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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 V8 h4 {# ^# v  e' Z
netlogo自带的social science--traffic grid这一例子当中,3 _5 Y, C5 g4 h8 B4 i4 I
globals
: a; a6 s8 @! a[4 u; m6 W9 ?: M& L
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
  M# F# m; h7 X- p* O  grid-y-inc               ;; the amount of patches in between two roads in the y direction9 M# g) e4 ~5 c
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if6 y1 T) s% ]# ]' J' @+ U
                           ;; it is to accelerate or decelerate
7 I" I& {4 V7 |& f& Q1 L% O9 K, y' E9 w  phase                    ;; keeps track of the phase
! Z' O8 d9 N( O/ V) h  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure+ F" Z4 ~- }% s' O* c+ i* L) H' [
  current-light            ;; the currently selected light
, \$ Z0 W% A$ S# s/ \: u6 w* `3 Y3 {1 w
  ;; patch agentsets! C' f) b, P7 v' b, [; H% \
  intersections ;; agentset containing the patches that are intersections
$ d9 l" o  B( X+ A# I# M  roads         ;; agentset containing the patches that are roads
3 ~( V6 |2 p: x/ L& a* [5 x]$ I; [9 l. M$ a1 j" O0 x+ A$ o
( g& i. b& H; S: V
turtles-own. V" g. G# X2 T8 u
[  O% D$ L1 y: X1 ]
  speed     ;; the speed of the turtle1 `9 ?" y, h2 V: r, A
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
( M* Y0 p) q5 r. D+ f  wait-time ;; the amount of time since the last time a turtle has moved
, U$ Y* U0 F1 p, N7 q/ S! `! h]
$ a' `% R: S( T& l& F" s2 j# F6 Y2 K$ O' l2 I( B) }( P
patches-own
4 H  n/ E- q& n( C+ M[- ~5 E' T0 h: F3 P8 d
  intersection?   ;; true if the patch is at the intersection of two roads  r9 j+ i. I: p; a* M
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
: x# ?& f  U7 `- p$ t                  ;; false for a non-intersection patches.
5 R7 l2 v. F& Z# Z4 V, s4 g  my-row          ;; the row of the intersection counting from the upper left corner of the( N% d6 {+ j6 R5 p0 J
                  ;; world.  -1 for non-intersection patches.  W( r2 s/ k; c' n
  my-column       ;; the column of the intersection counting from the upper left corner of the5 M; I" n  Y2 r2 n  g* S8 a& F# {
                  ;; world.  -1 for non-intersection patches.
; y) N7 x& {+ P/ L/ j  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
5 w$ N: {6 d3 n+ G: ]- L9 i- p  auto?           ;; whether or not this intersection will switch automatically.3 a/ g! r+ J# k# E- j
                  ;; false for non-intersection patches.2 S3 H3 r- G4 b, {" k4 F
]4 q8 \) p$ E9 {/ n6 ^8 p

! }) g7 p8 I* Z6 W  ]- Q! R1 V2 R4 W2 P5 ~, i
;;;;;;;;;;;;;;;;;;;;;;9 d9 C( B; t. S# V
;; Setup Procedures ;;- O8 }3 k' n9 d. f/ y
;;;;;;;;;;;;;;;;;;;;;;0 q2 Y. h  A2 H& A$ G3 E
  q+ B- I" ^9 V
;; Initialize the display by giving the global and patch variables initial values.( J/ ^. N. r7 {- N6 X3 N) R
;; Create num-cars of turtles if there are enough road patches for one turtle to
$ r  X) y  E! r6 g/ n- S) C1 q# x$ C" `;; be created per road patch. Set up the plots./ G9 w* M0 z' `* I: J" t
to setup
- C( \( `: w1 m2 K& H& D  ca
: O" K6 G8 i* L: X  setup-globals
; q# G1 b) ]7 ]. [) F4 W8 g" s
$ }6 L/ ~  O9 R# j" u  ;; First we ask the patches to draw themselves and set up a few variables
  N# ~& ^( O6 d8 N" |  setup-patches" c. k6 y- R# n  |( `5 m3 H4 P* @
  make-current one-of intersections: F% P. K9 b' ~  k" N- V' O
  label-current
- `1 n/ B8 N" a* s8 d# ]
  V, s! V2 y! L  x9 F$ ?1 }5 E- J  set-default-shape turtles "car"
8 z) T4 \4 n8 b3 \8 M4 c$ }! f. A6 b$ J5 L* _, x2 Z$ m
  if (num-cars > count roads)
8 c1 `* f% I: m& ?9 {  [
" ?: R- Y: e$ c6 P5 `    user-message (word "There are too many cars for the amount of "; Q9 y* j0 x3 f: ~
                       "road.  Either increase the amount of roads "
. y0 i8 Z+ X2 M                       "by increasing the GRID-SIZE-X or "
9 o2 _! C" [5 n& A$ @( }                       "GRID-SIZE-Y sliders, or decrease the "
0 H# i, @, f$ |, h  u8 l0 U                       "number of cars by lowering the NUMBER slider.\n"
9 m6 ^* i- A3 {, q: [) ?+ u                       "The setup has stopped.")
" m% U) E2 G7 b; p( ^4 t    stop# Q. r& |- Y9 e! l5 s9 A
  ]
# @9 y% {9 e: U  s; |+ y. M
1 ^) I8 v. }& g( o3 X# Z  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color  X5 X1 [/ Y8 F9 o1 J5 }! d
  crt num-cars
5 R( j/ q; s% D+ p, e  [
5 M9 r0 d& k0 ^    setup-cars' e# B1 s# }4 y  ^" M
    set-car-color8 n3 j8 {  k, Q) B5 b4 F
    record-data8 R7 N* s0 g5 X' i; N
  ]
4 J, Z5 ]9 O5 d! |
( v2 r& v! N6 f  d+ E, Y  ;; give the turtles an initial speed
) l8 ?. M) i& P: R1 {$ I2 ]1 o+ V  ask turtles [ set-car-speed ]- e6 k. N; |4 k2 I
' s5 M! o( C8 U3 s  g
  reset-ticks3 }7 v: m7 y6 }, M4 ?
end
! C& i' V9 ~+ S* i! \5 j* z- O0 ?5 P/ r
;; Initialize the global variables to appropriate values
- v% @4 [) u% I1 I/ Pto setup-globals. p  ]3 Y5 j% l
  set current-light nobody ;; just for now, since there are no lights yet' S2 Y9 m( Z) Q4 f1 p% v
  set phase 0: n2 M# j+ p5 H% ~6 A$ z
  set num-cars-stopped 05 H* U5 G' `' |. H
  set grid-x-inc world-width / grid-size-x$ W& N" Y9 z6 j4 E4 J5 H# C7 P! Y
  set grid-y-inc world-height / grid-size-y
& A2 }7 X( c% S# R; X: C/ m5 }6 M, Z- R) M9 _4 X  R, b% k
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary% N% u' g, s5 c
  set acceleration 0.099$ o$ w; Y& f2 H9 G
end
& q  x4 `2 k  v1 Z/ P7 E  L2 O% x% S2 t  l
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,  \1 M9 H$ T% o! \8 o
;; and initialize the traffic lights to one setting1 k0 u2 K3 x. P4 A9 ?* E
to setup-patches9 H2 ^9 }7 ~0 {# g
  ;; initialize the patch-owned variables and color the patches to a base-color5 x4 B1 t0 R9 h' g5 [
  ask patches
6 U5 A2 Q9 G- T5 }8 y  [
+ k; D8 U3 ]( y( D4 y( N1 B    set intersection? false
' Y" Y/ B9 q3 w& |  T    set auto? false
+ k0 _1 `6 X  b, d: ?$ F6 i    set green-light-up? true- A) H0 R' J$ h
    set my-row -1. s# ^, L6 P; R' `# r7 P
    set my-column -1
" t( W2 b  V8 u+ z6 }8 A    set my-phase -17 Q8 ?9 t- k( y
    set pcolor brown + 3! }* V, [# d: V/ W# |
  ]! J, r4 F5 e' L& |1 C6 ]. t

$ K* I8 {; ^6 n  X  ;; initialize the global variables that hold patch agentsets- ~9 t% j6 _; f  ]. ]: c% f7 Z( F
  set roads patches with
' {+ r2 P% ?6 p& ~3 Y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
# J2 k! V) [" q% S    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 j9 y9 ]0 \6 |& b7 X. O5 e  set intersections roads with
+ r/ P- @: b& N4 p$ C! X    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
" v5 j6 x8 g. G  q    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% y4 G" q0 g. }' c% V! B; X: y# V* ~* H( e2 u% q& Y( d
  ask roads [ set pcolor white ]% d) G; S* r9 O) m- G% x" A
    setup-intersections
6 c3 R8 P" s. K8 m1 J! Wend
9 w! p( @! j; T其中定义道路的句子,如下所示,是什么意思啊?* H- g, {: L: N  C) n! E2 S
set roads patches with8 b; K8 ~" _% F' V. X' P0 d8 V
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or0 Y  H! _1 f- v
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  N9 X6 m1 t; k) g7 e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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