s+ c5 A( y+ s- }% U  ]# z

- W0 Q/ V! C$ o! T- I$ m. o: p# [8 J8 W3 b  Y, d, Q
;;;;;;;;;;;;;;;;;;;;;;
- G8 S- m  A  R8 G1 l3 S;; Setup Procedures ;;
; ^& k) e  Y; X' g. V8 R;;;;;;;;;;;;;;;;;;;;;;1 l9 I$ v) f* s* z
6 i+ e6 g& C6 h. V
;; Initialize the display by giving the global and patch variables initial values.
9 S! F; D, ]& b1 k2 M$ [- k$ i/ ];; Create num-cars of turtles if there are enough road patches for one turtle to
2 U: n3 a% ^0 D! C;; be created per road patch. Set up the plots.5 O% j) ~, H: I1 S  Y8 }
to setup) H3 A5 h& v, ~5 ?% m  o- C
  ca
+ f7 h5 v/ U, ^1 a: }% [  setup-globals* {/ C4 x6 e' w. z
: p1 ]+ T. a- x" i- I  o- W5 m
  ;; First we ask the patches to draw themselves and set up a few variables: T' B: J" o3 I' j! R' Q5 S9 E
  setup-patches
9 j- o# ]4 K* e7 K( y2 i5 }  make-current one-of intersections7 L# B+ j* p+ z- ]4 x: [7 @) _" U
  label-current9 g6 O' K2 w8 C. p! A

9 A& \8 `( m6 v. I8 Z) q( n  set-default-shape turtles "car"# r3 M) `5 p4 j" z
1 G+ g% W. O; E; M% P
  if (num-cars > count roads)6 f7 Y& |7 o- e( X2 c& o8 a
  [
- u8 z0 B- z( K0 v3 p5 q    user-message (word "There are too many cars for the amount of "
( |0 k, S: Q& M9 J) g  h' d! `                       "road.  Either increase the amount of roads "6 L7 ^% X8 [2 H6 p: _
                       "by increasing the GRID-SIZE-X or "
! e+ M; [8 s  K! P                       "GRID-SIZE-Y sliders, or decrease the "
: \+ Q- }+ M' _+ d                       "number of cars by lowering the NUMBER slider.\n"; T5 s! N& ^5 c* T
                       "The setup has stopped.")' Y7 X" r/ Z7 o# |: g
    stop
' c9 \5 \% }) A, G4 P/ U  ]: f; ~# m; e$ Z/ g  x
$ m$ _( S3 k+ z, V8 m4 f! i5 O
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color- V. t9 `( K: S0 A
  crt num-cars* L. ^- f" ^- c3 p. Z
  [! M, N% `" o& }
    setup-cars4 c8 w" p! D6 b. }% ~* H# x6 \
    set-car-color) |) a5 a7 n# ^/ T
    record-data
0 F  T" W$ r) G, |6 z  ]
! Q) @7 m: e/ N8 E
# a' L, n) V8 x  ;; give the turtles an initial speed  W: |0 d  k: u: i
  ask turtles [ set-car-speed ]
9 U, E& i4 Q# {  g; o% |' E. m  `  R+ {$ l, c8 {
  reset-ticks" p0 J7 }- b& s, \
end' m0 W( b+ u; ~. [# f+ T0 I

3 s& d! J7 O7 F! \0 l;; Initialize the global variables to appropriate values$ ^1 `1 _3 T; Y* ?
to setup-globals
( V  {, r0 W6 F5 l  set current-light nobody ;; just for now, since there are no lights yet2 G4 o5 c. _. q4 Z3 ?
  set phase 0: G, _) |) M5 _' O" Q. K
  set num-cars-stopped 0
( Y5 W8 H, O2 L' ?4 Y8 f  set grid-x-inc world-width / grid-size-x
/ f1 w6 ^9 z/ h+ A' v  set grid-y-inc world-height / grid-size-y
$ P9 L- Z& B5 U" f) _) O
0 r' t3 g% B, D5 S9 K  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
: Z: D4 B& i$ k# K  set acceleration 0.099
" R2 D4 r* C7 j- `, v# s; kend) B* M5 l' n( B

" _1 g7 D- |0 d& t! S# P# o;; Make the patches have appropriate colors, set up the roads and intersections agentsets,0 ?3 h7 D# i, u
;; and initialize the traffic lights to one setting: Y* E: G5 @* P. W
to setup-patches
0 d" z0 S3 D# ^$ Q  ;; initialize the patch-owned variables and color the patches to a base-color
* t5 s2 N% J: s7 ]% n$ w* }! y  P  ask patches/ v& z' c- ~4 C7 \! \  z) U& J
  [
+ k  T4 k2 j, n; A( o& `" ?- u2 J    set intersection? false
+ m& l3 |2 J3 o" R    set auto? false
# C2 v+ ^- D" V; P, |    set green-light-up? true
8 O$ S$ q. ~) y9 ]    set my-row -1" ?6 m8 q9 ?* ?1 g$ |& v% H
    set my-column -11 R3 j) `1 B7 h1 g: o
    set my-phase -1  u: e6 S# ]5 c$ C% A
    set pcolor brown + 3
& o( o1 G7 Y( c5 N  ]+ Y: R) U+ Z; C' l  `: E' _3 u

' Z3 e: }1 Z  \. v* ^) d  ;; initialize the global variables that hold patch agentsets
$ I4 R) _; Q% B4 u8 q" b  set roads patches with. j- {6 v8 T8 v2 _& H
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
0 v, b5 B# I5 L4 O- Q9 ~    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
( j5 M' i9 J5 _! C- g  set intersections roads with% p' L) h" z% p8 g
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and1 G+ d5 r' @% A
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
2 a* w6 Z3 j1 e+ P" b' Q  ]$ N+ j, w7 G4 f( U7 H- @
  ask roads [ set pcolor white ]) y* I; b5 u# B
    setup-intersections
4 D9 l7 u) x% ^, j; j9 d# yend' Y( \2 c' [# ?* X
其中定义道路的句子,如下所示,是什么意思啊?% a  ~! q" c2 |" L" u" r
set roads patches with! n5 v9 f5 S4 L* U( O, l! \
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
2 z, {: A0 z9 x: C/ v    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
+ G, f$ `$ L/ w/ R3 G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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