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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。
+ D7 N; Z7 s- `# a8 n8 o. u+ Tnetlogo自带的social science--traffic grid这一例子当中,
2 q, G  G  t* F8 Rglobals( H% n) d4 z+ W3 Z! {
[) l; G9 w( R; J+ K' q
  grid-x-inc               ;; the amount of patches in between two roads in the x direction* ]% `6 m7 j' z4 N9 o3 @2 n( ]
  grid-y-inc               ;; the amount of patches in between two roads in the y direction) T2 G: `- i" g5 X7 D8 n% h
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if2 ~# N7 u4 x$ |6 D: I3 D
                           ;; it is to accelerate or decelerate  F2 A; p9 g3 w- Q; s/ i! ^
  phase                    ;; keeps track of the phase
# [/ D8 @" z/ H% H0 Z7 a7 |  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure( I7 `$ i% f+ m2 z# Y9 p0 l5 X
  current-light            ;; the currently selected light
. F: a. E2 t  X3 t) ~3 R* }+ e  }" v) ?9 l  X
  ;; patch agentsets6 I" O' F) T3 i" Q; N, P
  intersections ;; agentset containing the patches that are intersections
& l% l4 ]$ O% f0 f. p  roads         ;; agentset containing the patches that are roads+ v$ G; B/ w8 y/ @% o8 u
]
2 z; [9 e# F- a" K" K6 |3 q* f; z& H& t. t& x) E
turtles-own" u- k6 l3 @' N/ G+ q8 Y
[
  |4 w# d, ^# o1 j1 B8 }5 Y  speed     ;; the speed of the turtle
' h  r9 g. ~/ [) V; V4 o% y  up-car?   ;; true if the turtle moves downwards and false if it moves to the right' J/ e& B, b5 X! }0 e( N% \
  wait-time ;; the amount of time since the last time a turtle has moved
+ Q2 T" K+ s5 E: I* _]1 b# R4 b) q) R4 x* P3 M/ a
# F3 B8 ~7 D5 v5 v/ y
patches-own
9 o% v3 t& S. x  u& u" c$ d" ?+ B[
6 |3 _$ L! L5 I/ f& n! B+ p$ T  A" g  intersection?   ;; true if the patch is at the intersection of two roads
/ ?& V% L* V% q1 V/ x/ l" Q, j  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
! @* s0 Z2 L7 L3 h. x! K* D- S# a                  ;; false for a non-intersection patches.  U8 h& s. Y4 V! P9 ^$ |2 W: S
  my-row          ;; the row of the intersection counting from the upper left corner of the0 }- t4 }3 H1 T5 O5 _# q: F
                  ;; world.  -1 for non-intersection patches.( B+ j: f8 G2 s& ]* D; p4 I5 E4 O
  my-column       ;; the column of the intersection counting from the upper left corner of the+ h: k0 N0 V( D% v4 F% r
                  ;; world.  -1 for non-intersection patches.
, I3 t& |, v) L/ N  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
5 e8 r7 J2 [( i7 U- ]  auto?           ;; whether or not this intersection will switch automatically.
" W0 b, R+ b5 ]2 _# ]3 Y/ B                  ;; false for non-intersection patches.
% L' b% |* }& e4 v]
! }9 @" x2 v6 F  P: U+ I8 Z2 k* _" Y/ h, E+ T) F( @4 j1 M
: S! Z- }& I0 G/ M$ c
;;;;;;;;;;;;;;;;;;;;;;) I8 X1 f4 v7 s# ^
;; Setup Procedures ;;
, A$ k+ C7 ^- T) K' L& [;;;;;;;;;;;;;;;;;;;;;;
7 V; M7 X6 _, |/ Q- F3 G& \: l4 i0 K8 h4 J& f. @
;; Initialize the display by giving the global and patch variables initial values.- l2 R" E; T* R9 H& x: u
;; Create num-cars of turtles if there are enough road patches for one turtle to9 r# z5 R1 G" e3 P, k
;; be created per road patch. Set up the plots.* Y7 p3 i8 Q) X9 K; K
to setup% C& J2 N2 X2 Z* j* d, i" {* z
  ca' v$ k" p: Y8 x- F" Y9 r8 a9 O
  setup-globals
! M. c$ I0 a- a+ ~) g& M2 o# s2 f) a' J  V
  ;; First we ask the patches to draw themselves and set up a few variables/ Z! b9 ^- o; E2 l5 T/ z
  setup-patches6 Z# ^- D9 _: Z+ \
  make-current one-of intersections" Y1 V* t: d% Y8 v* A. a8 u1 ~. V
  label-current
! E" [! c, K% ?& x
2 u- L) |- w$ ~& t  set-default-shape turtles "car"5 |1 {3 }6 S4 L; F/ R3 }' A" o

: N6 Q6 J5 V! p7 a( O! N  if (num-cars > count roads)3 U& L0 ?7 ^1 o4 K" Z' W4 u% @
  [5 e" ~9 E  _, @# p
    user-message (word "There are too many cars for the amount of "
4 U7 t, |# j# h1 ]                       "road.  Either increase the amount of roads "5 H: [8 X  S; B- l. T
                       "by increasing the GRID-SIZE-X or "" h+ h  r, y$ e0 g# V
                       "GRID-SIZE-Y sliders, or decrease the "  ?; C0 k1 T# y- [: @; w- O$ F, G
                       "number of cars by lowering the NUMBER slider.\n") L# Q* x7 ^0 T7 c
                       "The setup has stopped.")
7 s6 E; w" M3 t5 w    stop
& a$ S! U7 E  }) ?( ~6 x* e7 Q  ]
% y: u6 u5 T3 r% E8 y. m/ I5 w0 H. t/ p+ b! W
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
. ^2 b5 l' }. H. s" i  crt num-cars+ f& ^9 U$ M& R# G
  [& \& p, l6 Q6 |+ _2 u
    setup-cars9 Q$ p( z) R# U* P: o$ `
    set-car-color1 [/ J, Z$ ~9 k0 g
    record-data' `2 K& A, b. ?# I
  ]# i  O+ _3 s" ?0 T

$ O, M6 L( Q( A% `+ s  ;; give the turtles an initial speed
* r. f; I2 P1 N- ]) W; z$ U  ask turtles [ set-car-speed ]
+ B6 k' ?4 c, a7 M+ K( N
; q: C0 {" R7 f1 ]  reset-ticks, V2 [$ l2 t5 `( i2 b3 }1 k
end3 ]* L( ]( }3 v; x

6 [7 w" L3 p& Z;; Initialize the global variables to appropriate values4 H: I+ D  k; v
to setup-globals
+ g7 x  e& J0 N. l9 S- J  set current-light nobody ;; just for now, since there are no lights yet( ~) M- `, A  h0 o1 y
  set phase 0
  ]2 }, a) d# d6 l  set num-cars-stopped 0
1 q$ i. W' O2 y# N* Q4 i: @0 p  set grid-x-inc world-width / grid-size-x
/ y. B. r" Y( x2 D3 X) L  set grid-y-inc world-height / grid-size-y
2 U' u3 Y0 Z0 g+ D! v
7 a7 o- x2 P( S8 E* H4 c$ j  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary: a9 S  U& |* g
  set acceleration 0.0995 k; u! d. D' s; f
end' D) H. _( V3 P; O# k
* R) ^* E3 r7 t
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,* ?5 i( r6 O( Z* C! X+ q
;; and initialize the traffic lights to one setting0 Q* N5 T2 y) A
to setup-patches& u1 }) C& o# u: D, X0 h4 k5 [
  ;; initialize the patch-owned variables and color the patches to a base-color. h, n8 C0 J5 v1 G; J- v
  ask patches! U& R2 ]6 r5 b3 ]3 h* {
  [5 @, o" F- I4 M
    set intersection? false
5 k( v2 e, z3 v" m( b2 `6 S    set auto? false
( ]* A9 A6 T+ [( I9 D! h4 e* y2 @  f    set green-light-up? true0 u  T: Q, Y) }" G) V1 h
    set my-row -1
4 I1 y( p5 F2 D; _0 L- C- D    set my-column -15 w1 W5 i1 P% b5 e" T
    set my-phase -12 ]0 b5 y* M8 X% m. I
    set pcolor brown + 3# b9 D& F1 r8 w5 G0 S  Z* T* N4 X
  ]1 E$ [  V; u. Q4 T! [
: q* h$ i. Z2 l. j+ ~  h
  ;; initialize the global variables that hold patch agentsets
9 C# ^' _3 }5 E' H, t# H3 |  set roads patches with6 M, r/ ~, i6 ~) f+ E
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
! g- T1 V! R3 w" a: {7 D5 v% q    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]- ]/ A  @9 N; P* d, C/ v
  set intersections roads with! s7 q* e& [7 A0 B$ {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and& k# }6 Y8 }' a8 W( y( G$ a
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ n4 L- w7 d  Q4 {! y8 O. K2 K
& N7 {; G1 E, M$ Y# P: |1 N6 N1 ?" A
  ask roads [ set pcolor white ]8 E" y7 \" j0 _  M
    setup-intersections2 C/ M, n3 D, P# w
end. N& E8 c& J7 U% f- `9 \& O  S
其中定义道路的句子,如下所示,是什么意思啊?
+ D; ^1 v  t4 C7 }' t+ \9 ] set roads patches with
+ F$ ]+ e' v/ f* g    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
4 G" U& b! Z, j$ X' A    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
' q. Q5 T  J+ B- w! v7 S9 G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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