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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。* t4 H" p6 F6 J7 N* i
netlogo自带的social science--traffic grid这一例子当中,4 \* z- s1 u5 Y1 s- N6 Y
globals" f; H+ x/ T- x+ [) j1 m$ v
[
8 K% ^: I  x7 F0 e  grid-x-inc               ;; the amount of patches in between two roads in the x direction
4 J, j  a9 e* X7 G! i  grid-y-inc               ;; the amount of patches in between two roads in the y direction
# |$ o* s1 `% ?: F" m4 q/ V7 z  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
& m; p9 s& v9 z6 U4 p: p                           ;; it is to accelerate or decelerate+ Y5 w6 Z6 ~9 P7 ~) x
  phase                    ;; keeps track of the phase
% z5 _* e  \. u  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure8 z1 u$ f: d5 I9 @' ^
  current-light            ;; the currently selected light
, X( ?! J, r5 X, M  q- ~* D9 x* _8 ]6 V7 b6 o7 r/ _# d( j% P
  ;; patch agentsets! s3 K! k' r+ I/ L  X6 h2 L, n
  intersections ;; agentset containing the patches that are intersections
) Q; B4 m, n' `8 G4 Z- B" b; O  roads         ;; agentset containing the patches that are roads/ y+ s* B; r( W9 c: v# {2 i- T
]4 A/ A8 P; j* W  F
7 I0 v) X4 V1 P- w# ]
turtles-own6 t: Y5 y! Z- i' M, B* T
[
+ v2 S7 L3 k! W! i7 f2 R& M3 R1 B" Q  speed     ;; the speed of the turtle
- F, q8 e' s- E: @( ?  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
; d0 I) c+ _5 V* o5 Q9 ?  wait-time ;; the amount of time since the last time a turtle has moved6 i! F# T* z' o* S& K6 w
]
7 r6 s! t: N; J5 O# F. ^3 C5 p5 ~' Y) S+ S
patches-own
" G; R; y( t3 U2 \( E2 H+ g  k" S[
: M' j; A8 V6 ]/ `  intersection?   ;; true if the patch is at the intersection of two roads
& }1 [  c8 D4 R# i- `  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.5 k" H+ |: l8 P) S1 {
                  ;; false for a non-intersection patches.- O8 M- j) m; q
  my-row          ;; the row of the intersection counting from the upper left corner of the
! F) Y( V! u! K- e% _; N$ b                  ;; world.  -1 for non-intersection patches.) d. }, s. P7 u) d5 s
  my-column       ;; the column of the intersection counting from the upper left corner of the0 v6 |" Z0 G; i/ o4 Q) S1 }
                  ;; world.  -1 for non-intersection patches.( c9 R0 ~$ ~  ~
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.4 ~+ t* D1 \2 F9 T5 E  H$ ]( P
  auto?           ;; whether or not this intersection will switch automatically.
; W4 u7 w. m0 O' N# \. s                  ;; false for non-intersection patches.3 N4 o& t+ \# F8 l
]' x. o' i6 v: I) [8 y
" D; Q& `5 o$ W# c' e

/ n9 O2 ?7 v- s, n: D5 @1 j( f5 ]" C8 L;;;;;;;;;;;;;;;;;;;;;;
% b# \, s% [# e5 R;; Setup Procedures ;;
. ~+ K. }- w( V: n;;;;;;;;;;;;;;;;;;;;;;
) c; v1 M2 n% ?% n/ [: _; S( G5 C! _) `/ }' D8 F8 [. l$ d' }
;; Initialize the display by giving the global and patch variables initial values., L) M# ]& c* f3 A$ J
;; Create num-cars of turtles if there are enough road patches for one turtle to, r/ E' R! L6 x" `; ~# ]/ b* D
;; be created per road patch. Set up the plots.0 g' i$ H  `5 p* D! M! i1 a
to setup8 M5 f( f: J) B# l, b
  ca' |: W! M' `: L, Z3 c" ]/ H, V
  setup-globals5 S) k) W0 P# R. U" d

  n, j. b: C0 O8 q/ n  ;; First we ask the patches to draw themselves and set up a few variables) S5 Y0 [3 e( N) \) s  i
  setup-patches5 q/ ~- v9 i) Z" k' U
  make-current one-of intersections
5 y# M+ @0 l5 ]( m! |& B9 ?  label-current& I- s# n; d- l: q

5 h8 @& B5 ?" l- }  set-default-shape turtles "car"
3 T; n4 ~" ?. ?, e3 F
$ V, {: v9 ?. s, b% [  if (num-cars > count roads): v8 v7 b: i; |3 p. v
  [
5 u$ O* \- P7 j$ f9 @    user-message (word "There are too many cars for the amount of "
) A" X* Y. j  I: H  B4 \& X: ]                       "road.  Either increase the amount of roads "
& _8 l# G" r  v: \7 v1 x: Q) |                       "by increasing the GRID-SIZE-X or "1 |/ ]9 I1 f4 @) ^
                       "GRID-SIZE-Y sliders, or decrease the "
( I  c1 z  |  G. h. Y                       "number of cars by lowering the NUMBER slider.\n"% @) l/ U0 g4 D) P7 @0 w
                       "The setup has stopped.")
* c" x7 e  H( P! ~' @  X    stop
6 G( y* A$ c# C3 ?* G) j" {  ]
* y9 p, J# i7 Y. U- g9 u) j% p' H
1 P9 d# B1 S  o9 p0 O1 D' _* K  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color! N6 ~& T3 ?+ I1 I" V* e
  crt num-cars" Z7 x4 }) \- G; J" a7 T
  [6 B$ S  |; X: G* |$ Y% R: q9 A
    setup-cars
5 N7 q' ~8 v; N. e% W    set-car-color
" Q& T4 _9 X  J! w- G    record-data
4 z: s# D) }; z3 O% ~  ]- E6 ?8 f3 D% }# U2 s0 y4 n4 D

* r; L+ _3 G0 Z; _+ `- [  ;; give the turtles an initial speed
. {! @; a8 D) t% ^  ask turtles [ set-car-speed ]& z' y( a. E/ q& Z7 C

: R. s2 x# y; q4 y/ I4 a  reset-ticks
# ?8 T) j3 U/ d5 k2 X2 oend
! n( J; J- i# @1 k
6 R: u( c6 ~& D5 y8 F+ K' H+ k& ^# F;; Initialize the global variables to appropriate values
4 F$ V3 \& ~  J, j& _to setup-globals
# V" d$ e8 s( f& G' L! n0 V  set current-light nobody ;; just for now, since there are no lights yet7 A: T/ g6 s$ Z3 @: t4 c
  set phase 04 \2 t5 ~5 s! t; g6 ]* Z
  set num-cars-stopped 0
4 P* N" i1 {# }8 o7 j$ o3 T! E' N  set grid-x-inc world-width / grid-size-x
/ _6 ~- z' ?" A+ O2 H& z  set grid-y-inc world-height / grid-size-y
+ l8 {2 |4 g8 c/ ?, j
0 o$ s" m1 f1 {' ^7 {+ ^  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary( X8 k! u" Q9 ^6 c
  set acceleration 0.099
$ d, s- [- P/ e: nend
4 r4 V7 r& g- E$ x9 l# c' A4 J( Y% q9 Y
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,5 H, O( @6 y0 X! Q) {, l
;; and initialize the traffic lights to one setting
8 v8 w* n: @! q# O0 k: hto setup-patches
) w9 l" a7 b6 l- u) f5 V  ;; initialize the patch-owned variables and color the patches to a base-color
. ~8 |0 l+ i3 y  ask patches8 d; v; d  E  S9 f. B
  [
- u; o" D# |& k    set intersection? false9 C3 G& {3 E7 y8 }  W
    set auto? false
% ]) O# I9 w3 S8 Y, E    set green-light-up? true! l8 I/ b3 i. Z2 i; `# W; @7 W
    set my-row -1
: x' Y! W# ^6 b3 B' E    set my-column -1
8 O" ]' G9 I8 `. n, b: c8 g# E    set my-phase -1
7 ?" ], S" U! w1 q# ]" a& w    set pcolor brown + 39 C0 n# W" S- n& G, v2 |
  ]  D+ k2 y! G. M  z7 ]1 N
! w* ?% |( V/ L9 m
  ;; initialize the global variables that hold patch agentsets
- S' Q+ ?- }: e8 ?! [/ S  set roads patches with* `" q6 ^$ Z, C
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
; y, {2 l9 p* E1 Q5 l1 T    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]: ?7 A) Y" \3 E6 l8 W  Z0 q
  set intersections roads with( r: M2 }; y6 U7 ^6 ~
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and' y9 e: [& s- U. H1 k
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]& k$ D6 t  |+ O
& y8 P  J) K, ?# c3 t
  ask roads [ set pcolor white ]9 O3 v# o6 M: y, v! z) ^# t% n1 t
    setup-intersections
3 q8 A0 U" N; T& }: F" F! [" C3 ^end
) u$ @2 S, P( I/ n8 w其中定义道路的句子,如下所示,是什么意思啊?8 h  G+ ?% G) i4 h
set roads patches with
1 g& q8 q7 }8 D7 f    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or2 W) e  p5 p: U8 d, @. t6 e
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
* |1 F# |" L1 b: x% s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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