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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。$ ~! f# {  d' d5 \/ t- b
netlogo自带的social science--traffic grid这一例子当中,
+ m& t! }( Q( z: @& o3 D+ Rglobals; u- u8 H& n) M" k" r: B! b
[
( q6 m7 f: ~# K1 y8 i3 b7 D  grid-x-inc               ;; the amount of patches in between two roads in the x direction
; X( V1 ]1 J" j0 r6 Z, b8 e  grid-y-inc               ;; the amount of patches in between two roads in the y direction4 ~6 U+ x. A; w* W+ a0 a7 ?
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
$ p' @1 D* b7 N2 |# O                           ;; it is to accelerate or decelerate
8 C: e* v4 m4 O1 ]: @; \  phase                    ;; keeps track of the phase5 ?/ p* p- E0 p3 M. \; V. s; }
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
: @: y# j$ [4 J3 o- i  current-light            ;; the currently selected light4 h; U8 W' v) O4 z/ M. N/ ]: z( K- |
  g/ M5 N, D/ i1 Z, W
  ;; patch agentsets
9 D- G# ?$ m# \; g( o  intersections ;; agentset containing the patches that are intersections1 I4 {2 O6 x# R# N
  roads         ;; agentset containing the patches that are roads  w6 Z2 {; @# m4 l1 O: u/ X8 v' z
]1 B; I2 C: }! p

$ z. N$ z) M4 q3 s0 t7 B9 }turtles-own
! Z% ~3 n& M' o$ v9 L; `' I% J% w[
0 m7 I6 s- v% F* r$ T  speed     ;; the speed of the turtle
0 _7 W; I( c, ]9 K6 z2 E5 ~  up-car?   ;; true if the turtle moves downwards and false if it moves to the right5 x. D9 P7 m! f6 [1 h/ P
  wait-time ;; the amount of time since the last time a turtle has moved
# T: z! x: I6 _: w$ ~4 R* q: L" g$ []
. G" s$ A2 \# C/ _5 \9 {( u# X: [& i8 N, d: ]+ U; s9 O$ B
patches-own
" q. B& L2 K4 E& `4 ]8 O* h2 D[% [5 X( \1 r' x% M& s$ }
  intersection?   ;; true if the patch is at the intersection of two roads" P* O1 B9 u' E
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.% Z) _9 Y% [. t
                  ;; false for a non-intersection patches.
7 ~7 H. h0 P) p# w5 i  my-row          ;; the row of the intersection counting from the upper left corner of the
) w- l. A" o2 [                  ;; world.  -1 for non-intersection patches.; k) f0 X; b4 |6 j. \# K
  my-column       ;; the column of the intersection counting from the upper left corner of the# J; E0 i& _* v7 F9 [7 e, y, k
                  ;; world.  -1 for non-intersection patches.7 w) F# T8 t- N) b
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.5 p+ G/ ~. c8 z, }7 O, U
  auto?           ;; whether or not this intersection will switch automatically.
8 M5 V. [( p- W, c& z" z                  ;; false for non-intersection patches.
! b& {! s9 v/ x1 b- x2 C, X; r]
/ z. c8 |0 G& t5 N) \3 y5 H# q* G8 P( I8 d5 M! r6 `: _/ p6 N
' b# |% Y( U- o
;;;;;;;;;;;;;;;;;;;;;;
. X2 z7 q- z% @/ j;; Setup Procedures ;;+ {9 T8 H; V  n1 S( J) `) ~8 K* C
;;;;;;;;;;;;;;;;;;;;;;
. A( ]9 k: x. n& J! q" e+ R3 e0 }5 S& R" _; J( J! J# |$ h8 E
;; Initialize the display by giving the global and patch variables initial values.
8 D  ?) X& \% H% n5 Z0 A;; Create num-cars of turtles if there are enough road patches for one turtle to; D8 l7 C7 y# v" |) H# H
;; be created per road patch. Set up the plots.1 n7 P" U: @# D
to setup
8 m! q9 x; s" J; d: k/ f4 c5 e  ca
6 h& ~& y, T/ i% h% K  setup-globals. h" `; M2 W/ D4 B! Y1 x
( O: K6 E# \. t% Y" A# z
  ;; First we ask the patches to draw themselves and set up a few variables9 b- R3 P7 r& P
  setup-patches
+ t0 u3 l# j  R* f  make-current one-of intersections
3 v/ g% O( p2 C$ ~  label-current
. p/ q% K0 p& k
& u( E& `( W5 X. K9 c2 ?/ w  set-default-shape turtles "car"( j4 b* g/ o0 e3 [0 i, F. g8 ]' }
& t: r0 b4 b5 E" D1 I
  if (num-cars > count roads)
# h5 V0 U( _: z# v) [& V7 m6 r! ~1 ]- a  [$ G2 r  T" t3 ?. v' g7 ~
    user-message (word "There are too many cars for the amount of "$ f. \6 e1 R" s
                       "road.  Either increase the amount of roads "
  _" K$ q4 ]  `" _                       "by increasing the GRID-SIZE-X or "
+ Q+ ~4 E! p3 ^* y4 M! h' M+ W% n% A                       "GRID-SIZE-Y sliders, or decrease the "8 T3 J. f* J2 [3 `$ H7 ]
                       "number of cars by lowering the NUMBER slider.\n"" c5 [6 U: G' k$ V; f: }/ z8 O
                       "The setup has stopped.")' U, W5 @1 e8 n& Y4 i
    stop; {/ |" C5 M* z
  ]& n; J& P6 ?0 I; I4 m8 n

" C3 s9 f  E- T! w/ H  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
" K5 o' d: o- x% M  crt num-cars+ @* \) {% ~/ d% u4 I" y6 f
  [
! E7 I# E4 I+ V, t( A, A5 W    setup-cars9 i/ Y+ [! r% c  t3 t, m
    set-car-color
7 y3 r$ C1 k2 Y) O5 }, W    record-data0 v# p- r1 S& i1 e" \. f* `
  ]$ }5 v0 G* l  J$ r3 v# f* I
6 W& T( {" D; J7 _# w9 _% }5 b
  ;; give the turtles an initial speed
0 j& y9 F: {8 m+ I  ask turtles [ set-car-speed ]
  I8 Y! |: O5 c; g5 N: L# E7 l8 [$ N7 z1 |# g& S6 N
  reset-ticks
9 O/ S) `4 t  gend2 N  \/ r2 U) e' _  f
* N/ R$ y$ b; G* _
;; Initialize the global variables to appropriate values
) G  [" U, f* }% rto setup-globals0 v/ N' W$ ]* _! Z
  set current-light nobody ;; just for now, since there are no lights yet
0 H+ x) t, e4 a% h& Q$ Y7 j  set phase 0
5 j. V  `' a  S6 S* E7 i  set num-cars-stopped 0( |8 f% d% _/ v0 x* E
  set grid-x-inc world-width / grid-size-x; ], |2 i' J9 }! c- J8 o+ b7 |
  set grid-y-inc world-height / grid-size-y, u' W' @3 E4 w8 x
, z+ r/ K2 g$ ^6 t9 X) \
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
- e( \# f2 K9 P. ^8 H  set acceleration 0.099
/ X* Q& H- H/ l, I7 y, [  d5 H1 Tend
7 K2 C* G9 [( _4 i& X+ O' w
$ r+ W* `% m# q;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
6 @6 d. W/ g8 x; t% r1 \8 C;; and initialize the traffic lights to one setting2 Y2 G% X4 [% J$ Y9 c' ]
to setup-patches
9 W/ g2 ]7 p( ]% L  ;; initialize the patch-owned variables and color the patches to a base-color) _& K% y& |& k( C7 u1 z: u+ Z% P
  ask patches
$ _% a$ i  n$ s, h7 T, ^/ ~  [5 n4 d' y, v: u7 |3 M" `. Y
    set intersection? false+ v7 F5 z; x" \0 a" y% m' k$ d
    set auto? false
. V/ X* i0 f% J) v0 g4 C    set green-light-up? true  g. b* r" P1 i
    set my-row -1% |( a# a2 X, j! K% X
    set my-column -1
% k7 y# r7 ^/ z1 `; A8 [+ S9 G    set my-phase -15 S# X; u. D# r9 A' `3 Y4 z- c
    set pcolor brown + 3% F# O' L! D4 }
  ]2 r* {  g3 Z( p. M9 m5 \

; D" Q. z  A4 f- R8 e  ;; initialize the global variables that hold patch agentsets1 V6 L# ^1 w$ x
  set roads patches with$ B1 |/ U' @- t
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
$ D5 p  p0 a& d0 l% w$ ~    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]* x' z, @0 B" e2 \- b' l6 P; g
  set intersections roads with6 e+ L+ ]  i' D' u% \2 A7 P( y  ]3 R
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
7 V, ]4 R# k3 w" n6 H    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
4 }' p2 t+ O# ~8 L% ]
& h& J' V+ B# C: d+ F  ask roads [ set pcolor white ]
5 i* @1 u# f+ h, ^# F    setup-intersections6 v( x4 v6 Q1 K
end
1 [! q' A# n" y& y其中定义道路的句子,如下所示,是什么意思啊?
( \$ V+ t) A* c6 l set roads patches with
$ M4 |  L% R0 V: h    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or8 N* e5 c, B* O( [1 O
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]( _$ \5 d. d7 ]5 l
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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