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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。, x$ b7 ?. O3 A+ o% h0 }
netlogo自带的social science--traffic grid这一例子当中,9 A2 Y5 k. h7 X5 d8 j1 u4 p- j
globals) X* i( L7 b- u- s; @6 p
[
3 k% U, M8 N: d  grid-x-inc               ;; the amount of patches in between two roads in the x direction
0 v, ~. _- o: ^  grid-y-inc               ;; the amount of patches in between two roads in the y direction  ?  u% @" |3 v  Q8 E* U0 c: Y
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
; r8 H" ~/ S+ {. l! e  V* b; @+ Z                           ;; it is to accelerate or decelerate$ u& d# G9 d1 D$ T1 P. f2 h: k
  phase                    ;; keeps track of the phase
/ o& t) T0 j) u- ]* {9 k  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure: f, F6 j/ ^2 r+ c- }
  current-light            ;; the currently selected light
( L! K+ \2 l+ e/ u# {% W& i/ a, f4 z; B& [
  ;; patch agentsets
, z$ B: w+ i+ @: d* V  intersections ;; agentset containing the patches that are intersections9 p6 m! }. }" ^
  roads         ;; agentset containing the patches that are roads
% f+ I  T0 q  p! L4 G]# t7 D0 ^4 E' z  _# ?) B5 `3 H7 E
0 y! [$ s/ y8 D9 {8 |- g7 P
turtles-own
2 N6 T! w0 I4 h6 W! Z[
' l; R. u' V8 s, r  speed     ;; the speed of the turtle' P" B+ Z' o  h  j2 }- h, A* M$ K
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
- V6 G& D" Y' ~5 o) s- [; r; |  wait-time ;; the amount of time since the last time a turtle has moved: v5 E3 @" l) C: J
]
  S  u9 g. z7 Z1 O" t# I5 Y5 ?( \) J$ X& z9 U' a; P7 g. v9 K
patches-own3 g) q' h7 Z+ n% P: q- e1 e# j8 ?
[
. w- @0 v1 _5 B( |; X  intersection?   ;; true if the patch is at the intersection of two roads
4 m6 p& w6 `# L, s. @, \5 t. I  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.4 s. [$ b( Y" f, W) \4 }
                  ;; false for a non-intersection patches.7 j, z  D% Y* k+ L2 O" p
  my-row          ;; the row of the intersection counting from the upper left corner of the+ p2 D. [* c! N8 ?. t1 R( w. ~% e
                  ;; world.  -1 for non-intersection patches.
5 `6 |7 y7 T" P  my-column       ;; the column of the intersection counting from the upper left corner of the$ [9 h5 z, W! C% ?, B
                  ;; world.  -1 for non-intersection patches.3 T# K6 b( w6 a( \" @/ s
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.( O% o/ a/ \% v
  auto?           ;; whether or not this intersection will switch automatically.
9 q5 ?( _  I( H1 P* E& S                  ;; false for non-intersection patches.! Y* |( z- B3 s& J) [) A
]
  o8 }+ w  g. c5 U# `
/ a7 T, K  x  O9 T3 x; M7 d
- M+ U3 l# m2 \$ r;;;;;;;;;;;;;;;;;;;;;;
9 F2 w: K) r+ U4 I) j+ z- r8 G;; Setup Procedures ;;
$ H, S) g* K  C$ N8 @+ }6 V;;;;;;;;;;;;;;;;;;;;;;9 e* {  e* `3 Z8 ?! L. a0 X* x% L

! |% s1 r1 x+ @7 k;; Initialize the display by giving the global and patch variables initial values.
. F* _5 O5 ?# C( x4 A) W;; Create num-cars of turtles if there are enough road patches for one turtle to
9 _+ t5 ?+ P$ ?% a* ~;; be created per road patch. Set up the plots.+ p/ A2 e( I! _, e' U( h
to setup
& K. Z/ b) K  Z% g% l  ca
' O5 A& S8 x9 k  p  setup-globals
4 c+ }" R( @, Y- F' w- [+ N
, a& N. S/ }( A  ;; First we ask the patches to draw themselves and set up a few variables9 {! z( H3 L, g
  setup-patches/ k# @& k/ X+ v7 ]$ k8 `
  make-current one-of intersections
/ s& ^& a: q7 {( [) O9 K  label-current" h3 u- w/ ]1 ^: m0 l8 o2 D8 A
: K( h3 _/ P% y, d5 Z1 Y
  set-default-shape turtles "car"+ K* f- [( b) }& m* U2 q
7 u3 p& n) [1 ^9 z
  if (num-cars > count roads)
9 x  E' B0 x! R6 z& O9 c# ?& t' s' w0 M  [
$ `3 S) L2 _2 e& w    user-message (word "There are too many cars for the amount of "9 C% _+ O# f8 C6 |8 |/ A: y
                       "road.  Either increase the amount of roads ". j6 c& ]$ _; L' F+ {
                       "by increasing the GRID-SIZE-X or "
: T- i- e* [. ?! _& z                       "GRID-SIZE-Y sliders, or decrease the "
0 x; Y; z- J+ a; w: D                       "number of cars by lowering the NUMBER slider.\n"* Y" n2 r& s) Y$ y
                       "The setup has stopped.")1 E, h+ L: z& {
    stop+ @& e) A. z: ]6 ~
  ]4 N1 D9 m: ?7 U5 M! v' i% D; a5 z

2 H. M, f/ h+ v, F3 m  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color) v0 e- h3 v$ t+ ^0 x
  crt num-cars$ u0 E1 R, ?, f- F1 i+ o% f& n+ i
  [
- b% y. }4 |# p( R    setup-cars! y3 R( q3 `* S- y7 {
    set-car-color
. g, h" ~3 k& J" b- ]0 t2 Q) N9 i    record-data
3 i! h1 C# a, T% b. p3 J  ]
  v2 S4 ?9 L% I) J2 B' g' I- Q5 K+ O2 L
  ;; give the turtles an initial speed* d2 }9 _9 T% }, N7 h: _$ w& _
  ask turtles [ set-car-speed ]# A; I6 |+ C1 u! s

2 m+ D1 d( t+ a  reset-ticks& t  H- m4 M  W6 e4 U, F4 M
end
+ \7 Y' b0 V; {0 v2 e! \7 D* f( D) C& v
;; Initialize the global variables to appropriate values
1 v; ?- ~9 |% z6 A" w4 H1 E6 `0 X$ X- yto setup-globals
, }+ x5 |& H' C! j) K  set current-light nobody ;; just for now, since there are no lights yet8 Y# f4 Q0 {' J
  set phase 06 H. t% _) b* h: `
  set num-cars-stopped 0. G9 ?; S7 e+ h
  set grid-x-inc world-width / grid-size-x
9 @( l  j( w9 r; {6 f7 ~- E8 v" a/ V+ Y  set grid-y-inc world-height / grid-size-y
. X5 @% ~6 `4 a+ l4 H$ n3 L+ }  u
" n4 N# ^  G0 v% P2 b  v1 {  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary& \: e# U$ b! M+ R; p5 ~
  set acceleration 0.099
7 u" R; [  n0 _- q, u2 F# Eend
+ ~6 A3 X* B; h. N. R- y: f# [9 u! q! |& x' u. f. N
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
! T: Y+ [% G# Q$ T;; and initialize the traffic lights to one setting
0 O) p- `" T: ~$ E* qto setup-patches: e' |5 G5 q7 E4 x! T. }
  ;; initialize the patch-owned variables and color the patches to a base-color5 Q! _6 \7 J' t: A4 z9 x
  ask patches
+ R* _0 f1 |8 g# b: H  [
9 q1 s3 [. ~5 n    set intersection? false
0 o  N: J, w1 i6 f, z7 o. x    set auto? false
. N/ [/ h" q% E" Q    set green-light-up? true* h7 J7 Z+ y* K% `1 z! \0 ]- O
    set my-row -1" Y, U+ t8 @7 A# A  h4 |+ k
    set my-column -1
% F+ O3 T0 Z" e1 ]( n' G$ O    set my-phase -1( Z& h4 A& F* y  m. X7 |! Z0 I
    set pcolor brown + 3( Y/ k, t. v! ?; w1 ^3 G
  ]
1 q- V8 M& ~) M7 b7 N' x6 z( C$ w9 @+ w
  ;; initialize the global variables that hold patch agentsets8 m& A% ]4 i: u8 t2 Z* n6 D
  set roads patches with0 Z- g, ]2 i8 k# r5 y; o2 x
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
: [5 A7 a- G1 e$ G/ a  d  d    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
7 a: @  S7 h( @- F  set intersections roads with
6 w2 l* s, U* O/ y7 E    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and( N1 o3 Y! O' v  x9 u+ p! o
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
$ F* A7 b  H8 M6 G+ q* e- X7 {, ^) U% ~' H; B8 o+ i
  ask roads [ set pcolor white ]
% c5 O9 c) W% w1 Z2 z7 E    setup-intersections
: @  i! c8 Z- s& h/ h6 W$ mend, W. D: B9 B/ |1 k
其中定义道路的句子,如下所示,是什么意思啊?
" S3 x& A. p! u5 \) f2 c8 N$ A set roads patches with+ c5 X- [" j$ o* n* L$ z
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or, F3 s/ @! E) X; X/ g# W
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]* S$ g( M4 M% K6 K- k  ~  S$ Q
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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