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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。3 d9 {3 V) N7 _- J! x9 U! \; m! b
netlogo自带的social science--traffic grid这一例子当中,# z: `! v- P! c$ B5 J5 N4 |$ f% [# [
globals
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  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 l/ K( Z6 B" z/ S0 `* B2 C0 Q
  grid-y-inc               ;; the amount of patches in between two roads in the y direction# s, ]9 A7 O; I0 W; H# U1 s
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if* ~- u& z5 Q& l6 C! z; ]: p  c) W4 h* }
                           ;; it is to accelerate or decelerate
7 t7 s7 G2 L7 ~: @; ~* i  phase                    ;; keeps track of the phase" l% |8 s6 ]+ E- k1 E* L( {
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
; q! S% Q' R) P' {  current-light            ;; the currently selected light
4 V# {) J$ T% I4 o3 q$ l0 }  M: _/ |+ L( R
  ;; patch agentsets5 [) P8 A' O4 T$ F1 x+ R$ A  S
  intersections ;; agentset containing the patches that are intersections
5 ?* S7 r& @9 f1 n: a7 z$ M8 f  roads         ;; agentset containing the patches that are roads
( p; ]) o& I- E+ d$ \/ h1 f" J' D]. B+ Y, A8 b. X7 Y+ o( D! w
4 S* k) [: h0 j$ g5 }: m3 P
turtles-own. S5 f- Q( c$ }9 J& ?
[
" O7 \2 z6 P& p' b  Z  speed     ;; the speed of the turtle
; K% [. S) Z+ [# L, J7 ^& |" r# L  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
, y- g. r6 ]$ g% E  wait-time ;; the amount of time since the last time a turtle has moved
/ M' Y- R% S7 i7 {  v% l]6 @1 O4 j1 [! Y! A

. x$ r! s$ h! U" C- u0 e7 V! wpatches-own
6 D/ N% H( R6 ?1 x1 y2 l[* g8 H5 O$ W! G" D* s4 Z0 w3 p
  intersection?   ;; true if the patch is at the intersection of two roads9 I5 k9 B0 _2 Z9 a6 K  W
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
2 I4 G# L+ ~# c7 X. y8 H9 r                  ;; false for a non-intersection patches.& D2 E5 k1 g3 r& _: s) d* S
  my-row          ;; the row of the intersection counting from the upper left corner of the
. `7 Z4 I: Z9 J                  ;; world.  -1 for non-intersection patches.
+ H* Y& ?8 f. ^, g  my-column       ;; the column of the intersection counting from the upper left corner of the
* C6 N+ w. E0 o! H: s                  ;; world.  -1 for non-intersection patches.
  \+ }+ {* T1 l  j& R: g1 h  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
1 C; I5 i' z/ E6 A  auto?           ;; whether or not this intersection will switch automatically.
. s9 g9 I" f8 \' @                  ;; false for non-intersection patches.
- x1 s5 z, ~; I4 b. L4 e5 m9 N]
/ A  S' x% w% }$ D; G2 [7 s0 Q" J. C4 ]1 X8 r- x

8 k5 i7 n6 p( }: s6 W+ w- C;;;;;;;;;;;;;;;;;;;;;;
  H2 j, K9 F, L/ l2 h0 L; ^, |. r;; Setup Procedures ;;
; J$ @0 D; g, S: Q& E;;;;;;;;;;;;;;;;;;;;;;
  M  Y8 b( N, R/ ]8 x, D3 L- Y2 v4 p+ b( H8 R2 b
;; Initialize the display by giving the global and patch variables initial values.
3 x/ [3 \$ H* g7 a( D3 Q- Y0 y;; Create num-cars of turtles if there are enough road patches for one turtle to9 l/ u+ ^" ^$ f' v* h
;; be created per road patch. Set up the plots.% M  g3 i0 e/ P. t" @6 q
to setup
. {7 ~1 }" @0 h: \0 T  ca) N$ O" o$ \6 |/ P
  setup-globals
) l: u$ z% g5 M' _4 p0 U/ E3 y
- |0 A7 I- ?% m4 N$ b* v  ;; First we ask the patches to draw themselves and set up a few variables
" ?& m) B9 j7 k# G- F; K" P  setup-patches% `5 V6 {" g5 O' D  j' K7 }
  make-current one-of intersections
* {8 J6 {! P2 ^2 a5 Q8 n4 c  label-current
  }5 r. e1 ^8 D! ?# N/ g: g, x* @! f: u7 ~; A0 N$ V) P: _6 [
  set-default-shape turtles "car"' r4 Z- P( q* c  ?; ^
3 y/ g! N: k7 {" W3 G
  if (num-cars > count roads)
( o9 |! t, P- u( R' Y% b7 ~- ^& |  J  [: B6 k9 N; D- C) `7 o
    user-message (word "There are too many cars for the amount of "& D- p# y- u: H7 K/ e! c
                       "road.  Either increase the amount of roads "% K1 B( x- _8 `" f, ~( o. i) n7 E0 f
                       "by increasing the GRID-SIZE-X or "# D/ w. p, v; y
                       "GRID-SIZE-Y sliders, or decrease the "
# b+ ]( v9 ^1 r+ @1 ~$ j( x                       "number of cars by lowering the NUMBER slider.\n"
- R, x' p+ p0 m5 ]) w                       "The setup has stopped.")
: w, j" l2 _; ^% L4 _/ J* t    stop
: s! l( J" Z+ V+ E  ]
3 ^9 G& M; G7 |" ^1 X# ^4 B" G2 O. L# U, x! }
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
0 N& b( S5 |1 n) x4 q  crt num-cars6 m6 W  A; u& K
  [
; y, k6 C7 R5 Y2 G    setup-cars
' r  Q6 I  m' d4 O9 G    set-car-color
# v6 d/ |& _  Q( f0 J- b& g    record-data
( \$ H$ ^1 \' ]# s  ]6 G% h  I- J$ p5 H) S- s

+ P" B; a/ R- u0 J9 O) n  ;; give the turtles an initial speed
1 k$ E& ^" H# H4 ~' h2 w9 l  ask turtles [ set-car-speed ]
* `: Z) s1 Y8 o: v$ Z" M: P
. a6 J( U) j" e. u( w  reset-ticks* v4 d# t  P& b& H( G' O5 X+ Y1 E# O$ X
end& r8 ]2 I2 W1 |8 X( j) o

1 R- \  Q4 l  }0 t  g  ^;; Initialize the global variables to appropriate values
( p" \/ ^4 S" L- \9 F+ }to setup-globals& U5 ^- h# p% k/ t9 n; y
  set current-light nobody ;; just for now, since there are no lights yet7 v( T  \6 d8 L9 @4 o, e+ a3 j
  set phase 0
$ Z9 l, I  U  P8 b/ N# [( q  set num-cars-stopped 08 W% G$ ]0 a% V" g0 }5 K
  set grid-x-inc world-width / grid-size-x
$ F: @; s  j/ `3 R3 A! u  set grid-y-inc world-height / grid-size-y' b# G. _  o" K/ B

7 S9 V% E1 r5 i  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary! v& ~2 P$ V" o7 u! R" u3 j
  set acceleration 0.099! h; Z: M/ `- m6 z
end
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;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
. G/ `* ?% }" f9 T* A/ @;; and initialize the traffic lights to one setting( ~/ k/ Z4 {. S* q# k
to setup-patches0 Z/ L7 i$ p( b% Q: @/ n* i
  ;; initialize the patch-owned variables and color the patches to a base-color' B3 u" \; }: r( a, z" g6 n; I
  ask patches
7 B" D& g1 J* n5 y  T  d  [
6 L! u( x7 y5 n! A  W9 U    set intersection? false, K3 I$ h3 |) _5 N/ V
    set auto? false
5 Q0 z- K% u. S1 u. ]    set green-light-up? true
- p8 v9 ~- w! Z3 d$ h+ y6 g. J    set my-row -17 x6 F6 D, d5 o+ F0 n+ Z
    set my-column -1
* C6 R( x% a, O    set my-phase -15 @9 Q# ]; s* i1 Z
    set pcolor brown + 3
- l) X4 v+ P9 L8 ]) F2 ]9 V4 x  ]2 \% o. z; N" K9 X( |
& Y+ v8 ~$ u' G* w2 x
  ;; initialize the global variables that hold patch agentsets4 _. H( X/ u: K+ z+ k6 D) ~
  set roads patches with+ X% H6 V& C" s! ~/ H) D
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
; b8 r6 J* j) v    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]. t7 I/ C. S  a8 Q/ ^9 [
  set intersections roads with
) T* z# C! ]# N  c  D    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
- P' D+ o% M& D; n' f    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]" n2 n1 W* a& U0 f2 E6 M6 ?
; u, m5 k5 t- Y- ~" y8 }$ [
  ask roads [ set pcolor white ]% A9 M" @! O  w8 V* r
    setup-intersections4 g# j5 R9 Z! Z. d
end  @5 N6 O: o, P; r3 N. H# _
其中定义道路的句子,如下所示,是什么意思啊?
& s; ?8 x2 Q0 j set roads patches with; k% S/ f5 W" k4 _) T
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
- ~! c, u8 ^/ p7 y    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]: Q4 p& G6 M' A3 h* \% {
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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