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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。4 r% ?" g: M0 \) }+ I) \
netlogo自带的social science--traffic grid这一例子当中,
" K! |- G8 y1 P) h. R/ \% Jglobals/ @% h/ i. j4 X  m
[
9 p$ d9 H: [7 Y6 L  L) F- E  grid-x-inc               ;; the amount of patches in between two roads in the x direction
/ r8 x% H! U* t# q; M& r  grid-y-inc               ;; the amount of patches in between two roads in the y direction
' _- z% }( f1 c, P' n+ t+ k  acceleration             ;; the constant that controls how much a car speeds up or slows down by if; G0 J; X3 [( K- N( b1 Z6 D
                           ;; it is to accelerate or decelerate7 S7 [0 {: T. t* y
  phase                    ;; keeps track of the phase
( y; ^/ b5 y" v# z4 V0 e. T. G  x  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure: g, k- G- c# O, U4 W! u8 S) G( f# d
  current-light            ;; the currently selected light! d9 |$ o" C9 y4 l
6 o3 D2 q3 G, G- p+ l0 S
  ;; patch agentsets
$ a- t9 \# {; a- o& v! b& H  intersections ;; agentset containing the patches that are intersections: e) L2 y; A  F; Q& }
  roads         ;; agentset containing the patches that are roads
3 Y  M# V3 s% M; U$ n* v' M# |]
0 |: [. X: `4 j7 @& }: Q) j4 T1 V: X) V. ^5 Z
turtles-own
$ A. A; B; w' `. |/ X[% U- I* O) Z; L! |
  speed     ;; the speed of the turtle
* X. o- F2 E- }0 r  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
# G: o# m& k% Y$ u; q  F  wait-time ;; the amount of time since the last time a turtle has moved  I2 |7 J  c. J3 T; X
]8 w# _& k( r9 q  X5 z% r, t
- ]1 @3 [/ [: {, ?6 k) A7 J0 z
patches-own( e  I' \, Q: j: N  q3 M* \& C
[  n9 h, T. w4 [' K. F- }
  intersection?   ;; true if the patch is at the intersection of two roads6 g8 U% D; k$ [
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.$ `& d( }& O" r3 I2 q
                  ;; false for a non-intersection patches.+ b7 p' ]. E3 t& c
  my-row          ;; the row of the intersection counting from the upper left corner of the% h/ M: S7 C2 e% ^; z) t
                  ;; world.  -1 for non-intersection patches.3 a7 u* K% m1 V# k
  my-column       ;; the column of the intersection counting from the upper left corner of the4 H  A" ^7 G, O  w, H' j
                  ;; world.  -1 for non-intersection patches.
6 O( s8 ?( b1 |4 A& c7 Y  g  @) w+ Q  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches., `9 ?( }' i+ X: J& M" e. ~
  auto?           ;; whether or not this intersection will switch automatically.
9 U2 [, X5 {+ Z6 p5 H                  ;; false for non-intersection patches.! i6 d! i0 P# @+ X' Y7 x
]
' U6 A0 f9 F$ \: [- }) w
& x7 ]7 j2 c; L# @7 d3 n; I  k3 l3 f& D% B3 o( q" w
;;;;;;;;;;;;;;;;;;;;;;
: V1 r( r  c2 s; h/ w5 P3 n4 F;; Setup Procedures ;;+ W" r. f8 ~; u0 v( v4 }
;;;;;;;;;;;;;;;;;;;;;;  n* K" ^2 C% h3 L

+ v6 h  @; n6 m8 J;; Initialize the display by giving the global and patch variables initial values.* I) r& P% I& i9 t" f
;; Create num-cars of turtles if there are enough road patches for one turtle to; H# l: E8 x' A
;; be created per road patch. Set up the plots.
+ _9 E; a: v+ a; N( Z9 u% q: Lto setup
$ {- I% r" ]# d8 Z& A0 \  ca
. c# s8 o' N- Z: P3 C- m7 e6 q0 k  setup-globals
& C6 Y$ @$ Z5 W: \, c+ e5 J- r
: w, a3 `3 q; S1 D3 M) i6 z  ;; First we ask the patches to draw themselves and set up a few variables0 b  _6 R- B" w& F& ]1 u
  setup-patches
1 O/ c! \& _: a+ n8 s5 w1 u  make-current one-of intersections
/ n5 K- E  v2 Z. j! [* G( A  label-current
/ Y+ U" v/ D1 k2 l5 U6 ?3 s( x
8 e4 B* `1 f# H  set-default-shape turtles "car"
% y/ _  _' A  e9 l# n+ m" o! P! i8 X6 k  C- `
  if (num-cars > count roads)
% K5 ^9 d+ A) Z% S8 j* M4 p  [- N) s4 Y" ~- Y2 ~; k: c
    user-message (word "There are too many cars for the amount of "
) i9 H0 t3 d$ F* _# {                       "road.  Either increase the amount of roads "
: F& j8 P3 G8 R3 K/ t, y; b                       "by increasing the GRID-SIZE-X or "
5 C7 r6 ?- q) m2 K7 l" {                       "GRID-SIZE-Y sliders, or decrease the "7 P7 t# D9 b" m% L2 Q/ D2 {# s
                       "number of cars by lowering the NUMBER slider.\n"
7 ]* R* a/ |8 m4 S! a0 R$ A                       "The setup has stopped.")
1 I2 g" X& J1 `+ E    stop5 q+ K6 z- Z4 ]( \
  ]7 }  L; r* s, x: i! Z. q

; v6 m( |& }) U) A  e2 M) `  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color4 l6 y& o- Z/ t: ~, o! L2 U
  crt num-cars
* s. n4 d5 M% F$ }  [3 M( o3 U. {& R8 t. ?
    setup-cars$ i( @! U4 {. X$ {; P
    set-car-color8 c# C: F2 _% ?( E/ n  S0 z
    record-data
% ?# h2 g  C7 ^% w3 ~- q2 Q7 y  ]
# ~2 X4 H3 w$ p( L' q; w
7 c& I; c% T/ I  ;; give the turtles an initial speed
$ \- X9 I( p/ l. D0 b5 a* W  ask turtles [ set-car-speed ]
/ V- d; P) c4 F
! Q3 D; ^& J  F- t3 q( r  R  reset-ticks
) w9 R8 Z! S. oend6 p! V. ~# `4 b- D3 W; |
9 g; V9 r; k$ v/ ^# o$ v% w
;; Initialize the global variables to appropriate values
: i7 M- p6 ]1 i- {# z6 gto setup-globals; Z5 X1 }+ S- Y/ W! U
  set current-light nobody ;; just for now, since there are no lights yet
! S  |& Q( E; L* I9 i; P  }  set phase 0
" b$ _% Z8 i6 F  set num-cars-stopped 08 c3 z' F8 B5 [6 O0 z$ a
  set grid-x-inc world-width / grid-size-x& |6 @7 E5 g8 F5 `4 E% q3 P
  set grid-y-inc world-height / grid-size-y3 I8 S, t+ y5 F
7 O5 }1 c( u. W$ d+ l
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
+ z1 n1 c# W% F/ n- V. `  set acceleration 0.099( {* x9 _( c' E: A4 F3 S
end
3 ^! P# C+ D5 k
4 N& q: P7 _1 w" x* a;; Make the patches have appropriate colors, set up the roads and intersections agentsets,  R. z. _4 C2 ]4 q  ~+ K
;; and initialize the traffic lights to one setting
+ l6 x* C: L- v; E$ s$ zto setup-patches
$ B3 R) o% ]1 w. w0 `  ;; initialize the patch-owned variables and color the patches to a base-color
' P$ k; l8 C& ~! f( P  ask patches7 n7 Y! `. l4 o1 K9 p
  [  ]$ z3 I. d3 ?4 V1 v! Q. f
    set intersection? false) \1 r2 O* D2 y8 u% p: O
    set auto? false7 W0 e9 D: c& \8 H8 j! m
    set green-light-up? true3 n+ y6 [5 x& h( h3 M
    set my-row -13 e. f  w; T5 j
    set my-column -1& t4 M6 d0 R6 Y4 Q
    set my-phase -15 X: m- p- B% r/ }
    set pcolor brown + 3
# c* f6 `; c/ L2 n, i2 }+ a  ]' c$ f+ _8 S" V- x

( j  _# a( z: T: t2 N4 B! z! Z6 L  ;; initialize the global variables that hold patch agentsets
) D$ u6 m4 ~1 f9 |' C5 r! X5 s  set roads patches with
5 _4 w) ^0 B; m    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or( g; F% u' f! o9 P: S2 Z! ?
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]4 Y3 p4 e' n  W- e
  set intersections roads with1 x) u! W4 L% Y9 y/ _# c9 I
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and) ?3 c9 }5 m" r8 w. E7 W* _$ ]
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
- E+ v( p' p! T2 C# s9 E1 i
/ y1 r  G, c9 T+ B5 o0 N; S  ask roads [ set pcolor white ]# j* C' e; E8 [( |# s) _5 h
    setup-intersections
5 |6 R. H6 y0 H- dend  N3 p8 p& Z" e) c* u! ^2 }2 v
其中定义道路的句子,如下所示,是什么意思啊?
1 `# `# M; [  J9 R set roads patches with
* U$ n: F# d( N6 F, ~, [: ]% r    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or: Q5 o7 Y0 f( _' [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]! L6 A' n& ]. C+ J
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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