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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。0 k* i; I3 D/ f' D, H
netlogo自带的social science--traffic grid这一例子当中,* g: e, C( d# _5 u. j) _# {
globals
0 z/ M7 o- a6 a2 j[
  e3 g5 U% a- c- `  grid-x-inc               ;; the amount of patches in between two roads in the x direction" K  c& w  ~6 F7 `
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
( A4 O# K0 _: w1 X7 e5 p# s, \  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
) _0 Y: a* {7 n6 A                           ;; it is to accelerate or decelerate8 s# \' E; X/ x
  phase                    ;; keeps track of the phase
4 F4 a4 m6 T& j, C6 g0 V' |  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
# E# O. m, b  E4 Q! l% E. N% [  current-light            ;; the currently selected light7 G6 o* H. K* E* U

6 j% G% j" G* }) H  ;; patch agentsets+ N* q& h# b: E1 L+ i2 R
  intersections ;; agentset containing the patches that are intersections9 s0 E, o/ [4 z8 I5 w
  roads         ;; agentset containing the patches that are roads- }- K& p5 }( \
]
; t6 S* r0 \+ y; }# q
' z# B5 h& \+ G' P+ yturtles-own
. z# Z/ t$ }, d+ s[
1 n9 G+ @: r# \) M+ y# `( ]  }  speed     ;; the speed of the turtle( k: Q0 t4 ]6 s6 w) N5 T5 U
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
7 j) _( A0 ]) y1 N# I6 B5 H6 ]  wait-time ;; the amount of time since the last time a turtle has moved/ E  X9 `& l* N
]
! C7 f" F, _' @+ b5 H( ?5 ~4 H3 {
7 ]3 b* F3 `4 C" |patches-own
$ N; l( o( ~) R2 d[6 \6 p& Y7 }1 W& E3 U
  intersection?   ;; true if the patch is at the intersection of two roads
$ Z' R7 t) ?! t( l0 U  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.5 |. [8 J2 z; n  v
                  ;; false for a non-intersection patches.7 _1 W" U# f! x( U
  my-row          ;; the row of the intersection counting from the upper left corner of the, F7 t# f  {+ |1 M* \; r$ g- a
                  ;; world.  -1 for non-intersection patches.
; w8 F7 m' M3 g  R4 U8 _1 T  my-column       ;; the column of the intersection counting from the upper left corner of the
$ U% l& W. i; E- G( S                  ;; world.  -1 for non-intersection patches.1 [4 h7 [1 l9 q! Q# o: q4 s
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
+ Z. Z! l7 E: n' z* p% ?  auto?           ;; whether or not this intersection will switch automatically.
; D: a  m4 u# X/ b9 |8 z                  ;; false for non-intersection patches.
( F# ^# ?) h/ H- k( r]1 L; c' X4 K; T% ~: w

: Y6 }) d; h& q; u* p( G! {4 [
! Q: U/ {; [% A% H;;;;;;;;;;;;;;;;;;;;;;! K* y; Q0 ?1 t, X' [
;; Setup Procedures ;;+ J; V" e( {' C2 N' }- l
;;;;;;;;;;;;;;;;;;;;;;
7 C8 s% S) v; `2 d6 |% g& S  o% b6 C6 P% _
;; Initialize the display by giving the global and patch variables initial values.
* V$ q3 R8 Q7 k/ ^;; Create num-cars of turtles if there are enough road patches for one turtle to" }, |4 s- b, @
;; be created per road patch. Set up the plots.1 K1 s# f) Y! C$ w: U
to setup$ X; i$ U5 q: A8 s1 h$ p3 c; Q
  ca" b7 D/ g( M; j) M/ m! R8 a
  setup-globals9 b8 l* B! i! H. ]

! i) Z7 y, b1 g" X: L. R  ;; First we ask the patches to draw themselves and set up a few variables+ t' \# T5 o9 P: i
  setup-patches, e; J& `/ b+ u; n# ^% J
  make-current one-of intersections7 H+ t6 H$ S  U  W# F
  label-current
) {! h& ]9 D: R% G! F) {) |9 S  y" L  V& b/ t; D
  set-default-shape turtles "car"( K3 T# Z" `/ f. @; R; p, A$ U4 P" Q
& ^  A( X  |. C3 Y; W9 G& I( h
  if (num-cars > count roads)* ], J$ B% C) W$ z1 C) E9 B
  [
" ~. a- }3 f/ ~' ~+ q5 {5 ]. h    user-message (word "There are too many cars for the amount of "- W& b& s7 B+ ^1 ^- x2 c
                       "road.  Either increase the amount of roads "
3 s" O8 p3 K6 |                       "by increasing the GRID-SIZE-X or "
( b  B  _/ ~* w5 U7 ^$ A4 ]. L                       "GRID-SIZE-Y sliders, or decrease the "4 j# e" n  j5 q# }
                       "number of cars by lowering the NUMBER slider.\n"* m' Q% M! ]9 v
                       "The setup has stopped."), F+ K" ^" `! c( `8 Y& X/ G
    stop
2 e6 l( N/ a' v( K9 Q$ n) z4 {" u  ], Q) D, T7 t# R! x
: _' A2 H6 |* u+ V
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
% J8 B0 X: f8 t6 x# C5 m0 _  crt num-cars
- n3 H9 d% i- G0 h  A  [
& Y: z2 r- W0 D3 q5 u  f# `    setup-cars8 a, a: w* B8 S+ f/ H2 a
    set-car-color
. [: E7 t/ ]; B% x! D    record-data* b, m  ~- c/ J
  ]- S6 w0 e7 t: W) M5 R

! B: l+ p1 D& D. O# ]  ;; give the turtles an initial speed( v. Y: n( J. M: f# Q
  ask turtles [ set-car-speed ]) f6 y; ]- k- |$ {  [( F* k$ W8 K8 ]

2 H. S% H( Z$ c  reset-ticks5 e7 ~8 }4 }, w: y7 l5 z  b( y8 m
end9 G( C. _& I0 {

! B$ D2 R- M, A! J- s) t;; Initialize the global variables to appropriate values
3 [! n. R/ C% u* `/ x6 cto setup-globals4 k4 n  B4 m" E
  set current-light nobody ;; just for now, since there are no lights yet' e" S6 r) f: `+ h8 H' W8 M
  set phase 01 z8 r1 ^4 }3 }" g
  set num-cars-stopped 0: p5 b0 v; Y. C2 ?; N: d8 d& y
  set grid-x-inc world-width / grid-size-x4 i' h" V+ K$ i# ]9 t
  set grid-y-inc world-height / grid-size-y
+ @3 i# ~3 ~- \+ @/ v. I% R! e4 a; V# `' Z
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
0 J9 ^1 h+ E/ a5 N8 v  set acceleration 0.099) f3 R" `! t# T3 s% {
end5 _) q9 B1 u' [% y$ u: J( D* k
! a6 n) [- V' t
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,; U6 t" A! D/ S6 f
;; and initialize the traffic lights to one setting
# P. l! o  J5 l- r6 l  N' [, b" Xto setup-patches6 D( r% B6 ?4 L+ a( T6 K
  ;; initialize the patch-owned variables and color the patches to a base-color/ O( }, G/ `4 X% g* y
  ask patches: S; ?/ X! Q7 \( {5 g
  [
8 A9 \) J* w5 @    set intersection? false
+ h5 o7 [! T& ?3 y    set auto? false) u/ S0 ^7 Y! x4 \- p
    set green-light-up? true
, _0 @4 e. J  |9 T9 P/ C+ A    set my-row -1
5 [, L  |! G& o    set my-column -1' b9 q: ]( V9 ^0 U7 u' F
    set my-phase -1* ^% F- o  M1 c; g' ]
    set pcolor brown + 3
' p& i2 _6 ?- X9 {; n. A# L4 u  ]6 I* x5 M; [8 F  }* H9 t# k7 e, U# E

: U& q$ A/ E  t4 u" p  }: g  ;; initialize the global variables that hold patch agentsets
, U, s+ R  Q( v+ ], m$ {) w  set roads patches with
: u+ I3 q2 K, V* D' W    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or* @) v" l$ f4 _9 A* N9 z
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
$ i8 }, o  o6 a% p8 V  set intersections roads with4 }5 p& L  D0 A$ h" \0 Z  g# Y
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and( a% ~% W% e' N% K8 ~
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
7 q; h% b! k2 f' {# |( v" S! {3 ?7 P) P
  ask roads [ set pcolor white ]
" u% ]( l. k  b1 F3 A  \) b" ~* w5 Z    setup-intersections3 h+ I- k5 u$ z* e
end
8 O- f4 S0 H2 i$ T& W' `/ }$ P其中定义道路的句子,如下所示,是什么意思啊?3 g0 V. Y8 O; n! \4 ^
set roads patches with
3 Y* p3 r! y) b9 T* Y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
4 s. U! n* P/ o+ g" E% X) W& \) b+ P    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]$ w0 ^/ E* D' o0 U. I  G
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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