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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。+ v1 g+ j& V" O$ n6 ~1 ~6 A
netlogo自带的social science--traffic grid这一例子当中,2 u, W) w, T2 T* \  u8 N- [% C
globals
) h5 b/ p. A! ]) X% k7 p5 F/ x- H[
$ u; \- o) [0 X7 D; B  grid-x-inc               ;; the amount of patches in between two roads in the x direction2 w9 C6 ]' I* k9 }% n2 P* z; c; T+ I
  grid-y-inc               ;; the amount of patches in between two roads in the y direction0 Q, P9 ?$ c! K' r1 r# f
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if8 j' |9 Y: m$ d6 F. U. f. V
                           ;; it is to accelerate or decelerate! ~$ \" S5 |* J1 o6 f* s6 O% U
  phase                    ;; keeps track of the phase0 z/ m0 n- t& w* Q7 i" O
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
# T/ O6 _0 Z' |$ t5 l0 x  current-light            ;; the currently selected light; z! S- r- w! c; D, B8 O

, H& ~& {& Z- J6 y  ;; patch agentsets
" U8 w; s& U& s, A# M/ J  intersections ;; agentset containing the patches that are intersections
) ]1 O8 j# Z) q7 C2 Y/ M: J% a4 r  roads         ;; agentset containing the patches that are roads( Z. f. |2 W! T. w3 a/ N' |
]! m* s8 }+ a# i( Y3 D$ v
0 s3 c0 }, u( k
turtles-own
" @& h$ a% |5 Q! S* j[
, M( t( ^% L* S" _3 D  speed     ;; the speed of the turtle
' b. G0 o: Z7 ^6 P. ?  up-car?   ;; true if the turtle moves downwards and false if it moves to the right6 E8 n3 I) v4 [8 E
  wait-time ;; the amount of time since the last time a turtle has moved3 i2 P6 J' g) ]
]5 Y" e0 E' X8 y) \# V

* t5 l* G, N, [8 f  V. s- P) _0 a" {patches-own
. ]9 Q9 g' }8 u& I3 t3 K[+ H9 Y" i: d6 A
  intersection?   ;; true if the patch is at the intersection of two roads
/ ~' A5 D' U' r) @  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.4 C8 l3 W$ M5 z, H5 Y. a. D5 C
                  ;; false for a non-intersection patches.: x9 s. d$ s  k8 F
  my-row          ;; the row of the intersection counting from the upper left corner of the
4 b9 @" }* d$ D+ D- r+ l- Q$ u                  ;; world.  -1 for non-intersection patches.5 h) t9 j1 R3 d) }0 g3 R7 ~
  my-column       ;; the column of the intersection counting from the upper left corner of the+ p& C7 J' p3 ?# S/ n$ I
                  ;; world.  -1 for non-intersection patches.9 l) h2 P$ k( ?1 n7 N
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.: t/ y! r: C% ~8 }* X' ]- a
  auto?           ;; whether or not this intersection will switch automatically.
  n% D/ P1 {/ R: k* ^                  ;; false for non-intersection patches.8 H2 w( [! C4 b
]
. B/ \  W* O2 ^1 w7 E5 I9 P+ B' C% ^7 b

$ o# I' ]; {) T; d;;;;;;;;;;;;;;;;;;;;;;
) K) v; b& v. H4 p& };; Setup Procedures ;;
  m2 ^4 ]' d- V8 O4 L. k;;;;;;;;;;;;;;;;;;;;;;( Y; F. M8 w* {- S3 [& P
3 e2 O5 ^* J0 L6 [( }, z
;; Initialize the display by giving the global and patch variables initial values.
! Q0 }+ }+ n" @;; Create num-cars of turtles if there are enough road patches for one turtle to4 N$ i* T& f, O. `# H7 D
;; be created per road patch. Set up the plots.
" w5 @5 }. N/ y: ?/ bto setup1 n/ y% U) ~9 z& J" s& L  u
  ca. t6 o+ }4 @' R5 R3 S4 V7 s, z
  setup-globals
; \3 J# ?* r8 \4 n" F$ ^3 j! H1 @6 g% w, o9 X2 @* C
  ;; First we ask the patches to draw themselves and set up a few variables6 |: ?) M1 ^: \) l
  setup-patches
2 w3 L# p7 M. j) p# ^# L1 n; m" B  make-current one-of intersections
6 C/ D2 J( d; P- ^+ m7 S( h& A) z' c/ Y  label-current
" N4 W0 O7 s4 u: B
4 r% h: {$ K9 I/ `3 }$ h  set-default-shape turtles "car"; O$ b) c/ u& ]
/ r$ U! ]$ k- }  r% L
  if (num-cars > count roads)
. j2 g" v; |) k2 S2 \  [7 o% f& v6 [, v% r6 H6 V
    user-message (word "There are too many cars for the amount of "
+ C1 N5 S1 A) J  G                       "road.  Either increase the amount of roads "
1 D. B/ o, ~, g& M# ~6 n3 r                       "by increasing the GRID-SIZE-X or "
6 Z& U$ E2 i/ |) o6 ~/ w                       "GRID-SIZE-Y sliders, or decrease the "
1 m( a0 t: i& o/ C; E                       "number of cars by lowering the NUMBER slider.\n"
9 {4 j# A" V% E6 h                       "The setup has stopped.")4 O) K# @. T+ P" [1 t
    stop
7 N- @$ E- j( u& f, q  ]& x$ b: j3 |. r" x5 C

: V( |% c1 L  r" ]& I/ [2 P! B  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
+ Z7 q" p/ x0 N  s% U  crt num-cars* M" Q1 Y! j9 x" m! a) F
  [2 ^$ x; c, ]* G8 j5 j" E2 S6 D
    setup-cars& }9 ?7 `+ a& R4 ^  Y8 f# ^+ {
    set-car-color
5 k0 l5 D3 G# j0 [    record-data, C# E/ U  \+ ?: _6 _) a
  ]
# A, @" F2 w' E; t1 J" ?% e0 b  U0 ~
  ;; give the turtles an initial speed
7 M% J: j1 _4 E1 c7 R' m. F  ask turtles [ set-car-speed ]2 i5 F+ e3 w9 O& p* |* _& O8 {

9 ^) K3 u8 o9 H( M8 D- H  reset-ticks# I/ |/ ]- I! j$ t6 u
end
6 y$ C: I" Y4 s- F1 U. Y
, H$ T$ I( C5 h: `3 p- U;; Initialize the global variables to appropriate values, B+ W4 q* K; v0 C; t; \
to setup-globals
- B8 }2 e) Y8 \& J( e% N' h% D: I% g  set current-light nobody ;; just for now, since there are no lights yet) P) |9 k/ p: o: n
  set phase 0. }4 n& T# s- `7 z' F) i" Y( E* K# H$ I
  set num-cars-stopped 0
6 O. L9 r; L# F, n. Q$ r% g  set grid-x-inc world-width / grid-size-x
: f  t% i3 _6 r* V6 {" Q  set grid-y-inc world-height / grid-size-y8 `4 k6 n1 [2 v+ L0 i8 ~

' C0 @8 [$ j9 c9 M% W+ n  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary$ {# r. X$ Q  j9 x- K: V
  set acceleration 0.099
( t$ U3 D  ^& P- i) w" jend! I% ]/ @8 t. R! E  h
5 Y$ _- G1 Y- l9 O! G3 a) a2 o3 v
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,- Y6 b, E8 H" E  K5 l% ?) [6 v8 D
;; and initialize the traffic lights to one setting
: ]! m; q" j' B9 ]$ G2 w/ ~2 @6 Jto setup-patches
# f5 b/ O. p9 x. i# O& }  ;; initialize the patch-owned variables and color the patches to a base-color
" x+ @7 l5 t. Z1 U& S2 r% E/ ?( g  ask patches
% D. [7 z' W; i) U) T  [
( w  q9 M9 g" j  N- T9 n    set intersection? false5 |+ J# Q4 P5 K9 _8 v$ y# {
    set auto? false
' j( E9 e1 b3 J0 k    set green-light-up? true- z" V7 t8 R  w! R3 X) _
    set my-row -1# y( g8 d6 U! _" C/ `* Y4 I( Q- F
    set my-column -1. t& ]. C# L# I, J
    set my-phase -1
. t; P1 k- o9 y& h( C8 [9 v  ]! g  N    set pcolor brown + 3
6 T! J( d; z" F) C: N4 I! g  ]
. i4 k: s; }* Y/ H! `0 E/ P+ d4 j/ i) _% K6 O5 W/ O1 u* D3 {/ S, G1 l
  ;; initialize the global variables that hold patch agentsets
/ v$ \  |, F8 p% q9 J  set roads patches with( G* p7 w4 A9 m# q
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 E( V; o- F: F  p" x7 Q( F& ^3 L
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
: r) q5 q2 a7 p8 N6 ~, U; y  set intersections roads with
7 W5 Q( f/ o! K' v# h  m3 x4 Q    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
# t' z. w& t  U2 U1 @; H    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
+ |1 m# N( a- m3 A2 V! ~) ?( w* @) S/ n3 J/ U/ A- P* J- w
  ask roads [ set pcolor white ]
6 }( E; V9 O, ]0 D( w; Y$ k; x    setup-intersections1 z" y! i) @9 w
end/ D( \& _. }. r" I& x; w: N
其中定义道路的句子,如下所示,是什么意思啊?
- O; z7 f; @2 l; y; l set roads patches with; q1 j$ O! k7 j0 ]+ {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or* O$ X; m" j$ F) T" U
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
+ m" Z9 |9 f6 I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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