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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。' s. a8 i- z7 m9 X; z7 g0 _
netlogo自带的social science--traffic grid这一例子当中,
- }! u$ m$ M: u2 D1 H3 xglobals( l) V2 i8 ^# c; J# B7 h  G! ]
[) o3 b% ^; V. ^+ ]3 x
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
; Y1 [4 B0 o" F7 ?$ v3 e8 |5 [  grid-y-inc               ;; the amount of patches in between two roads in the y direction
9 D1 B" V, I, x  acceleration             ;; the constant that controls how much a car speeds up or slows down by if! C7 b5 d* |3 g- e3 [# q' B
                           ;; it is to accelerate or decelerate9 l1 g( e9 R4 @6 v( ~
  phase                    ;; keeps track of the phase% M, ^- H$ K% _" ?, ~0 z: {) d
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure( ~" J. P+ d; f
  current-light            ;; the currently selected light
9 `1 y7 H8 o3 c) V2 O4 U& B3 ?* X; Q$ A6 P
  ;; patch agentsets/ A* j0 ?+ t+ g7 q6 p2 I9 z
  intersections ;; agentset containing the patches that are intersections
2 n. c' @- X7 l0 F  roads         ;; agentset containing the patches that are roads  T! m" @1 ]" N+ R, w$ y
]
2 k% @$ ~" U; [8 q+ \: B4 ~$ q' A) n/ Z9 x: w
turtles-own
* P+ F+ D% P! x) [& H3 N. v[2 @' R8 f0 k, w9 @
  speed     ;; the speed of the turtle
; E5 l9 s0 m5 N$ `2 ~  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
' Z( b& R- T) W! @& h5 R, g/ C  wait-time ;; the amount of time since the last time a turtle has moved
" U" m/ }3 l2 A9 ?: Y7 @]
7 G4 W3 p8 r/ V$ F- b$ ]9 u# n) g
) C" v: L7 @- zpatches-own# F9 I0 x' W6 j% |* T
[: q. m2 `: d) V4 m6 t) J4 D, d( c+ \
  intersection?   ;; true if the patch is at the intersection of two roads
" Q# P. I$ }( B: v+ g# J  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
2 V( q- F- T  _5 i                  ;; false for a non-intersection patches.
7 X0 A- Q, `* J9 c  my-row          ;; the row of the intersection counting from the upper left corner of the
1 o# p. l* q: V8 A7 y                  ;; world.  -1 for non-intersection patches.$ \5 B9 f9 {$ D/ {2 o
  my-column       ;; the column of the intersection counting from the upper left corner of the# y. z* j( j- h% ?2 f: b- ~/ H
                  ;; world.  -1 for non-intersection patches.
4 e6 u. k" w5 }- @7 H5 z3 o$ x  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.8 m; H. Z0 _& D. x
  auto?           ;; whether or not this intersection will switch automatically.
' l4 F6 a2 y9 g: d& A- j/ E- t# G                  ;; false for non-intersection patches.
$ k0 Z- @' `/ D2 T3 `: m]" i. `9 f9 F: Z9 A3 n

% U* [) `+ \2 |& W4 w8 z6 |$ ^# n4 f7 z1 [" t
;;;;;;;;;;;;;;;;;;;;;;0 E& `, _$ N' m% p7 ~+ R8 H
;; Setup Procedures ;;3 o9 J/ z- T- e# Q
;;;;;;;;;;;;;;;;;;;;;;
$ I- z% I* N( N# x. o' u' C8 E
) a. }9 C' R. G) Y* }; W: u4 J;; Initialize the display by giving the global and patch variables initial values.
* K5 k9 B- k/ ]* z5 @;; Create num-cars of turtles if there are enough road patches for one turtle to8 u1 ?& v6 f* R  A" }& u5 O
;; be created per road patch. Set up the plots.
9 b* K1 v/ [. i1 J, j- rto setup
: ]( E$ o' V- I2 Q' v  ca
2 x7 [# M/ P. j! Z  setup-globals$ _/ [5 P2 j- b! u# }+ R2 ]
* y' `3 e% T1 k
  ;; First we ask the patches to draw themselves and set up a few variables
7 X- A0 X0 U7 M! w8 M  setup-patches' w/ r* M4 y1 A& h5 q$ Y
  make-current one-of intersections
0 e- i5 x2 ?8 G, ~/ O  label-current! R1 B' w2 j5 K1 H# B# \
+ U: {* S# T) t4 t: O( [8 @. P8 n
  set-default-shape turtles "car"# |( `' }& r4 J6 J( m& ^+ N
2 a8 ^  n5 p( i
  if (num-cars > count roads)
' V/ c* K' N/ ]" |( {! H  [4 k2 B2 j4 n4 B- J6 a9 S1 D4 t7 @- J4 u
    user-message (word "There are too many cars for the amount of "& u2 }6 M  \& c& ?
                       "road.  Either increase the amount of roads ") P# N& ^/ v& q+ w* `
                       "by increasing the GRID-SIZE-X or "
8 d6 ?; M2 K2 |9 V1 p& w                       "GRID-SIZE-Y sliders, or decrease the ") H1 ?. F6 b! @. q/ a- a
                       "number of cars by lowering the NUMBER slider.\n"
# D  N; s2 i5 S( K9 D                       "The setup has stopped.")
6 f2 Y, _: \3 a" S7 j    stop; _8 k4 A9 _2 u
  ]% @) I% s6 f, p7 N9 t3 ~! K! e

8 }5 O; {; f9 b( p/ t& c  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
5 Y$ N6 l% C) y! S5 a. a; r) D  crt num-cars
" s0 C/ ?1 S% o3 f( U7 f9 R  [
( k8 Z% W& G" m. |& v    setup-cars
  }' U2 v1 i9 g. ]/ X    set-car-color
7 q, J. f( w# E- R, v$ _: O    record-data3 |* [: P7 E, W1 |
  ]
) Y5 u) c3 m: B
+ H5 I* E1 `* j2 C. g/ z# M; A  j  ;; give the turtles an initial speed
$ d: L+ V# j- M* I4 Y$ w/ c+ E  ask turtles [ set-car-speed ]2 i! R" f$ Q6 S# a
$ d& Q5 p' R" F$ x% D
  reset-ticks
; V! w9 E# m6 c9 [4 v9 }0 h) uend  y4 J: A! B# {. P
3 U: U6 Y! Y  M
;; Initialize the global variables to appropriate values5 Z% N* \+ S7 j" {1 c# \/ E
to setup-globals( Y' _6 Y9 m9 q- E3 [6 Y4 |1 J2 f9 k
  set current-light nobody ;; just for now, since there are no lights yet% M3 o6 V' D; {2 w6 Q* T" J
  set phase 0
. |& t( Y. ^' |3 S' n5 D  set num-cars-stopped 0
1 [2 Y. |. ^3 h8 F4 y  set grid-x-inc world-width / grid-size-x7 M' t: s) p4 @# z" N
  set grid-y-inc world-height / grid-size-y
( q! S  X8 J" x! j/ u1 O+ A2 d8 ~
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
/ |3 `4 Z& ]5 s4 }3 R1 [' o! b) U  set acceleration 0.099
8 P* i5 X& c# Rend* @' B$ T- @$ D" z* M/ i
/ o  O* `, o* y$ |# {
;; Make the patches have appropriate colors, set up the roads and intersections agentsets," T; U) e( E* Q( i2 U* f
;; and initialize the traffic lights to one setting0 k4 R! A& {% e; P1 ^6 P' p) F
to setup-patches
8 R( C* n+ |9 X8 }0 N# k  ;; initialize the patch-owned variables and color the patches to a base-color- m9 s$ G& d& ^4 }
  ask patches
1 W$ w2 {8 x4 T" _- |" i/ z  [, z( {/ w: v  k
    set intersection? false
4 D/ n, {8 m( ?4 B    set auto? false9 a% l+ P& f, E
    set green-light-up? true4 i4 m. l/ T: h, T# K' h( `2 T
    set my-row -1$ v$ p4 @8 E6 m6 H
    set my-column -1/ a" H- `* J) c* W
    set my-phase -1
- a+ k2 C4 d. v: S! X& o    set pcolor brown + 3
6 D' h% Y& B1 V+ f6 F. C  ]; T/ d6 H/ A# F, F/ w" v

9 J3 [+ E: h& v# d% b6 Y  ;; initialize the global variables that hold patch agentsets
7 ^8 u5 r( {: d7 Q2 P. \  set roads patches with
7 [8 ]6 I  m5 n$ W    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) `5 n5 X! U/ E4 d
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]: R5 h8 g* E% M6 ]8 @7 }. H& F
  set intersections roads with  @) O  j6 ~2 i, t1 o/ v
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and# U( C1 {8 o% |3 t
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
' [3 X9 K2 P9 R1 n9 R$ Y- h
. A7 e0 J1 _3 z$ t$ _- G  ask roads [ set pcolor white ]) a' S/ N9 `, h& E
    setup-intersections
# ~' p( K# g8 M0 L; V( K+ jend
3 }; a! K5 c) @3 e! o其中定义道路的句子,如下所示,是什么意思啊?
, _3 L: t' d; I, P$ e set roads patches with
# \' Y! F) g/ G% \# C! w    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or- d2 C- A) l* M# ?; Z) S; R1 ?
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  b+ b/ g  h! ?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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