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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 _0 A+ a8 u9 b4 C" lnetlogo自带的social science--traffic grid这一例子当中,5 f6 G8 N2 P$ u# b+ j8 ~/ v
globals
, ]& w4 n; y1 w& b- t, Z[
. {! n/ Q/ X" x5 A+ u3 Y  grid-x-inc               ;; the amount of patches in between two roads in the x direction
9 f+ s) R5 }8 ?( B* K  grid-y-inc               ;; the amount of patches in between two roads in the y direction
# d: R4 j$ v: {. J, d) c5 A' C  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
& \% J5 h3 i# e& d/ |$ q& Y                           ;; it is to accelerate or decelerate
5 y( V0 W; s$ @4 q" a6 W. m  phase                    ;; keeps track of the phase
. u7 H  b; L1 Z1 Y: \1 n9 Z  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
- w! `; G# t( j1 q( m8 F3 B- p  current-light            ;; the currently selected light
# [8 h5 }6 G2 W# S( p
1 `# ]% {; o1 c/ j, W. n  ;; patch agentsets
, Q) j5 B0 d2 ]* k  intersections ;; agentset containing the patches that are intersections9 {) J4 P* r5 [; F0 j' u
  roads         ;; agentset containing the patches that are roads
0 r  U  f0 X# Y, `) ~5 z8 u# h8 X9 L]
9 J/ V! n; k6 P# W' v- r9 X/ h' B7 f. c5 t
turtles-own* u" l6 e) B( [+ {
[
7 a# b+ ?) `$ ?8 D& O  speed     ;; the speed of the turtle
: v7 J  B8 x: y/ i  up-car?   ;; true if the turtle moves downwards and false if it moves to the right; U2 |& [% w) k/ q1 e8 |
  wait-time ;; the amount of time since the last time a turtle has moved
' ?% S' ^5 ]# ~3 x$ t$ ]0 {]0 @7 |. n; C& G; D! G
  k9 A- h; j  ~
patches-own) z. k( `, L9 _) p* I
[" O. t. w% v2 m
  intersection?   ;; true if the patch is at the intersection of two roads6 ]( N; Y4 a9 N! z+ R9 L7 g
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
/ I9 Y6 u; \0 W1 y* ^                  ;; false for a non-intersection patches.4 j* a& a5 C! |3 T, A1 T
  my-row          ;; the row of the intersection counting from the upper left corner of the9 K: M' t% d3 G) B" ]% r
                  ;; world.  -1 for non-intersection patches.
0 y$ [# f8 t- [9 j+ |2 B  S  my-column       ;; the column of the intersection counting from the upper left corner of the' N9 O, K$ ^0 z6 ~& o6 \
                  ;; world.  -1 for non-intersection patches.
4 i) J: C. W: d) n# L" f+ w  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.2 }! K. S7 T% H+ c' _/ M, N
  auto?           ;; whether or not this intersection will switch automatically.! P' \; `0 g7 z- R4 i& t1 M2 V
                  ;; false for non-intersection patches.
5 H; C& J' V& ~5 b# L]! J6 e# g2 z) |; x0 z# d

9 L8 d2 z; D8 I* {% F) u
# ?5 d5 s4 G# K" a;;;;;;;;;;;;;;;;;;;;;;
: ?: q& Z/ C( P6 `: O! r* {;; Setup Procedures ;;
4 s, F/ E6 d" E  D+ H;;;;;;;;;;;;;;;;;;;;;;6 X. \7 a7 m7 F" K; ^# w
% T+ q5 u- {# A' a$ R% j
;; Initialize the display by giving the global and patch variables initial values.
& ~# {; j" H* q" ^& d;; Create num-cars of turtles if there are enough road patches for one turtle to8 Q/ r: m& c4 |; Q' Z! E
;; be created per road patch. Set up the plots.
& R$ s1 e' F: ato setup
- B2 k7 J# l9 c' |  ca7 t- ?" [$ y4 i0 H4 V. Z; d# v
  setup-globals2 O# E# l8 B  I$ Y1 o# y

/ B/ u, [4 O- s& }$ r  ;; First we ask the patches to draw themselves and set up a few variables8 P5 _; r0 |. ~6 ^" n
  setup-patches
6 I! _" U3 Q0 [  make-current one-of intersections
% E+ H( c8 l7 e% X, |) c* ?2 p, b! R  label-current
  L0 D* |+ y& w" y3 i& @$ V, ?5 b
$ [, m; ~& k/ h( W1 N: O2 Q  set-default-shape turtles "car"2 {8 h% F7 \" t2 W
# ^& b) ~3 {- b0 g0 K
  if (num-cars > count roads)
1 V  ?' _% b/ Y6 A# e  [2 T. [; {) }( ]4 M! O2 [  u3 W
    user-message (word "There are too many cars for the amount of "
) ^) c6 j0 h# e; g                       "road.  Either increase the amount of roads "
7 y$ v$ W( D0 S# K  y" R3 ?& k                       "by increasing the GRID-SIZE-X or "
& D- ~6 Z. J5 o# U! `                       "GRID-SIZE-Y sliders, or decrease the "
/ }8 c- u' ]; x. X2 a                       "number of cars by lowering the NUMBER slider.\n"4 z% M; y" _) N- c( a' D$ @
                       "The setup has stopped.")9 H' |0 B0 z! o- t/ u' |* W3 i" ?2 z
    stop& T4 A* c5 a% T$ j
  ]
' W& G* T. A$ ]6 o3 H0 A# q- e& @; I- J( S1 @9 m& P
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
, y+ R/ o6 f* `: g7 a  D4 L  crt num-cars# _' M! {+ b' u5 c
  [
& u6 w; i3 m5 t9 J    setup-cars: R6 f4 z. \1 B, C
    set-car-color
6 [+ h  L/ G/ O: R8 v+ g- R    record-data
# z; o: p  t; d# p- b" C  ]
9 W& Z/ X- q3 V7 Q8 L& C6 I1 Z3 I% @9 i* t
  ;; give the turtles an initial speed
+ U3 p/ B7 I) m, G  m" M  ask turtles [ set-car-speed ]* t4 C8 G1 L; B9 V% i6 B

0 x4 G* L8 {, T* p# m. h0 Z  reset-ticks
) o: n9 y" L6 _end
- t6 Q# L- W, }- E5 k5 m+ e: [1 V3 i
;; Initialize the global variables to appropriate values' Q( R1 A: E8 w
to setup-globals$ _. b3 n  r3 Z& ]  G
  set current-light nobody ;; just for now, since there are no lights yet3 U$ g; q  e4 F. N
  set phase 0
" b7 u  i7 c/ e& [( U6 X  set num-cars-stopped 0
8 F9 N5 i# i& k  set grid-x-inc world-width / grid-size-x
- p( c" u; B" g) S- Y  set grid-y-inc world-height / grid-size-y. ^5 N' I+ l7 i, B  n/ F+ G* k

8 h( l3 D7 t% A! p+ G. \7 C  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
5 T3 k1 b: i; v# E- K; }( u  set acceleration 0.099
5 E) {- Y( ], u7 |3 {3 Q- d* xend: [5 [: g9 d+ r6 I

3 ?4 ]  ?. ]$ n4 l7 z: @2 o;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
6 D9 P$ t; v: g$ K: C! S;; and initialize the traffic lights to one setting
5 U# @* ~" `- G; P$ v# g# _' |& xto setup-patches( B+ x- q  }* C0 J6 q! @. V+ f' U) b
  ;; initialize the patch-owned variables and color the patches to a base-color$ T& M" ]+ J4 ?
  ask patches' |/ W+ Y5 w5 d0 s/ |
  [$ P6 T$ j. \1 q! W8 M* ^& O
    set intersection? false
, p# d- t' d1 L9 ]" k    set auto? false
1 I& g. c1 x3 o! M$ a0 z$ O    set green-light-up? true
: C% D: d' Q& U  O, S: O% G: g    set my-row -1
, J+ K% Q" R; ?/ e6 B    set my-column -1
3 S! I$ h' O- A- H& C    set my-phase -1+ h; @- _4 x: r/ n
    set pcolor brown + 3+ \6 K8 q/ e& A1 u
  ]- \7 }0 H- [9 R1 @* n( n
4 L/ l7 N  I% P2 C5 h* u+ Y/ ?- ]
  ;; initialize the global variables that hold patch agentsets
- X0 k+ I5 _* y9 X8 }8 \: x3 [  set roads patches with7 ?, U" T" `  U& n6 I
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or, d5 ~: `6 l4 A+ I
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]7 O, A( y9 g" g& D7 i
  set intersections roads with
6 ]) ^( T9 d7 A8 y( Y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and( D8 r9 q1 j8 R) d/ v# T$ j
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  `2 H0 g* ~4 y/ z6 `
5 F3 N" F0 v7 M- Z) Z9 p# {$ F+ g; o  ask roads [ set pcolor white ]- d* o, V* t8 t8 B7 Z' W
    setup-intersections
" H4 b( X3 l. a$ r1 ]" o: bend( h3 F( L8 p. c: B
其中定义道路的句子,如下所示,是什么意思啊?
/ ^( q9 j6 z: C set roads patches with% u- D! ~! N$ X8 A+ P
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ p6 O+ Q7 X  {8 k3 g) }    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
* D0 f% {/ `  ~/ S- y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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