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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, K4 B0 U$ `7 v
netlogo自带的social science--traffic grid这一例子当中,, C; o* r+ f' G
globals
  j3 N6 E+ I( R, y  a' q[# r! G8 w4 f6 U# ^/ l' g- c
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
! U: n' ?, M# s' `/ J6 i3 ^  grid-y-inc               ;; the amount of patches in between two roads in the y direction
) G/ {- m, |: R4 x  Q) i; l  acceleration             ;; the constant that controls how much a car speeds up or slows down by if  w: N7 e( M( Z, F
                           ;; it is to accelerate or decelerate
, o# Q' m) s6 |8 m8 e1 ?0 M& z  phase                    ;; keeps track of the phase1 F9 _  w/ p$ |
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure2 P* I$ m! d$ y' x" k. c& j
  current-light            ;; the currently selected light6 [0 I) q& F3 B' R
- j8 q9 S& ^' [. q  X2 I* D, f8 @
  ;; patch agentsets( D, O2 `6 t! t% @/ Z7 U8 r* O
  intersections ;; agentset containing the patches that are intersections0 f: }2 X+ l5 W6 y+ I" j, D% C
  roads         ;; agentset containing the patches that are roads/ |( l& Y; R) U$ x. i5 l2 h. ^  f
]& u# Q/ R- y* w: a; b
( c8 T8 ^$ u6 J9 S+ r8 j* S
turtles-own
* _/ H1 P( m! f6 E" g[3 p3 ^3 i: C; c- f9 M6 H' }% p! C
  speed     ;; the speed of the turtle
) i- M. g6 A( a& m  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
; |2 w& ?8 T2 k" {$ n  wait-time ;; the amount of time since the last time a turtle has moved9 k* W5 ^8 J) p$ Y
]" R( v4 t& W" ]* N* u% s6 L: V3 f

3 q0 E( d! P4 v  X/ Q7 x5 npatches-own
. w' [" C# Q# n( }$ J[7 Q& y) U+ `- B: b: |
  intersection?   ;; true if the patch is at the intersection of two roads" p* l) V$ H! r) w: ]
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.& A% b4 A8 d4 }$ h! v
                  ;; false for a non-intersection patches.
% ^/ z0 H' ~! v+ M( U  my-row          ;; the row of the intersection counting from the upper left corner of the# ]: D3 }% J; o' U0 @, @2 W6 j5 S
                  ;; world.  -1 for non-intersection patches.6 }: F- V: ~8 p( {; y5 _
  my-column       ;; the column of the intersection counting from the upper left corner of the
' F! p' [* U- }+ m9 y, M; c  T' V                  ;; world.  -1 for non-intersection patches.
: G) [4 }4 q5 h" i/ ?  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
' k( |# h" Y8 [. b1 z  auto?           ;; whether or not this intersection will switch automatically.+ e0 |- P1 z. F' b- t
                  ;; false for non-intersection patches.0 R+ B# o+ ^( _
]2 o5 E3 }$ u0 v0 d
$ n  v" y7 Q8 R' C( y  x

7 u# c& ?+ b0 s# H' R;;;;;;;;;;;;;;;;;;;;;;
' \- ~! l5 x( D% r% g0 g;; Setup Procedures ;;8 X1 ?1 j* A- Z: d+ F
;;;;;;;;;;;;;;;;;;;;;;
4 l  d, r1 A8 w2 o6 r) {" u- i
2 G' ]: h4 {! a( M# A; v$ R;; Initialize the display by giving the global and patch variables initial values.
$ V' H5 i& i- p; B7 D' t5 x" B8 t;; Create num-cars of turtles if there are enough road patches for one turtle to! Y# @, i0 \2 x7 E' I
;; be created per road patch. Set up the plots.
* `: r; |7 s3 jto setup
/ ?8 O6 A) B$ ?6 Z: Y% `9 ^4 B  `  ca: q6 u6 n7 `! \- C  m+ t% S
  setup-globals8 C. {4 V* l5 L( u3 s* `
. y" z5 G1 E! n2 y7 S
  ;; First we ask the patches to draw themselves and set up a few variables0 p) D8 q% t2 ?: p( Y
  setup-patches
7 V" x# f8 O3 g8 T/ o! F  make-current one-of intersections! c- j% ]0 K7 B9 Y
  label-current
; m7 E6 |; {: t
6 Z6 |$ e7 N( `: o$ m  set-default-shape turtles "car"
! E7 R; v: l. G6 w5 V* p/ r" ?5 ~  R" [9 |+ g& V
  if (num-cars > count roads)
4 m8 a, p9 k) g4 C! b6 t7 i; w  [
# [7 G9 f# q; w( @$ M2 l' k; @    user-message (word "There are too many cars for the amount of "5 |# G' B0 |/ {2 h3 T5 `* C# C4 H
                       "road.  Either increase the amount of roads "# e! r+ ?3 _9 |/ J: X
                       "by increasing the GRID-SIZE-X or "1 u; q" N2 Z& A' ^  w
                       "GRID-SIZE-Y sliders, or decrease the "1 B* W9 V. z/ U  n
                       "number of cars by lowering the NUMBER slider.\n"5 N! `- t, N; D6 P) D
                       "The setup has stopped.")
1 t( w' s& c5 Y2 h! l    stop* Z+ @# p0 ~: K6 H- \9 F
  ]( B8 V+ d7 |$ F' g
2 Y/ n# }4 f- d- e$ V) x
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color0 S% v& H7 [, L$ B
  crt num-cars5 n) f  p3 R' y+ g7 ?2 Y
  [# I% t0 y: V* J7 k; j* W
    setup-cars0 S! b2 @% n0 J; K
    set-car-color
2 j# s/ u1 T+ d+ X( K) o" K2 e    record-data
5 [% d/ r- |! _9 B  ]
2 ~; r7 ^0 Y' y3 m0 J1 b( b4 ^5 q7 h" K0 F/ U
  ;; give the turtles an initial speed
4 {4 ?6 R* ^0 d+ }0 M1 T' F  ask turtles [ set-car-speed ]0 ]/ L2 k9 E" M! ~4 H. t
0 w  Z, W# `/ x
  reset-ticks
7 o, i% r: c. qend5 Z" m: j, [# h5 i& F* n
- s; ^) @0 c' y# A! w9 {& X1 U
;; Initialize the global variables to appropriate values
4 v0 a* n! b- G! K# ato setup-globals
$ E! O9 T! m0 n# C$ d  W  set current-light nobody ;; just for now, since there are no lights yet1 ]+ K! J5 N( g+ h- I& y0 D
  set phase 0
! Y% Z+ @. p$ ?- D3 C& E  set num-cars-stopped 0" s2 t, V  R$ I2 I- l3 B
  set grid-x-inc world-width / grid-size-x
/ v' V, H- T% t* u! F  set grid-y-inc world-height / grid-size-y
4 ~1 z, V4 }! x6 F# ]( ^' E! Q" ]& Y
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
6 q2 y9 i, ^2 A! D  set acceleration 0.0999 D# L7 C# q, _5 S3 B
end, s3 ?7 h: W2 ?" p2 g
9 k! H  s" [, m6 x5 }
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
( D% a" R" [- M; z9 c1 Z) e;; and initialize the traffic lights to one setting
( m: B5 T* C* F! {/ U* d9 L0 ~2 l# o# J, Eto setup-patches
1 h6 C3 T+ z" ~- F& I+ j; Y8 R- E  ;; initialize the patch-owned variables and color the patches to a base-color# {8 O9 \# n- _6 e; J
  ask patches* j6 D# _' {3 U8 p; _2 b8 h9 h) z( x
  [
* [: c* l0 e) R, I1 K* W% [    set intersection? false
$ T% Z3 ]0 K8 {3 E8 Q    set auto? false
  T, E7 K6 l5 `; ]    set green-light-up? true3 s7 ~" q* y5 @  y* Z+ ]
    set my-row -1
0 V9 n: }# E7 J& X* c5 Z    set my-column -1: w6 Z, Y8 H1 l1 s
    set my-phase -1. q* O( B6 i- E3 F
    set pcolor brown + 3
: U/ L8 Y" \7 U4 A, _  ]
8 e/ ~# ~/ a/ `3 X0 k/ @# r+ \5 h, ]" |  ]  M
  ;; initialize the global variables that hold patch agentsets& ~3 Z- Q: w) W5 j, m
  set roads patches with$ W( X5 ]. ~6 o; \; G
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
! W& `, O3 R  A  Y& u; |    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]% j) H4 T9 n6 z
  set intersections roads with
4 x! q7 U3 W9 Q4 u    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and# a$ R$ ~& U" p4 Z; N. i
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% Y+ m5 Q! |$ X4 J- B
! l  C; _; ?( D# B- ~* E  ask roads [ set pcolor white ]# I  a7 o6 \9 \3 O. s. J
    setup-intersections6 e4 D4 X8 S/ o
end
! \' y, F; `3 ~4 X7 I其中定义道路的句子,如下所示,是什么意思啊?4 Y1 D( y& i9 u1 z; C* L% M1 e
set roads patches with
5 ~0 m+ Y9 I+ y1 ~: n    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
* p3 f; }8 [$ f7 U    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]; V! r; [  x+ k* b2 z$ \: H7 K4 V
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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