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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。% Z; L9 b1 f) W+ e3 r
netlogo自带的social science--traffic grid这一例子当中,0 Z" G9 V- m9 p' K' _
globals. \" j+ H" f' I9 R
[8 s) x) m  \3 a$ B$ _- @7 m
  grid-x-inc               ;; the amount of patches in between two roads in the x direction# Y, J5 h1 W' S: O
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
# x! D5 {. O! J3 H: w/ e  acceleration             ;; the constant that controls how much a car speeds up or slows down by if1 @3 S/ e( j, g6 @
                           ;; it is to accelerate or decelerate: s! {+ R3 E- r, C" y
  phase                    ;; keeps track of the phase
  f9 g+ Q% _4 W  \- x  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
% A# S% _  o( N7 J  current-light            ;; the currently selected light
, q, E1 }) z0 w- q! T5 f4 s/ }+ s( m3 J) p7 V
  ;; patch agentsets$ W. y: K) y* c* E3 H) }& i  }& _9 q
  intersections ;; agentset containing the patches that are intersections: o. v+ j1 j. H9 \* _$ ?
  roads         ;; agentset containing the patches that are roads
  ]0 N0 q/ M$ [1 y+ c; a6 g]
2 ^5 k" a2 \% M' s: }5 d- R  E2 b5 W- y8 J7 U" [1 y
turtles-own4 N! u) Q2 X: i  h
[) a, Q4 \1 O% S9 E8 N6 q- w
  speed     ;; the speed of the turtle2 K! w1 y' c$ k% K% b0 S3 M: A
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right& i2 h, n; B1 U
  wait-time ;; the amount of time since the last time a turtle has moved0 @  N( P: Z2 @3 Q6 y& K' V
]
- |$ m; ~. v4 ?8 N# D* T; h4 j; V8 S4 r
patches-own
# s* m# h* n4 t1 y8 A[
( j. a: y2 W9 D7 f9 j& u& U3 u  intersection?   ;; true if the patch is at the intersection of two roads
  S/ q) ^; l- e& j  i* H# ^  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
. V8 a* ?  w7 G, C) H- Q& I                  ;; false for a non-intersection patches.
, g: D. ^, |  P2 z& H  my-row          ;; the row of the intersection counting from the upper left corner of the
2 I7 ~6 q* q) A; y                  ;; world.  -1 for non-intersection patches.
1 e6 ~* K% b' |- |! a  a  my-column       ;; the column of the intersection counting from the upper left corner of the
  v0 O, Z/ P7 u8 N) d* b                  ;; world.  -1 for non-intersection patches.
+ s- [- b" w& H& p  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
: G% v8 M7 N" N  auto?           ;; whether or not this intersection will switch automatically.
8 W) h8 Y( C' L2 p                  ;; false for non-intersection patches.1 t6 K& g# R5 `; j. o
], ~' W7 E) v6 h1 I5 e, S$ b
6 U9 g9 c% {6 }, p' y: u9 r
; q% z) ^( H( Q1 M1 a& {( n4 B3 K) e7 |. a
;;;;;;;;;;;;;;;;;;;;;;, C3 K$ q5 {8 Y; X
;; Setup Procedures ;;, x" A' e5 |: v+ }% M2 e: F
;;;;;;;;;;;;;;;;;;;;;;) {! ~: n- V" l& l: P3 a" S

$ v+ |  P. Y9 M$ H: ], }$ Z8 U;; Initialize the display by giving the global and patch variables initial values.3 C0 K8 v2 r/ s! u" f9 K
;; Create num-cars of turtles if there are enough road patches for one turtle to: b3 f) B. Z& I' E2 E$ A
;; be created per road patch. Set up the plots.
7 m) B$ p4 q( T1 yto setup! {  q- y0 ~9 H7 v, p  l
  ca( n$ ~/ ^1 _4 d: Z# [  F8 A
  setup-globals
: x! \2 ^* H& ~: j$ f8 `# X( x) _* @# h8 V3 ^. E9 f
  ;; First we ask the patches to draw themselves and set up a few variables
9 F/ \0 ]& a, e8 q  setup-patches) t/ g- i/ A* n4 f" u' n& V
  make-current one-of intersections) C9 `) E: ^8 C0 O
  label-current
0 q( V5 M, K5 i8 W% t8 r
3 D1 }( V2 b3 e  set-default-shape turtles "car"
9 Y' |; f, J' }. l& i; D( k* ^+ I  S- O  t. W6 t
  if (num-cars > count roads)
9 n' p: f/ s8 M  [
: M9 X' Z. n" s+ F! d$ C- E( o! y    user-message (word "There are too many cars for the amount of "
( t) n1 k+ ?* y( Z8 J( Q0 t: b                       "road.  Either increase the amount of roads "
" b6 b# C- v3 e                       "by increasing the GRID-SIZE-X or "0 `* @6 ?7 |2 {: ^$ G/ J
                       "GRID-SIZE-Y sliders, or decrease the "1 I7 b) W& N, q/ _; z3 i- \
                       "number of cars by lowering the NUMBER slider.\n"
+ t; {1 ^7 a  x+ F) B' i3 E                       "The setup has stopped.")
% s1 D! G6 H# a3 x) Y. X% _. [    stop% ~' r, ?8 m& l! R- e
  ]
- i8 M7 l  `& w5 [, E8 J+ L
4 @; a1 o. C/ [2 {" t. w  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color+ W+ ?1 ^. A/ V) H8 ~: ~
  crt num-cars) `+ C4 ?  s8 J3 D$ `
  [" j4 X, M6 z/ K& K5 N% W+ m
    setup-cars
& U, t: j% k3 o! Q* f; R- W    set-car-color' }- l( _+ U9 [, ]- s
    record-data0 |. y/ |) u  H' T- b8 f" W" R
  ]
# K6 [9 v/ Y- M. d. N& E, S0 T0 A0 K' o
  ;; give the turtles an initial speed! u" \5 f( ?( J& `
  ask turtles [ set-car-speed ]5 S$ ~/ s) y2 h6 y( a3 V6 K
2 \$ B' N" [4 i5 R" |* n+ b
  reset-ticks% _9 ~) C7 u: X9 |. l' {
end, A6 E$ }) N+ R5 s& U, K: ~! X  }

, q0 ?+ A8 w2 n9 Z- K;; Initialize the global variables to appropriate values% e: v% S- x$ m+ ~* z2 q( d
to setup-globals5 a' S6 f+ \" {" B% m0 l
  set current-light nobody ;; just for now, since there are no lights yet
+ t2 w1 s" c3 I+ R0 n" ]& j8 H  set phase 0
3 s! d+ v: ^6 S- j7 z" k  set num-cars-stopped 04 j. h) u9 F( q$ m
  set grid-x-inc world-width / grid-size-x: m9 h$ K+ A* n) U- S
  set grid-y-inc world-height / grid-size-y
4 c' B0 U% S/ f. [5 Q7 o+ }6 j1 v9 B- [2 c" v$ ~" t8 a
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
3 m1 C$ f$ F5 w6 _. q  set acceleration 0.0992 ?- [/ t7 E  f9 `6 w
end
2 v  E  A. v; R) h. x3 Q& i( l! A+ Q% |, H- M0 v9 F9 b
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,3 b. c# y+ @0 c: X
;; and initialize the traffic lights to one setting
% K6 V- {4 N0 T. V' Gto setup-patches
6 F' T1 ?# A" k$ T  @5 {  ;; initialize the patch-owned variables and color the patches to a base-color
$ u/ _( e. e7 R# d+ d% [9 S  ask patches
' ^) J7 ?5 _5 x+ }8 r6 b  [
: |( M/ s+ \" Z% }9 ^    set intersection? false
; F* `- t& y1 F; Q* l) @, A    set auto? false" W/ K  v* A: t7 x; _
    set green-light-up? true' V/ T  ~( q3 G; _! ~
    set my-row -1
3 I! ~) k  r) y  m+ i" D* ]6 F    set my-column -16 `6 _# w2 u& }  [, r
    set my-phase -1
0 [' h+ I. q6 X3 X6 w: A" ~: }    set pcolor brown + 3
) s1 f* K! b( T5 L/ n! Q' t  ]4 I- n/ |1 l. w$ U: B! W4 r

4 K  {' ~, X9 V( ?7 L  ;; initialize the global variables that hold patch agentsets
! D7 x5 Y' w- ?5 \4 S: `  set roads patches with
' C+ _- z6 X# T7 H" e7 O+ Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) K, O! _1 D! ^2 ]2 @2 |' Z8 J
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ N, Y( g. i4 R9 Y0 P7 ~/ a3 E: T
  set intersections roads with* F: t5 q5 ~. ]$ Z- f
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and1 d! l/ Z; t. ]' N2 [3 {
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
* r. O/ h5 l1 |  j5 D, J, \" c4 L6 r5 A9 a4 ?
  ask roads [ set pcolor white ]
( e1 e5 w! l& b; W' G    setup-intersections
# T& y; r  P+ x7 o' Y3 c6 p7 F6 V3 cend
, l6 A$ N$ |# D" C( i其中定义道路的句子,如下所示,是什么意思啊?
( _" u& o: G( Z) T3 e( R# Q, p set roads patches with
$ w, y9 U; v" N5 p) F+ ?8 A    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or9 y: \8 v1 [* U
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 D3 W4 }% b5 q" B3 u+ q: z  }6 W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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