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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。% r- X3 \# C& a0 O' }
netlogo自带的social science--traffic grid这一例子当中,
3 T, K, \/ o/ Z- H% O- Z+ Vglobals
! e4 w5 o2 [5 ?[0 {  ]. q, z  V3 Z
  grid-x-inc               ;; the amount of patches in between two roads in the x direction4 `' u9 l% t. h# A/ p2 l
  grid-y-inc               ;; the amount of patches in between two roads in the y direction+ `1 X* t1 q, n- d5 G4 h+ Z
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if- F! f! e" h$ E, D
                           ;; it is to accelerate or decelerate
8 s* g* a( x2 b) R* d: U  phase                    ;; keeps track of the phase2 W) j8 k$ |) s) q  _( W
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
4 d8 b1 O6 g/ c0 s( {" L  v# W  current-light            ;; the currently selected light
2 i; k) G: f) g8 j3 Y2 b2 F" e4 d2 g6 V5 b
  ;; patch agentsets, f5 T& F* v% \
  intersections ;; agentset containing the patches that are intersections6 Y* P7 \/ Y$ v% A* w
  roads         ;; agentset containing the patches that are roads: q' v5 q& U8 W  U1 S
]! s- C+ _& T7 c4 B9 @3 A

3 C- X$ c* }2 B6 t0 [7 A7 Dturtles-own
4 m/ o% S, t+ k( n6 z5 W  p8 o[: V/ i* c5 |: c) `
  speed     ;; the speed of the turtle" z6 i9 ^; I6 {0 H
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right( ]' ~/ |7 c: A# B0 V
  wait-time ;; the amount of time since the last time a turtle has moved
  q4 a7 R1 m' G* e& w! V- b$ V2 U]* M; E5 b# Y5 s* n

+ y! V7 n+ ^& p" w: ^patches-own
0 s) x  g! J7 Z[
4 l+ c) a- H+ `7 y9 Z  intersection?   ;; true if the patch is at the intersection of two roads# T) K9 V% _. e/ M  ^3 Q+ b) Y
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
: M6 A2 k* r  \# H                  ;; false for a non-intersection patches.1 s! \0 o( f/ L
  my-row          ;; the row of the intersection counting from the upper left corner of the
9 }) t: p" y9 G  \0 h                  ;; world.  -1 for non-intersection patches.* D( Y5 r8 c( o3 B# R$ T7 f+ U
  my-column       ;; the column of the intersection counting from the upper left corner of the
/ a9 z5 Y% s9 H                  ;; world.  -1 for non-intersection patches.' q+ E: y) }" j# ?7 h
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.  X5 U. K! f, B: T* I; ^: e% ~
  auto?           ;; whether or not this intersection will switch automatically.+ B+ P6 k7 O6 q8 X" B
                  ;; false for non-intersection patches.
& T& E, ]3 H# V. f]
7 ?! @$ Q, G  b* B& s" T/ g2 R5 k7 M/ ]$ a5 b, F3 w

  C) {% G9 U1 t  u3 g: u! L7 N;;;;;;;;;;;;;;;;;;;;;;
  H. I) \$ V, a5 I& h;; Setup Procedures ;;! C7 \2 D% ?8 ^  k* Q" t: B/ {
;;;;;;;;;;;;;;;;;;;;;;. d& u- s# w$ q( g- u
$ T# t8 V0 `6 U/ m3 R  I8 G5 [: ~# b
;; Initialize the display by giving the global and patch variables initial values.1 S' Z2 Z5 ~" j$ f0 F% q
;; Create num-cars of turtles if there are enough road patches for one turtle to* m; d: ]/ P$ J
;; be created per road patch. Set up the plots.
8 g3 T5 a# w0 n3 w" wto setup) l6 ^3 Q  T1 b9 `& N& D& ^
  ca
; O2 E! h4 k  e+ T  setup-globals- I. m; l. `; L7 ~2 J! }
' b7 }# O* M0 P$ ^3 {0 T
  ;; First we ask the patches to draw themselves and set up a few variables
# \" S* A3 n! r! {" n. @  setup-patches8 ~, n9 E3 w; v4 d. ?6 S5 P
  make-current one-of intersections7 u; V: `- w- e
  label-current9 O' Z! R% d1 [# ?/ }

0 F7 o6 [, A. m; `  set-default-shape turtles "car"
( ]6 {  g  x. o! O5 Z  [% _
, {' w- E4 @" E) u3 J: F' C  w  if (num-cars > count roads)1 x9 g5 Y1 }$ f# Z/ A  z) f
  [, \$ E2 `8 d3 |2 \" J
    user-message (word "There are too many cars for the amount of "& b/ C  v# R, m- G% R+ J
                       "road.  Either increase the amount of roads "
$ ?* O+ n" y8 B                       "by increasing the GRID-SIZE-X or ": m8 y$ d6 g0 u# v) y( r! I
                       "GRID-SIZE-Y sliders, or decrease the "6 Z! S6 J, t0 L3 u0 U( T
                       "number of cars by lowering the NUMBER slider.\n"
( K+ D2 [; S4 j6 T/ N4 \                       "The setup has stopped.")  P: @( ], Y& ?) i  V' G
    stop: ~5 T$ b: U/ t5 m( q3 W% ?
  ]
3 X9 b2 k. g& K2 m8 S. Z# [
9 M) V8 a. o5 b" d0 v+ m  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color7 K; t3 E  w6 y9 w
  crt num-cars
/ I; V4 w3 V8 ~  [
" a8 W# Q0 i0 C7 K, V5 m) O* \( Z, J    setup-cars% B* P+ ~; d0 D# b0 D. v' ?
    set-car-color7 I/ X) q1 b- B% |8 u* @& v
    record-data8 P2 Z/ h& s. H: x, ^  U
  ]4 G9 D. X6 Z1 ?/ n- p! o) n
8 L  g7 j+ c# J2 E2 O3 f
  ;; give the turtles an initial speed
/ h' Y& d+ g, E. v- {' Q9 U  ask turtles [ set-car-speed ]3 E- s& _( x7 Q
2 y+ ?. \" \5 e+ f0 r4 w/ r
  reset-ticks* O  ]& X$ D  x
end
1 {, ^6 h8 u) u- @+ c3 v
, c% O2 s" j8 V8 _;; Initialize the global variables to appropriate values& R8 m# c; f% x# d1 R* S; i
to setup-globals
; V  n$ W; z2 K# w& t6 K  set current-light nobody ;; just for now, since there are no lights yet
9 {) s3 j8 V3 s  set phase 0& g4 G8 ?! R. Z  O& R9 S
  set num-cars-stopped 0
, a8 U# |5 i5 W/ w6 A" e% l  set grid-x-inc world-width / grid-size-x! e" A+ v9 A+ I7 D6 a
  set grid-y-inc world-height / grid-size-y  U* e# k* n( L+ H0 S

8 Y1 \8 j& f. d7 q% `  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
3 l' Q7 |# `$ p; |9 k! Z0 h9 k! O  set acceleration 0.099
* S! T1 w3 Y0 ^. ]- q, w; M+ {1 Kend
9 L( I0 {+ b' y7 _+ T- g* l" ?( T, [6 b  S6 P
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,( y2 R3 D) F9 t6 R6 b+ l) C
;; and initialize the traffic lights to one setting# ?8 k0 c# N: c% A
to setup-patches  A7 N( v. g, n3 |9 J* w
  ;; initialize the patch-owned variables and color the patches to a base-color
* M. c  ?/ w* I' [  ask patches; L% j7 C& g  y- N; y+ Q
  [
# Q6 h, H) m) O! B6 i) N    set intersection? false
' A5 k: k! {6 x    set auto? false/ j  b1 y6 \$ ], Z5 W- W
    set green-light-up? true! g6 D! v. ]3 m; j& y
    set my-row -1+ k$ Q) ~. t+ p5 `$ R
    set my-column -1
3 C1 a6 F8 f) L+ G/ E/ ?    set my-phase -14 L$ D8 A# G3 q6 j
    set pcolor brown + 3
% ?& T$ ~6 q7 A9 Y0 L% }, j7 U5 m  ]) E# [) h  [% q+ A5 [% p& y

. |9 X, \2 P) u# }( ~  R7 _  ;; initialize the global variables that hold patch agentsets1 I, z( d2 q7 r* `5 Y* @2 _1 [6 o8 q# Q- D
  set roads patches with
+ r, N! m% G& @; Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
* z% U' J  m( Y  r6 G3 o    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]: W# H0 E4 L( v* c( n2 K- e
  set intersections roads with
4 Y. K  }4 y2 V    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and: L( f0 l1 D5 `* V2 ?
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) F6 o2 N+ F' b! j) \+ [& z- H

& G: G/ q+ z, R+ F& P  ask roads [ set pcolor white ]
3 `- G0 ~9 u, O    setup-intersections
/ ^; X  w' W# N, ]- `& v, Cend
. u  L3 U9 m/ b1 Z. v其中定义道路的句子,如下所示,是什么意思啊?1 y4 w2 z  P8 T" n" L: r
set roads patches with
# F  P! ^) }' d4 b( d* g    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 J" b( r0 B. s
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
! \/ O  d8 `1 Q- _( \; \  C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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