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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 P. a( E# e$ M' Z; @netlogo自带的social science--traffic grid这一例子当中,& e; U; S! k7 o1 S' x
globals5 O  m6 N: N; T! [+ w
[, j' K( q9 d: n1 |, }
  grid-x-inc               ;; the amount of patches in between two roads in the x direction1 K# v. t. \) t: I
  grid-y-inc               ;; the amount of patches in between two roads in the y direction$ h& S* T4 ?7 F5 E6 [. P
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
5 l# j4 d" Z" l; j  t# q                           ;; it is to accelerate or decelerate; o  h8 p$ f+ K& P" U
  phase                    ;; keeps track of the phase
  o5 _6 w' n- K. z) |! i$ D  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure2 j0 w) x+ {/ H, }
  current-light            ;; the currently selected light: R( ~0 l; N( l4 h4 h
/ o: R$ A7 P/ C) v
  ;; patch agentsets
% J6 i& x* R1 j  intersections ;; agentset containing the patches that are intersections, Z7 o" A8 F9 A2 o
  roads         ;; agentset containing the patches that are roads) c4 h0 Q2 s' y% l
]
0 s2 t9 ~, \: S) I* w; L
+ s) q" V) S( Q6 J/ Mturtles-own
6 G! e8 `, V8 g* `[0 ^8 g  k6 e& P  X8 P2 p
  speed     ;; the speed of the turtle
8 q$ H5 P. }7 y  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
! u* F! o6 C( T2 k  wait-time ;; the amount of time since the last time a turtle has moved
; n8 d9 t9 s# J+ z1 c) F$ q/ l]( R7 h  k; m* g" V& ]" B0 Q/ j
2 f0 T* Z& D* s3 K* O- h3 l
patches-own1 ^* U  u1 u8 [, l( @7 M) n8 @* W
[: ~: w3 p. \, h0 s) j* U
  intersection?   ;; true if the patch is at the intersection of two roads
" k' _1 X8 z# ], v. A; X/ b  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.( S; V+ y! Y; x" h' `' A  L
                  ;; false for a non-intersection patches.
/ A/ r" ]- S# F( ^  my-row          ;; the row of the intersection counting from the upper left corner of the
! e/ T. ~* h0 h6 d                  ;; world.  -1 for non-intersection patches.
: m$ U: e  X/ ~8 V  {  my-column       ;; the column of the intersection counting from the upper left corner of the+ G/ e, n7 p! [/ `- D6 U8 g
                  ;; world.  -1 for non-intersection patches., ]* b9 G: f3 V
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.# F1 J4 O% x: Y$ H% g& j9 ?% i4 {& b
  auto?           ;; whether or not this intersection will switch automatically.* s3 l0 r7 x0 ~5 a
                  ;; false for non-intersection patches.
  W/ @% L* n: U- C2 J0 l4 v' k]
  D3 Z# v; X/ }: ~
& U9 P8 [# Z! F  o
/ Z- c9 m- M& k+ E8 T% d/ y$ i;;;;;;;;;;;;;;;;;;;;;;9 W# B; \9 h$ ^: J( R* d7 W7 D
;; Setup Procedures ;;/ H8 _/ A: ?* p
;;;;;;;;;;;;;;;;;;;;;;
& @! O4 @0 E% a; C# v1 Q
1 v; Q1 d: |+ m8 V" J& s: t; u;; Initialize the display by giving the global and patch variables initial values.) q& i3 ?4 O6 q# W! }, l. x) O4 i
;; Create num-cars of turtles if there are enough road patches for one turtle to9 k! M% L0 _& i( e$ `
;; be created per road patch. Set up the plots.
+ S2 N2 K$ S9 L9 C- ]to setup# y% a1 R- B$ w4 n7 J
  ca
6 m. [+ {5 O) t" L  setup-globals1 z& `+ y9 l1 S2 k! M
0 g& D$ W/ R, X( H# V* I
  ;; First we ask the patches to draw themselves and set up a few variables$ j. |* \3 H4 H
  setup-patches
- S+ K9 y# n; W+ B$ S4 ^1 C  make-current one-of intersections5 e5 @, v9 R8 [, k; i; s
  label-current
& a6 r: A4 u. Q! L
! P. b8 ?! y) V! Q+ T  set-default-shape turtles "car"
6 B' [2 ]9 y& _, o4 ]; ^6 x& {- G' U9 T" o$ X4 `$ J
  if (num-cars > count roads). \6 N# }$ c0 _( c( R) V
  [& f7 f% Z/ t6 P! |
    user-message (word "There are too many cars for the amount of "
1 f! c* u7 v, K! j  D* P  z( G2 u                       "road.  Either increase the amount of roads "2 t  Z- r7 ~* c7 P3 A, t
                       "by increasing the GRID-SIZE-X or "# R7 U) z( s. h9 h
                       "GRID-SIZE-Y sliders, or decrease the "0 m, C! b% H8 |* ^: |
                       "number of cars by lowering the NUMBER slider.\n"( o7 `9 l4 x$ q" i
                       "The setup has stopped.")
3 I( U8 @& r+ R    stop1 X+ i' Z# _/ N
  ]# O2 v+ ]& N9 |* U" s4 f" P

( y9 p# G! T2 z2 L  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color4 |' y- C& T2 ^7 i
  crt num-cars
7 i: y  g# Z  H6 y  [: e( o! v: ~9 }& v* y" V! O) o
    setup-cars
% i, G5 a2 I& x1 l4 R8 K    set-car-color+ w! Z& O$ E: S$ y+ R& A
    record-data, g2 i& H  [6 K8 U
  ]$ ^. E9 ]# f& j5 P0 h* V- W

! t8 ?+ I8 ~  _- C" o' b) D  ;; give the turtles an initial speed
' _. t$ d" r6 M( }0 z$ j0 N" D  ask turtles [ set-car-speed ]
3 n2 `0 a! \/ {. L; X( }
/ m7 V* w' ?$ v  reset-ticks1 S" O) Q1 u0 l4 `. [; b: [" z
end
. ?$ k" W. x+ ]' p% k
$ c1 y. S2 s* b% M0 h5 F;; Initialize the global variables to appropriate values5 i4 M7 ~0 P* K1 M
to setup-globals
7 \  L& o5 s, E$ U3 e& S. A" v: o  set current-light nobody ;; just for now, since there are no lights yet
" ~3 e9 y9 u. [% J  E* F  set phase 0
7 A( J% b+ p7 V, ?7 L( Y7 g  set num-cars-stopped 0
" E6 i- C* b& t' w2 B6 ]  set grid-x-inc world-width / grid-size-x& O) u3 G) T# A! w2 A
  set grid-y-inc world-height / grid-size-y/ _& @& o- q+ x1 l3 R* k
) v# }9 K) n! P
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary, ?- ^  \& s9 K8 E4 H
  set acceleration 0.0996 _' t; D  g8 N+ c
end) {0 q  `! \( E, u+ u( ?

1 T/ V. [9 g+ m# {9 l4 `& H;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
* l: x1 J$ o2 F;; and initialize the traffic lights to one setting- [7 \$ O' V0 P5 |& Q  Y( `
to setup-patches9 W" V* _9 }, `+ x2 k
  ;; initialize the patch-owned variables and color the patches to a base-color+ F8 \4 B# b( H+ T- [- m6 H5 q
  ask patches- t- r3 q6 d% r; e  K' J" p) s; I
  [
( l- K. K# S2 P6 x  q. q    set intersection? false, @) ~& l" g+ Y; n. _
    set auto? false
! n, w: X' B! ^$ ~/ i5 ?    set green-light-up? true
0 R( y' P1 Y% c& x) o6 Y    set my-row -14 F/ g8 ^% b! g* i9 }" `
    set my-column -10 A8 c7 O0 R5 T" P4 |) U+ Q
    set my-phase -1, h' M  C: W" D9 t
    set pcolor brown + 3
9 {" p4 w7 k( r5 p3 R( W  ]
: |1 D1 V5 t: L0 \. O% g. v1 w! Z9 ~. @  `  M2 Y% ]
  ;; initialize the global variables that hold patch agentsets7 `9 h+ [. w- w" G# z7 P
  set roads patches with6 B) D) k6 i( {$ L& O/ h) M" V; w
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or& H  j7 E8 I. L9 J7 r4 j
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
$ n6 ]: ?/ d% |% P; o" }: w  set intersections roads with
7 `, S+ p9 w8 a4 D    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
$ e$ |% E+ |9 ]. d; Y* P; t    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]3 n) Y, @0 t; Q2 ?, h  g

1 k" _  u  w% m6 `( e  g" b  ask roads [ set pcolor white ]1 c) _3 O! ]7 _# x* u% S+ Y  @/ o
    setup-intersections, I5 x3 T# V4 Y) Q0 a1 T* y" \
end
5 A" ~+ w) E1 I4 A7 n& ^其中定义道路的句子,如下所示,是什么意思啊?0 h& f) `0 M+ g( O6 H' N
set roads patches with
6 D6 t. y0 f6 d8 @    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ A5 S. H; ]+ U, @- E    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
) }3 r# b' s, \$ e+ i8 \3 ?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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