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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。! V& M2 `7 g9 x5 f$ u: E
netlogo自带的social science--traffic grid这一例子当中,
& f( W) a1 q% a2 Qglobals
/ B. _: G( N/ D! f[
3 V; G$ q/ m8 i  grid-x-inc               ;; the amount of patches in between two roads in the x direction/ t, O6 p( B. d4 U- x& u; h
  grid-y-inc               ;; the amount of patches in between two roads in the y direction, J6 I+ ^( B% o0 r5 F
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
5 l' [' c* s; G2 E6 S. @9 R                           ;; it is to accelerate or decelerate
0 ~$ n: F  K$ k0 w( p  phase                    ;; keeps track of the phase6 n  D! j: P: x* o
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
, P) D& n% S$ n, s5 W( \  current-light            ;; the currently selected light: O* G+ e: C1 F
, g, i8 S/ k! `* u: ^
  ;; patch agentsets
$ p- a, I" Y; D$ ~, C/ l  \. |  intersections ;; agentset containing the patches that are intersections
9 R5 w+ v, X# I+ g: _& f  D  roads         ;; agentset containing the patches that are roads
! J) X* X3 j7 {1 L9 a]  K# k* m2 O5 Z  R1 a( U
% m' C4 g: D! u8 N
turtles-own
8 O: O7 Q. J1 A0 X* f1 m[7 s% l! F* g3 h
  speed     ;; the speed of the turtle  T7 {7 q( R/ m; Z. m
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
+ i8 W3 S% n  |3 A4 J+ ~5 a  wait-time ;; the amount of time since the last time a turtle has moved
3 }# d9 M8 |: ^, D5 I. \) D], A4 J* N# N2 t5 v+ l& B. m% t
; b* m0 E: m: ~+ Y* M6 J) u
patches-own
  p  {4 T, n, C+ j4 i: M' I[2 ]9 V) v8 c. ~! K/ q! A/ ?, B
  intersection?   ;; true if the patch is at the intersection of two roads
4 [% Q3 d4 i$ L% W1 h: o- U4 |" a$ ^  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
- Z8 W: _8 {; W7 q( L1 p$ Q                  ;; false for a non-intersection patches.) e0 i8 C# F; I; N/ E
  my-row          ;; the row of the intersection counting from the upper left corner of the* T4 Y/ ]/ D1 U: q2 V
                  ;; world.  -1 for non-intersection patches.
2 Q4 x) j3 t6 k2 y9 o' o( I  my-column       ;; the column of the intersection counting from the upper left corner of the
, h/ O) j& @% L# A# a# p                  ;; world.  -1 for non-intersection patches./ t0 N  B) A# C5 _
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches., _0 R5 O$ I0 r9 X0 l! s  c9 F
  auto?           ;; whether or not this intersection will switch automatically.
7 n) z& n- ^4 \2 Z# a                  ;; false for non-intersection patches.3 K% K/ X$ @2 E" A) H9 r5 Y
]- @7 y$ s9 u5 F$ d9 |  |- K

3 f. j1 t4 d0 k8 Y0 h5 n' @6 ^$ L
; ]' v1 H1 R8 [. O! w5 P;;;;;;;;;;;;;;;;;;;;;;
; g9 I2 K1 [/ |& A6 d;; Setup Procedures ;;' r! f; Z6 ?3 ^: ^
;;;;;;;;;;;;;;;;;;;;;;
( g2 B* M7 J! i7 s2 F# s  F# y$ }! h; x% g7 C9 C
;; Initialize the display by giving the global and patch variables initial values./ A& D5 r4 P' L1 x- n* o
;; Create num-cars of turtles if there are enough road patches for one turtle to4 L4 z1 F& Y, h4 F/ I4 {
;; be created per road patch. Set up the plots.2 L8 M3 U- D  U' G8 a0 ]
to setup
( _; E* @4 B4 P8 P; E0 ?  ca7 g, ~- B/ V% u# j8 P4 ^& b0 [0 y
  setup-globals, l2 E- p1 h* F
# a+ D% k6 i/ {+ [* t  G# g
  ;; First we ask the patches to draw themselves and set up a few variables2 p+ r4 V# v6 s# t! }+ C
  setup-patches
( P/ \, ^. W$ d( ~! {+ D  make-current one-of intersections
1 M- v/ C2 ~/ Y  label-current3 a/ x/ d' B8 ~& T% _$ o

+ a9 L+ W. \1 U7 U9 L( V  set-default-shape turtles "car"1 u* F" M! V1 f

8 C, e7 _, ]6 p7 t  if (num-cars > count roads)1 k- d1 ?% f* j$ j$ a9 G
  [2 z5 V1 w( P0 r1 b% e7 z! ?
    user-message (word "There are too many cars for the amount of "
% Z/ A" d% c0 `4 _7 f- ~% r$ I                       "road.  Either increase the amount of roads "
9 e3 {9 b2 d# B6 |                       "by increasing the GRID-SIZE-X or "
; B: o, Z0 H! r+ C9 }$ I9 U                       "GRID-SIZE-Y sliders, or decrease the "
: y1 q$ Y0 \" [/ @                       "number of cars by lowering the NUMBER slider.\n"
) X/ x! A: U9 A& P2 x$ V                       "The setup has stopped.")
/ s  y1 p9 O% ~! f: ]& V    stop9 ~+ Z! m) d: k$ H% M
  ]8 O# @0 w' t$ q: R& L. |0 a
$ n1 P$ r; D& q# e
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color. r9 a" {+ O  k4 N+ k
  crt num-cars
% V$ d7 M. u) q$ P5 M6 I9 x  [
; [: G# [/ R$ R& P  h! c    setup-cars
, S1 {8 l% Z, k4 w    set-car-color
' }, s/ @6 r' o$ P* l    record-data
# Q7 p- K% |* V( O8 H  ], h- v, d( h' a# }( Y- |; m
8 P% d5 [4 |3 X: M
  ;; give the turtles an initial speed! I; F( p$ C# v0 r' i
  ask turtles [ set-car-speed ]/ ~- x  a. z* \: U6 b
# i4 `: c0 l$ b* C$ d3 t
  reset-ticks
7 e( {1 w" h: Q; F3 Q% ]$ cend
- E+ Y+ P( W  R9 H9 u9 ], k' i5 s, f( R! ^8 Q* F" S
;; Initialize the global variables to appropriate values  k1 V4 _% j: G
to setup-globals9 r: P0 G* L0 B; `* ~) |
  set current-light nobody ;; just for now, since there are no lights yet
6 r( j3 _; D! x4 v  set phase 0# V" m. h+ E7 q- W; p+ ~
  set num-cars-stopped 0! f) [3 w1 o: h; ^1 v  {7 D, \
  set grid-x-inc world-width / grid-size-x" a2 z/ h- H% \6 |
  set grid-y-inc world-height / grid-size-y4 c# |8 |  {* a* L) a0 _
& ?0 f6 \9 u1 r3 y
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
5 W0 a2 F4 O6 t9 L- n" P* t  set acceleration 0.099
, L0 n0 h2 q& Yend
2 A3 I4 m' i( {, y" a, `; X# ]: h! c8 c: p
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,/ q  C( E; o5 \6 V
;; and initialize the traffic lights to one setting: q6 {5 X% T+ j( l
to setup-patches
- n: u  @, D) M$ S  ;; initialize the patch-owned variables and color the patches to a base-color
2 H5 H7 y6 @) g  ask patches4 t! R$ E* \, l9 |; w* _
  [. J$ A6 s- T2 {3 l0 @
    set intersection? false
7 k- y& b5 g3 h/ d+ F    set auto? false3 X! h+ j+ u  K7 F& z# \3 x% i4 v
    set green-light-up? true2 [4 M; @" J2 r, J$ y4 P
    set my-row -1
8 ^; ^) L. k3 k    set my-column -1
% v7 j6 }8 L4 v. U" k    set my-phase -1& k7 y: a) o* J0 y" Y
    set pcolor brown + 3
: H# ^6 V: u8 O4 \  ]
) o$ V# T  Y5 L" {
1 `# |5 t' v7 ?( N2 B4 X8 A  ;; initialize the global variables that hold patch agentsets; u# t  F& R0 D0 N3 @: z: _4 A
  set roads patches with. ]) r: Q" u/ G7 j& q7 Z+ X- i
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 m# A8 c) M+ V1 [( S) H8 W% Z$ E) X
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
; i  \, b3 C$ }. A3 {) \- ^  set intersections roads with
; c) }7 K/ |) c3 L' B( f8 n    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
. @1 O' j' Y7 Q- s' v" O    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]9 ^  A+ g; t6 u' a8 T  h

. U+ B8 ]. E: |9 y  ask roads [ set pcolor white ]
5 U: X9 x( F) z: S- `    setup-intersections# a# Y* D% c3 C/ \1 m& E* e
end
" t8 j- @" P" I: f其中定义道路的句子,如下所示,是什么意思啊?. Y# \; B" m0 H+ U1 ~0 |. @
set roads patches with5 u/ ^4 G% u; K% e  X# `
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
: ], d! d! X. ~# q) z: E- V7 U    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
) T  L, }' d; K/ |# E$ B# E( N$ o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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