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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。
2 J* @; i: b# |3 r/ Enetlogo自带的social science--traffic grid这一例子当中,  B) y6 ]* g$ g) V; x4 p
globals- `  R9 ?3 Y: F$ W2 E
[
, m, y5 e. k% O7 g5 [  i  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 u! G3 d$ L- h' t- J0 \/ t1 l% V- `
  grid-y-inc               ;; the amount of patches in between two roads in the y direction$ j. D; d: }) `2 r/ A; w' ?. _
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
3 v: N7 y5 v- o& x5 F6 ?. X! E                           ;; it is to accelerate or decelerate, U# _' O: b- t! Z$ J
  phase                    ;; keeps track of the phase
  Q2 u3 c& a2 V. d* X- l3 O  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
2 s2 j7 X; T# N: e  current-light            ;; the currently selected light5 O# p1 P* g  z0 ?# Q% ]$ V8 f3 _

& |/ ~" H, m3 {1 w9 H, [7 O  ;; patch agentsets& Y( b" G$ `9 }' A1 D5 t. m- w
  intersections ;; agentset containing the patches that are intersections! i/ I( b2 N# u% w
  roads         ;; agentset containing the patches that are roads
2 Y) p$ w3 V. `/ B* i  ]]
# m& p& ~9 M+ ?! L0 M
! ]8 i2 \7 m( K4 L* qturtles-own0 u0 _" \# v3 [3 e; q
[
: C0 B% F. m$ U) W8 ]% T5 w% l" Y  z  speed     ;; the speed of the turtle7 g3 W  b, w& q0 h9 X4 @
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right6 Q3 ]: R0 }6 i: d  M
  wait-time ;; the amount of time since the last time a turtle has moved. ~+ o* }9 c& b3 U# l/ R
]
% {* x3 e8 Q3 w  F; B8 n
. s* ^" Z" q/ Dpatches-own
0 M- g* @8 J5 W4 l4 P, g7 }[6 a+ B' x8 @, L5 W( x2 X
  intersection?   ;; true if the patch is at the intersection of two roads6 M; ~% D) b4 _7 b
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false." E  k; @8 E1 m. Q
                  ;; false for a non-intersection patches.3 m2 b! Y2 Y# F9 Z+ G( g# s5 |
  my-row          ;; the row of the intersection counting from the upper left corner of the
, R8 v! s4 k2 O! i! O$ }! j( x                  ;; world.  -1 for non-intersection patches.
, l  {* J9 A5 Z* R& d2 ?, l$ T  my-column       ;; the column of the intersection counting from the upper left corner of the0 [0 |7 W8 j5 y
                  ;; world.  -1 for non-intersection patches.
0 n9 u/ c* h9 u" [$ d  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
8 \% C+ a. T& U  auto?           ;; whether or not this intersection will switch automatically.7 g1 G( t0 a+ q" g! z
                  ;; false for non-intersection patches.
+ Q* O! t5 p( y+ S0 p. v. f]
7 ^7 k9 ?$ M$ _4 B  G/ n5 X
6 [9 \' A# L3 W5 I4 [% i" I
/ I5 K2 v$ ~: I1 z# _  E$ G, w; o;;;;;;;;;;;;;;;;;;;;;;$ W9 O% c7 A! W5 f3 w
;; Setup Procedures ;;
4 }% s: q; o/ b0 V& B5 n9 K% x;;;;;;;;;;;;;;;;;;;;;;3 T7 G) L) G) B0 |

% `& P4 _& Q! y+ {9 C;; Initialize the display by giving the global and patch variables initial values.
' }; J) z& O1 i, I+ ]8 C1 \* r- E/ Q;; Create num-cars of turtles if there are enough road patches for one turtle to( v5 d' D' L1 ?
;; be created per road patch. Set up the plots.8 s7 p8 K: Z* o5 v; V. Z
to setup
# }2 K/ ^6 A4 H" `/ k7 f; g! z) I, ~  ca+ J5 ^1 F! ?, _3 t
  setup-globals% |- e- M1 g# y5 Y. H  ?9 j- I# h. L

- B% N, S- U' C7 I; j  ;; First we ask the patches to draw themselves and set up a few variables3 V; n1 W4 t8 ~- G" }
  setup-patches
2 P+ N- T, f4 O, g+ E6 S4 o8 x  make-current one-of intersections/ L- n8 ?) N7 E' u& X4 P. h
  label-current; B/ G& `* F- J1 {1 ^
- E' K8 d8 k- i# ?  i5 `% ~6 N
  set-default-shape turtles "car"
. O" ?- J1 b% g5 e8 L) {0 f! h5 ?2 l$ X8 p. W8 E' k
  if (num-cars > count roads)' k9 H# e, [, l% I; L7 O
  [4 G' f9 p) e  W0 N
    user-message (word "There are too many cars for the amount of "% Y  L! i& [) q' ?( Z# k& @
                       "road.  Either increase the amount of roads "
% ~: K* y$ F. L+ r) o+ }  ?1 m                       "by increasing the GRID-SIZE-X or "
2 J$ ~) N4 N2 N. Q: v8 n" n0 f2 D3 }* u                       "GRID-SIZE-Y sliders, or decrease the "
  p; k  H& O- W# q5 ^1 I- c                       "number of cars by lowering the NUMBER slider.\n"9 l$ U4 w/ }: Z3 W
                       "The setup has stopped.")# l# J# B8 h! i4 U
    stop
. R1 s; \0 m, U  N  ]  d; h! b( j5 _  O( }

4 f8 |; u; B9 [, D* Q' N9 u1 ?  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
; A' o0 V' H3 Z1 I. ?  crt num-cars5 C9 n& I# o$ f0 _
  [
- L  `- k( ?. C% y  B% X* U% s    setup-cars; A  A4 ^1 F  _- B9 A: T: u2 x
    set-car-color8 y# \6 `" Z. P* X# V2 S
    record-data; K- u0 r2 x0 `/ o. k2 y. t( F6 Q
  ]
/ \# S6 H2 D: ], u( b6 D( A5 j- s( f1 W9 s4 R& Z' W
  ;; give the turtles an initial speed
" d# \8 d( @6 \) }( \) \  ask turtles [ set-car-speed ]
, a, E1 h/ a9 w% e" v1 H/ r7 ~
5 V8 D( u5 N) @; `: c  reset-ticks7 ]! {/ ]7 e7 k- C7 \
end* p5 _6 G5 x* U5 L8 `' n

0 D4 }5 Y& i% J& n5 Z. w;; Initialize the global variables to appropriate values( \4 m: c, N  j+ n' w( w
to setup-globals
) J) Z% [' M2 a3 [3 C  set current-light nobody ;; just for now, since there are no lights yet
, h0 q; r5 R. V# h  p4 ]" b  set phase 01 W; B: n1 B  J1 E0 M- S5 N
  set num-cars-stopped 0
  A! i; ~- y5 T$ N+ c& M  set grid-x-inc world-width / grid-size-x! l! `: V# D9 v  w! O
  set grid-y-inc world-height / grid-size-y
" |6 F. n& H) L: o9 {
, }! E/ W# ]1 r* U6 W9 a  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary& y/ d/ N/ ^/ c
  set acceleration 0.099
6 Y4 N9 {4 y9 @1 w0 L, u- s# Hend* I2 Y" T( d; e
) T& D0 H- w( }# B$ y, Y
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
7 R8 D1 f( N' V2 Y;; and initialize the traffic lights to one setting
0 e: z2 f1 T4 z) S5 x7 C6 L% j) Lto setup-patches) k. d$ F& \- k
  ;; initialize the patch-owned variables and color the patches to a base-color/ f" M9 Y5 u5 L- S4 P/ g1 P
  ask patches
- W' p5 ^+ ~" j3 @6 v4 b  [
# |7 V* k& O; {3 i    set intersection? false1 Z+ K& Q! c: R3 \( t! I
    set auto? false
. @( u' K5 u2 L- L# R8 c    set green-light-up? true
5 B0 k5 ^) K/ D" ^- }* Y" G    set my-row -15 {7 [, D. t4 J% }# m$ R; n8 u) N
    set my-column -1
" T8 |0 y/ b6 ~. x    set my-phase -1
8 [1 O1 s$ H, z9 ^6 u' X# k    set pcolor brown + 3
. E# z' P: y  }$ ]/ y  ]
+ h) j& ?& s. Z5 [* g; F( n
+ a: f& J/ p0 V- m& y  ;; initialize the global variables that hold patch agentsets' _7 V# n; l4 B! p/ h
  set roads patches with& m- ]- n2 J# {6 b% H
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
5 N, Z5 V6 H: P    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]4 p& @( `5 T% T. o8 c5 V* f  l5 _
  set intersections roads with( H3 u' J2 U6 X( _6 ?  K
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and/ I# O$ B5 `3 f. W% D
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]$ [+ y. x0 Y) w) \* A* L8 C
% `, u5 e3 x7 P' H- T' _% k0 i. I) \
  ask roads [ set pcolor white ]
- b( q* p% o! v( Q    setup-intersections/ [8 W( H9 J; q) w3 D
end; x: ]! z# B+ T6 b
其中定义道路的句子,如下所示,是什么意思啊?  Q1 e8 F; O* g
set roads patches with- I$ ]& H1 c1 k! g# S, y
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
3 y; W% D' o& V) {+ F$ C. }1 r% [    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]' h& x( t. d( [" j8 d/ ^  _
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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