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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。9 I+ O5 `8 O% i
netlogo自带的social science--traffic grid这一例子当中,
4 c# A4 h" @1 J. b# U6 Nglobals$ @' Y# m! i3 ~$ c1 e
[
& b$ B5 `! Z) O7 I  grid-x-inc               ;; the amount of patches in between two roads in the x direction
; T  |5 }6 t0 g5 ~- i  grid-y-inc               ;; the amount of patches in between two roads in the y direction
( Q! Z6 ~9 F) G0 D% y3 ?8 o2 Q  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
4 Q! ?/ d) F1 ]& p& o( S                           ;; it is to accelerate or decelerate
. ~# C7 T! U! K# l+ W& \7 K  phase                    ;; keeps track of the phase1 J8 n5 z& [) _" u8 c: E4 m$ V
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure' N0 j) B- d4 c. K- p
  current-light            ;; the currently selected light
; _6 {5 [3 d3 b! d. S2 t; }% C5 ]% T
  ;; patch agentsets  i, f5 Z9 e* Z1 ]/ k0 W
  intersections ;; agentset containing the patches that are intersections) E' k" O/ i2 a& ]
  roads         ;; agentset containing the patches that are roads
( V5 X9 t' I5 G2 ?5 R]+ l3 f5 N/ ?* Q" o& |& W1 S

  p5 {* w/ r! M+ }5 J2 dturtles-own
  S6 \- Y- |# O- s5 ^[3 d8 f0 H- W- j1 a9 |6 P+ p9 f
  speed     ;; the speed of the turtle/ ?' a5 D( \, s, v
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
3 K* q1 }: j$ E* o1 X1 h+ G  wait-time ;; the amount of time since the last time a turtle has moved! b1 ?7 i. ~  b0 m
]
' |  r8 \: O% K/ }, c+ l( _1 [6 }
patches-own' c' f5 O; g1 m
[! ?2 T& g9 Y( n4 z8 G  I+ P) U
  intersection?   ;; true if the patch is at the intersection of two roads
6 }; U" P, \+ D- }  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.+ U" S) b7 V, {; _' M$ o
                  ;; false for a non-intersection patches.
. q* z& b" N( _( G6 P- ]) q, g% Z& D  my-row          ;; the row of the intersection counting from the upper left corner of the' s4 M. h  g' ~) I" I3 q
                  ;; world.  -1 for non-intersection patches.
& N; I: D6 ~  b' Q$ z4 g  my-column       ;; the column of the intersection counting from the upper left corner of the
5 a( p2 n# F! V- |                  ;; world.  -1 for non-intersection patches.
( [+ W: ?0 ?1 x+ U, |  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
/ Q3 x! u6 Z5 R6 \; a6 O( z& ^! R7 B* f  auto?           ;; whether or not this intersection will switch automatically.+ C. _9 R9 ~# o5 [, W* {. M9 c( s
                  ;; false for non-intersection patches.' l) G3 b# M/ L# W+ C1 y
]
: `7 W+ m& y; c# S& H% v# R) K) c: J' w
2 ]* G0 T9 C  y! Y2 i4 w
;;;;;;;;;;;;;;;;;;;;;;
; U! s" f7 t7 e( ^;; Setup Procedures ;;
6 Q* M: m3 C& x: C, h* n;;;;;;;;;;;;;;;;;;;;;;5 {! j3 u+ J1 i% c2 z
: d2 j* l0 F/ L
;; Initialize the display by giving the global and patch variables initial values.- U" H4 Q) I& ^& p
;; Create num-cars of turtles if there are enough road patches for one turtle to
  {) ]) t, i$ s1 m8 Z;; be created per road patch. Set up the plots.( d& u- J0 a. C7 W. A! K! E* y; N
to setup+ R. W$ e- [/ @6 c  l
  ca
5 b8 C3 @+ z+ @5 P3 P  setup-globals% A8 Y- W; {$ ^* P4 A! ]
$ C5 M( p7 R" s0 [  c& J" u+ f
  ;; First we ask the patches to draw themselves and set up a few variables& a# a9 {  T7 l5 s" m3 _- \
  setup-patches/ X# k* h) n8 k$ J4 f
  make-current one-of intersections
# r9 C" }0 q8 j4 _. N  label-current
  q( U, y0 N9 q5 e+ |* C+ H
: o' D3 u# g  f  set-default-shape turtles "car"
8 v( T  B: l( P* e& t9 O/ H. {9 N$ @( W* \+ j% n/ F4 v/ v0 O7 m8 a4 z2 _
  if (num-cars > count roads)2 q" s4 b' m4 Y7 o
  [7 s9 o; B! g) j4 \* Y
    user-message (word "There are too many cars for the amount of "
0 |# \9 v$ M0 u/ v/ y! L+ ]6 |                       "road.  Either increase the amount of roads "
* s$ d( z1 ]& g% i8 I9 x                       "by increasing the GRID-SIZE-X or ": H1 W$ l, u' k! {
                       "GRID-SIZE-Y sliders, or decrease the "$ s4 l! z; ^6 f1 M
                       "number of cars by lowering the NUMBER slider.\n"
5 D+ M1 m; V4 q) X0 V8 r9 U                       "The setup has stopped."), G# N# ?6 _& m4 N) B1 @
    stop
$ h; _/ F$ t; p* t  ]1 }( S) D# D0 e5 E7 e6 l

1 x! C( p( K5 L' _8 t4 c, {# D8 {  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color3 Y% x( C8 u2 Z8 Z0 i
  crt num-cars: W3 f' s) n$ B8 Y) N! i& W. A, u  ]
  [( {6 J" F) T; i+ ]5 u5 v
    setup-cars  \. N1 [- }9 q- k# G$ L
    set-car-color& o/ Y( k* k! B8 h% P, y
    record-data
5 k- O; O) N6 g2 `$ U  ]3 o) M$ \+ ?% L8 m& s, j0 p
" M( N! L4 x) ~& }: D: @
  ;; give the turtles an initial speed& t" P* T+ `$ D4 N( t  I2 L) M
  ask turtles [ set-car-speed ]' I8 Z9 z4 E; x9 J; ^  O

% ?8 p/ @: q) c  R( y; z  reset-ticks. z( D3 x3 g" P; [+ n
end" K( p) @" I3 K) {7 C

0 a$ i5 r7 @5 K0 p6 _;; Initialize the global variables to appropriate values6 i2 O- A" \; }4 n
to setup-globals' r2 T9 R! G, e9 I/ u# K+ y& F
  set current-light nobody ;; just for now, since there are no lights yet
6 |* l0 D7 k9 ?  set phase 0
- @% Q0 Q) ]/ |/ M2 o% @6 U  N  set num-cars-stopped 0' J, ~1 Q# s$ o1 O# |4 T  b5 ?
  set grid-x-inc world-width / grid-size-x: }- S- J3 h3 \# @& [: K: _
  set grid-y-inc world-height / grid-size-y
& F$ w; V7 u! B4 S
: e4 T; T4 A9 u$ Q0 H# |  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
4 ]$ W' I; U0 z( s& t7 f. }  set acceleration 0.099
5 f- y9 Y+ R2 s& S2 Y" ~% Send, R" R) \) u6 @; Z$ P$ e

2 H4 D! D9 l+ V, W) a;; Make the patches have appropriate colors, set up the roads and intersections agentsets,1 o5 ]2 R5 ?; U8 o0 }6 L: t
;; and initialize the traffic lights to one setting
- Q: J+ g' |. v- Q- ~" Q" kto setup-patches0 w! J9 o1 H- m: y
  ;; initialize the patch-owned variables and color the patches to a base-color+ I' c1 U7 ]1 M) \
  ask patches
$ P) M. P8 K1 m/ F* G/ p  [/ T7 _- I- s+ |% w; P7 \
    set intersection? false
- C# Q6 l& P* u4 [- v" Q    set auto? false/ U8 v2 n* {6 w- ?7 k. h
    set green-light-up? true
" v3 k$ ^* y  B% F    set my-row -1% R* m7 L  C# g" ?$ B% L9 Q5 _
    set my-column -1
  l! O# c9 s. P! `3 F+ t    set my-phase -1( v8 c* [2 `6 z$ j
    set pcolor brown + 3
. `" \; n. E& j7 |7 c, z  ]
7 j5 I9 E7 v5 H) g  T2 ]9 [- Q1 Z' T+ M3 I$ f0 T0 H
  ;; initialize the global variables that hold patch agentsets
/ V  T  D+ k# h( P  set roads patches with
0 u8 ~# ?- \0 s. M2 M    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or' k( b% E. F2 d" |; F* {* h9 F
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]5 E" B* u* L+ ^+ y* G+ ?
  set intersections roads with% ?" Z& h/ w! S# o$ Z* W( a" ~
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
) D$ R& U+ n" z% Z    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 s0 I4 b% I+ V
( g8 ?5 r, r# V+ q$ a8 ~, Q' F1 y# f
  ask roads [ set pcolor white ]9 M" m0 E, s$ k) U$ C  ]
    setup-intersections0 _" a5 S; }- z
end+ M0 U6 ~- K" `5 X
其中定义道路的句子,如下所示,是什么意思啊?
6 v' n3 S! R& Z9 m( H set roads patches with
, ]9 k( |0 ^/ F1 X1 u/ P9 D    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or$ j, H1 Q* I* p& {1 P& k8 T
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
: w# `4 s6 w3 Y' A5 ?. l( I9 X% G1 n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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