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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。9 o$ P8 U# `! k4 e/ D, A5 m' N9 F
netlogo自带的social science--traffic grid这一例子当中,# G" X) V* M. ^* @" I% x! ^" T
globals
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4 I5 t8 d% d; m9 K" P9 w/ j  grid-x-inc               ;; the amount of patches in between two roads in the x direction
: o! V4 @. r' G; m% u& M' m  grid-y-inc               ;; the amount of patches in between two roads in the y direction8 E0 q, s* A# M' r
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if) d; m& I& q+ n6 J" M/ i. j
                           ;; it is to accelerate or decelerate& a9 z4 t  k8 h6 i3 y  o
  phase                    ;; keeps track of the phase! H" P& t, w2 v6 F9 }% \
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure1 r) A+ R2 A/ X! ]' N
  current-light            ;; the currently selected light
* r0 {+ D5 x6 Q2 w
0 T5 [5 b& P5 _1 \' t  ;; patch agentsets4 i- t. P+ [0 R" _
  intersections ;; agentset containing the patches that are intersections2 ?& }" c& X! P) n; e, ~, S6 S
  roads         ;; agentset containing the patches that are roads
8 I: ]# G# X1 {. v4 [$ o]5 A" X# l* U$ k' C" e6 A2 ?
" I3 j: s- `! r5 y
turtles-own
( ~" ]( p& h3 |( U[* i2 a! B5 P7 c- ]8 Z- g7 E
  speed     ;; the speed of the turtle
) m2 h4 s' p) U. A  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
& B# m- b  y6 d8 q( v1 W1 _. \  wait-time ;; the amount of time since the last time a turtle has moved
( [- M9 V. ^% Q( G% ~]0 k" a* w& c1 l# D' z! I# N& `4 `& P

& Y) }- |, g5 gpatches-own- F9 J& N; k! a* W1 W
[
( d. _* F6 }3 D' y9 {4 x$ d  intersection?   ;; true if the patch is at the intersection of two roads
& M3 T: |* n5 A3 _' i  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
. S5 l. _, f. M4 ^                  ;; false for a non-intersection patches.
! K$ O3 u1 @9 P  my-row          ;; the row of the intersection counting from the upper left corner of the
- L7 p. h6 r. p( C; R8 Z0 Y( Z                  ;; world.  -1 for non-intersection patches.
2 S% R4 o# s& F) Y( D6 m! A0 J  my-column       ;; the column of the intersection counting from the upper left corner of the  W5 G' L8 d/ `3 \: j
                  ;; world.  -1 for non-intersection patches.! X7 _; N) V- Y, g9 G2 t
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.2 i5 k# D7 C0 m& f' \! @- P; k
  auto?           ;; whether or not this intersection will switch automatically.1 e; l" m: p8 p/ H- j
                  ;; false for non-intersection patches.
2 {( F3 q3 k% c- n]4 I0 A. y! V) P
8 m3 n+ r2 d: p; Z! I" W# `9 T
3 A- Y+ l8 h% ?7 e& ]) Q$ p
;;;;;;;;;;;;;;;;;;;;;;
# B5 F! k: Q; N1 K$ i;; Setup Procedures ;;
6 a% u" Q, T  |# Q6 ]  w, f4 O1 I;;;;;;;;;;;;;;;;;;;;;;0 ]" h6 l! C4 j- S6 N  w6 H! p
2 E7 M! L$ {$ }# O  V
;; Initialize the display by giving the global and patch variables initial values.
' g8 g9 h; r) ?# _/ n9 p;; Create num-cars of turtles if there are enough road patches for one turtle to) h7 H5 u" H% K' E* H( A$ W6 f
;; be created per road patch. Set up the plots.
& _6 ^9 c, [  ^4 z* Z4 K* B+ eto setup! D! H9 c7 J8 Q8 W0 @
  ca
- T9 M- L  D5 s( G  setup-globals/ j% ^3 ~3 r+ ^& L0 H- |# y9 ]
) P+ @3 y8 h8 i
  ;; First we ask the patches to draw themselves and set up a few variables* x/ w  K" y3 k3 f2 |1 P( F
  setup-patches
' U/ O% D- D& g) d  make-current one-of intersections! ~* P. A) W6 y. Y
  label-current
9 X/ C$ X! y9 |, _  _' h0 O
8 u( W2 J3 e1 e( }1 [' C  set-default-shape turtles "car"5 Z& U# j2 u" X

! e, k- @! }# J  if (num-cars > count roads)5 V( f' s4 _2 E6 J$ K7 z$ F2 V, n
  [
" @: J  f. N; {, x4 ~$ L, I( o* A" N0 z    user-message (word "There are too many cars for the amount of "  U3 k( F$ }) K$ E6 S/ g" I
                       "road.  Either increase the amount of roads "1 p: _9 B( S* ^2 H: A1 u
                       "by increasing the GRID-SIZE-X or "
& D& S# T2 `  O5 ?! x$ F0 P9 X- ~; s                       "GRID-SIZE-Y sliders, or decrease the "
0 |! E( G1 b. G& ^, s! a5 t6 ~                       "number of cars by lowering the NUMBER slider.\n"
6 e: E8 J1 P6 I* Q2 p                       "The setup has stopped.")( G$ L7 S2 C7 K! \
    stop5 p$ M9 a" x5 Q( V! x) z
  ]
! h1 `5 E4 g! D4 p9 x$ s) |9 K, ~/ t- N6 V
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
3 ?5 f5 B: i$ K4 r  crt num-cars$ r8 R5 v& x% m
  [
6 |* Q$ |  _( X    setup-cars
2 D6 |% F/ w5 t7 B  u    set-car-color, u! x8 x/ |/ q8 z
    record-data2 f( `) J1 f6 E- B# o/ d  Z! F
  ]
6 n$ p8 F5 D% K8 ]
; s1 ?- b( P8 T6 S. r. q  ;; give the turtles an initial speed
8 Q* Y5 |: n9 T" }0 j7 c  }6 T2 k; J  ask turtles [ set-car-speed ]- ?  _2 O: O! |5 M+ I! q

: g" ~$ q- F, k) x  reset-ticks) K+ u# C) w4 ^* `& Y9 E
end6 r; R" ^8 [  J$ K4 N
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;; Initialize the global variables to appropriate values
6 g( T# V. a, R$ g9 v% O* {to setup-globals6 Z4 B" W5 L* G* B3 p. H
  set current-light nobody ;; just for now, since there are no lights yet. s: }/ r( m/ b8 o! F3 l
  set phase 0
" j# X+ L* L2 {9 T! b. O. L0 n  set num-cars-stopped 0
$ e" m1 w, N6 D. {  set grid-x-inc world-width / grid-size-x% b' {2 V1 e* ^' c9 p
  set grid-y-inc world-height / grid-size-y
, w* G; x- O3 O+ G5 @' c' J' V1 v8 f0 P% K2 Y. o8 W/ G* Y  v
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
2 M# O5 Z/ J/ }4 d5 H$ h  set acceleration 0.099+ D+ o" H4 J$ N4 ~& _6 J% W% y
end+ @$ P/ N( H) c6 Z: h9 D

" w2 }/ b' x! _) J' F0 i0 ?;; Make the patches have appropriate colors, set up the roads and intersections agentsets,! L' K: p9 Z& r& i7 D* i2 V
;; and initialize the traffic lights to one setting3 d" E  o+ @2 e
to setup-patches8 s9 c4 i! G% p) W  D
  ;; initialize the patch-owned variables and color the patches to a base-color7 Z; N6 K+ C8 g( w/ q
  ask patches
/ ?% u, `6 S+ G5 E9 ^  [+ D3 Q2 a4 q" q( _. C' l
    set intersection? false6 r0 l5 z! \) Q$ T
    set auto? false
% o8 Y' |+ h$ w! n1 @: @8 G    set green-light-up? true
; h4 O6 q. W8 G: F& I    set my-row -1; K5 R! t+ p* j7 V! w5 z* @6 L
    set my-column -1$ f( g  z2 T5 e8 _/ T. \, G
    set my-phase -1
) ^& S  @- `1 c3 w    set pcolor brown + 3
# M% C9 _1 T. o  ]
6 B2 N0 ^$ {, L! H
; k' N7 R) C- D, G" a  ;; initialize the global variables that hold patch agentsets
" W2 Q' H; `$ i- R$ ]  set roads patches with2 p6 j( @4 F1 k! \
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or# S! \  ^( ]1 \
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
) Y' R( p5 x9 t  set intersections roads with
: x: t" V+ }( a: l4 r" _    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and. v6 l+ e0 O3 [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
9 }  m% s6 l1 o+ [+ e
' K. P* E2 ]1 J8 i& \6 |) w. T  ask roads [ set pcolor white ]
1 n- R- D6 h- g/ ^9 q/ |" J: I* K    setup-intersections
% j( W0 k2 e4 Q, s. Rend0 h* h+ g& P8 ]- i3 w
其中定义道路的句子,如下所示,是什么意思啊?' w/ h, {3 m+ n  @
set roads patches with: M3 D0 ^( u8 r  g' x5 c
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or/ K8 X; m2 A$ n9 j- {' @. ^
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
; d5 `; F8 Y( N4 x8 o" Z/ g5 ?% 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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