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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。
, ]: f( _% J" v7 Bnetlogo自带的social science--traffic grid这一例子当中,: E+ q: [1 o& d8 v/ M9 L# ^
globals
( \$ V0 X# Y+ b3 I. o  G[
) T; B! l8 f( p5 x0 N# Y  grid-x-inc               ;; the amount of patches in between two roads in the x direction
6 r! C# I+ X* y5 b7 K5 w  grid-y-inc               ;; the amount of patches in between two roads in the y direction
+ S4 s6 m5 w. {+ H8 k+ M  acceleration             ;; the constant that controls how much a car speeds up or slows down by if5 q: H5 k) j8 Z# y" B
                           ;; it is to accelerate or decelerate
# J  @. @3 h9 y7 E8 c; S' X  phase                    ;; keeps track of the phase3 \7 @6 k1 Z. k$ Y7 W
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
6 s2 @: E. Y" F5 O! p. x8 Q4 o' `  current-light            ;; the currently selected light) s& P6 _$ [3 v" n# A7 P
* B& Z8 y7 w& p
  ;; patch agentsets
( r$ O3 r, a  i" {# V' G8 R  intersections ;; agentset containing the patches that are intersections+ A8 l2 y, J/ _, \+ J
  roads         ;; agentset containing the patches that are roads4 ^2 m: k1 O* A2 h
]
* P: P# a( I; Q% ~0 Q8 u, a$ t" k/ ^, O
turtles-own3 U  Y& U: l$ u, j
[
) T) l) X& u7 f% b. Z' K  speed     ;; the speed of the turtle. s- f; u3 J0 U# t+ @* C8 q( n
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right3 M# H3 E3 `6 ^7 f
  wait-time ;; the amount of time since the last time a turtle has moved
1 S7 V4 p9 w7 \6 V' z1 |$ J2 l]
+ O; A9 m$ d3 R* {
4 s* u( N% n+ t' y! D; ]- tpatches-own. A- j& i7 {1 E  y) ?
[
5 Y8 {0 C' _* e6 u, h) s  intersection?   ;; true if the patch is at the intersection of two roads
! ?8 A. t9 e9 `7 }  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.% v8 d5 }7 o. f5 y0 [3 E
                  ;; false for a non-intersection patches.& [" F4 ^+ c6 V
  my-row          ;; the row of the intersection counting from the upper left corner of the3 [  K/ \! t6 z
                  ;; world.  -1 for non-intersection patches.
3 _# w" b/ o5 X. G* M7 B! K! y  my-column       ;; the column of the intersection counting from the upper left corner of the
. v! e$ a4 |; }- X                  ;; world.  -1 for non-intersection patches.
. z( `* b8 Q5 L  Q4 Q& ]  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
9 U0 g' m6 _2 x  x" P5 Z5 M  auto?           ;; whether or not this intersection will switch automatically.$ A) ?% L# Y7 k, U+ ]% K# d3 V
                  ;; false for non-intersection patches.
! W! x2 i( Z- p+ y  T: C" W]
( O& [0 B! F$ u( I/ ~& e) f/ _! |2 J3 e% S

! _; j  q, o$ A7 w;;;;;;;;;;;;;;;;;;;;;;( a9 K7 i* j( y" H. M8 f0 w
;; Setup Procedures ;;
0 q2 w* g3 d& o* f;;;;;;;;;;;;;;;;;;;;;;
, C; G- U( Z, y! c7 [
4 ~4 R6 A7 ?+ J;; Initialize the display by giving the global and patch variables initial values.
0 k; ~4 b1 O* ]5 u6 O# u;; Create num-cars of turtles if there are enough road patches for one turtle to- u3 _9 Y8 B- C' A
;; be created per road patch. Set up the plots.! U0 F* ?3 X- z6 }# j! J7 f
to setup9 x; }  m, d" ^. g6 q
  ca2 X. }, I7 }0 T! o8 c4 h" J
  setup-globals
* o8 b; l$ _( \1 Y6 f' |% t: [4 M: s# e
  ;; First we ask the patches to draw themselves and set up a few variables
* @/ X2 T9 J5 S& z: V& M2 y. L8 k6 B, O  setup-patches, z% \. \0 a# k3 @$ `! t; v0 \
  make-current one-of intersections
- u6 |- u1 {1 r! r$ F  label-current
& h. s7 o, T# s/ Q+ i3 U4 F* W# s( o/ x+ p9 Y1 S1 T* n
  set-default-shape turtles "car"! G# f7 H3 K+ l7 L! f9 d

2 W- h& z$ v( F8 \  if (num-cars > count roads)* H: A4 @+ x1 W1 c  G
  [+ r: f% b- k3 [. i  v
    user-message (word "There are too many cars for the amount of "
) S$ y: W, B% M3 n6 M8 b' @0 O                       "road.  Either increase the amount of roads "% Q7 n! X0 s& }$ y
                       "by increasing the GRID-SIZE-X or "
; ^* A) e$ s6 b5 n, ^* V0 Y                       "GRID-SIZE-Y sliders, or decrease the "
4 H' h; \& X( z$ e                       "number of cars by lowering the NUMBER slider.\n"# ?5 F! a4 \- i) B
                       "The setup has stopped.")
& _$ Q6 ~* G- B& P! I3 D# E    stop
6 G7 T4 x6 S' u3 {4 S3 m  ]
5 p; S" D7 S; H. m4 T1 _+ W1 }4 k( _" ?2 G
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
- g0 X1 w. C; U3 Z- E  crt num-cars
  j$ u5 G3 m9 [# @, \' Z  [# C; F2 p( L9 t: ^* Y3 T
    setup-cars, o5 d  P# N0 ~( H% x5 T% }- \
    set-car-color  x0 z- E& n5 l" n% w! g. O# }
    record-data
7 M+ r# C$ V' S1 m# f  ]  ?/ p6 v% u9 H
1 K! D2 e3 N3 L) U
  ;; give the turtles an initial speed4 k' H  U0 H( y  W
  ask turtles [ set-car-speed ]
) [5 m  M! x" {5 g7 h" ^
8 i2 y0 J- C9 H- L6 F  reset-ticks
. t6 W% M# ]- I; M8 iend  n# L: Y0 G* O$ Z$ i) U, S
( n) \: k$ h. d$ [- G
;; Initialize the global variables to appropriate values
+ G. w) ~6 z" h% |to setup-globals4 g8 \5 h/ \& c6 ?4 u% f4 N7 `
  set current-light nobody ;; just for now, since there are no lights yet
+ T0 k4 C3 ^/ L; f) S  set phase 0
# \$ S5 }0 y* a3 }. r, F# f  set num-cars-stopped 09 k. L' P' _9 t* p, z9 T+ H6 V
  set grid-x-inc world-width / grid-size-x8 u% }3 C- `  [
  set grid-y-inc world-height / grid-size-y
" z5 l. I$ Z8 c: [% Y
/ _$ f4 S3 k# O4 h  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary7 m* M; k8 V7 p/ J. X) V
  set acceleration 0.0991 Z* A5 \1 l9 U; ?: h
end( {/ H9 Y% V; ]% R* n2 ]
* S+ I% G/ v1 f$ t% h
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,' g- m* z9 d, I$ e' ?% Z4 ?
;; and initialize the traffic lights to one setting- I' k% w/ k" A9 s/ J- V
to setup-patches
: a2 ^1 k; A7 w  ;; initialize the patch-owned variables and color the patches to a base-color
* |$ }/ W( l- `" h5 ^* H  ask patches' r0 Z5 i# O) o8 A% w
  [
5 J6 a2 M+ }* r# q. I; O( t    set intersection? false
, C& P" P7 \, m+ b, `  ^    set auto? false
* t7 H$ l- G! D" e    set green-light-up? true3 ]# f* z5 b- |; ^, m. t5 x
    set my-row -1
. q- U# M" l" g- D9 U7 L+ c6 d    set my-column -17 p9 n. M+ g$ }7 s) v3 v2 k, p
    set my-phase -1" V1 c5 r! |$ a4 F
    set pcolor brown + 3
0 }* {; C. ?; f  ]7 Z/ }# t* P$ X, Q

& z2 v9 \! }8 _. F  ;; initialize the global variables that hold patch agentsets- _  z0 B9 y8 \
  set roads patches with
2 t8 g" @# @* W7 R    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
. G2 t  i7 |* \# N% E    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]( g$ v- Y2 N6 o( P8 S: V0 u. Q
  set intersections roads with2 U3 a3 g" L* y
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
7 C* h3 i- x2 F0 `" b; K    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 j/ S+ |+ `$ z7 S" r( S0 }7 ^6 e
& n! a7 W/ `5 v& B7 e/ T
  ask roads [ set pcolor white ]) [3 n8 R$ r' r- S  k& K3 G
    setup-intersections
! D% l5 m2 W9 @. |' K# Bend
* Q. j8 x7 t+ `! \- Z* I( p2 [  r4 j其中定义道路的句子,如下所示,是什么意思啊?# s( S/ n9 h9 [# l
set roads patches with
0 j! s& x* y7 Z6 s+ T    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or9 J. A) p6 V: m% y% _7 s0 R
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]1 ^0 T$ k, v8 U2 c; Q% H8 @9 n4 r
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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