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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。! w/ T0 E: ^3 I" g$ i' c
netlogo自带的social science--traffic grid这一例子当中,
! J" K0 ~7 }+ ~& fglobals9 @! M/ F6 m; n$ Y) p4 B7 |
[/ l% T% {7 X; D: s  N
  grid-x-inc               ;; the amount of patches in between two roads in the x direction: c8 B1 i6 c0 N' n0 C$ v
  grid-y-inc               ;; the amount of patches in between two roads in the y direction. U! M% ^# M; ?+ j8 Z9 ]
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
6 E0 h. I6 N. ~) j3 m7 Y                           ;; it is to accelerate or decelerate: I9 l) K4 s/ M  I: G
  phase                    ;; keeps track of the phase8 n! J3 r; [6 n/ p6 x9 P: l  j/ F
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
! `2 f& R( @! H+ j. W$ r  current-light            ;; the currently selected light" R7 m" ]8 Q2 j8 B* Y

8 ~  R: a0 h4 o3 n. w% h' A9 T  ;; patch agentsets
; N( H* D- @" T" A- t6 t! l4 a) j  intersections ;; agentset containing the patches that are intersections$ Q" m4 ^7 p/ }
  roads         ;; agentset containing the patches that are roads
9 C, p5 o0 f$ S+ J" u: G, i]
8 J4 j6 C' |& w: ^- k
. t. d7 }7 N- m$ o2 m$ k( aturtles-own1 d& x1 n, K, d# G" U
[6 m, r* `/ A/ r: D  |' [
  speed     ;; the speed of the turtle
; I# p8 @0 Q( F( \+ o+ K7 ^  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
7 |7 Q& U7 D" @- ?2 |+ v9 t$ ]  wait-time ;; the amount of time since the last time a turtle has moved: l6 e2 F  `6 s
]1 A4 ]7 Q8 u% f
$ A& e; r- K' k( [' f0 Z2 |9 ^& i
patches-own  |: t- J: p4 x7 E' A. o  T
[
: k7 u+ ^" y" J+ M  intersection?   ;; true if the patch is at the intersection of two roads
& I: e9 ?9 r2 L* {: H  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.+ w3 f: @: I0 u- v$ q: M
                  ;; false for a non-intersection patches.
3 d5 h, }& Z/ J& y2 N! A. z  my-row          ;; the row of the intersection counting from the upper left corner of the
: F0 W% ~9 ]9 K/ T8 _1 u- B                  ;; world.  -1 for non-intersection patches.
) q- q2 q6 f, _, _0 G% N  my-column       ;; the column of the intersection counting from the upper left corner of the
! y7 S, o$ P) E2 M5 o                  ;; world.  -1 for non-intersection patches.
& p# G0 Z  X! A# x3 ^( A1 K; u  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches./ I$ J7 @% [$ g+ X$ G) G- J
  auto?           ;; whether or not this intersection will switch automatically.
  O2 N7 E( n$ o- Z                  ;; false for non-intersection patches.
' w3 R6 z; L8 F% `]
8 E5 R7 H$ i" Q) x
4 ?0 i: [% T* J; M/ q  F/ \6 Z3 D6 _1 ?0 _' T' T  H7 z" V5 \
;;;;;;;;;;;;;;;;;;;;;;) i2 C9 X+ G- W/ I7 J; z1 ?  g( @
;; Setup Procedures ;;
3 ?4 I# t$ m( v7 }* Z+ k;;;;;;;;;;;;;;;;;;;;;;* Y4 n  Y: G: {4 S; V1 w6 x0 |( h
9 b3 ]) ?0 f1 d) M1 `" k" |5 O
;; Initialize the display by giving the global and patch variables initial values.& U4 H. m3 \, l
;; Create num-cars of turtles if there are enough road patches for one turtle to( K. j, x% F2 w5 N. P
;; be created per road patch. Set up the plots.
8 R; W4 {- i. y$ M2 a. qto setup
3 s* Z+ Q4 L: Z1 y& H, }  ca
9 o" X9 |+ Z7 p) o. [  setup-globals
0 O4 [: s7 {; T) s1 s# I. [
- s, f3 g  v* M/ P! q5 \  ;; First we ask the patches to draw themselves and set up a few variables5 X; u$ l. N/ b8 X" P
  setup-patches7 ^- v) c7 @6 j, L
  make-current one-of intersections
$ t) }$ U$ d9 B  label-current" M, C7 R' Z6 a% @. M

3 ]# @7 j2 {5 [0 I/ F' L; ?0 l  set-default-shape turtles "car", |& j" b8 y, n3 [: v1 |/ l$ s) E
* d2 N+ g& y/ U$ z4 Z& D
  if (num-cars > count roads)1 `6 u) _0 g; x0 ^- F  D
  [
% E2 Z+ J+ T$ j" D; c; j. U    user-message (word "There are too many cars for the amount of "& [" {! H) e& N5 }' k* q& A* y
                       "road.  Either increase the amount of roads "1 f7 r7 A% n: m
                       "by increasing the GRID-SIZE-X or "
+ E1 u; }0 z2 W% ^. ]                       "GRID-SIZE-Y sliders, or decrease the "' i' [4 `7 J( X' }5 P
                       "number of cars by lowering the NUMBER slider.\n"
  `  [: H! X8 c/ B; W/ R                       "The setup has stopped.")
" I1 ]; s3 p% m3 u, b    stop
3 a/ r9 G' C4 p: G! B3 F- q9 H4 y  ]! V, w# A- z1 y* M3 i
$ R$ {% X- ^% }
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
' `5 p! c: ]7 r6 m& [8 e  crt num-cars
+ o: b7 p; b  ~1 r  [
3 X, q( ?8 Y: ^! ~" ?7 x. |    setup-cars
0 h2 k9 K9 f/ Y4 E    set-car-color
0 [- H3 H- M! r: ]+ _    record-data! T: l# o2 @- A+ M  {8 z0 x) w( B
  ]
. u8 M; v8 M4 [6 d8 b* \
% v3 _) S2 @4 o  N5 q4 e  ;; give the turtles an initial speed
, K( k; m. O# Y, Q  ask turtles [ set-car-speed ]6 l9 u2 B1 q5 P8 L

5 |5 K: q, g5 H8 }  reset-ticks
& [4 [  l% H1 |+ q6 Dend
; G- C: a" o: G1 s8 {* Q- M/ E7 k6 X, X' Z
;; Initialize the global variables to appropriate values, O0 U' g& @6 ~- l% `. d
to setup-globals
  H3 G0 w9 l; f+ p  k9 V8 `  set current-light nobody ;; just for now, since there are no lights yet
/ j+ ?, i" F6 {& j  set phase 0
4 m5 R+ A3 Z6 [5 m  set num-cars-stopped 02 G# ?' |0 T( [4 L! b* w# P
  set grid-x-inc world-width / grid-size-x* M4 K( e7 p, t0 y- b9 c* L$ P
  set grid-y-inc world-height / grid-size-y
" N+ B' _% w0 K" a
" G5 `/ R: D) w' ?2 f  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary) V! ^* X5 R: F) @
  set acceleration 0.099
# O( E8 j0 u3 q& e- l$ R% Jend3 y+ j6 J2 A0 |+ u) w
( ~: H! w0 \. b' ^- N1 g# C
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,# V6 e9 w# O, E2 y6 E2 H, K
;; and initialize the traffic lights to one setting7 t; m" a$ A9 g' n- ^
to setup-patches
& z! K  N* ^+ S9 s2 m4 T  ;; initialize the patch-owned variables and color the patches to a base-color. J$ Y# B9 M; c/ A
  ask patches
2 k6 N6 s  i( n" t0 ?  [
$ ~) g, c; S# ~$ t/ ^    set intersection? false
) v1 g$ b7 D1 f% O* w0 m    set auto? false
" K/ E% x& A+ P+ m8 R! V+ U    set green-light-up? true
+ _$ z5 a  J9 h: T    set my-row -1
/ }. S! [& O: M# x    set my-column -15 y( j3 _: S7 O& w9 z
    set my-phase -1
0 Z  e3 J* f1 W* C9 w. e6 E    set pcolor brown + 3
& a" [; W' M% x/ k$ d" ]  ]
2 e; e6 _5 [. B$ |. @& R, {+ C, i- ?
- x! M1 R. y. i  ;; initialize the global variables that hold patch agentsets
0 H" X5 t" M8 s  set roads patches with" b! U- }! l  S
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or# \' j+ r0 K; }, o5 b" q
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]- q8 b; j" n3 Q; u. C
  set intersections roads with( v5 h3 l5 V- d$ v& Z, o
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and; q2 ?( S2 U' }; `2 K( F4 t' R
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]# C) v4 D5 {! P* }8 K: D

7 r3 a! i) \/ [) m. p7 h0 W* g  ask roads [ set pcolor white ]
9 d+ L; }1 u# x    setup-intersections
  e8 F; u. B0 d6 k  i0 ?1 i# Oend  @9 O7 U3 W+ G. H
其中定义道路的句子,如下所示,是什么意思啊?
6 I* S5 i1 C( z  [ set roads patches with2 N: e- ]1 o  W. U  {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 b2 K1 Z% U6 C& {$ T  e- J8 }  e% w
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
. X  P2 F9 m7 g( x6 A( |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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