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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。& ]1 A6 ]" h! E
netlogo自带的social science--traffic grid这一例子当中,2 j7 f( q' ?# ^8 J: b
globals; u& o! }# T5 K- y; v
[) t& ]" @- a& r5 @
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
0 q* A8 r  D7 k% S% B/ P5 d  grid-y-inc               ;; the amount of patches in between two roads in the y direction( c5 z& }$ v2 t1 o% p
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if# g+ o5 ]8 u& s1 r
                           ;; it is to accelerate or decelerate7 z2 i; R& G' Q' |1 t  G' K
  phase                    ;; keeps track of the phase
+ }( }/ O* ?3 f0 d* W  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
7 S! ]: i% V. D5 T) C0 @7 d  current-light            ;; the currently selected light; ?  g  r* x/ A  A% R

6 N& Q1 `+ r4 s1 P0 `4 P  ;; patch agentsets8 ^2 X* U4 s5 t0 F. r  l1 y# m
  intersections ;; agentset containing the patches that are intersections
( _" _7 ?. F6 I2 S$ |; V! L# O, q  roads         ;; agentset containing the patches that are roads; P8 V3 X8 O+ i+ I/ ?
]
/ E7 [- R, g- D- _' B( O. I# s. D4 w& C9 y8 G1 w, r* d- `2 P* D
turtles-own9 O% y) m# T$ |8 x1 |$ y8 V/ I5 |
[, C- D' ?. A8 L* `: e; i& \
  speed     ;; the speed of the turtle, M8 a) t6 C( g' B5 {
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
5 W0 `' t1 }! T1 g  wait-time ;; the amount of time since the last time a turtle has moved
7 X1 M; b8 C: M( H" ]8 h! m( O], {, Q! p3 \2 w% n8 b+ o
4 J, T& n* S( K" A4 M4 ~
patches-own
+ Q$ l6 |( ]/ I( G8 G[
$ \( o% @4 M4 z  D8 X& K  intersection?   ;; true if the patch is at the intersection of two roads6 Y. J1 E; M$ O" |% r' s
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.: l# `% E6 }/ Q: Z
                  ;; false for a non-intersection patches.& x5 {/ f  S; O" M8 A. J& ^
  my-row          ;; the row of the intersection counting from the upper left corner of the
3 K1 q/ L5 n* e9 M0 W0 d                  ;; world.  -1 for non-intersection patches.3 N$ U) n! u. @( A; v- v; d
  my-column       ;; the column of the intersection counting from the upper left corner of the
0 h+ i/ S& u, `% _                  ;; world.  -1 for non-intersection patches., W7 k( y/ a& L
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.) L+ G" ~# j% r# G
  auto?           ;; whether or not this intersection will switch automatically.8 N4 h7 Z7 h# R
                  ;; false for non-intersection patches.
& m; G( f3 p& s; s" m4 D/ h]
9 @, F/ H) N0 ]/ C  g/ _' M
9 c6 x4 s% F: u+ }" |6 v  v! b( P, x  b7 K* a' C5 W* \- C
;;;;;;;;;;;;;;;;;;;;;;
8 b/ y( H- T% Z% p& B; @3 O;; Setup Procedures ;;
0 ?! J; e: B* a( f: };;;;;;;;;;;;;;;;;;;;;;) P; f5 N& \1 C: `, R2 u
; v, N9 X) ~% Y6 Y; H* y: Q, y9 d
;; Initialize the display by giving the global and patch variables initial values.
; g5 X5 p" S. R' C5 c& v;; Create num-cars of turtles if there are enough road patches for one turtle to" h& j9 A: P9 T) b$ h* \6 e9 M/ C; [
;; be created per road patch. Set up the plots.3 N; Z, v" S4 t: r6 L. b$ [2 {- e
to setup& w# u; o+ [) h/ o1 d
  ca7 j' d: D2 v) Q9 F, h& A" e2 Z
  setup-globals# d1 g$ `% Z* w6 k& D
5 k4 o6 f; c; H! R8 k/ h7 s
  ;; First we ask the patches to draw themselves and set up a few variables% k* L+ A* `& w9 _  F
  setup-patches' Y% v' U0 |: N9 c
  make-current one-of intersections9 t: E/ P1 N$ ~# ^, h: ~
  label-current, K; S/ Z  \* Y

: _0 J# J4 C) g+ k* Q  set-default-shape turtles "car"
( Y# W. K1 D( `8 q$ l% N$ O5 t& v: r$ m% {
  if (num-cars > count roads)8 \2 A$ h- L8 \0 F- q% ~. i
  [
* f5 g$ c3 Y) A" y/ }/ L8 r    user-message (word "There are too many cars for the amount of "' h9 L3 d7 p) ~" A  j
                       "road.  Either increase the amount of roads "
0 b& Q6 }  k' Q% C                       "by increasing the GRID-SIZE-X or "( X; l  {* K4 N
                       "GRID-SIZE-Y sliders, or decrease the "
9 a) f$ z- S$ E5 l8 o) k                       "number of cars by lowering the NUMBER slider.\n"2 l* b0 M# {6 r( R1 B4 k
                       "The setup has stopped.")3 g+ V3 `$ r8 j/ I% Q
    stop
: b5 O' k8 L: \( J$ y" q  ]
0 {' Y: o5 h& H+ }" N  P; b# C; \
7 h3 A, n6 r% R* D7 z5 W: |4 L2 U. o  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color% v0 J7 X$ H, m% H, E
  crt num-cars
# O/ [/ W8 E7 d5 E+ i& T  [1 K0 D9 l( O9 |0 H
    setup-cars& F. r, W) R1 U5 V0 R
    set-car-color2 ?& s/ x/ R5 d* {& ?
    record-data
. {% ~! E6 F3 k  ]6 d2 Z+ Q# K( `9 r: d# i" Z2 O

6 J0 g  c! o- d( _4 p0 H5 V  ;; give the turtles an initial speed) k3 V6 r( U! ~  J& u
  ask turtles [ set-car-speed ]+ o/ s# `! Z+ [0 z& K

) ]& ]1 e! h; j8 \* Q  reset-ticks
/ E" |$ S1 l4 M3 U2 Y* mend
% |6 ~5 u; b- ]# H! z+ i; J
9 o% D/ w! ?0 ^. z' O: h/ _( S# r& l;; Initialize the global variables to appropriate values
0 X3 p7 |( D5 A8 P7 t" s3 R4 @to setup-globals: T; }1 \: D3 ^5 V' o$ N0 p
  set current-light nobody ;; just for now, since there are no lights yet' f5 \4 b0 ^; y$ g
  set phase 0) S0 {, C8 o) N9 O. l
  set num-cars-stopped 0
) V) `5 z9 W- G4 G' T7 _  set grid-x-inc world-width / grid-size-x
* T3 _+ O6 C$ r2 \7 Y( r  set grid-y-inc world-height / grid-size-y4 g3 \  ^3 \9 W4 h

3 I4 c; M" n" m5 l. v/ Z7 j$ }$ v  w. g  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary/ a& k# [7 d! B5 \
  set acceleration 0.099
# l9 m6 g1 T. v! B2 O1 @$ bend
; F# L8 y& e& t; p% O  `5 c$ |3 _  \8 a7 b& i# R2 b
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,2 b# }$ a6 T/ L: ]% E  m+ t. D
;; and initialize the traffic lights to one setting' E7 N, a( B# @1 u  {# T* y
to setup-patches
' ]$ |: Y8 e" E5 L4 i$ `  ;; initialize the patch-owned variables and color the patches to a base-color
: L& b0 Y. L1 b. U5 j9 P* A  ask patches& N& G  F2 T3 @8 n6 e3 t3 A. G1 R
  [, r0 E) i6 V, L( o, U+ h* A- n9 W
    set intersection? false" _) A+ ^  `6 f9 a% e& T
    set auto? false
/ J4 ^3 \  A' |2 _: q$ I9 n    set green-light-up? true
: R! o' D  ], |    set my-row -1
: C4 x. Z, F$ s+ F/ K$ u0 K1 T! E% n    set my-column -1
* H, f; c% Z9 \% `( ~    set my-phase -17 _! q4 Y: f8 i9 x
    set pcolor brown + 3
* r  ~; a, u' |2 K4 I" j  ]; X8 T1 g$ N" O8 t$ _, E
& [* z( h5 B0 {8 Y( D) q. T, `
  ;; initialize the global variables that hold patch agentsets
1 [: q+ P% B# I& K. w  set roads patches with1 i! U" N- f7 l( R( s
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ }! |" B# l8 y. v$ s/ l2 O3 Z    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]! U! T0 e: N+ v, R. [1 @# T
  set intersections roads with
! J/ P( m4 w. u7 K0 j0 K( M    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
0 ]* ]& s+ w9 D. u3 X8 R" h    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]( \. W  X' B+ k( v4 I
7 N6 b5 Z) j9 k5 I
  ask roads [ set pcolor white ]
( X+ j8 ]2 F8 E9 f2 o    setup-intersections: N& g$ e8 ?2 x5 l3 R
end! ], |/ t0 V: v" X2 `
其中定义道路的句子,如下所示,是什么意思啊?
1 X7 M1 e7 j" D/ I set roads patches with$ l" \: `) H2 T9 o6 a$ p; K0 X
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
- J6 ^& V# J/ e    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
/ W2 u  V- s. S4 t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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