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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。( [9 }6 y' u/ f4 t+ M: ^! O
netlogo自带的social science--traffic grid这一例子当中,- Y8 @5 e. S. u( k5 a
globals) t" H1 y& h3 X; f
[
3 k/ g. ]6 H4 k' y  grid-x-inc               ;; the amount of patches in between two roads in the x direction- {* `% d. L2 I# s. B: W9 E
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
% @5 k# e7 B! V8 V% a5 ]  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
( l+ g- ~( @3 s3 S                           ;; it is to accelerate or decelerate
& H. r" r7 q8 q4 a  phase                    ;; keeps track of the phase
& U7 q" p, {. D, K4 {9 f& v0 i' y3 h  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
3 y6 @, e& }9 R. y! U% p  current-light            ;; the currently selected light: F1 r5 g' g& J# E1 z1 ~# W" |4 u

4 w8 q$ x; x" o  @* @0 I  ;; patch agentsets
( D4 d0 V: @0 ?: R; `7 {  intersections ;; agentset containing the patches that are intersections- H- A/ K7 J' `. ?
  roads         ;; agentset containing the patches that are roads
! c- B& T4 s- @6 ^: P+ |]( o. C8 t2 n" ~' D/ `  l
1 k4 |& u6 _, @! {8 k- I1 u
turtles-own
) v4 x( W' e; R- y: X$ `5 P* s[
9 P- j0 B$ ^6 U  i; Y* ^  speed     ;; the speed of the turtle
* [% q7 G- x  {) ~  e7 O  up-car?   ;; true if the turtle moves downwards and false if it moves to the right% Y/ n5 ~0 Y' L9 z3 F/ X+ N
  wait-time ;; the amount of time since the last time a turtle has moved
! @% k) x2 X2 j0 Z7 z  D4 p" k) W]* ?! Y8 r9 z. h( p7 Q
8 r0 ~  D1 Q# _1 `# b/ g
patches-own) a  b  M6 \: N0 v4 O- \* V" J
[
0 U/ _3 R1 U, m7 ]5 ?9 P  intersection?   ;; true if the patch is at the intersection of two roads
+ U* _6 C' @) e/ a. h. C  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
" z. w; H1 p+ C7 y  N                  ;; false for a non-intersection patches.4 a  t# q" ?6 P3 N/ {
  my-row          ;; the row of the intersection counting from the upper left corner of the5 f+ s& c& [: u: T! ~* T2 ]
                  ;; world.  -1 for non-intersection patches.
, ~) R; F: n8 S# a, l2 I) P  my-column       ;; the column of the intersection counting from the upper left corner of the
) _5 l9 X0 J5 A0 |5 c( E/ y                  ;; world.  -1 for non-intersection patches.3 `  |% P, ?" H2 S
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
1 `' G  N6 D* S  auto?           ;; whether or not this intersection will switch automatically.+ u) J& ?& J; F) j
                  ;; false for non-intersection patches.
3 {9 N+ Q! g4 M0 i]! w. `+ T! u$ Z: m) ]8 J

* }5 Z! C' K6 [- J  M
% z% a3 {1 B! |3 h;;;;;;;;;;;;;;;;;;;;;;
/ r, |, F1 Y. V4 w;; Setup Procedures ;;
( ~- B8 N1 p6 f' l. V6 r9 N( N;;;;;;;;;;;;;;;;;;;;;;
) ?4 i, X3 ~$ K; ?7 z8 X0 ~5 F4 n
7 q6 d8 H, g/ s+ \;; Initialize the display by giving the global and patch variables initial values.+ z: F, e( \$ P) W* G$ j$ a1 @
;; Create num-cars of turtles if there are enough road patches for one turtle to
0 Y; Q5 m; Y" i% j3 Q5 [8 f4 a" F: h: ^0 W;; be created per road patch. Set up the plots.; \: {3 E4 l) L, z* c2 m: A
to setup
7 y+ y4 b% e1 {' c" R% T$ w4 E3 W: B  ca
0 a) i, C5 V: r7 ^, X3 Q/ i, ]  setup-globals
! c  S" W; K, A" K' \: `& n# w4 n5 O- c* r
  ;; First we ask the patches to draw themselves and set up a few variables( U' U( J4 j  N: J3 r& [  ~4 b
  setup-patches  b( [# G8 b4 R5 h
  make-current one-of intersections
. ^( O) V) n$ O4 R- C* G' f6 o8 g  label-current
8 b& p6 \$ _# j6 z& R0 \6 a9 n9 i
& p) O, {: V% \# \' V# q  set-default-shape turtles "car"
4 V6 t9 |; B- B  \2 c0 Z' O' w+ A9 s0 k6 q
  if (num-cars > count roads)
8 ~, o3 V2 M8 i5 w2 z. o  [% `- M  a# _. S* y7 x: C
    user-message (word "There are too many cars for the amount of "
; M" L0 a9 L4 S, k: s: |5 I# c                       "road.  Either increase the amount of roads "
1 P2 B2 H' _( K; n                       "by increasing the GRID-SIZE-X or "
  m( M3 ?+ S# p0 y/ R                       "GRID-SIZE-Y sliders, or decrease the "
% {8 d: R( m  d. }' w                       "number of cars by lowering the NUMBER slider.\n"
: X& u0 |5 W3 z                       "The setup has stopped.")
+ f  H* \2 i8 J+ L0 x! R    stop: a& }7 o2 r8 C+ S3 N
  ]
: G: v3 @/ U* f( s& [8 f8 j- L( c& Y1 q, L9 ~$ a; [7 u
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color. u. J5 ~, V7 F6 L. n
  crt num-cars: j) a" Q, p$ Q$ u) v( W
  [3 r8 p9 Z8 W- C+ q: r* P
    setup-cars
1 a( n( w& e+ D  ~    set-car-color
# Y3 ]% W5 ^; r' h# w/ O    record-data$ g2 \" |6 Q8 t2 m
  ]
/ `7 `1 Z' J: ^2 E* G5 f
  y0 ^2 J/ D# C, q  q, J  ;; give the turtles an initial speed1 O5 t. i$ p1 I: Z4 k+ G
  ask turtles [ set-car-speed ]
" s, `1 c0 u- _5 B
8 G0 S; s$ g. K8 d) A$ }* b. S  reset-ticks8 |5 O* g1 t% O' m
end
' G" G  r: f2 X& x
7 e3 F$ J1 u1 n;; Initialize the global variables to appropriate values
  Y# z* I  _" O  ]4 xto setup-globals
; i7 N! H8 m3 \2 ?5 O) h  ^  set current-light nobody ;; just for now, since there are no lights yet6 a# b( Y0 K5 w7 ]* S
  set phase 0
1 U5 i4 o6 b1 z8 Z0 n  set num-cars-stopped 06 L" i! d1 H. P  `
  set grid-x-inc world-width / grid-size-x0 C/ r/ Q) a+ K5 F" ^# k( _
  set grid-y-inc world-height / grid-size-y
" {7 \3 y& g0 G, |1 r! \! R; |
4 X$ r9 x( T" C+ _* K0 |, Q  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary3 [4 C5 s* U* K
  set acceleration 0.099
# P) r6 G( {& A$ n/ yend
& U  i: I1 l7 ]1 X. D/ z; N  j/ p% T" R7 e2 b. ~( M) M
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
4 r/ y& B7 C$ V! V;; and initialize the traffic lights to one setting( V$ ~( K9 l; n
to setup-patches
9 N* {5 `! K6 s2 ~& }6 {2 _* I3 F  ;; initialize the patch-owned variables and color the patches to a base-color0 ]  V4 M. b+ f) }: n( ?
  ask patches( ~+ d: [" |9 |- q3 T
  [
+ ]( G1 A, q0 @; D$ M' m6 }% Q" ^    set intersection? false+ k3 ~% J# ]! E  O( W7 B- F
    set auto? false7 |& b. s# M/ z4 q: X! ^; ]9 S( M" y
    set green-light-up? true( M, Z! e8 b; P( r3 H
    set my-row -1
4 z. @7 p! n. T4 l9 D3 C' d4 U    set my-column -14 H' h! d! W0 f; N; k; ]' F
    set my-phase -1
2 u- ?& ~2 ?, ^) L( [    set pcolor brown + 3
. p8 w8 G4 x5 U9 ^: f  ]  G0 V% F/ j5 M, g7 d0 j
7 B' _8 K( B5 c" b
  ;; initialize the global variables that hold patch agentsets
6 G3 p: P/ {& Z) @; ^. {# u  set roads patches with
$ \& b* w" v  q    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or5 h7 C1 {7 |8 s) a8 v
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]# j, l$ G, R4 }
  set intersections roads with
8 V0 X/ U1 f* i# n9 o/ `( _    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
4 L. e0 L. o) S) `& v6 o    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% O+ a( H: {8 ]
+ a/ b2 |" H# j- M  ask roads [ set pcolor white ]8 f2 I& j# w8 N: g0 K( }3 [& Z
    setup-intersections
8 }# K8 z, E1 Pend+ G; X, S( H! t  j
其中定义道路的句子,如下所示,是什么意思啊?/ N* r6 h  u9 [
set roads patches with
$ A6 f9 V* I8 s/ O% M    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or; a4 t6 M0 C# Q0 K
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
% u" @- W" Q5 t, f# q- 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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