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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。, v3 M+ R  d' }6 x1 K) e: P
netlogo自带的social science--traffic grid这一例子当中,% A( L0 f% w) g9 p- l5 z+ Q: ]# t' P
globals% s; r* P; A0 n* y( Z  ]: @
[7 q1 r( Q; d' H# s3 w
  grid-x-inc               ;; the amount of patches in between two roads in the x direction/ s" O. A1 `8 f/ b. O  d) Q
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
; R' v4 `1 X3 b. F  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
) C+ v7 x2 t$ |                           ;; it is to accelerate or decelerate
2 S9 N  P% D7 M  phase                    ;; keeps track of the phase
+ P& c4 ?) A1 P- M1 O& ?+ t9 S' N  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure: b7 o7 ~  w6 E8 W5 A- t* G
  current-light            ;; the currently selected light
! q! f# G: x/ N  E6 Z: E, C" v1 D2 X- z
  ;; patch agentsets
& A7 S; _+ a0 o% _$ N) O5 K, }4 m  intersections ;; agentset containing the patches that are intersections
8 H6 @* {: A8 C& F0 m2 c  roads         ;; agentset containing the patches that are roads
, p  f7 J4 Z! n; S- O7 `4 L) o]+ X- P" a& w/ l% v5 b3 ^# M

- F% c, h% Z( O2 Z3 zturtles-own
5 ]: h  s7 @1 Y* l2 q3 c[1 ~6 n8 w3 b9 s& X$ x
  speed     ;; the speed of the turtle. ]% ~4 `  x. d7 i  ^
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right4 U9 E( I! w) I: \3 z8 T; J
  wait-time ;; the amount of time since the last time a turtle has moved
( b( A- [, U1 {( k* m]4 F7 G: U1 S0 t2 |0 u) ~

( t. J6 b8 g9 Z3 C' x9 W$ Y1 R& ?patches-own
' C! p* N- h) [5 H5 I[
: l7 _9 d) R7 i2 L  intersection?   ;; true if the patch is at the intersection of two roads
) {7 R/ G7 L7 w9 S# e" E8 t; U  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
+ y. z! r6 \5 f2 P5 u                  ;; false for a non-intersection patches.1 Z) R" R! O4 q( o! p1 `
  my-row          ;; the row of the intersection counting from the upper left corner of the# k$ w1 b& r; @) o4 j
                  ;; world.  -1 for non-intersection patches.
9 G" l8 d; {# ]: Q. l3 T9 k1 M  my-column       ;; the column of the intersection counting from the upper left corner of the
7 i3 t+ Y. R* \                  ;; world.  -1 for non-intersection patches.9 f' [0 K% v3 U/ ?
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
7 N- J/ ], b% c4 y  auto?           ;; whether or not this intersection will switch automatically., [, y( h4 B0 N6 X! O
                  ;; false for non-intersection patches.; g6 k/ ]6 b, j& ]; f
]
1 x6 R; g1 @# n' k) y) L! H9 G' b/ _3 ^1 `. p* z; D- B7 _
' ?, b' H+ N* P+ j+ R, n- l7 n
;;;;;;;;;;;;;;;;;;;;;;0 e- Y4 {: N& I* ~2 c
;; Setup Procedures ;;
" {1 T8 U9 ~# Q;;;;;;;;;;;;;;;;;;;;;;0 ?8 t3 _* Q. K5 k

0 ]4 T# {$ B$ Q, x( w7 ?8 P, P, o;; Initialize the display by giving the global and patch variables initial values.& Z1 M1 M$ J8 w
;; Create num-cars of turtles if there are enough road patches for one turtle to
  O) D  R, x/ k- G2 V;; be created per road patch. Set up the plots.4 Z- M* Y( E( n) L
to setup
5 w, x  A% Q0 h4 \+ s  ca4 s6 U. f! |- Z
  setup-globals/ m2 D  [! f  i) P
2 d2 o0 _  z' [/ e; l+ D( q% m! H
  ;; First we ask the patches to draw themselves and set up a few variables& c# h$ ^, U& }! q8 |3 ?/ c9 S0 h
  setup-patches8 ^) w( t$ n3 O# p7 x! N- q; r
  make-current one-of intersections
( D2 M/ L7 K' ?7 `6 X1 [  label-current
) T9 w0 |" f, G
9 A* e; T5 Z; Q  set-default-shape turtles "car"
2 z; {) D% [' \! k5 F: K/ @
5 o& @5 _" ?- U( W/ E1 `  if (num-cars > count roads)
# B6 |$ p: O9 I3 Z$ _+ K: C  [
4 B& ?- ~$ T. b  ~, m    user-message (word "There are too many cars for the amount of "7 V% D1 K7 a( b
                       "road.  Either increase the amount of roads "$ y( q- @/ I5 g7 k  r7 z6 |6 Q
                       "by increasing the GRID-SIZE-X or "  A$ o/ J0 M0 v  l+ J/ X2 P4 \2 o% a2 A
                       "GRID-SIZE-Y sliders, or decrease the "
) v( O. Q4 q' J& U% ]5 \- p, X                       "number of cars by lowering the NUMBER slider.\n"2 z. a8 U. m2 N2 E; E
                       "The setup has stopped.")  T7 T+ B, _; U
    stop
/ o. w# a) z& ?- {' b- ?  ]
/ x& `) x. z/ W6 p# ]% d
8 G! x: B& I* N/ f( Q: g  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
8 ?' p7 }& _! X4 V! v  crt num-cars/ C. N. e/ J( D, d2 L8 k
  [3 L$ N4 h, N+ |- f% z
    setup-cars
* h. s% e  _: D, h    set-car-color( c6 s4 R$ a2 H
    record-data
- z9 g0 M# o/ S  ]" m' A0 @7 V8 E$ L

1 v4 D. A7 R$ ?8 Y1 V+ K( }# h  ;; give the turtles an initial speed
# R* T  @! G# W4 g0 I; N2 E% f  ask turtles [ set-car-speed ]
, t- X1 F. M* j4 {; v: r5 u/ F
- K/ D% \9 t& L  reset-ticks
$ s: X" e& E, m' g# ]end
( V( g, i* l4 a$ n, F+ \# `, h. w4 r, h5 u0 q
;; Initialize the global variables to appropriate values8 P9 b" G" ], S
to setup-globals6 X$ C9 Z6 ~/ F
  set current-light nobody ;; just for now, since there are no lights yet
  g9 q# A" p+ s9 b8 m' }/ W  set phase 02 `& m& J2 l/ a$ J* A& A$ p. b% M
  set num-cars-stopped 05 s. U8 l0 o) R; A5 E2 c8 i- O
  set grid-x-inc world-width / grid-size-x- I* t" `7 h: A4 ~7 K* E
  set grid-y-inc world-height / grid-size-y) k$ R  {5 m% W
1 O6 o8 q! ]$ |& O! {
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary0 W! g3 e: l' v
  set acceleration 0.099+ i5 @; ^1 p4 F3 j5 ^' m$ P
end  r3 v4 ?; M7 i2 ]3 D* c4 Z& S

# d" T4 m; d  y: l# s;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
& b( Q! q# @8 u1 L;; and initialize the traffic lights to one setting
* a8 H' v. F' rto setup-patches
2 ^& ~5 v; _/ d$ l- H$ E1 s  ;; initialize the patch-owned variables and color the patches to a base-color6 m2 G8 e0 ?7 d- a! v' T# c
  ask patches) K7 b3 p1 ]+ v- @4 O# b9 s
  [% p9 |# g# [: n5 \. V
    set intersection? false
2 k/ G. ]/ L& `. q0 q    set auto? false5 I: w+ X+ {) `9 m" g
    set green-light-up? true, `3 F/ I  P5 R  _
    set my-row -14 c, {' W3 g) X2 J. V! M) o0 y% H( ^
    set my-column -1
" F1 g: h( F" }! q    set my-phase -1
5 N! x$ F( {2 C1 X7 M    set pcolor brown + 3
9 o! Z+ p4 i2 U( E" b; l9 h' x) r8 O  ]
- a3 f6 y3 c/ W! t, r( T* p
7 Z5 V" x9 l8 Q$ E  ;; initialize the global variables that hold patch agentsets
3 S3 H7 r1 c1 q  R; {+ P1 k" L  set roads patches with
9 X( b% q& I/ F7 W" s" i) P  r    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
) U9 e; r/ g7 j) R7 Y  H" W& S    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
9 `( }: Q1 a( W4 v, u  L  set intersections roads with
  j: D' B, |- q. J    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and0 c! e4 ^6 k+ X9 e! D6 B) P8 d
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
. V/ X1 u" I" N3 ~. k
9 b5 E1 \# F- O7 m3 ?- c( h8 x, g1 j( \  ask roads [ set pcolor white ]+ o! h3 a, |1 H3 j( k* D
    setup-intersections( ?9 E& o7 w3 k) e
end' [* k! b0 z. ^5 [" z, N: \5 |2 w+ H
其中定义道路的句子,如下所示,是什么意思啊?- c2 W" R8 l0 q, y
set roads patches with
! |( t1 f" S. c) H. Q2 T4 @    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
# p8 D8 e  s0 V/ @    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
, c" T' Y& E$ a/ V5 e  F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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